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Activated charcoal adsorption of volatile anesthetic agents for anesthesia machine preparation of malignant hyperthermia susceptible patients



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Content may be subject to copyright. AANA Journal June 2013 Vol. 81, No. 3 169
Activated Charcoal Adsorp-
tion of Volatile Anesthetic
Agents for Anesthesia
Machine Preparation of
Malignant Hyperthermia
Susceptible Patients
To the editor: We would like to
share recent advancements regard-
ing the utilization of activated
charcoal filters to adsorb volatile
anesthetic agents (VAAs). Although
activated charcoal has been known
for many years to adsorb VAAs,
has only recently become commer-
cially available and endorsed by the
Malignant Hyperthermia Association
of the United States (MHAUS).
MHAUS has put forth updated
recommendations for the prepara-
tion of anesthesia workstations to
be used in malignant hyperthermia
(MH) susceptible patients. In these
new recommendations, MHAUS rec-
ommends longer flushing times and
the use of activated charcoal filters
for the absorption of VAAs.
“Recommendations (4 alternatives):
1. Flush and prepare worksta-
tion according to manufacturer’s
recommendations or published
studies; this may take 10 to >90
minutes. Most studies also physi-
cally disconnect vaporizers from the
workstation; use a new, disposable
breathing circuit; and replace the
carbon dioxide absorbent. During
the case, fresh gas flow (FGF)
should be kept at 10 liters per min-
ute to avoid ‘rebound phenomenon’
(increased release of residual vola-
tile anesthetic agent when fresh gas
flow is reduced after a set period of
2. Use commercially available
charcoal filters that have been
shown to remove trace levels of
volatile anesthetic agents within
10 minutes of application, without
additional preparation. These filters
may have to be regularly replaced
during the anesthetic (see below).
3. If available, use a dedi-
cated ‘vapor free’ machine for
MH-susceptible patients. The
machine must be regularly main-
tained and safety-checked.
4. If appropriate to the institu-
tion, use an ICU ventilator that has
never been exposed to volatile anes-
thetic agents.”
The reasons for these updated
recommendations are twofold: the
commercial availability of activated
charcoal filters and the variability of
flush out times in newer anesthesia
machines. In the past, anesthesia
machines were designed and manu-
factured relatively the same from
year to year, and model to model.
Preparation of anesthesia machines
in the past was relatively simple and
straight forward, remove vaporizers
and flush (cleanse) with high flow
oxygen. The goal of flush has been
to reduce the patient’s exposure
levels of VAAs to under 5 parts per
million (ppm).
Meeting the rec-
ommendation of VAAs under 5 ppm
can be accomplished by a variety of
methods. A commonly employed
technique is to remove or disable
vaporizers (by taping them in the
“OFF” position), flush the machine
with high-FGF greater than or equal
to 10 L/min using the ventilator for
at least 20 minutes, and replace the
fresh gas outlet hose, CO
bent, and breathing circuit.
Unfortunately, many of the
internal breathing components in
modern anesthesia machines utilize
more plastic and rubber parts than
older traditional machines. As a
result, a significant reservoir exists
that retains VAAs and therefore
are particularly difficult in “cleans-
A review of the literature
has shown that past recommenda-
tions for preparing the anesthesia
machine for an MH susceptible
patient are outdated and unreliable.
Previous guidelines were devel-
oped for, now “older”, anesthesia
machines that utilized simpler
internal breathing circuits and were
free from the highly soluble reser-
voirs for VAAs that are common
in modern machines.
demonstrate that in order to achieve
a safe level of VAAs under 5 ppm,
modern machines should undergo
washout with high-FGF rates at 10
L/min for a minimum of 122 min-
It should be noted that
this minimum of 122 minutes flush
with high-FGF is assuming that the
ventilator diaphragm and ventila-
tor hose have been autoclaved.
Without meeting this step, the flush
time increases to a minimum of
151 minutes.
Regardless of time
spent in preparing the anesthesia
machine in washout mode, the lat-
est studies also point out a common
occurrence, the rebound effect.
