Comparison of integrated evoked EMG between the hypothenar and facial muscle groups following atracurium and vecuronium administration.
ABSTRACT In 17 healthy patients undergoing O2.N2O.isoflurane anaesthesia, following atracurium or vecuronium administration, we compared simultaneous integrated evoked electromyograms (IEEMGs) during spontaneous recovery of the adductor digiti minimi (ADM) and orbicularis oris (OOM) muscle groups in response to train-of-four (TOF) stimulation of the ulnar and facial nerves, respectively. In all patients, the onset of neuromuscular recovery occurred first in the OOM. The time required to recover to a T4/T1 = 0.70 +/- 0.01 (SD) was earlier in the OOM compared with the ADM muscles in both the atracurium (33.4 +/- 5 vs 46.5 +/- 8, P less than 0.005) and vecuronium (46.5 +/- 12 vs 60.3 +/- 20, P less than 0.005) groups. When the OOM attained a T4/T1 = 0.70 +/- 0.01, the simultaneous T4/T1 in the ADM was 0.29 +/- 0.15 (P less than 0.05) in the atracurium group and 0.41 +/- 0.16 (P less than 0.01) in the vecuronium group. We conclude that (1) the facial muscles (OOM) recover earlier than the hypothenar muscles (ADM) and (2) an EMG T4/T1 = 0.70 in the facial muscles may not indicate adequate recovery of neuromuscular function.
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ABSTRACT: The use of muscle relaxant is an integral part of anesthetic management in present-day practice. Clinically, the neuromuscular blockade is evaluated by determining the thumb twitching to train-of-four (TOF) ulnar nerve stimulation at elbow.(1-3) There are many ways for the assessment of twitch response, such as the use of electromyography(4,5); force displacement transducer techniques(2,6-9); and most recently, the acceleration transducer-based system of neuromuscular monitoring.(10-15) These equipments are, however, bulky, cumbersome, expensive, or time consuming for operation. Because of these limitations, the routine use of such monitors is impractical. The evaluation of neuromuscular blockade, at the present time, relies on either visual or manual (tactile) thumb twitch responses to the TOF nerve stimulation. Visual or tactile evaluation of neuromuscular blockade is subjective and involves uncertainty, especially in the recovery phase. Furthermore, in certain surgical procedures, such as those on the head and neck, both hands are tucked in the sides of the table and become inaccessible, rendering visual or tactile evaluation of the thumb twitch impossible. In such situation, muscle relaxant is often given in the light of guessing rather than on objective basis. Clearly, there is a need for a simple and practical way of measuring the twitch responses to TOF stimulation during anesthesia. Based on the current method of stimulation of the ulnar nerve over the ulnar groove at the elbow, which elicits a string thumb adduction (because of stimulation of the flexor carpi ulnaris muscle), a simple method that can objectively monitor and record the thumb twitch is developed. The unique features of the method or device are its simplicity and its ability to adapt to any pressure transducer to display the twitch response to TOF simultaneously with electrocardiogram, arterial, or central venous pressure.Acta anaesthesiologica Taiwanica : official journal of the Taiwan Society of Anesthesiologists. 09/2011; 49(3):109-13.
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ABSTRACT: The effect of different concentrations of rocuronium bromide used for anesthesia induction during thyroid surgery on the intraoperative recurrent laryngeal nerve monitoring was evaluated. One hundred patients undergoing thyroid operation were randomized into five groups (20 patients per group). Patients in group I were operated and monitored without the use of rocuronium bromide. Patients in groups II-V were respectively injected with 0.5x, 1x, 1.5x, and 2x ED95 rocuronium bromide intravenously. The time from injecting the rocuronium bromide to the beginning of tube insertion was recorded, the conditions of tracheal intubation were evaluated, and the changes in blood pressure and pulse during the intubation process were monitored. Vagus nerve/recurrent laryngeal nerve evoked muscle potential was monitored using the NIM-Response3.0 nerve electromyography monitor. The amplitude of electromyography signal was recorded every 5 min during 30 min after successful tracheal intubation. The tracheal intubation success rate was 100 % in all groups. Compared with group I, intubating condition scores (Cooper scores) in the patients of groups II-V were higher (P < 0.05). The stability of intraoperative neuromonitoring signal amplitude in groups I-III met the monitoring standards. The findings suggest that the use of 0.5x or 1x ED95 rocuronium bromide during the anesthesia induction can improve the tracheal tube conditions without affecting the intraoperative recurrent laryngeal nerve monitoring. The use of 1x ED95 rocuronium bromide induction was associated with the best results.Cell Biochemistry and Biophysics 08/2014; 71(1). · 2.38 Impact Factor
