ArticlePDF AvailableLiterature Review

Abstract and Figures

Background: Energy administered during soft-tissue treatments may cauterize, coagulate, seal, or otherwise affect underlying structures. A general overview of the functionality, procedural outcomes, and associated risks of these treatments, however, is not yet generally available. In addition, literature is sometimes inconsistent with regards to terminology. Along with the rapid expansion of available energetic instruments, particularly in the field of endoscopic surgery, these factors may complicate the ability to step back, review available treatment options, and identify critical parameters for appropriate use. Methods: Online databases of PubMed, Web of Science, and Google Scholar were used to collect literature on popular energetic treatments, such as electrosurgery, plasma surgery, ultrasonic surgery, and laser surgery. The main results include review and comparison studies on the working mechanisms, pathological outcomes, and procedural hazards. Results: The tissue response to energetic treatments can be largely explained by known mechanical and thermal interactions. Application parameters, such as the interaction time and power density, were found to be of major influence. By breaking down treatments to this interaction level, it is possible to differentiate the available options and reveal their strengths and weaknesses. Exact measures of damage and alike quantifications of interaction are, although valuable to the surgeon, often either simply unknown due to the high impact of tissue and application-dependent parameters or badly documented in previous studies. In addition, inconsistencies in literature regarding the terminology of used techniques were observed and discussed. They may complicate the formulation of cause and effect relations and lead to misconceptions regarding the treatment performance. Conclusions: Some basic knowledge on used energetic treatments and settings and a proper use of terminology may enhance the practitioner's insight in allowable actions to take, improve the interpretation and diagnosis of histological and mechanical tissue changes, and decrease the probability of iatrogenic mishaps.
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REVIEW
Energetic soft-tissue treatment technologies: an overview
of procedural fundamentals and safety factors
N. J. van de Berg J. J. van den Dobbelsteen
F. W. Jansen C. A. Grimbergen J. Dankelman
Received: 19 December 2012 / Accepted: 25 February 2013
ÓSpringer Science+Business Media New York 2013
Abstract
Background Energy administered during soft-tissue
treatments may cauterize, coagulate, seal, or otherwise
affect underlying structures. A general overview of the
functionality, procedural outcomes, and associated risks of
these treatments, however, is not yet generally available. In
addition, literature is sometimes inconsistent with regards
to terminology. Along with the rapid expansion of avail-
able energetic instruments, particularly in the field of
endoscopic surgery, these factors may complicate the
ability to step back, review available treatment options, and
identify critical parameters for appropriate use.
Methods Online databases of PubMed, Web of Science,
and Google Scholar were used to collect literature on
popular energetic treatments, such as electrosurgery,
plasma surgery, ultrasonic surgery, and laser surgery. The
main results include review and comparison studies on the
working mechanisms, pathological outcomes, and proce-
dural hazards.
Results The tissue response to energetic treatments can
be largely explained by known mechanical and thermal
interactions. Application parameters, such as the interac-
tion time and power density, were found to be of major
influence. By breaking down treatments to this interaction
level, it is possible to differentiate the available options and
reveal their strengths and weaknesses. Exact measures of
damage and alike quantifications of interaction are,
although valuable to the surgeon, often either simply
unknown due to the high impact of tissue and application-
dependent parameters or badly documented in previous
studies. In addition, inconsistencies in literature regarding
the terminology of used techniques were observed and
discussed. They may complicate the formulation of cause
and effect relations and lead to misconceptions regarding
the treatment performance.
Conclusions Some basic knowledge on used energetic
treatments and settings and a proper use of terminology
may enhance the practitioner’s insight in allowable actions
to take, improve the interpretation and diagnosis of histo-
logical and mechanical tissue changes, and decrease the
probability of iatrogenic mishaps.
Keywords Instruments Technical Endoscopy Tissue
Safety factors
Due to the ever-growing amount of energetic soft-tissue
treatment technologies and the development of new hybrid
methods, the surgeon is left with a difficult task to differ-
entiate and evaluate available options and find a suitable
approach for his or her patient. In addition, the function-
ality of single instruments is expanding as more application
tips and energy settings become available. In particular,
when dealing with new techniques and instruments, back-
ground information regarding appropriate use would be of
great value. Generally, surgeons have to rely on pre-
liminary experience with comparable instruments and
some marginal instructions provided by the manufacturer.
N. J. van de Berg (&)J. J. van den Dobbelsteen
F. W. Jansen C. A. Grimbergen J. Dankelman
Department of Biomechanical Engineering, Delft University
of Technology, 3mE, Mekelweg 2, 2628 CD Delft,
The Netherlands
e-mail: N.J.P.vandeberg@tudelft.nl
F. W. Jansen
Leiden University Medical Center, Leiden, The Netherlands
C. A. Grimbergen
Academic Medical Center Amsterdam, Amsterdam,
The Netherlands
123
Surg Endosc
DOI 10.1007/s00464-013-2923-6
and Other Interventional Techniques
Although, in the past decades, an increased focus on new
training systems and surgical simulators developed to
overcome risks associated with procedural learning curves,
a clear-cut analytical fundament to link the basic theory to
practice may be of equal importance in becoming a profi-
cient user of energetic surgical devices.
A thorough analytical overview of existing energetic
soft-tissue treatments is, regardless of the immense quan-
tity of literature published on this matter, not yet generally
available. This review consolidates research findings on
commonly applied energetic treatments in the endoscopic
field, such as electrosurgery, plasma surgery, ultrasonic
surgery, and laser surgery. Of each of these techniques, two
subgroups of criteria are discussed: (1) tissue impact,
describing the principles of cellular interaction that lie at
the base of the produced end effect, and (2) safety factors,
including the relevant considerations encountered in liter-
ature that deal with the patient’s and surgeon’s safety. It
provides insight on a more qualitative basis on both the
selection of a safer alternative and the recognition of pit-
falls as they occur. Subjects that are touched include the
production of smoke, the rates of instrument heating and
cooling, and the chances on energy leakage from the shaft
or other out of sight components.
During the construction of this overview, the necessity
of shedding some light on current inconsistencies in used
terminology became apparent. Due to some closely related
working mechanisms, the merging of companies, and other
technological evolutions, the used terminology in this field
has become quite diverse. As an opening chapter, a brief
description of the original use of words is provided.
Methods
A literature review was performed (March 2012) using
online databases of PubMed and Web of Science, along
with findings from Google Scholar. Search terms included
the main energetic dissection technique under evaluation;
electrosurgery, plasma surgery, ultrasonic surgery, and
laser surgery, and their derivatives or synonyms (e.g., ul-
tras* OR harmon*). These terms were accompanied (AND)
by keywords related to (1) operational functionality (prin-
ciple* OR fundament* OR function* OR mechanism* OR
review), and (2) safety factors (safe* OR hazard* OR
problem* OR risk* OR complicat*). During the plasma
surgery search, an attempt was made to exclude (NOT)
blood plasma studies. Due to the broad scope of this
review, results were screened on behalf of generality and a
search reduction was achieved by excluding studies which
focused on a single surgical specialty or clinical procedure.
The remainder typically included review articles and
comparison studies among different techniques or
instruments. The resulting papers were screened for further
leads and the total (n=427) was filtered on clinical rele-
vance (e.g., what instruments, methods and tissue types or
phantoms were used?) and analytical detail (e.g., did the
article merely provide a presentation of results or also a
credible interpretation? How well was this supported and
does it align with other studies?).
Results
Terminology
To prevent the selection of improper settings, instrument
misuse, misconceptions regarding device functionality, and
careless instrument handling, practitioners would require
some basic knowledge on the underlying working princi-
ples and biophysical tissue interactions. One inevitable and
preliminary step would be the adoption of a clear and
consistent language to distinguish different techniques and
their functionality.
Before the introduction of antibiotics, tissue heating was
a widespread technique in wound treatment. A piece of
metal would be heated over fire and subsequently applied
to a wound. The rapid temperature increase would cau-
terize the wound, leading to disinfection and control of
bleeding. Nowadays, these primitive methods have largely
disappeared from medicine. Although electrocautery and
chemocautery still exist, their use is not nearly as frequent
as suggested by literature. A simple title search on the word
‘cautery’’ in Web of Science produced 106 results (19-7-
2012) from the past decade (2002–2012). Findings inclu-
ded articles, conference proceedings, and abstracts. One
result was not accessible and 17 gave insufficient context to
the word cautery. The remaining publications used cautery
to describe tissue heating phenomena with an unspecified
origin (n=11, this also includes papers that describe
‘cautery-free’’ procedures), electrosurgical procedures
(n=49, of which 10 unspecified, 12 monopolar, and 27
bipolar), and cautery procedures (n=29, of which 7 used
electricity, 18 used chemicals, and 4 used other heat
sources).
During electrosurgery, an electric current is sent through
tissue [1]. Electrosurgery differs from electrocautery as
heat is actually generated within the tissue instead of the
instrument. The end effectors of electrosurgical tools are
the poles that can generate a potential difference, whereas
the electrocauter is a closed loop, often battery powered,
circuit in which heat is generated (it has no end effector
poles). The fact that a search on cautery returns this many
electrosurgical studies definitely relates to the difference in
popularity between both techniques. Nevertheless, the
terms often are used interchangeably, whereas the risks
Surg Endosc
123
associated with these devices, one (generally) operating at
much higher temperatures and the other providing an open
loop electric circuit, are quite diverse.