This rebound effect occurs when
modern anesthesia machines, that
have been prepared using the tradi-
tional recommendations, have the
FGF rate reduced to under 10 L/
min. When flow is reduced to 3 L/
min, a surge in VAA concentra-
tion occurs exceeding 50 ppm, well
170 AANA Journal June 2013 Vol. 81, No. 3
above the safe level of 5 ppm.
the current studies conclude that
in order to keep the VAAs under
the concentration of 5 ppm, high-
FGF of at least 10 L/min must be
maintained for the entire anes-
Due to variations in newer
anesthesia machine component
parts and effectiveness of flush out
times, recent research has shown a
one time flush-out approach to all
anesthesia machine preparation for
MH susceptible patients no longer
Therefore, previous
recommendations based on older
anesthesia machine VAA flush out
times should not be considered reli-
able. Updated recommendations
need to be used. High flow oxygen
(10 L/min) for at least 122 minutes
with continued 10 L/min carrier
gas flow rate during anesthesia
machine use for an MH susceptible
patient is one such recommenda-
tion. A separate anesthesia machine
that is kept VAA free or a critical
care ventilator are also options
although not necessarily feasible
for all facilities. Activated charcoal
filter adsorption of residual VAA
is a recently re-introduced option
that studies have shown to be both
quick and efficient.Vapor-Clean fil-
ters (Dynasthetics Inc) are activated
charcoal filter disks that are placed
between the breathing circuit and
the anesthesia machine inspiratory
and expiratory ports, shown in the
Adsorption of VAAs
occurs immediately within the fil-
ters, and circuit carrier gases will
contain VAAs of less than 5 ppm
within 90 seconds and maintain this
low level for up to 12 hours.
FGF rates are not necessary with
Vapor Clean charcoal filter disks.
How Carbon Absorption
Activated charcoal is simply
charcoal that has been prepared
with a maximum amount of
pore space to increase surface
area. The increased surface area
ensures that aromatic, uncharged,
organic molecules passing over or
through the charcoal will come
in contact with the charcoal sur-
face and be adsorbed. Adsorption
[emphasis added] is surface
attachment of a fluid (gas is con-
sidered a fluid) whereas absorption
[emphasis added] is dispersal of
a fluid throughout the absorbent.
Activated charcoal adsorption sur-
face binds VAAs through Van der
Waals thermodynamic forces.
These forces are weak noncova-
lent forces but strong enough to
remove the VAAs from the carrier
gas flow and prevent their reaching
the patient. Greater surface area
equals greater adsorptive ability.
The average carbon surface area
is 10-15 m
/g, activated charcoal
averages a surface area of 700 and
1,200 m
/g which is up to 120
times increase.
We share current developments and
MHAUS recommendations regard-
ing VAA adsorption by activated
charcoal and preparation of anes-
thesia machines for MH susceptible
patients. This newly re-introduced
option of carbon filter adsorp-
tion of residual VAA in anesthesia
machines in preparation for MH
susceptible patients fulfills a need
for newer anesthesia machines and
addresses the shortcoming of previ-
ous recommendations. Regarding
the use of activated charcoal
adsorbers to assist in removing the
volatile anesthetic triggering agent
in the event of a MH occurrence,
we cannot point to any definitive
recommendations. The significant
drop in VAA ppm with the use of
activated carbon filters suggests
that their use may also be useful
in the event of a MH episode but
current treatment for MH remains
1. Holscher Fr. Zur beseitigung der aus-
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2. Holscher Fr. Zum schtze des operateurs.
Dtsch Med Wochenschr. 1928;38:794-95.
3. Epstein HG, Berlin DP. Removal of
ether vapour during anesthesia. Lancet.
4. Preparation of anesthesia workstations
to anesthetize MH susceptible patients.
Malignant Hyperthermia Association of
the United States website. Available from:
UI9CjbS9xSM. Accessed October 21, 2012.
5. Kim TW, Nemergut ME: Preparation of
modern anesthesia workstations for malig-
nant hyperthermia-susceptible patients: A
review of past and present practice. Anes-
thesiology. 2011;114:205-12
Figure. Activated Charcoal Filters Attached to the Inspiratory and Expira-
tory Limbs of the Anesthesia Workstation AANA Journal June 2013 Vol. 81, No. 3 171
6. Birgenheier N, Stoker R, Westenskow D,
Orr J. Technical communication: Activated
charcoal effectively removes inhaled anes-
thetics from modern anesthesia machines.
Anesth Analg. 2011;112:1363-70.