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ABSTRACT: Neuromuscular blocking agents have generally been avoided during intraoperative neurophysiological monitoring (IOM) where muscle responses to nerve stimulation or transcranial stimulation are monitored. However, a variety of studies and clinical experience indicate partial neuromuscular blockade is compatible with monitoring in some patients. This review presents these experiences after reviewing the currently used agents and the methods used to assess the blockade. A review was conducted of the published literature regarding neuromuscular blockade during IOM. A variety of articles have been published that give insight into the use of partial pharmacological paralysis during monitoring. Responses have been recorded from facial muscles, vocalis muscles, and peripheral nerve muscles from transcranial or neural stimulation with neuromuscular blockade measured in the muscle tested or in the thenar muscles from ulnar nerve stimulation. Preconditioning of the nervous system with tetanic or sensory stimulation has been used. In patients without neuromuscular pathology intraoperative monitoring using peripheral muscle responses from neural stimulation is possible with partial neuromuscular blockade. Monitoring of muscle responses from cranial nerve stimulation may require a higher degree of stimulation and less neuromuscular blockade. The role of tetanic or sensory conditioning of the nervous system is not fully characterized. The impact of neuromuscular pathology or the effect of partial blockade on monitoring muscle responses from spontaneous neural activity or mechanical nerve stimulation has not been described.International Journal of Clinical Monitoring and Computing 09/2012; · 1.45 Impact Factor
Comparison of inte-
grated evoked EMG
between the hypothenar
and facial muscle groups
M.D. Sharpe MD, C.A. Moote MD, A.M. Lam MO,
P.H. Manninen MD
In 17 healthy patients undergoing 02" N20' isoflurane anaes-
thesia, following atracurium or vecuronium administration, we
compared simultaneous integrated evoked electromyograms
(IEEMGs) during spontaneous recovery of the adductor digiti
minimi (ADM) and orbicularis oris (OOM) muscle groups in
response to train-of-four (TOF) stimulation of the ulnar and
facial nerves, respectively. In all patients, the onset of neuro-
muscular recovery occurred first in the OOM. The time required
to recover to a T4/TI = 0.70 • 0.01 (SD) was earlier in the
OOM compared with the ADM muscles in both the atracurium
(33.4 • 5 vs46.5 +. 8, P < O.O05) andvecuronium(46.5 • 12
vs 60.3 • 20, P < 0.005) groups. When the OOM attained a
Tn/Tt = 0.70 +-- 0.01, the simultaneous T4/Tt in the ADM was
0.29 • 0.15 (P < 0.05) in the atracurium group and 0.41 •
0.16 (P < 0.01) in the vecuronium group. We conclude that (I)
the facial musc&s (OOM) recover earlier than the hypothenar
muscles (ADM) and (2) an EMG T4/Tt = 0.70 in the facial
muscles may not indicate adequate recover), of neuromuscular
Nous avons compare les traces dlectromyographiques int~SgrEs
de l'orbiculaire des paupiOres (ORB) et de I'adducteur du
petit doigt (ADD) dvoquEs simultanEment par stimulation en
train-de-quatre des nerfs facial et cubital; cela, pendant
I'anesthEsie avec 02, NzO et isoflurane de 17 sujets sains aprEs
injection d'atracurium ou de vEcuronium. Chez tousles pa-
tients, la recuperation de la fonction neuromusculaire survenait
d'abord d I'ORB. Le temps requis pour retrouver un ratio de
T4/TI +- 0,7 +- O, I (Ecart-type) Eta#plus court pour I'ORB que
pour I'ADD, ~ la fois avec I'atracurium (33,4 • 5 vs 46,5 • 8
min, P < 0,005)et avec le vEcuronium (46,5 +- 12 vs 60,3 • 20
min, P < 0,005). Quand le T4/TI de I'ORB atteignaitO, 7 • O, 1,
celui de rADD n'Etait que de 0,29 +-. 0,15 (P < 0,05) avec
l'atracurium et que de 0,41 • O, 16 avec le vdcuronium (P <
0,01). AprEs I' injection de myorela.rants, la fonction neuromus-
culaire des muscles du visage (ORB) r~cupEre plus rapidement
que celle des muscles de I' dminence hypothdnar (ADD) de plus,
un ratio T4/TI = 0,7 ~ I'EMG de la foce n'est pas synonyme
d'une r~cup~ration adequate de la fonction neuromusculaire.