Electrosurgery can be divided in monopolar and bipolar
applications, reflecting the amount of active cutting elec-
trodes that are used. During monopolar electrosurgery, a
single cutting electrode is used and a grounding pad, large
enough to avoid local tissue heating phenomena, closes the
circuit. During bipolar electrosurgery, two active cutting
electrodes are used in close proximity and both affect the
intermediate tissue structures.
The application of radiofrequency currents in a mini-
mally invasive setting to thermally affect and remove
unwanted cells, such as tumors, often is called high fre-
quency or radiofrequency ablation (RFA). The largest
difference of this technique compared with electrosurgery
relates to instrument design, the (dis)ability to deliver
forces with the device, and ultimately the zone of inter-
action that is reached. During RFA, often needle-like
instruments are used that can deploy multiple electrodes
under visual guidance in a monopolar or bipolar setting.
Other treatments that operate by means of an electric
energy supply, e.g., plasma surgery and diathermy, also are
regularly stigmatized as electrosurgical modalities. In some
energetic applications, radiofrequency currents are used to
create plasma. The currents leap from one pole to the other,
i.e., in a bipolar setup, while exciting the surrounding
medium. This plasma medium is subsequently used to
affect tissue. However, note that typical plasmasurgical
tools with two poles can have a spatula or hook shape in
contrast to the commonly seen bipolar electrosurgical tips.
In addition, some hybrid instruments exist that can switch
between plasmal and electrosurgical energy to generate a
cutting or coagulating effect.
Although it should be noted that an eventual distinction
was made between medical and surgical diathermy, where
the latter would be a synonym for electrosurgery [2], the
general term was coined to describe a nondestructive pro-
cess of electrically deep heating subcutaneous tissues,
muscles, and joints. It describes a therapeutic process that
is still regularly used by physical therapists. Its working
mechanism is, however, closely related to electrosurgery in
that an electric current is sent through tissue. However,
during diathermy the power levels and pole sizes are
adapted in such a way to prevent permanent tissue damage.
Diathermy is achieved by means of either electromagnetic
radiation in the radiofrequency regime (typically
27.12 MHz [3]), the microwave regime (915 or 2,450 MHz
[3,4]), or by means of acoustic waves in the ultrasound
regime (800–1,000 kHz [3]). One closely related technique
that can, however, be disruptive is called high-intensity
focused ultrasound (HIFU); sound waves are focused on a
specific location to increase the wave density and localize
the heating effect, leading to a noninvasive thermal abla-
tion of tissue.
Then, there is the use of ultrasound or ultrasonic.
Although ultrasound is primarily used to denote the fre-
quency range above the human hearing limit (approxi-
mately 20 kHz), in actual applications ultrasound is
preferably used to describe imaging techniques that operate
by means of sound waves. Ultrasonic, on the other hand,
refers to sound waves that are used to change or disrupt
materials. The term Harmonic scalpel also is frequently
used synonymously to ultrasonic instruments, although this
term is based on a brand name (similar to the Bovie for
electrosurgical tools) and should perhaps not be seen as a
universal equivalent.
In the field of laser treatments, many different operating
principles and gain media are used, resulting in a wide
variety of terms. They will not be listed here individually.
However, each technique often has been developed for a
specific purpose. As a result, tissue effects can differ lar-
gely. Practitioners should be well aware of these differ-
ences, especially when they have multiple instruments to
their disposal. Also in this field, the energy source can be
put to use for the thermal ablation of tissue. This process is
called laser- or photoablation.
Overall energetic interactions
Although many energy forms are used during soft-tissue
treatment in clinical practice, their damaging mechanisms
often can be traced back on a primary level to mechanical
and thermal interactions. During electrosurgery, for
example, shear forces can be applied by means of the
electrodes, blades, graspers, or scissors, and heat is gen-
erated by means of electrical resistivity in tissue. Alterna-
tively, during laser irradiation, energized particles
(photons) will disrupt underlying structures by the partial
absorption of kinetic energy and the subsequent conversion
of this energy into heat.
Mechanical impact
Mechanical interactions with tissue are largely described by
the tissue’s stress-strain response, extending in the positive
and negative strain direction. Stress is defined as the exerted
force divided by the specimen’s cross sectional area,
whereas strain is defined as the change in length per unit of
the original length. It is important to incorporate these
specimen dimensions as the resulting (stress-strain) curve
can be used to deduce some valuable material properties.
This is not possible with simple force-displacement data.
Strain in the positive direction is based on the realign-
ment of structural molecules and is characterized by some
viscoelastic properties, such as stress relaxation, creep, and
Surg Endosc
123
hysteresis. These mechanisms lie at the base of surgical
interventions performed by knives, graspers, or shears.
Local pressures exerted by these instruments lead to high
shear forces (and strain) in the surrounding structures.
Ultimately, molecule bonds are distorted and tear results.
To determine when this happens, several models have been
developed where biological soft tissue is interpreted as an
anisotropic (due to present fiber types and orientations),
hyperelastic material [5,6]. However, as current models
extend to the large deformation range, analytical com-
plexity increases significantly and the physiological inter-
pretability of necessary variables is easily lost.
Thermal impact
When tissue is kept at temperatures around 50 °C for
sufficient time, irreversible thermal damage starts to occur
[7,8]. In the 60–80 °C range [8,9], tissue starts to blanch
and collagen denatures. The intramolecular hydrogen
bonds of proteins are broken, the triple-helix structure
unwinds and the highly organized crystalline structure
transforms into an amorphous state [10,11]. Although
collagen denatures, elastin networks do not. As a result,
soft tissue structures will shrink up to approximately one-
third of their initial length. At the macro scale, the dena-
turation process changes the material properties, leading to
the formation of thermal strain. There is a trade-off
between the achieved shrinkage and the mechanical elastic
tissue property [12]; shrunken collagen is rubbery with a
Young’s modulus of approximately 1 MPa [13]. Upon
further increase of the tissue temperature, at 90 °C, water
starts to evaporate and tissue starts to dry or ‘‘desiccate’’ [7,
8]. Tissue can swell up during laser treatment due to the
elastic and plastic deformations caused by this evaporation
response [14]. The sudden conversion of cell water to
steam leads to a relative increase in cell volume of the
order 10
3
[15]. As a result, at approximately 100 °C, cell
walls tend to rupture. As the cell wall is disrupted, the
steam will escape (steam popping) [8]. The leftover cell
debris is susceptible to carbonization, combustion, and
charring as the temperature increases greater than 200 °C
[8] in the absence of a water heat sink.
To enlarge scientific insight in the thermal damage
associated with different energetic treatments, the impor-
tance of adopting a standardized quantification protocol
should be stressed. So far, measured thermal spread values
of different techniques have been found to vary with an
approximate factor 10
4
, ranging from 2 lm[16]to25mm
[17]. As a starter, a more universal definition of the word
‘damage,’’ and a means to reliably quantify this factor,
would be required. Table 1shows a range of mean thermal
spread values extending in the lateral direction of the pro-
duced cut. The selected studies all include a comparative
approach, inspecting porcine tissue histology by means of
hematoxylin and eosin (H&E) stains; a coagulative dena-
turation of collagen results in an eosinophilic homogeni-
zation of tissue [18]. This technique is proposed as standard
because it is a readily established approach [1826].
However, judging from the large variation in spread among
different organs [19], the selection of a standard test
material would still be an interesting topic.
The simultaneous administration of mechanical and
thermal energy by squeezing tissue with an energetic forceps
may lead to the homogenization of collagen in a process
called sealing. It is generally used to permanently close
tubular, e.g., vascular, structures. Histologically, it results in
gland profile distortions, epithelium detachment, cell
welding, nuclei lengthening, and chromatin homogenization
[27]. In particular, bipolar and ultrasonic instruments have
been described to exhibit a sealing potential [2123]. Seal
quality often is assessed in a pass/fail setting during blood
vessel burst pressure experiments. The seal is considered to
pass if it is able to withstand a certain pressure, e.g.,
300 mmHg [28]. Tested vessels are usually split up in dif-
ferent groups based on their type (vein or artery, although
mostly arteries are used) and their outer diameter. Other
factors that are thought to influence seal strength, such as
tissue tension during the experiment [28], and the collagen
content of the vessel types [28,29] (for instance the differ-
ence between muscular and elastic arteries), are usually not
taken into account. However, these factors may just as well
be better predictors for burst pressure than merely vessel
size, e.g., the collagen/elastin ratio [29]. In this regard, the
large spread in data found within test groups and especially
among studies may be partially explained. Table 1includes
burst pressure values obtained from currently available lit-
erature, looking only at porcine arterial models. Measure-
ment range or variance in data is usually not provided;
hence, a range of presented mean values is shown.