7. Larach MG, Gronert GA, Allen GC,
Brandom BW, Lehman EB. Clinical pre-
sentation, treatment, and complications
of malignant hyperthermia in North
America from 1987 to 2006. Anesth Analg.
8. Whitty RJ, Wong GK, Petroz GC, Pehora
C, Crawford MW. Preparation of the
Dräger Fabius GS workstation for malig-
nant hyperthermia-susceptible patients.
Can J Anaesth. 2009;56:497-501.
9. Shanahan H, O’Donoghue R, O’Kelly P,
Synnott A, O’Rourke J. Preparation of the
Dräger Fabius CE and Dräger Zeus anaes-
thetic machines for patients susceptible to
malignant hyperthermia. Eur J Anaesthe-
siol. 2012;29(5):229-34.
10. Crawford MW, Prinzhausen H, Petroz
GC. Accelerating the washout of inhala-
tional anesthetics from the Dräger Primus
anesthetic workstation. Anesthesiology.
11. Prinzhausen H, Crawford MW, O’Rourke
J, Petroz GC. Preparation of the Dräger
Primus anesthetic machine for malignant
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Anaesth. 2006;53:885-90.
12. Gunter JB, Ball J, Than-Win S: Preparation
of the Dräger Fabius anesthesia machine
for the malignant-hyperthermia susceptible
patient. Anesth Analg. 2008;107:1936-45.
13. Shinkaruk KS, Nloan K, Crossan M.
Preparation of the Datex-Ohmeda Aestiva
anesthetic machine for malignant hyper-
thermia cases (abstract A279). Presented
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Society of Anesthesiologists 2008.
14. Vapor-Clean Brochure. Dynasthetics. Salt
Lake City, Utah. Available at: http://www.
Accessed January 8, 2013.
15. Vapor-Clean Instructions for Use. Dyn-
astetics. Salt Lake City, Utah. Available
Clean/Vapor-Clean-IFU.pdf. Accessed
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16. Activated Carbon: Manufacture, Structure
& Properties. Cameron Carbon Incorpo-
rated. Havre de Grace, Maryland. Avail-
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Joseph W. Martin, RRNA, BSN, BA
Texas Christian University
Fort Worth, Texas
Mark D. Welliver, CRNA, DNP, ARNP
Texas Christian University
Fort Worth, Texas
3-in-1 Block: Are We Still
Using This Misnomer?
To the editor: I would like to com-
ment on the study by Wallace et
“Comparison of Fascia Iliaca
Compartment Block and 3-in-1
Block in Adults Undergoing Knee
Arthroscopy and Meniscal Repair”.
As the authors state, the term
“3-in-1” refers to the ability of one
high-volume block to cover the
lateral femoral cutaneous (LFC)
and obturator as well as the femo-
ral nerves. Unfortunately, this has
never proven out scientifically, as
coverage of the LFC and obtura-
tor nerves is inconsistent, and now
this technique is thought of as just
a femoral nerve block.
We do our-
selves a disservice by continuing to
use this misnomer in light of evi-
dence to the contrary.
The authors may have mis-
taken the ability of their blocks
to anesthetize the obturator nerve
because of the way they evaluated
the blocks’ onset and quality—sen-
sory changes in the corresponding
dermatomes. The success of an
obturator nerve block cannot be
evaluated by sensory distribution,
as there is overlap with the medial
cutaneous branch of the femoral
Motor blockade was mea-
sured in the study, but it was not
used as the sole determinant of
blocking the obturator nerve.
Finally, I agree with the authors
that the fascia iliaca compartment
block (FICB) has a role in the field
or in austere environments, where
availability of a nerve stimulator
or ultrasound and a practitioner
skilled in using them may be limited.
This study and others
show that
the FICB is an efficacious analge-
sic modality for arthroscopic knee
surgery, but so is the femoral nerve
block, which is a basic block and easy
to learn. Therefore, I do not agree
that in the OR setting, the FICB is
a preferred technique for teaching
trainees or inexperienced providers
over the femoral nerve block. In my
experience with trainees, they master
the femoral nerve block without diffi-
culty and having an “easier” block to
teach them is unnecessary.