MEASUREMENT TECHNIQUES" electromyography,
NEUROMUSCULAR RELAXANTS: atracurium, vecuronium.
From the Department of Anaesthesia, University Hospital,
University of Western Ontario, London, Ontario, Canada and
Department of Anesthesiology, University of Washington,
Address correspondence to: Dr. Michael Sharpc, Department
of Anaesthesia, University Hospital, 339 Windermere Road,
London, Ontario, N6A 5A5.
Accepted for publication 22nd November, 1990.
The importance of adequate reversal of muscle relaxants
following a surgical procedure cannot be overempha-
sized. Accurate detection of any residual neuromuscular
blockade predisposing the patient to respiratory muscle
weakness is essential in order to prevent hypoventilation
and/or upper airway obstruction. ~.z With the introduction
of the peripheral nerve stimulator using train-of-four
(TOF) and tetanic stimulation, the anaesthetist has a
bedside monitor of neuromuscular function. 3'4 Studies
stimulating the ulnar nerve and measuring the mechanical
response of the thenar muscles have correlated degrees of
neuromuscular blockade with indices of respiratory
function. 5-8 Due to its accessibility and convenience, the
facial nerve/muscle has also become a popular site for
monitoring of neuromuscular blockade. Its efficacy,
CAN J ANAESTH 1991 / 38:3 / pp318-23
Sharpe etal.: FACE VERSUS HAND EMG 319
however, as an accurate monitor to assess the degree of
residual neuromuscular blockade and therefore to predict
postoperative respiratory muscle function has not been
well defined. Our study was therefore designed to study
the relationship between the integrated evoked electromy-
ograms (IEEMGs) of the hypothenar and facial muscle
groups during recovery from neuromuscular blockade.
We wished to characterize the time course of recovery of
the T4T~ ratio from TOF facial nerve stimulation in
relationship to ulnar nerve stimulation, and in particular,
determine whether TOF stimulation of the facial and ulnar
nerves provided similar information regarding recovery
of neuromuscular function.
With institutional human subjects review board approval,
17 healthy patients (ASA physical status l-II) with no
known renal, hepatic or neuromuscular disease, aged
18-61 yr were studied. General anaesthesia was induced
with thiopentone (4-5 mg.kg-t), lidocaine (I.0 mg.
kg -l) and fentanyl (3 I.Lg- kg-~). Tracheal intubation was
facilitated with succinylcholine (0.5-0.75 mg.kg- t).
Maintenance anaesthesia consisted of oxygen/nitrous
oxide (FIO2 0.30-0.40 to maintain SaO2 - 96% (Nelcor
oximeter, Model NIO00) and isoflurane (0.5-1.0%
spired). Positive-pressure ventilation was used to main-
tain normocapnia (Nelcor Capnograph, Model NI000).
The two muscle relaxants were studied sequentially; nine
patients received vecuronium and eight patients received
Simultaneous IEEMGs were recorded with surface
electrodes from the OOM (facial) and ADM (hypothenar)
using two Datex NMT 221 monitors (Puritan-Bennett)
(Figure I). This monitor automatically delivers a supra-
maximal stimulus, stores the control response in memory
and displays the subsequent response to TOF stimulation
both as the ratio of the first twitch to control (TI/Tc) and
the ratio of the fourth twitch to first twitch (TJT0. During
the study continual recordings were made of the response
to TOF supramaximal stimuli delivered at a frequency of
2 Hz to the ulnar and facial nerves every 20 sec.
Before control IEEMGs were recorded, at least 30 min
were allowed to elapse following succinylcholine admin-
istration to ensure full recovery of the EMG. Atracurium
TABLE I Anthropometric characteristics
Age (yr) Weight (kg)
Group Mean ~ SD Range Mean • SD Range
Atracurium n = 8
Vecuronium n = 9
34 • 13
23 - 14
72 • 14
74 • 10
I j I ~-----
R Ref. S
and recording (R) electrodes on the face and hand. UN = ulnar
nerve, FN = facial nerve, ADM = adductor digiti minimi muscle,
OOM = orbicularis oris muscle, Ref = reference electrode.
Schematic representation of placement of stimulating (S)
(0.06-0.1 mg'kg -I) or vecuronium (0.03-0.05 mg-
kg -I) was administered (time 0) to abolish T4. The time
at which maximal blockade was achieved in each muscle
group as indicated by the T4/T~ digital display was
recorded as mark 3 on the recording strip. Spontaneous
recovery of neuromuscular function was monitored with
continuous display of Ta/TI and TdTc ratios. When the
T4/Tt ratio of the orbicularis oris muscle attained 0.70 -+
0.01, the simultaneous Ta/T~ ratio of the hypothenar
muscle was recorded. The recovery time (from time 0 to
T4/T~ ratio of 0.70) was measured for each muscle group.