Gas production
As a result of the thermal response when cells are heated to
the point of boiling, membranes will rupture and particles
will be dispersed into the surrounding air [30]. Although
the presence of surgical plumes may not always be (visu-
ally) apparent, special illumination techniques have been
used to demonstrate their existence during electrosurgery,
ultrasonic surgery, and laser surgery [31]. The smoke that
forms is made up of 95 % water and 5 % cellular debris
[32] and cannot be considered sterile. The particles can be
mutagenic [33] or toxic and can contain chemicals, car-
cinogens, irritants, blood, tissue, viral DNA, bacteria, and
sometimes even viable tumor cells [30,3436]. Patholog-
ical risks range from irritated eyes and headaches to tumor
recurrence and bacterial or viral infections [36]. Depending
Surg Endosc
123
on the applied energetic approach, particle size can vary
between on average 0.07 and 6.5 lm[37]. In general, the
smaller particles are of more concern from a chemical
standpoint, whereas larger particles and cells are of more
concern from a biological standpoint. High temperature
gases tend to include more toxic aerosols [35], whereas low
temperature gases may contain a larger degree of biologi-
cally viable particles [37]. Surgical masks do not always
provide protection, especially against the smaller (e.g.,
viral) particles [30,37]. The use of smoke evacuation
systems seems to be more effective [31]. Quantitatively, it
was estimated by The American Occupational Safety and
Health Administration (OSHA) that 500,000 workers are
exposed to laser and electrosurgical smoke or plume each
year [30]. This includes surgeons, anesthesiologists, nurses,
and surgical technologists.
Unintended interactions and other hazards
Although direct tissue damaging mechanisms often can be
described by considering the effective mechanical and
thermal interactions at the application site, the general haz-
ardous potential of an instrument cannot. Unintentional
damage can result from contact with either the instrument tip
or the energy flow before reaching the tip. Interactions can
result on various levels, be it mechanical, thermal, electrical,
(bio)chemical, or a combination of factors and may just as
well happen outside the work space of the surgeon. To per-
form a risk analysis, the entire energetic pathway, including
all energy conversions from the supplying source to the
eventual dissipation in tissue, need to be regarded.
Specific treatments
Electrosurgery
Electrosurgery describes the disruptive processes that can
result from electric currents running through tissue. A
potential difference is generated between two electrodes or
poles, providing a ‘‘path of least resistance.’’ Two main
techniques, respectively monopolar and bipolar electro-
surgery, referring to the amount (1 or 2) of active cutting
electrodes used, will subsequently be discussed.
Tissue impact
When low-frequency currents pass through tissue, ions will
start to move and produce cell polarizations, electrolysis,
nerve stimulations, and muscular contractions. This may
lead to acute pain, muscle spasms, and even cardiac arrest.
When the frequency is increased ([10 kHz), the vibra-
tional amplitude decreases and most effects besides heat
production disappear [1,38,39]. Generally, electrosurgical
equipment operates in the radiofrequency (RF) range in
access of 100 kHz.
During monopolar electrosurgery, current is sent from
the active electrode, through the body to a remote ground
pad or return electrode [1]. The current throughput and
the electrode surface in contact with the tissue determine
the volumetric concentration of dissipated current with
time; the current density. Multiplied by the potential
difference across the poles, this provides the power den-
sity [W/cm
2
]. As a power density of 7.5 W/cm
2
or more
is said to cause thermal damage [8], ground pad elec-
trodes are generally selected large enough to avoid this
(resorbing energy at 1.5–2.2 W/cm
2
). Because the rate of
heating is proportional to the squared current density
(Joule’s first law), and current density decreases with the
squared distance from the electrode (assuming a radial
spread from direct tissue contact and a homogeneous
tissue sample), a strong temperature gradient around the
active electrode would result. Whether the subsequent
conduction of heat plays a role is largely dependent on
the repetition rate of the applied pulses. The application
of high heating rates for short timeframes may help to
reduce thermal diffusion and isolate the thermal effects to
the area being actively heated [40].
Table 1 Range of mean thermal spread (H&E stained) and arterial seal strength values in porcine tissue
Monopolar ES Bipolar ES Plasma surgery Ultrasonic surgery Laser surgery (CO
2
)
Thermal spread [mm] 7–8.5 [25,43] 1.2–5.8 [1924,26,43] 5.13
a
[25] 0.3–5.5 [19,21,22,2426]1
a
[20]
Burst pressure [mmHg]
(vessel diameter \3 mm) 128–1,025 226–790
(vessel diameter 3–5 mm) 295–1,261 205–1,727
(vessel diameter 5–7 mm) 178–720 [2123,26,85][21,22,26,85,87]
Vessel diameter is split up in three groups. Beware that the variance in data, which often was not provided in literature, is not shown. Hence,
these values should by no means represent safety margins
ES electrosurgery
a
Only one source could be included here. Other plasma studies suggest quite a different spread [16]. Laser impact, determined by a rough
estimation from a graph, was highly dependent on beam focus. Other laser types (besides CO
2
) should lead to different spread values as well
Surg Endosc
123
The thermal effect also depends on the generator
waveform. Most electrosurgical generators operate with
two wave modes: continuous and intermittent [1]. While
operating at the same frequency and power levels, the
continuous mode is characterized by a sinusoidal voltage-
time curve, whereas the intermittent mode has repetitive
high voltage peaks. The intermittent mode has a duty cycle
of 5–6 % of the continuous mode [1,40,41]. These modes
are frequently classified the pure cut and coagulation mode,
which is roughly the desired tissue end effect. The true
surgical outcome, however, also relies on other factors
such as the selected power, the electrode size and geome-
try, and the application technique. Interstitial modes
(blends), where the duty cycle is varied, are used as well.
Their surgical effects are usually described as a mixture of
the two main modes (Fig. 1).
In combination with the applied waveform and power,
the type of tissue contact also can affect the thermal
response. By means of direct contact to a relatively large
surface, a desiccation or drying effect can be reached,
which can cause deeper protein coagulation and tissue
destruction. The degree of cellular destruction is, however,
somewhat self-limiting as desiccated and charred tissue has
a greater electrical resistance than normal skin [42].
Alternatively, at high voltage levels, a fulguration effect
can be produced by keeping the instrument tip somewhat
above the tissue. As a result, sparks leap to the surface in a
diffuse pattern [42]. This may lead to a superficial car-
bonization process. Fulguration most often is applied for
rapid control of bleeding across a wide area, such as an
oozing capillary bed.
During bipolar electrosurgery, the ‘‘return electrode’’
and the ‘‘active electrode’’ are of similar size and in close
proximity to one another. In fact, current bipolar surgical
tools often are embodied in a forceps, with isolated elec-
trodes in the beak. In contrast to monopolar electrosurgery,
in terms of tissue impact, the bipolar modality has a
symmetric character. Current density does not decay with
distance in a radial pattern but is somewhat focused and
confined between the electrodes [43]. As a result, the
power requirement for coagulation is significantly reduced
[7,44]. Bipolar instruments are regularly used to seal blood
vessels. The used electrical energy of currently marketed
bipolar instruments is, however, insufficient to effectively
cut tissue [44], and mechanical energy through squeezing
or the application of an integrated scissor or blade is gen-
erally required for full dissection.
Differences in electrical properties of to-be-processed
tissue types can affect device performance. Some bipolar
tools are therefore equipped with sensing technologies that
measure tissue impedance and auto-regulate the generator
power in a process called ‘‘Instant Response Technology’’
[45]. This extra control measure stabilizes the output
power, and surgical effect (according to the manufacturer),
independent of the encountered tissue type.
Safety factors
Because it is one of the oldest and best-studied energetic
dissection techniques under review, a large quantity of
literature is available on the possible hazards of monopolar
electrosurgery [1,8,41,43,44,4648]. Typical issues
relate to ground pad misplacements, leading to unintended
local power density peaks. Additional problems relate to
the unforeseen dissipation of current along the instrument
to nearby structures. Four different injury patterns are
usually distinguished: direct application, direct coupling,
insulation failure, and capacitive coupling [1,43,46,47].
These coupling problems become particularly important
with the reemergence of single-port laparoscopy [49].
Direct application describes sustained damage through
wrong positioning of the electrodes or device misuse.
Direct coupling refers to the unintended contact of the
active electrode to other conductive materials within the
abdomen [47]. Insulation failure is caused by a defect in
the insulation or coating and often results from excessive
use and sterilization [46,48]. Capacitive coupling refers to
the capacitor mechanism, where an electric potential build-
up results across close by materials without making actual
contact [8,47,48]. An intact insulator shields the direct
flow of current, but the attraction of charged particles
across the insulator remains. The electric charge that has
built up in adjacent tools will eventually be dispersed to
surrounding tissue. Warning signals that can signify cou-
pling abnormalities include a reduced efficiency of the
active electrode, a ‘‘snow storm’’ on the monitor caused by
coupling to the laparoscope, and a generation of arcing
sounds within the cannula [8].
In addition, monopolar tools have trouble operating in a
conductive (e.g., saline) medium, as this will alter the path
Fig. 1 Electrosurgical modes with different duty cycles ranging from
continuous waves to produce pure cuts (left) to intermittent waves to
produce a coagulation effect (right). Adapted from [1]
Surg Endosc
123
of least resistance. This was illustrated by Ramsay et al.
[50] by providing the required output power for performing
a certain coagulation task. The monopolar system was
completely ineffective in saline and required the maximum
generator power for coagulation in normal water.
Although the general applicability of monopolar
instruments is considered to be more diverse, bipolar
devices are notably safer due to the fact that both the active
and the return electrode are located in close proximity. This
way, coupling problems related to abnormal (electric)
return paths have been largely eliminated [8,49]. In
addition, bipolar devices are able to operate irrespective of
the surrounding media [50]. Finally, compared with
monopolar coagulation, bipolar electrosurgery was found
to be associated with a more efficient performance and less
thermal spread [43].