1. Wallace JB, Andrade JA, Christensen JP,
Osborne LA, Pellegrini JE. Comparison of
fascia iliaca compartment block and 3-in-1
block in adults undergoing knee arthros-
copy and meniscal repair. AANA J. 2012;
80(4 Suppl):S37-44.
2. Enneking et al. Lower-extremity periph-
eral nerve blockade: essentials of our cur-
rent understanding. Region Anesth Pain M.
3. Choquet et al. A new inguinal approach
for the obturator nerve block: anatomical
and randomized clinical studies. Anesthesi-
ology. 2005;103(6):1238-45.
4. Farid et al. Comparison of femoral
nerve block and fascia iliaca block for
analgesia following reconstructive knee
surgery in adolescents. J Clin Anesth.
5. Capdevila et al. Comparison of the three-
in-one and fascia iliaca compartment blocks
in adults: clinical and radiographic analysis.
Anesth Analg. 1998;86(5):1039-44.
Roland A. Flores, Jr., MD
Houston, Texas
I want to acknowledge Amy Toups, CRNA, for
her contribution to the letter.
Response: I would like to respond
to the comments to the AANA
Journal by Dr Roland Flores with
regard to our article, “Comparison
of Fascia Iliaca Compartment
Block and 3-in-1 Block in Adults
Undergoing Knee Arthroscopy
and Meniscal Repair”. Dr Flores
questions our use of the term “3:1
block”, stating that this is a misno-
mer because it frequently fails to
anesthetize the femoral nerve (FN),
obturator (ON) and lateral femoral
cutaneous nerve (LFC). The term
“3:1 block” as described by Winnie
et al
uses a single injection tech-
nique that aims to block all 3 nerves
(FN, ON, and LFC). In our study,
we were interested in comparing the
outcomes of the fascia iliaca block
and the 3:1 block because there
was a paucity of literature for this
172 AANA Journal June 2013 Vol. 81, No. 3
comparison. Though we agree that
this block has variable results in
achieving an adequate block of all
three nerves, it consistently achieves
blockade of the femoral nerve.
Unfortunately since both of these
blocks are femoral nerve blocks, it
was necessary for us to utilize ter-
minology that could differentiate
between the blocks for the reader.
Our intent with this article was
to describe the use of the fascia
iliaca block, a block that does not
require technology and has been
shown to be useful in situations
outside of the traditional operating
room environment.
Many practitio-
ners use ultrasound technology to
place blocks in an effort to get the
needle as close to the nerve as pos-
sible in an effort to increase block
efficacy and duration. However, one
of the interesting findings noted in
our study was that the duration of
action was noted to be longer in the
fascia iliaca block despite the fact
that the needle injection point is
at a considerable distance from the
FN. This was the point that we were
attempting to emphasize and the use
of a comparison with the 3:1 block
technique was chosen since this is a
block that is well known and is still
used by many practitioners.
Dr Flores’s comment is inter-
esting because it brings to light
the confusion created when using
terminology that has been used to
describe skin marking techniques
to refer to a block under ultrasound
guidance. We do not disagree with
Dr Flores’s assertion that the 3:1
block may be a misnomer and sim-
ply chose this block for comparison
because of its long history and use
among anesthesia practitioners.
We also agree that both the fascia
iliaca block and the 3:1 block are
simply different approaches to block
primarily the FN and perhaps it is
time to develop terminology for the
subtle differences in approach for
ultrasound-guided blocks because
the same problem exists for other
extremity blocks as well.
1. Winnie AP, Ramamurthy S, Durrani Z,
Radonjic R. Plexus blocks for lower
extremity surgery. Anesthesiology Rev.
2. DeBuck F, Devore S, Missant C, Van
de Velde M. Regional anesthesia out-
side the operating room: indications
and techniques. Curr Opin Anaesthesiol.
CDR Lisa A. Osborne, CRNA, PhD,
Bethesda, Maryland
The views contained herein are the private ones
of the authors and are not to be construed as
official or reflecting the views of the Depart-
ment of Defense or the Uniformed Services
University of the Health Sciences.