For statistical analysis, comparison of the recovery
time for each muscle group was made using paired
Student's t test. Comparison between T4/T~ ratios of the
hypothenar and orbicularis oris muscles when the latter
was 0.70 was made using the Wilcoxin ranked-sum test.
Results are expressed as mean --- SD.
The anthropometric characteristics of the two groups are
shown in Table !. The time of onset of neuromuscular
blockade was similar in both muscle groups. Figure 2 is a
representative study comparing the TOF response in the
CANADIAN JOURNAL OF ANAESTHESIA
FIGURE 2 Simultaneous integrated evoked electromyograms of the adductor digiti minimi (hand) and orbicularis oris muscles (face) following
vecuronium administration. 1 = baseline IEEMG, 2 = vecuronium injection, 3 = point of maximum depression, 4 = TJT~ = 0.70 --- 0.01.
face and hand following vecuronium administration.
Although this particular study suggests a more intense
block in the facial muscle, we found no significant
difference in intensity of block between the two muscle
groups following atracurium or vecuronium administra-
tion. Note the earlier recovery of the facial EMG. The
orbicularis oris muscle group was first to recover in all
cases. The OOM recovered to a T4TI ratio = 0.70 --- 0.01
approximately 13 min earlier than the ADM muscle in
both the atracurium and vecuronium groups (P < 0.01)
(Table II). When the OOM had recovered to a T4TI =
0.70 --- 0.01, the corresponding T4TI of the ADM was
only 0.29 +-- 0.15 in the atracurium group (P < 0.05) and
0.41 --- 0.16 in the vecuronium group (P < 0.01) (Table
During the conclusion of a general anaesthetic, it is
essential to detect any residual neuromuscular blockade
prior to extubation of the trachea in order to prevent
respiratory insufficiency as a result of obstruction of the
airway due to upper airway muscle weakness. Presently
there is no direct bedside method to measure the integrity
of the upper airway muscles involved in maintaining
patency and providing protection of the upper airway as
well as the muscles of respiration. Historically, several
clinical tests such as head-lift, 9 armlift I~ tongue protru-
sion and intensity of hand-grip ~ have been utilized to
assess the adequacy of neuromuscular function and as
indirect tests of respiratory muscle function. However,
TABLE 11 Time (min) required to recover to a TJTt ratio =
0.70 --- 0.01 for facial and hand muscle groups
A tracurium (rnin) Vecuronium (rnin)
33.4 • 5*
46.5 --- 8
46.5 • 12"
60.3 4 20
Mean --- SD.
*P < 0.005, between muscle groups.
Sharpe etal.: FACE VERSUS HAND EMG 321
these tests require an awake and cooperative patient and
are not always accurate. 2'~2 Moreover, Pavlin et al. have
recently demonstrated that despite having adequate spon-
taneous respiration during recovery from d-tubocurarine
neuromuscular blockade, the patient may not be capable
of maintaining a patent airway. ~3 It is, therefore, an
established practice to monitor the neuromuscular junc-
tion using a peripheral nerve stimulator and observe the
mechanical response (MMG) of the thenar muscles to
TOF stimulation of the ulnar nerve. ~4 Studies have shown
that MMG T4TI ratio of 0.70 measured in the thenar
muscle groups is consistent with adequate recovery of
respiratory function. 5-7
Our results indicate that the facial nerve/muscle prepa-
ration recovers faster than the ulnar nerve/hypothenar
muscles; the OOM attained a T4T~ ratio of 0.70 by
approximately 13 min earlier in both atracurium and
vecuronium groups. At this time the T4T~ ratios of the
ADM muscles were only 0.41 in the atracurium group and
0.29 in the vecuronium group. Our results are in agree-
ment with previous studies 15- ~7 which qualitatively indi-
cated that the facial nerve recovered earlier than the hand
muscles. Caffrey et al. k6 had previously compared the
orbicularis oculi with the adductor pollicis as a monitoring
site for neuromuscular blockade, and although they
studied the MMG (mechanical myogram) and we used the
IEEMG, the results are remarkably similar with the hand
muscles lagging behind the facial muscles by approxi-
mately 13 min during recovery. In contrast, Paloheimo et
al. m8 attempted to study the comparative IEEMG of
orbicularis oculi and the hypothenar muscles and found
the results to be too variable to be conclusive, although
their results are consistent with an earlier recovery of the
facial muscles. The variability in their study, an observa-
tion we had also made in earlier pilot studies, may be due
to direct muscle stimulation. Such variability was not
observed using the orbicularis oris as we had done in this
study. Based on these findings, we conclude that adequate
recovery of the EMG response to facial nerve stimulation
is compatible with considerable residual neuromuscular
blockade and therefore does not ensure adequate respira-
tory function. It should be mentioned that not all facial
TABLE Ill T4/T~ ratios of hypothenar muscle when orbicularis otis
muscle T,/T~ = 0.70 --- 0.01
0.70 ~ 0.01
0.29 -+ 0.15;
0.70 --- 0.01
0.41 --- 0.16"
Mean --- SD.