Compared with laser and ultrasonic surgery, it was
discovered that electrosurgical smoke contains small par-
ticles [32,37]. This means that electrosurgical smoke is
relatively hard to filter and that it remains airborne for a
longer period, allowing it to travel a longer distance within
the human body upon inhalation. The chemical composi-
tion was found to contain many toxic components [35].
One particular concern in laparoscopic procedures is the
release of carbon monoxide (CO), which can bind to
hemoglobin and cause hypoxic stress in healthy individuals
as a result of the reduced oxygen-carrying capacity of
blood [30]. It was found that by the end of an electrosur-
gical procedure, the median concentration of CO present in
the abdomen was 475 ppm, whereas the U.S. Environ-
mental Protection Agency limits 1-hour exposure to
35 ppm [32].
Plasma surgery
Plasma is regarded as the fourth state of matter and can be
generated by means of heat, radiation, or electric discharge
[51] in practically any environment. During plasma cutting,
an intermediate medium is used and excited to transfer
energy from the tooltip to the tissue structures.
Tissue impact
In practice, noble gases, such as helium and argon or plain
air, often are used as plasma medium. The soft-tissue
cutting ability of plasma results from the transfer of kinetic
energy by means of particle collisions. By gradually
increasing the potential difference across the plasma
medium, a transition phase is found from thermal heating
by Joule dissipation to the formation of plasma that con-
sists of free electrons, ions, and excited radicals. This
transition phase depends on the energy density (plasma
manifests at a discharge energy density in the order of
1 kJ/cm
3
[52]) and is associated with a drop in electrical
power and temperature, as illustrated in Fig. 2[53]. As a
result, plasma cutting can be associated with a strongly
limited region of thermal damage [54]. Selective cutting is
possible due to different mechanical and thermal tissue
properties. For example, retinal tissue was cut at consid-
erably lower pulse energy than was required for the
dissection of retinal blood vessels [52].
Liquids are bound to contain microinhomogeneities,
such as microbubbles of free gas and solid microparticles.
Under the application of tensile stresses, leading from
pressure variations, vapor bubbles can develop and grow
on these impurities (nucleation sites). Under specific
external loading conditions, bubbles that have reached a
certain threshold radius are bound to implode, causing
a shockwave. This principle is called cavitation and plays a
very important role in cellular destruction by means of
plasma surgery [52].
In some instruments the plasma formation at the
instrument tip can be switched between two modes of
interaction. A low power produced a corona, which was
associated with a significant modulation of charged particle
densities through the period in the discharge domain [55].
Above a certain threshold a transition to a glow mode
occurred, characterized by high-density plasma spreading
along the tip, shown in Fig. 3. The corona was dominated
by a displacement current, whereas 80 % of the total cur-
rent in the glow mode was accounted for by a conduction
current [55]. Appropriate selection of the operating mode
may have a significant influence on the treatment. Stronger
and more uniform radial particle fluxes can lead to faster
treatment in the glow mode [56]. On the other hand, due to
the lower dose, the corona mode may be more suitable for
Fig. 2 Electrical power and tissue temperature as a function of the
different voltage settings for a commercialized plasma cutter.
Adapted from [62]
Surg Endosc
123
materials that are more sensitive to plasma exposure. In
addition, plasma in the corona mode is relatively insensi-
tive to electrical tissue properties and therefore a nonuni-
form area can still be treated more or less evenly [56].
Cell exposure to low-intensity helium plasma was
observed to affect cell adhesion. Cells can detach, move,
and reattach elsewhere, while remaining viable [51]. Cell
proliferation has been reported 5 days after the treatment
and presumably results from the release of growth factors
by plasma damaged cells [51]. In addition cell membrane
permeability can alter by short-term exposure to helium
plasma. Energized particles may collide with tissue and
disrupt molecular bonds [54]. UV radiation can some-
times be produced as a side effect [51]. Reactive species
can get involved with the regulation of physiological
functions and signaling pathways [51]. Plasmas can
induce the aggregation of the coagulation protein fibrin-
ogen into fibrin. Fibrin catalyzes factors that cause clot
formation. The coagulation effect induced by this process
occurs at much lower temperatures than during the
application of, for instance, cautery. The coagulation rate
in plasma-treated samples was 15 times higher than in
control samples [51]. Coagulation also can be regulated
by a synergy between superoxide (O
2-
) and nitric oxide
(NO). NO prevents platelet aggregation under physiolog-
ical conditions. O
2-
is usually released by activated or
dysfunctional endothelial cells and prohibits the function
of NO, thereby inducing coagulation [51]. Another
example is the regulation of cell apoptosis by the inter-
action between NO and H
2
O
2
. The concentration of NO
determines the inhibition or enhancement of this pro-
grammed cell death. Careful selection of a plasma med-
ium and analysis of the resulting reactive species is of
great importance. Most risks can be avoided through the
appropriate design of the applicator and selection of the
plasma medium. It was demonstrated that plasma surgical
tools neither have to form a biochemical nor UV toxic
threat [57].
Safety factors
Compared with other energetic treatments covered in this
review, plasma surgery is relatively new and, as a result,
procedural risks are less extensively documented. Some
initial concerns deal with the biochemical interactions
between tissue and the reactive chemical compounds that
are created (as described above). In addition, the odds for
secondary hemorrhage, requiring return to theater (after
tonsillectomy procedures), were found to be increased after
use of the Coblation device [58]. Perhaps this presents the
existence of application limits associated with the pro-
claimed lower tip temperatures and decreased lateral
spread.
Approximately 5 % of the discharge energy of a col-
lapsing cavitation bubble is converted to mechanical
energy [59]. With an inappropriate instrument design [57,
59] or pulse waveform [60], the affected zone can extend
far beyond that of primary energy deposition. Distant tissue
up to 1.4 mm can sustain damage by the formation of high
speed (up to 80 m/s [59]) water jets resulting from col-
lapsed cavitation bubbles [57].
Gaseous by-products from plasma surgery are said to be
greatly reduced [61]. However, no quantitative information
is presented and it can only be assumed that this statement
is purely based on empirical observations.
Ultrasonic cutting
The ultrasonic field uses vibrations, with a relatively low
frequency (between 23.5 and 55.5 kHz) and high vibra-
tional amplitude (between 80 and 360 lm), to disrupt
tissue [62]. The term ultrasonic is derived from ultra-
sound, which refers to the frequency limit ([20 kHz)
that has to be met to prevent operation in the audible
range.
Fig. 3 Period averaged total ionization rate of a low power plasma
corona (top) and a high power plasma glow (bottom) at the instrument
tip (shown in white). Adapted from [64]
Surg Endosc
123
Tissue impact
The desired vibrations can either be realized by electro-
strictive or magnetostrictive means, where a material is
deformed under the influence of respectively an electric or
a magnetic field. However, newly developed ultrasonic
devices almost always operate by means of a piezoelectric
element. Piezoelectric crystals form a subgroup of elec-
trostrictive materials and are characterized by a linear and
reversible relation between the electric field and the
material deformation. A generator creates a potential dif-
ference across the piezoelectric element. The polarity
changes induce vibrations with the same frequency in the
piezoelectric material [62]. This vibrational energy is
subsequently led to the working tip of the device.
Although macroscopic damage caused by this energy
modality is not always clearly present [17], histological
injury does result. The supplied energy causes collagen
denaturation and breaks tertiary hydrogen bonds between
collagen and other extracellular matrix proteins [45]. This
leads to the formation of a viscous, adhesive coagulum that
can be used for sealing purposes [63]. At the application
center, tissues and vessels transform into an amorphous and
condensed necrotic structure [45]. Tissue separation can be
achieved through the principles of frictional heating and,
when the tip contacts a liquid medium, through cavitation
[64]. In tissues with high water content, the cavitation
principle can be dominant [65].
The thermally affected zone largely depends on power
settings, application duration, and tissue properties, such as
the specific heat and thermal diffusivity [64]. Blood per-
fusion plays a crucial role in heat dissipation away from the
tip. This is clearly illustrated by the in vivo and in vitro
temperature distribution measurements shown in Fig. 4.
Compared with other energy sources, hemostasis can be
achieved with relatively little heat [63], at temperatures
between 50 and 100 °C[66].
Safety factors
Throughout literature, large deviations in sustained thermal
damage are found, ranging from a few millimeters [27,64]
to 1 cm or more [17,45]. This may result from different
application methods, tested tissue types, and definition of
the word ‘‘damage’’. Because the temperature increase is
steep (Fig. 4), small changes in activation time can lead to
large variations in thermal build up. In addition, it was
shown that the instrument temperature is largely influenced
by the processed tissue type [67]. Knowledge on instrument
heating and cooling is essential for the patient’s safety. In
this regard, cooling rates were found to be quite slow for
ultrasonic devices [67,68]. Some studies therefore advice
the use of energy bursts not exceeding the 5 s [17,69].
The potential to coagulate with ultrasonic instruments is
at a maximum in the direction of the applied force, whereas
the lateral spread of energy remains relatively low [70].