Malignant hyperthermia is a potentially fatal condition, in which genetically predisposed individuals develop a hypermetabolic reaction to potent inhalation anaesthetics or succinylcholine. Because of the rarity of malignant hyperthermia and ethical limitations, there is no evidence from interventional trials to inform the optimal perioperative management of patients known or suspected with malignant hyperthermia who present for surgery. Furthermore, as the concentrations of residual volatile anaesthetics that might trigger a malignant hyperthermia crisis are unknown and manufacturers' instructions differ considerably, there are uncertainties about how individual anaesthetic machines or workstations need to be prepared to avoid inadvertent exposure of susceptible patients to trigger anaesthetic drugs. The present guidelines are intended to bundle the available knowledge about perioperative management of malignant hyperthermia-susceptible patients and the preparation of anaesthesia workstations. The latter aspect includes guidance on the use of activated charcoal filters. The guidelines were developed by members of the European Malignant Hyperthermia Group, and they are based on evaluation of the available literature and a formal consensus process. The most crucial recommendation is that malignant hyperthermia-susceptible patients should receive anaesthesia that is free of triggering agents. Providing that this can be achieved, other key recommendations include avoidance of prophylactic administration of dantrolene; that preoperative management, intraoperative monitoring, and care in the PACU are unaltered by malignant hyperthermia susceptibility; and that malignant hyperthermia patients may be anaesthetised in an outpatient setting.
Riassunto L’ipertermia maligna (IM) dell’anestesia è una patologia farmacogenetica che si manifesta in modo incostante con uno stato di ipermetabolismo del muscolo scheletrico in seguito all’esposizione a un agente anestetico volatile scatenante. I numerosi progressi nella fisiopatologia dell’IM hanno permesso di evidenziare il gene RYR1 principalmente implicato e l’implementazione di procedure di screening mediante test genetici o biologici. Tuttavia, forme di crisi di IM fruste o interrotte con il miglioramento del monitoraggio anestesiologico o ancora dei decessi perioperatori inspiegabili possono portare a sottovalutare l’incidenza delle manifestazioni di IM durante un’anestesia. Benché siano stati compiuti notevoli progressi negli strumenti di genetica molecolare nell’esplorazione dettagliata dei genomi degli individui, essi si accompagnano talvolta a maggiori difficoltà nella diagnosi poiché mancano ancora le correlazioni genotipo-fenotipo che consentirebbero una diagnosi di certezza. Oggi, un’organizzazione nazionale ed europea relativa all’IM ha permesso l’implementazione di raccomandazioni in tutti i settori della patologia: procedura terapeutica urgente e uso del dantrolene in caso di crisi di IM, screening e valutazione del rischio di IM in un soggetto in visita anestesiologica, rischio di IM nei parenti, precauzioni anestetiche in pazienti con un’IM o considerati a rischio e procedura per diagnosticare la suscettibilità all’IM in un paziente in corso di valutazione o nei suoi parenti.
Resumen La hipertermia maligna (HM) de la anestesia es una enfermedad farmacogenética que se manifiesta de manera inconstante por un estado de hipermetabolismo del músculo esquelético durante la exposición a un agente anestésico volátil desencadenante. Los numerosos avances referentes a la fisiopatología de la HM han permitido evidenciar el gen RYR1, mayoritariamente implicado, y la instauración de procedimientos de detección por genética o prueba biológica. Sin embargo, formas de episodios de HM incompletas o abortadas por la mejoría de la monitorización anestésica o, también, fallecimientos perioperatorios inexplicados pueden conducir a una infravaloración de la incidencia de manifestaciones de HM durante la anestesia. Aunque se hayan realizado progresos considerables en las herramientas de genética molecular para la exploración detallada de los genomas de individuos, a veces se acompañan de dificultades mayores en el diagnóstico, porque las correlaciones genotipo-fenotipo que permitirían un diagnóstico de certeza todavía no existen. Actualmente, una organización nacional y europea dedicada a la HM ha permitido el establecimiento de recomendaciones en todos los ámbitos de la enfermedad: procedimiento terapéutico de urgencia y utilización del dantroleno en caso de episodios de HM, detección y evaluación del riesgo de HM en un individuo en la consulta de anestesia, riesgo de HM en los parientes, precauciones anestésicas en pacientes con una HM o considerados de riesgo y procedimiento de diagnóstico de la sensibilidad a la HM en un probando o sus parientes.