*P < 0.05, between muscle groups.
tP < 0.01, between muscle groups.
muscles behave in the same manner, as it has been
demonstrated that the masseter muscle is more sensitive to
neuromuscular blockade than the adductor pollicis. 19
Indeed, as a muscle partly responsible for maintenance of
the airway, this sensitivity may account for the partial
airway obstruction observed during recovery from neuro-
muscular blockade reported by Pavlin et al. ~3 However,
clinically the masseter muscle is seldom used as a
monitoring site for neuromuscular blockade.
As previous studies concluding that a T4TI ratio 0f0.70
is consistent with adequate recovery of respirator), func-
tion are mostly measured by MMG, a-6 our assumption
that the information provided by the IEEMG is compara-
ble to MMG needs to be addressed, Four separate studies
comparing these two monitoring modalities, EMG vs
MMG, have shown that the MMG consistently lags
behind the EMG during recovery from a non-depolarizing
neuromuscular blockade. 2~
studies, 22"23 the magnitude of these differences was
relatively small and considered clinically unimportant.
Our own study on correlation between IEEMG and
respiratory function also confirmed that a T4T~ of >0.7 is
consistent with adequate recovery. 7 In contrast, Kop-
man 21 demonstrated a difference of 0.15 between EMG
and MMG T4Tt ratios which was consistent throughout
the study. A recent clinical study by Dupuis et al.
confirmed that the EMG lags behind the MMG by
approximately 20% which is compatible with Kopman's
observations. 24 This disparity between EMG and MMG
measurement of neuromuscular blockade may be related
to the type of anaesthetic administered. For example, the
studies by Kopman 2~ and Caffrey et al. ~6 indicating a lag
of the MMG utilized a halogenated agent to maintain
anaesthesia whereas the studies by Harper 22 and Weber 23
indicating no significant disparity between the EMG and
MMG, utilized a narcotic technique. Since the MMG is
not only dependent upon neuromuscular transmission but
also upon the contractility and loading of the muscle, the
lag of the MMG may be explained by the effects of the
halogenated agents upon these latter two factors. These
considerations do not affect the validity of our study,
since we did not use MMG, and the anaesthetic technique
used would have little influence on EMG. However, they
do lend further support to our contention that the OOM
electromyography may not be a reliable indicator of the
integrity of neuromuscular transmission as its recovery
preceded ADM recovery in all cases. As well, observa-
tions made by Laycock et al. 25 and Donati et al. 26 that the
diaphragm is more resistant to neuromuscular blockade
than the thenar muscles suggest that this important
respiratory muscle would also recover earlier than the
thenar muscles. It is therefore probable that the recovery
of OOM EMG may parallel that of the diaphragm and
However, in two of these
322 CANADIAN JOURNAL OF ANAESTHESIA
indicate at least the onset of recovery of respiratory
function. Indeed, the relative time course of recovery of
the diaphragm, orbicularis oculi (OOC) and adductor
pollicus was recently studied by Donati et al. and the
recovery potential of the diaphragm and OOC were shown
to be quite similar. 27 More importantly, however, the
recovery of the adductor pollicus occurred later than that
of the diaphragm or OOC which suggests adequate
recovery of other important muscle groups, i.e., upper
airway muscles involved in airway patency, has not yet
In summary, the facial nerve/muscle preparation is a
convenient and accessible site of monitoring neuromuscu-
lar blockade, and the orbicularis oris may be a better
alternative to orbicularis oculi for EMG recording.
However, similar to orbicularis oculi, its earlier recovery
probably reflects the time course of recovery of the
diaphragm and underestimates the recovery of other
important muscles of respiration necessary to maintain a
patent airway. We conclude that recovery of facial
nerve/muscle EMG may not represent adequate recovery
of respiratory function and emphasize the need for further
clinical evaluation of adequate muscle strength.
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