This stands in contrast to techniques with less directional
preference, such as monopolar electrosurgery, during
which, in a homogeneous material, a more diffuse dissi-
pation [43] (a radial heat distribution) results. As a con-
sequence, the power density and essentially the
temperature gradient are more gradual and linear (focused)
during ultrasonic heating. Ultrasonic spread is better con-
trollable (more linear), but less ‘‘self-limited’’ [70]. In case
the application time is not properly regarded, it therefore
can still be associated with excessive damage [71].
A recent study compared the differences in metabolic
profiles, obtained by microdialysis, to quantify visceral
ischemia, a chemical measure of thermal damage, in rat
peritoneum after both electrosurgery and ultrasonic surgery
Fig. 4 Tissue (lung) temperature elevation versus time at various
distances from the heat source (Harmonic scalpel). Top without blood
perfusion (in vitro); bottom with blood perfusion (in vivo). Adapted
from [74]
Surg Endosc
123
[72]. They used an ultrasonic hook blade, which resulted in
short contact durations. Their conclusion was that ultra-
sonic effects are far more transient and that electrosurgery
caused more ischemic tissue damage.
So far, there is no consensus on the effects of ultrasonic
plumes [30,37]. The produced particles are in general
larger than those obtained during electro or laser surgery
[37]. Although larger particles will travel less far and are
easier to protect against, they might be associated with a
higher biological risk [37]. This would imply that, overall,
the risk may be more dependent on the tissue pathologies at
hand. In addition, ultrasonic scalpels can readily vaporize
tissue at relatively low temperatures [30], increasing the
chance of particles remaining biologically viable [37].
Laser surgery
As new laser instruments continue to emerge, often dedi-
cated to specific tasks in specific settings, a basic under-
standing of the principles behind their operation is
imperative to the operator. Light amplification by stimu-
lated emission of radiation describes a technique to pro-
duce a coherent bundle of electromagnetic radiation or
photons. Photon release is associated with the drop of an
electron of a pumped gain medium from a high-energy
level to its ground state. The difference between these
energy levels is indicative for the wavelength or ‘‘color’’ of
the released photon. Wavelengths used in medicine typi-
cally range between 308–10,600 nm and are selected based
on the target molecules, chromophores, found in tissue
[73].
Tissue impact
During laser surgery, a monochromatic, coherent, colli-
mated, and high-power [73] light bundle is focused on
tissue. A portion (approximately 4–7 % [73]) of the laser
beam is reflected at the tissue boundary and the remainder
enters the tissue. Photon penetration is characterized by the
wavelength dependent optical density of tissue [74]. The
part that enters is susceptible to scattering, remission, and
absorption [75]. Light scatter becomes relevant for shorter
wavelengths [76] in the visible and near-infrared spectrum,
causing a spread of light within tissue and increasing the
radiated area [73]. The absorbed photon energy is directly
converted into heat [76]; the fundamental goal of laser
irradiation. Although a precise and clean treatment theo-
retically can be obtained, this would require a certain
degree of skills and alertness together with the selection of
an appropriate laser type and instrument setting.
A complex set of chemical and thermal reactions can
result upon photon absorption (Fig. 5). The mechanisms of
laser-tissue interaction can roughly be divided in (1) pho-
tochemical reactions, which induce photobiological modi-
fications and activations that affect cell function, (2)
photothermal reactions, which relate to local heating by
photon absorption, e.g., coagulation, carbonization, and
vaporization, and (3) photoionization (or photoplasmal;
electromechanical) reactions, which result in ablation,
cavitation, and disruptive shockwaves [75,77]. In theory,
all laser applications are associated with a specific dose
delivery and can be fitted in this figure.
Characteristic properties that describe laser impact lar-
gely depend on the applied wavelength (the laser source)
and whether the laser is used in a continuous or pulsed
fashion. Continuous wave lasers emit a constant photon
beam that may result in a nonselective tissue impact [73].
Here, dosimetry is dependent on laser power, irradiation
time, and spot size [78]. Spot size is dependent on the used
fiber diameter and the distance to tissue as the exiting laser
beam is subjected to a slight divergence [78]. The mini-
mum achievable spot size is a function of wavelength and
therefore depends on the used laser source. The power
density, sometimes called the laser irradiance [W/cm
2
],
depends on the radius of the spot size in a quadratic
fashion. When considering energy administration on a
micro scale, irradiance usually varies across the spot size
with a Gaussian shape [78], sometimes necessitating
treatment with overlap to deliver energy to tissue more
Fig. 5 Medical laser interaction map. The diagonals show several
lines of constant fluence [J/cm
2
]. Two examples of energy dose
administration; extremely short-pulsed Nd:YAG used in the field of
ophthalmology (opht), and more general ‘‘hemostatic’’ Nd:YAG used
in gastronomy (gastr), are visualized by the associative marked areas.
Adapted from [87]
Surg Endosc
123
uniformly [73]. Secondary effects leading to tissue damage
are associated with heat spread through conduction and
convection within tissue. It has been shown that the zone of
thermal damage from laser irradiation could be reduced
substantially (here with approximately 27 %) by applying
air cooling during the procedure [79].
As for pulsed wave lasers, the pulse duration is of
additional importance. It enables a more selective photo-
thermolysis of tissue [73]. By selecting pulse duration
shorter than the thermal relaxation time of the target
chromophores, the effect of heat diffusion can theoretically
be eliminated, minimizing the spread of heat.
One of the most important chromophores in soft tissue,
due to its abundant presence, is water. The interaction
between laser wavelength and water absorption is shown in
Fig. 6. The CO
2
laser has a high absorption coefficient for
tissue water. At the frequency of the Nd:YAG laser,
however, a penetration depth of approximately 1 cm
-1
is
found [76], meaning that light intensity has decreased to
37 % (e
-1
by definition) at a depth of 1 cm. The relatively
large penetration depth of the Nd:YAG laser makes it quite
effective for producing hemostasis [2,76] (in contrast to
CO
2
lasers, for example, which produce a much smaller
thermally affected zone). Two other important absorbers in
soft tissues are melanin and hemoglobin [73,74]. Melanin
is predominantly present in the human as pigment and is
found in skin and hair, among others. The iris of the eye
contains large quantities of melanin granules, explaining
the high susceptibility to eye damage by some laser
sources.
Safety factors
With regard to the procedural safety of the patient, laser
surgery is sometimes said to have no proven benefit over
the usually less expensive electrosurgical systems [44].
Damage can result from beams reflecting off surgical
instruments [80]. Attempts to reduce reflection by scatter-
ing the beam or absorbing stray energy through instrument
surfacing techniques (wire brushing, sand blasting, or
glass-beading) have been adopted with variable success. As
a result, instruments often were found to heat up them-
selves, forming a potential risk for secondary burns [80]. If
irradiance is 10
8
–10
9
W/cm
2
[78], plasma will form. Def-
initely for pulsed laser systems, these values are feasible
[75].
As the temperature gradually increases during the lasing
of tissue, the dynamic behavior of laser-tissue interactions
becomes apparent [81]. The optical and thermal properties
of tissue change. An obvious example is the whitening of
transparent egg white when cooked. In general, light scatter
increases significantly, leading to a decreased laser pene-
tration depth and a more rapid superficial temperature
increase. Heat conductivity decreases with water content as
a consequence of evaporation. As the water heat sink
evaporates, and thermal convection through blood perfu-
sion is arrested, local temperatures can reach high levels
[74].
The pulsed (CO
2
) laser produces explosive plumes
during which aerosols are ejected at high speeds [31]. Gas
plume particles obtained from laser ablated soft-tissue
structures have an intermediate size compared with elec-
trosurgical and ultrasonic plumes. They seem to be asso-
ciated with both chemically toxic and biologically
infectious health risks [37] and can have a higher infectious
potential than electrocoagulation plumes [82].
Discussion
This review shows that a lot of the biophysical principles
that contribute to the soft-tissue response during energetic
treatments are readily understood. Most of them can be
reduced to a set of mechanical and thermal interactions on a
cellular level, which often are susceptible to the operator’s
choices with regard to instrument selection, application
technique, and procedure time. A better understanding of
these underlying interactions may help users to differentiate
the instruments to their disposal and identify possible pit-
falls and hazards. Such information should be available to
any user to operate at a knowledge-based conceptual level.
This paper provides its contribution by presenting an
overview of published findings up to this point.
One particular concern that was raised in this study
regards the use of terminology in the field of energetic
tissue treatments. A preliminary step to understand and
distinguish different techniques would be to separate them
systematically with words. In particular among energetic
Fig. 6 Absorption and penetration in water, (oxi-) hemoglobin, and
melanin against wavelength (adapted from [86]). The vertical lines
represent the wavelengths associated with commonly applied lasers in
medicine
Surg Endosc
123
treatments that operate by means of electricity, the used
language was found to be quite inconsistent.
As an example to demonstrate the value of a knowledge-
based conception by practitioners, let’s consider some useful
experimental findings obtained by a more recent publication
on capacitive coupling problems during monopolar electro-
surgery [83]. In this article, it is shown that the use of low-
power settings, with the device in the cut mode (instead of
coagulation), and the surgical technique of desiccation
(instead of fulguration) would help to reduce capacitive
coupling. Although this is important information in daily
practice, from an electric viewpoint these findings are quite
trivial. Two things should be considered: (1) electric cou-
pling problems in general result from alternative routes of
low electric resistance, and (2) the applied voltage is, in
essence, a measure of the insulation layer (the ‘‘electrical
resistance’’) that can be bridged by an electric current.