Full-text available
Malignant hyperthermia is a potentially lethal inherited disorder characterized by disturbance of calcium homeostasis in skeletal muscle. Volatile anesthetics and/or the depolarizing muscle relaxant succinylcholine may induce this hypermetabolic muscular syndrome due to uncontrolled sarcoplasmic calcium release via functionally altered calcium release receptors, resulting in hypoxemia, hypercapnia, tachycardia, muscular rigidity, acidosis, hyperkalemia, and hyperthermia in susceptible individuals. Since the clinical presentation of malignant hyperthermia is highly variable, survival of affected patients depends largely on early recognition of the symptoms characteristic of malignant hyperthermia, and immediate action on the part of the attending anesthesiologist. Clinical symptoms of malignant hyperthermia, diagnostic criteria, and current therapeutic guidelines, as well as adequate management of anesthesia in patients susceptible to malignant hyperthermia, are discussed in this review.
Full-text available
We analyzed cases of malignant hyperthermia (MH) reported to the North American MH Registry for clinical characteristics, treatment, and complications. Our inclusion criteria were as follows: AMRA (adverse metabolic/musculoskeletal reaction to anesthesia) reports between January 1, 1987 and December 31, 2006; "very likely" or "almost certain" MH as ranked by the clinical grading scale; United States or Canadian location; and more than one anesthetic drug given. An exclusion criterion was pathology other than MH; for complication analysis, patients with unknown status or minor complications attributable to dantrolene were excluded. Wilcoxon rank sum and Pearson exact chi(2) tests were applied. A multivariable model of the risk of complications from MH was created through stepwise selection with fit judged by the Hosmer-Lemeshow statistic. Young males (74.8%) dominated in 286 episodes. A total of 6.5% had an MH family history; 77 of 152 patients with MH reported >or=2 prior unremarkable general anesthetics. In 10 cases, skin liquid crystal temperature did not trend. Frequent initial MH signs were hypercarbia, sinus tachycardia, or masseter spasm. In 63.5%, temperature abnormality (median maximum, 39.1 degrees C) was the first to third sign. Whereas 78.6% presented with both muscular abnormalities and respiratory acidosis, only 26.0% had metabolic acidosis. The median total dantrolene dose was 5.9 mg/kg (first quartile, 3.0 mg/kg; third quartile, 10.0 mg/kg), although 22 patients received no dantrolene and survived. A total of 53.9% received bicarbonate therapy. Complications not including recrudescence, cardiac arrest, or death occurred in 63 of 181 patients (34.8%) with MH. Twenty-one experienced hematologic and/or neurologic complications with a temperature <41.6 degrees C (human critical thermal maximum). The likelihood of any complication increased 2.9 times per 2 degrees C increase in maximum temperature and 1.6 times per 30-minute delay in dantrolene use. Elevated temperature may be an early MH sign. Although increased temperature occurs frequently, metabolic acidosis occurs one-third as often. Accurate temperature monitoring during general anesthetics and early dantrolene administration may decrease the 35% MH morbidity rate.
Full-text available
In order to establish guidelines for the preparation of the Dräger Fabius GS premium anesthetic workstation for malignant hyperthermia-susceptible patients, the authors evaluated the effect of the workstation's exchangeable and autoclavable components on the washout of isoflurane. A Dräger Fabius GS workstation was primed with 1.5% isoflurane, and exchangeable components were replaced as follows: Group 1: no replacement (control); Group 2: autoclaved ventilator diaphragm and ventilator hose; Group 3: flushed ventilator diaphragm and ventilator hose; Group 4: autoclaved compact breathing system. The fresh gas flow (FGF) was set at 10 L . min(-1), and the concentration of isoflurane in the inspiratory limb of the circle breathing circuit was recorded every minute until an endpoint of 5.0 parts per million (ppm) was achieved, at which time the FGF was reduced to 3 L . min(-1). Six experiments were conducted in each of the four groups. The time to achieve an isoflurane concentration of 5.0 ppm decreased in the following order: Group 1 (151 +/- 17 min) > Group 3 (137 +/- 7 min) > Group 4 (122 +/- 11 min) > Group 2 (42 +/- 6 min) (P < 0.01 vs control). Isoflurane concentration increased approximately fivefold when the FGF was reduced to 3 L . min(-1). Anesthetic washout from the Dräger Fabius GS is relatively slow. Although washout was accelerated when the Dräger Fabius GS was equipped with autoclaved components, the reduction in washout time may be less than that required for this technique to be accepted into clinical practice. A dedicated vapor-free workstation may be preferable for rapid turnover between cases.