Because the coagulation mode uses a higher voltage than the
cut mode, the chance that other insulated paths can be
bridged (with a sufficient current density to leave an effect,
i.e., tissue damage) increases. In addition, because air is a
good electric insulator, the electrical resistance of the ful-
guration path will be much higher than that of the desiccation
path, during which direct tissue contact is made. Because the
relative resistance values determine the electric current dis-
tribution (parallel resistors), the chance on alternative loca-
tions for tissue damage increases again.
On behalf of the overall literature findings, the effects of
power density and application time (and in this regard also the
selection of a continuous or pulsed mode) appear to be of
major influence. As the combined effect of these two factors
would present a measure for the energy delivered to tissue, this
should not be a surprise. In general, a clean cut is achieved by
selecting a high power and pulse duration longer than the
tissue’s thermal recovery time. This allows structures to retain
their rest state after impact, preventing heat build-up and
reducing the thermal dissipation to surrounding tissue. This
mechanism is used during pulsed laser treatment and also
holds for electrosurgery [40]. Although the functionality of the
intermittent mode during monopolar electrosurgery (coagu-
lation) seems to contradict this,the difference between voltage
and power should be stressed. The high voltage used during
Table 2 Qualitative assessment of the functioning and risks of different energetic treatments
Functions Thermal dissipation Out of sight damage Gas production Risks
Monopolar ES Dissection ?? ?? ?? Ground pad misplacement
Coagulation Wrong direct application
Fulguration
Desiccation Direct coupling
Insulation failure
Capacitive coupling
Excessive thermal damage
Bipolar ES
a
Coagulation ?0?Excessive thermal damage
Sealing Wrong direct application
Plasma surgery
a
Dissection – 0 9Cavitation/shockwaves
Selective
b
Wrong direct application
Ultrasonic surgery Dissection ?? 9Excessive thermal damage
Selective
b
Slow instrument cooling
Coagulation Wrong direct application
Sealing Cavitation/shockwaves
Laser surgery Dissection ?????Excessive thermal damage
Coagulation Wrong direct application
(here also; eye damage)
Laser beam reflection
Cavitation/shockwaves
Safety scores are given on the thermal dissipation, chance on out of sight damage, and the gas production. For this, -(low risk), 0 (neutral), ?,
?? (high risk) scale is used. No consensus, 9, has been reached on the relative risks of ultrasonic and plasma plumes
ES electrosurgery
a
Excluding hybrid instruments using both plasma and bipolar ES
b
Referring to a potential for tissue-selective cutting
Surg Endosc
123
monopolar coagulation increases the tissue depth (resistance)
and thereby volume that can be actively bridged, regardless of
any secondary dissipation effects.
In combination with the application time, the used power
and ultimately the power density at the application site is of
interest. However, the physical quantity power often is
documented badly. Used power levels are then described by
the company-assigned settings (1, 2, 3, or the ‘‘amount of
eliminated bars on the device’’), which can be difficult to
match to corresponding values, definitely as articles and
instruments get older. In addition, a description of the tissue
contact area is frequently missing, disabling the determi-
nation of power density. Information like this may be of
great value in a broader, comparative context, regardless
whether power was chosen as an experimental variable.
An overall remark should be made in this regard that,
especially in complex systems (e.g., the human body) that
are largely influenced by environmental factors, which
cannot be properly controlled, comparative data easily
becomes sparse. The adoption of a standardized experi-
mental approach and a thorough documentation of both
methods and results become essential. The assessment of
arterial burst pressure, for instance, was complicated by
different presentations of results. One study provided
median values [84], whereas most used mean values [21
23,85]. Most studies properly specified sample size [21,
22,84,85], but others did not [23]. Some provided a
variance in data [23] (in graph form [85]), others a range
[84], whereas others did not [21,22]. All studies classified
vessels by their outer diameter, but between studies these
groups were not aligned. Bearing in mind that vessel size
may not even be a good predictor for burst pressure [29],
the ability to make any conclusive statements about the
totality of prior work was severely compromised.
For a quantitative comparison of procedural risks, a mea-
sure of boththe relative ‘‘magnitude of potential loss’’ and the
‘probability that the loss will occur’’ would be required. An
objective measure of potential loss is nonexisting and would
be extremely complicated to produce in such a general sense.
Also, the probability factors of these hazards often are not
sufficiently documented, so that a quantitative evaluation of
procedural risks, at this stage, is not feasible. Instead, a more
qualitative overview based on energy types, levels, produced
gasses, chances to affect tissue out of sight, and other reported
risks, was constructed as shown in Table 2. It was assumed
that these risks are related to the amount of investigations
performed topoint out or solve the matter.This table therefore
may be somewhat biased by popularity of different tech-
niques, and the ease with which research hypothesis could be
supported or disproven. In addition, different device functions
(e.g., fulguration or desiccation) should ideally be assessed
individually. However, withcurrent literature this was not yet
possible.
Important safety criteria that has not yet been covered to
full extend is the tissue selectiveness of a dissection
method (as shortly mentioned in the plasma surgery sec-
tion). Tissue selectivity refers to the ability to discriminate
between tissue structures; affecting one tissue type, while
leaving other nearby structures intact. This can for instance
be achieved by making use of the structural differences
between tissue types, e.g., water content as a thermal buffer
or collagen content as a mechanical barrier. Tissue selec-
tive responses have been described for ultrasonic [86] and
plasma surgical [52] modalities.
In conclusion, the relevance of a basic biophysical
understanding of energetic soft-tissue treatments by the
user should be stressed. A more consistent use of termi-
nology and some basic knowledge on the distinct appli-
cation mechanisms may increase the insight in allowable
actions to take, improve the interpretation and diagnosis of
histological and mechanical tissue changes, and decrease
the probability of iatrogenic mishaps.
Disclosures N.J. van de Berg, J.J. van den Dobbelsteen, F.W.
Jansen, C.A. Grimbergen, and J. Dankelman have no conflict of
interest or financial ties to disclose.
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... Active measures for reducing heat production and limiting cell damage include intermittent laser activation during the procedure, stopping at 10 sec of activation, decreasing the temperature enough to avoid dangerous levels, and achieving a reduction in fluid temperature inside the kidney [6]. Another technique consists of maintaining adequate irrigation during ureteroscopy (URS) by using an access sheath that improves irritant outflow and decreases the intrarenal pressure [9,10]. Few studies have established how the different variables to be regulated influence laser lithotripsy, such as time, energy, frequency, and flow. ...
... A height of 50 cm H 2 O was associated with a greater flow than at lower heights and a decreased in DT by 4.8°C compared to 30 cm H 2 O regardless of access sheath use and laser configuration. Among the various parameters that can be regulated in the lithotripter is the laser power (W), which determines the amount of energy it provides in each pulse that in turn depends on both the frequency and the energy [1,9]. Both works of Wollin et al. used in vitro models, such as the one carried out at the University of Patras with in vivo porcine models, have shown that at higher power there is a greater thermal rise after the laser pulse both in the irrigation solution and in the ureteral tissue [4,7]. ...
... Finally, we must mention the study limitations. When evaluating tissue temperature, the penetration of photons into the tissue depends on the wavelength, which is determined by its structure [9]. When using a porcine model, there is a difference in the composition and fat distribution of renal/ureteral tissue with respect to human tissues. ...
Article
Introduction: The aim of this article was to quantify the effect of the use of holmium laser during intracorporeal lithotripsy in an ex vivo model. Material and methods: A simulated model for laser nephro-lithotripsy was designed. Two ex vivo porcine kidneys were used. Electronic thermometer electrodes were inserted on the upper calyx. Intracorporeal lithotripsy was simulated with a holmium laser. Intrarenal temperature was recorded both at the beginning and after one minute of laser use with delta temperature (DT) defined as the difference between them. Measurements were made at different irrigation heights (30, 40, and 50 cm H2O), frequency (Hz), and laser energy (J) in addition to the presence or absence of the access sheath. Analysis of factors associated with temperature change was performed. Results: Thirty-eight observations were recorded. The measurement without the use of access sheath showed an average DT of 4.9, 5.1, and 6.5°C for 5, 10, and 15 Hz, respectively; however, with a sheath, DTs were 0.2, 0.5, and 1.5°C. In terms of energy, mean DTs of 4.3, 6.1, 5.2, and 13.9°C for 0.5, 0.8, 1.0, and 1.5 J were recorded; in contrast, with a sheath, averages of 0.4, 0.5, 0.5, and 3.8°C, respectively were noted. In the adjusted model, energy, frequency, and use of sheath and water height were significant. Conclusions: The configuration of the laser significantly modifies the intrarenal temperature and height of the bladder irrigation. The use of an access sheath provides lower intrarenal temperatures regardless of laser configuration and water height.
... Laparoscopic and hysteroscopic procedures are increasingly used to remove individual lesions in the abdominal cavity or even entire organs [1,2]. Paralleling this development, the fields of electrosurgery, laser, and plasma surgery continue to expand. ...
... Depending on the number of cutting electrodes used, the current can be monopolar or bipolar. It is important here to ensure that no damage is caused to the patient, surgeon or any implanted devices [1,2]. ...