Regional anesthesia is not only performed in the operating room. There are indications for the use of these techniques for pain relief in the emergency department and for anesthesia support of procedures outside the operating room. In this review, we will provide an overview of the indications for the regional techniques performed in the out-of-operating room environment. In the emergency department, patients may experience significant pain, and adequate analgesia is not always provided. Regional analgesia is effective and indicated for many trauma situations including hip fracture, reduction of shoulder dislocation, treatment of upper limb fractures and multiple rib fractures.Ultrasound guidance makes the performance of regional blocks more accessible and safer for use in the emergency department setting.For therapeutic procedures outside the operating room, regional anesthesia is possible for uterine artery embolization and for postoperative analgesia after implantation of cervical brachytherapy needles. Regional anesthesia is a valuable option for analgesia in trauma patients, enabling improved pain control in the emergency department and has benefits in the anesthetic management of therapeutic procedures outside the operating room. For many blocks, ultrasound guidance is useful.
Malignant hyperthermia may follow exposure to trace quantities of inhalational anaesthetics. In susceptible patients, the complete avoidance of these triggers is advised when possible; however, failing this, it is essential to washout or purge the anaesthesia machine of residual inhalational anaesthetics. This study examined the washout profile of sevoflurane from the Drager Fabius CE and the Drager Zeus machines. The washout profile of sevoflurane was measured from the Fabius CE and Zeus anaesthesia machines following a standard period of exposure. The disposable tubing, CO2 absorber and other components of each machine were then replaced to examine their impact on the retention of sevoflurane. The effect of autoclaving the ventilator diaphragm and non-disposable ventilator tube or substituting for a new diaphragm and ventilation tube were examined in later parts of this study. University teaching hospital. Time taken to reach 5 parts per million of sevoflurane when machines underwent standard washout with fresh gas flush. The concentration of sevoflurane reached 5 parts per million in the Fabius CE machines after an mean (SD) of 140 min (46) at a fresh gas flow (FGF) of 10 l min(-1). The time taken for sevoflurane to reach 5 parts per million was significantly reduced when the ventilator diaphragm and non-disposable tube were replaced with either new or autoclaved components [14 or 22 min, respectively (P = 0.017, P = 0.031)]. The concentration of sevoflurane reached 5 parts per million in the Zeus machines after an mean (SD) of 85 min (6) at a fresh gas flow of 10 l min(-1). When the fresh gas flow was increased to 18 l min(-1) (the maximum allowable), the time to reach 5 parts per million was reduced to 16 min. When preparing the Fabius CE for the malignant hyperthermia susceptible patient, remove the vaporiser, replace the disposable tubing, the reservoir bag and the CO2 absorber. Replace the ventilator diaphragm and non-disposable ventilator tube with new or autoclaved components and flush the machine at 10 l min(-1) for at least 36 min. When preparing the Zeus, remove the vaporiser, replace the disposable tubing, the reservoir bag and CO2 absorber and flush at a fresh gas flow of 10 l min(-1) for at least 90 min. In both the Fabius and Zeus, continue at a fresh gas flow of 10 l min(-1) for the duration of the operation.
If a malignant hyperthermia-susceptible patient is to receive an anesthetic, an anesthesia machine that has been used previously to deliver volatile anesthetics should be flushed with a high fresh gas flow. Conflicting results from previous studies recommend flush times that vary from 10 to 104 minutes. In a previously proposed alternative decontamination technique, other investigators placed an activated charcoal filter in the inspired limb of the breathing circuit. We placed activated charcoal filters on both the inspired and expired limbs of several contaminated anesthesia machines and measured the time needed to flush the machine so that the delivered concentrations of isoflurane, sevoflurane, and desflurane would be <5 parts per million (ppm). We next simulated the case for which malignant hyperthermia is diagnosed 90 minutes after induction of anesthesia and measured how well activated charcoal filters limit further exposure. Activated charcoal filters decrease the concentration of volatile anesthetic delivered by a contaminated machine to an acceptable level in <2 minutes. The concentrations remained well below 5 ppm for at least 60 minutes. When malignant hyperthermia is diagnosed after induction of anesthesia, we found that with charcoal filters in place, the current anesthesia machine may be used for at least 67 minutes before the inspired concentration exceeds 5 ppm. Activated charcoal filters provide an alternative approach to the 10 to 104 minutes of flushing that are normally required to prepare a machine that has been used previously to deliver a volatile anesthetic.