Article
Full-text available
Purpose The aim of this study is to evaluate feasibility and potential benefit of a diode laser in major laparoscopic procedures in gynecology. Methods Between 2018 and 2020, a total of 42 cases were enrolled in this study comparing standard electrosurgery with diode laser-supported therapy in laparoscopic supracervical hysterectomy (LASH), total laparoscopic hysterectomy (TLH), or laparoscopic myoma enucleation (LME). Dual wavelength 45 W diode laser light was used to cut and coagulate during laparoscopy in the prospective interventional arm consisting of 11 cases, while 31 matching patients who received conventional treatment with monopolar/bipolar current for the same interventions were retrospectively identified in our laparoscopy database. Recruitment in the prospective interventional laser diode arm was terminated after only 11 patients (instead of planned 50) due to intense hemorrhage and massive smoke development. Results A total of 42 cases were analyzed (11 LME, 19 LASH, and 12 TLH). Strong smoke development was evident in all 11 cases in the diode laser arm. It was necessary to convert to bipolar or monopolar current in all hysterectomies ( n = 9) with initial diode laser implementation due to increased bleeding and smoke development. Conventional current sources had to be used in LMEs ( n = 2) due to excessive bleeding and poor visibility during enucleation of the fibroid. A significant difference ( p < 0.0001) was observed regarding smoke development when comparing the laser arm with the control arm. Conclusion We found a 45-W diode laser to be inferior to electrosurgical techniques for major laparoscopic gynecologic surgeries regarding bleeding control and smoke development.
... Site burns (e.g. pads, prostheses, surgeon hand) occur more frequently while using electrosurgery [10]. There are 40,000 cases of patient burns from electrosurgical equipment each year in the USA [8]. ...
Article
Full-text available
Background Endoscopic and laparoscopic electrosurgical devices (ED) are of great importance in modern medicine but can cause adverse events such as tissue injuries and burns from residual heat. While laparoscopic tools are well investigated, detailed insights about the temperature profile of endoscopic knives are lacking. Our aim is to investigate the temperature and the residual heat of laparoscopic and endoscopic monopolar instruments to increase the safety in handling ED. Methods An infrared camera was used to measure the temperature of laparoscopic and endoscopic instruments during energy application and to determine the cooling time to below 50 °C at a porcine stomach. Different power levels and cutting intervals were studied to investigate their impact on the temperature profile. Results During activation, the laparoscopic hook exceeded 120 °C regularly for an up to 10 mm shaft length. With regards to endoknives, only the Dual Tip Knife showed a shaft temperature of above 50 °C. The residual heat of the laparoscopic hook remained above 50 °C for at least 15 s after activation. Endoknives cooled to below 50 °C in 4 s. A higher power level and longer cutting duration significantly increased the shaft temperature and prolonged the cooling time ( p < 0.001). Conclusion Residual heat and maximum temperature during energy application depend strongly on the chosen effect and cutting duration. To avoid potential injuries, the user should not touch any tissue with the laparoscopic hook for at least 15 s and with the endoknives for at least 4 s after energy application. As the shaft also heats up to over 120 °C, the user should be careful to avoid tissue contact during activation with the shaft. These results should be strongly considered for safety reasons when handling monopolar ED.
... Bipolar instruments are generally forceps dissectors or graspers whereby the active electrode is on one tip, and return electrodes are on the other. The current only flows between the tips, and not through the patient's body [103,104]. ...
Article
Full-text available
Just as laparoscopic surgery provided a giant leap in safety and recovery for patients over open surgery methods, robotic-assisted surgery (RAS) is doing the same to laparoscopic surgery. The first laparoscopic-RAS systems to be commercialized were the Intuitive Surgical, Inc. da Vinci and the Computer Motion Zeus. These systems were similar in many aspects, which led to a patent dispute between the two companies. Before the dispute was settled in court, Intuitive Surgical bought Computer Motion, and thus owned critical patents for laparoscopic-RAS. Recently, the patents held by Intuitive Surgical have begun to expire, leading to many new laparoscopic-RAS systems being developed and entering the market. In this study, we review the newly commercialized and prototype laparoscopic-RAS systems. We compare the features of the imaging and display technology, surgeons console and patient cart of the reviewed RAS systems. We also briefly discuss the future directions of laparoscopic-RAS surgery. With new laparoscopic-RAS systems now commercially available we should see RAS being adopted more widely in surgical interventions and costs of procedures using RAS to decrease in the near future.
... 140 The tissue responses to these kinds of treatments are thus possible to explain with known mechanisms for thermal interactions. 141 Increased blood flow in turn would increase nutrient and O 2 availability, improve tissue elasticity, normalize tissue pH, and also have analgesic effects. 140 The latter would have their origin both in the changed metabolic conditions and in direct neurobiological effects. ...
Article
Full-text available
The potential for using non-ionizing electromagnetic fields (EMF; at frequencies from 0 Hz up to the THz range) for medical purposes has been of interest since many decades. A number of established and familiar methods are in use all over the world. This review, however, provides an overview of applications that already play some clinical role or are in earlier stages of development. The covered methods include modalities used for bone healing, cancer treatment, neurological conditions, and diathermy. In addition, certain other potential clinical areas are touched upon. Most of the reviewed technologies deal with therapy, whereas just a few diagnostic approaches are mentioned. None of the discussed methods are having such a strong impact in their field of use that they would be expected to replace conventional methods. Partly this is due to a knowledge base that lacks mechanistic explanations for EMF effects at low-intensity levels, which often are used in the applications. Thus, the possible optimal use of EMF approaches is restricted. Other reasons for the limited impact include a scarcity of well-performed randomized clinical trials that convincingly show the efficacy of the methods and that standardized user protocols are mostly lacking. Presently, it seems that some EMF-based methods can have a niche role in treatment and diagnostics of certain conditions, mostly as a complement to or in combination with other, more established, methods. Further development and a stronger impact of these technologies need a better understanding of the interaction mechanisms between EMF and biological systems at lower intensity levels. The importance of the different physical parameters of the EMF exposure needs also further investigations.
... However, in most cancer surgeries, an electrosurgical instrument is used to cut tissue, resulting in an area of coagulated tissue surrounding the electrode. 31,32 Coagulation of tissue increases scattering multiple times and reduces photon penetration depth compared to normal tissue, significantly altering DR spectra and requiring us to treat coagulated tissue as a distinct layer. [33][34][35][36][37] In this paper, the size of the tissue area affected by electrosurgery and the effect of coagulation on DR spectra are studied using layered porcine adipose and muscle tissue to simulate breast cancer surgery. ...
Article
In breast surgery, a lack of knowledge about what is below the tissue surface may lead to positive tumor margins and iatrogenic damage. Diffuse reflectance spectroscopy (DRS) is a spectroscopic technique that can distinguish between healthy and tumor tissue making it a suitable technology for intraoperative guidance. However, because tumor surgeries are often performed with an electrosurgical knife, the effect of a coagulated tissue layer on DRS measurements must be taken into account. It is evaluated whether real-time DRS measurements obtained with a photonic electrosurgical knife could provide useful information of tissue properties also when tissue is coagulated and cut. The size of the coagulated area is determined and the effect of its presence on DR spectra is studied using ex vivo porcine adipose and muscle tissue. A coagulated tissue layer with a depth of 0.1 to 0.4 mm is observed after coagulating muscle with an electrosurgical knife. The results show that the effect of coagulating adipose tissue is negligible. Using the fat/water ratio's calculated from the measured spectra of the photonic electrosurgical knife, it was possible to determine the distance from the instrument tip to a tissue transition during cutting. In conclusion, the photonic electrosurgical knife can determine tissue properties of coagulated and cut tissue and has, therefore, the potential to provide real-time feedback about the presence of breast tumor margins during cutting, helping surgeons to establish negative margins and improve patient outcome.
... Principles relying on Plasma Glow Discharge would require a plasma to function, of which procedural risks to the human are less extensively documented compared to other energetic treatment techniques. 184 Wet laser cleaning techniques rely on a medium, a fluid, to clean a surface and thus introduce new problems such as how to establish the medium inside a cavity. Steam laser cleaning is more favorable in this respect, but adds the dangers of superheated fluids inside the body with acoustic pressure pulses. ...
Article
Full-text available
A clear visualization of the operative field is of critical importance in endoscopic surgery. During surgery the endoscope lens can get fouled by body fluids (eg, blood), ground substance, rinsing fluid, bone dust, or smoke plumes, resulting in visual impairment. As a result, surgeons spend part of the procedure on intermittent cleaning of the endoscope lens. Current cleaning methods that rely on manual wiping or a lens irrigation system are still far from ideal, leading to longer procedure times, dirtying of the surgical site, and reduced visual acuity, potentially reducing patient safety. With the goal of finding a solution to these issues, a literature review was conducted to identify and categorize existing techniques capable of achieving optically clean surfaces, and to show which techniques can potentially be implemented in surgical practice. The review found that the most promising method for achieving surface cleanliness consists of a hybrid solution, namely, that of a hydrophilic or hydrophobic coating on the endoscope lens and the use of the existing lens irrigation system.
... InnovationMeeuwsen et al Furthermore, alternative site burns (eg, pads, prostheses, surgeon hand) frequently occur. 11 According to the Association of periOperative Registered Nurses, in the United States there are approximately 40 000 patient burn cases annually due to faulty electrosurgical devices, and in 1999 alone, nearly $600 million was paid in claims for those injuries. 12,13 In addition, the prevalence of bowel injuries related to electrosurgery during laparoscopic surgery is estimated at 1 to 2 per 1000 patients, with high morbidity related to unrecognized injuries. ...