Patients with malignant hyperthermia experience an exaggerated metabolic response when exposed to volatile anesthetic gases and succinylcholine. The minimum concentration of anesthetic gas needed to trigger a malignant hyperthermia crisis in humans is unknown and may remain so because of the inherent risks associated with studying the complex nature of this rare and lethal genetic disorder. The Malignant Hyperthermia Association of the United States provides specific instructions on purging anesthesia machines of volatile agents to reduce the risk of exposure. However, these recommendations were developed from studies of older generation machines. Modern anesthesia workstations are more complex and contain more gas absorbing materials. A review of the literature found the current guidelines inadequate to prepare newer generation workstations, which require more time for purging anesthetic gases, autoclaving or replacement of parts, and modifications to the gas delivery system. Protocols must be developed to prepare newer generation anesthesia machines.
To compare the femoral nerve block with the fascia iliaca block for postoperative analgesia in adolescents undergoing reconstructive knee surgery. Randomized, single-blinded study. Full-service pediatric medical center. 23 ASA physical status I and II patients, aged 8 to 16 years, undergoing anterior cruciate ligament (ACL) repair. Patients received either fascia iliaca or femoral nerve block prior to reconstructive surgery. Pain scores by visual analog scale (VAS; 0-10) and morphine use were routinely recorded through to discharge from the hospital. Pain scores were assessed on days 1 and 2 at home post-discharge. There was no difference between the femoral nerve block and the fascia iliaca nerve block in VAS pain scores or postoperative morphine consumption. Either the femoral nerve block or the fascia iliaca block, followed by patient-controlled analgesia with morphine, provides efficacious analgesia for adolescents undergoing ACL reconstruction.
Anesthesia machines must be flushed of halogenated anesthetics before use in patients susceptible to malignant hyperthermia. We studied the kinetics of sevoflurane clearance in the Dräger Fabius anesthesia machine and compared them to a conventional anesthesia machine (Dräger Narkomed GS). Before each trial, the anesthesia machine was contaminated for 2 h with 3% sevoflurane and then prepared by changing the CO(2) absorbent, removing the vaporizer(s), and mounting a clean circuit and artificial lung. The basic flush procedure consisted of oxygen 10 L/min with the ventilator set to a tidal volume of 600 mL at a rate of 10/min. Residual sevoflurane in the inspiratory limb of the circuit was measured using an ambient air analyzer capable of measuring sevoflurane to < 1 ppm. Results were analyzed using log-linear regression of residual concentration as a function of time. This model was used to estimate the time required to achieve a desired residual anesthetic concentration. Times to achieve 10 and 5 ppm in the Dräger Narkomed GS were 11 and 18 min, respectively. For the Dräger Fabius anesthesia machine, times to 10 and 5 ppm were 75 and 104 min, respectively. Several maneuvers to accelerate clearance of residual sevoflurane from the Dräger Fabius resulted in only modest reductions in these times (10 and 5 ppm times 40-50 min and 60-80 min, respectively). Insertion of an activated charcoal filter (QED, Anecare Laboratories, Salt Lake City, UT) into the inspiratory limb of the Dräger Fabius circuit reduced the residual anesthetic concentration to <5 ppm within 10 min; this concentration was maintained for > 6 h despite a fresh gas flow of only 2 L/min after the first 15 min. Preparation of the Dräger Fabius anesthesia machine using conventional flushing techniques required almost 10 times as long as an older, conventional anesthesia machine. If a prolonged flush is impractical or impossible, we describe a procedure using an activated charcoal filter inserted on the inspiratory limb of the breathing circuit which can effectively scrub residual sevoflurane to a concentration < 5 ppm within 10 min. This procedure includes an initial 5 min flush without the activated charcoal filter followed by a 5 min flush with the charcoal filter, after which the machine is ready for use in the malignant hyperthermia-susceptible patient. The charcoal filter must remain on the machine for the remainder of the anesthetic, and the fresh gas flow should be maintained > or = 10 L/min for the first 5 min, and > or = 2 L/min thereafter.