Article
Full-text available
The benefits of electrosurgery have been acknowledged since the early 1920s, and nowadays more than 80% of surgical procedures involve devices that apply energy to tissues. Despite its widespread use, it is currently unknown how the operator’s choices with regard to instrument selection and application technique are related to complications. As such, the manner in which electrosurgery is applied can have a serious influence on the outcome of the procedure and the well-being of patients. The aim of this study is to investigate the variety of differences in usage of electrosurgical devices. Our approach is to measure these parameters to provide insight into application techniques. A sensor was developed that records the magnitude of electric current delivered to an electrosurgical device at a frequency of 10 Hz. The sensor is able to detect device activation times and a reliable estimate of the power-level settings. Data were recorded for 91 laparoscopic cholecystectomies performed by different surgeons and residents. Results of the current measurement data show differences in the way electrosurgery is applied by surgeons and residents during a laparoscopic cholecystectomy. Variations are seen in the number of activations, the activation time, and the approach for removal of the gallbladder. Analysis showed that experienced surgeons have a longer activation time than residents (3.01 vs 1.41 seconds, P < .001) and a lower number of activations (102 vs 123). This method offers the opportunity to relate application techniques to clinical outcome and to provide input for the development of a best practice model.
Thesis
Full-text available
Needle interventions play an important role both during the diagnosis and treatment of liver cancer. However, due to intermediate anatomical structures, such as the ribs and lungs, deep seated lesions are not always directly accessible. In addition, instrument-tissue interaction forces may cause needles to deflect during insertion. This leads to placement errors and possibly faulty diagnostic or therapeutic results. In literature, discussed methods to increase the reachability of deep seated lesions and decrease the chance on placement errors, include improvements of the medical imaging quality and of the initial needle-target alignment. In addition, the option to steer needles is actively being investigated. Needle steering involves the planning and timely modifying of instrument-tissue interaction forces in order to control the deflections in tissue. Currently investigated steering methods employ needle base manipulations, bevel-tip needles, pre-curved stylets, active cannulas, programmable bevel-tip needles, and articulated-tip needles. The technique proposed in this work employs an actively articulated needle tip.The aim of this research is to enhance our understanding of where needle-tissue interaction forces originate and how they can be effectively modified to steer needles. This is done by means of force measurements and device functionality evaluations during needle insertions in tissue simulants. The influence of tip shape on the formation of bending forces during needle insertion was studied in a fundamental and macroscopic experiment (Chapter 3). It was found that articulated bevel-tip needles are more efficient in building up bending force than matched conical-tip needles. However, increasing the tip articulation angle has a larger positive effect on bending force. Furthermore, it was found that the resultant force orientation depends on the insertion force and that the size of this vector rotation varies per tip shape. In general, the radial (bending) force component increases faster than the axial (insertion) force component. The study of these relations is relevant for the accurate estimation of tip-loads in mechanics-based needle steering models.To reach predefined targets, a teleoperation platform was developed (Chapter 4). The angle of an articulated, conical-tip needle was controlled in a closed-loop system. On-line feedback on the tip position was obtained through 3-D shape reconstructions, using fiber Bragg grating (FBG) based strain measurements. A simple PI-controller demonstrated the needle's nimble maneuverability by continuously amending the tip angle and navigation path. An advantage of articulated-tip needles is that they do not require axial rotations to change the steering plane. Optimal paths may in the future be defined with respect to the clinical task, the limitation of tissue damage, and (when applicable) the abilities of a human operator. Human operation of steerable needles is discussed by means of experimental results in manual and shared control steering tasks. In the implemented shared control setting (Chapter 5), a path planner determined a single-curved path to the target, in which the needle curvature and tissue straining conditions were minimized. The controller estimated the error between the actual and planned path and informed the human operator by means of low intensity force guidance. The ability of users to interact with the teleoperation platform and the acting kinematic needle steering constraints, was found to vary considerably. This stresses the need for studying the effective use of communication channels, e.g. by evaluating the weights users assign to the presented feedback. In the end, shared control may teach users how to cope with the acting needle steering constraints, and guide them in complicated steering tasks.Manual needle steering tasks were performed by means of a novel, tip-articulated and hand-held instrument (Chapter 6). Targets in five principal steering directions were successfully reached under visual feedback. An average targeting accuracy of 0.5 ± 1.1 mm is reported for 100 mm insertions. This shows that active manual needle steering allows for an effective compensation of the variability among insertion paths. This dissertation discusses important remaining challenges in the bridging of technical and clinical work fields and the realization of an operational steerable needle. The tip-tissue force measurements have provided insights in the ways current needle designs and mechanics-based navigation models can be improved. The tip-articulated needles show clear advantages for control systems, and allow for a manual approach in needle steering. Finally, the shared control of steerable needles was studied and may be of use to guide practitioners in case of a complex navigation task.
Article
There are 50 types of skin lesions which are sometimes amenable to various forms of electrosurgery. Development of expertise in this modality depends on experience based on a sound understanding of fundamentals. Any form of physical energy is capable of producing destructive effects when carried beyond the limits of physiologic tolerance. The use of such destructive effects of heat generated in body tissue through tissue resistance to high-frequency alternating current is the basis of electrosurgery. Unipolar current with relatively high voltage and low amperage produces desiccation: cells are shrunken and shriveled and their nuclei are condensed and elongated. Bipolar current with lower voltage and higher amperage produces coagulation: tissue elements are fused into a structureless homogeneous mass with hyalinized appearance.
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A test method was developed to identify those variables important for assessing the performance of ultrasonic surgical devices in ex vivo ligature sealing of porcine carotid and uterine arteries. Ruggedness testing using a small sample size in pilot experiments was conducted using a newly developed test method in an effort to assess the usefulness of this methodology and to identify test variables that might warrant further testing. The development of this test method included the use of a custom-designed prototypic tension device for load-controlled ex vivo vessel stretching during saline perfusion and subsequent seal and transection of porcine arteries with an advanced energy surgical device. The quality of the seal was evaluated as a burst pressure (mmHg). The experimental set-up allowed for either monitoring or controlling specific test conditions, including blood vessel tension during cutting and sealing, saline infusion rate, cutting time, pressure generated in the vessel during cutting, and burst pressure. Both muscular-type uterine and elastic-type carotid arteries were investigated, since energy based devices are most frequently used on muscular-type arteries but are developed and tested using elastic-type arteries. Although confounded with the age of the animal, in the ruggedness test pilot, it was observed that porcine carotid arteries yielded a comparatively lower burst strength seal as compared to porcine uterine arteries. The data generated during ruggedness testing suggests that the artery type and saline infusion rate during transection may be important variables in ex vivo vessel seal testing.
Article
Dissection and haemostasis using electrosurgical current has been used safely for nearly 70 years. It is used most commonly in the monopolar form in which the circuit is completed across the patient between an active instrument and a low energy density return plate and using two current waveforms (cut and coagulation) which are manipulated to produce a variety of tissue effects. In surgical laparoscopy the monopolar arrangement may create abnormal return paths to the patient plate by capacitive and direct coupling. If these paths have a cross-sectional area sufficient to raise the power density above 7.5 watts/cm2 tissue damage may occur. These risks can be reduced by modification of surgical technique and using instrumentation designed to eliminate the abnormal return paths.
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End-stage liver disease accounts for over 30,000 deaths annually in the United States. Orthotopic liver transplantation is the only clinically proven treatment for patients with end-stage liver failure. A limitation of this therapy is a shortage of donor ...
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Devices delivering energy to biological tissues (eg lasers, RF and ultrasound) can induce surgical smoke consisting of particles, vapor, gasses and aerosols. Besides interfering with the view of the surgeon, the smoke is a risk for the health of both the users and patients. In literature, it has been shown that surgical smoke can contain carcinogenic and harmful biological agents. However, the impact on health of the users and patients is widely debated. The use of smoke evacuation systems in the OR is usually governed by economical reason instead of safety issues. A special image enhancement technique is used to study the behavior of smoke and aerosols and the effectiveness of smoke evacuation systems. A back scatter illumination technique using 1 mus light flashes at video rate was applied to image the smoke production of various surgical devices without and with smoke evacuation while ablating biological tissues. The effectiveness of various smoke evacuation devices and strategies were compared. The ablative thermal devices produced smoke but also aerosols. If the thermal energy was delivered in high peak pulses, the presence of aerosols was more significant. Ultrasound based devices produce mainly aerosols. The distance to the target, the opening of the evacuation nozzle and the dimension of aerosols were leading for the effectiveness of the smoke evacuation. The smoke visualization technique has proven an effective tool for study the effectiveness of smoke and aerosols evacuation. The results can contribute to the necessity to use evacuation systems in the OR.
Article
A significant advantage of Er:YAG and Ho:YAG laser radiation is that it can be transmitted efficiently by fibre, unlike that of the CO2 laser. The important characteristic of excisions made by these mid-infrared-beam lasers is the depth of coagulation beneath the excised surface. Intuitive physical arguments are developed to predict the coagulation depths, which are estimated to be 12μmand 650 μm for Er:YAG and Ho:YAG lesions respectively. These values are in agreement with derivations using more sophisticated physics by the same author elsewhere.