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Results for “Neuromuscular Blockade”

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PubMed2004

Sleep monitoring in children during neuromuscular blockade in the pediatric intensive care unit: a pilot study.

BACKGROUND: Sleep is an important physiologic process that is known to be disrupted in the intensive care unit. Nevertheless, there is little information on how intensive care unit admission affects sleep in children. Because laryngotracheoplasty is elective but entails 5-7 days of neuromuscular blockade following surgery, children undergoing this procedure present a unique opportunity to analyze sleep during neuromuscular blockade apart from confounding variables resulting from critical illness. OBJECTIVE: To determine the feasibility of using polysomnography to assess sleep patterns in children during neuromuscular blockade. METHODS: Polysomnography recordings were obtained continuously for 4 days (96 hrs) in two children following laryngotracheoplasty. Medication administration (neuromuscular blockades, sedatives) and time of suctioning were also recorded. RESULTS: Both subjects had documented sleep. However, the proportion of time in each stage was markedly different from developmental norms, and a greater proportion of sleep occurred during the day. Furthermore, there was substantial day-night and day-to-day variability. Some rebound of consolidated sleep appeared by day 4. Sedative use varied considerably. However, neither bolus sedation administration nor endotracheal suctioning appeared to affect sleep. Few monitoring difficulties were encountered. CONCLUSIONS: Sleep can be monitored with minimal difficulty in children undergoing neuromuscular blockade in the pediatric intensive care unit. Sleep occurred throughout the day, and there was considerable fragmentation. To fully assess sleep in the intensive care unit, monitoring needs to be continuous over several days, rather than only at night or for < or =24 hrs. Further research is needed in the area to determine typical sleep patterns in children undergoing neuromuscular blockade.

Child, Preschool↗

PubMed1988

Comparison of neuromuscular blockade in the diaphragm and the hand.

Neuromuscular blockade was recorded in the diaphragm and in the adductor pollicis muscle using unilateral supramaximal stimulation of phrenic and ulnar nerves and measurement of the mechanical effect of each. After administration of atracurium 0.4-0.5 mg kg-1 to 10 patients, both onset and recovery of neuromuscular blockade in the diaphragm occurred before that in adductor pollicis and there was a linear relationship between recovery in diaphragm and adductor pollicis. After administration of vecuronium 0.08-0.1 mg kg-1 to a further 10 patients, paralysis occurred in the diaphragm before adductor pollicis in all except one patient, in whom it occurred simultaneously. Reappearance of adductor pollicis twitch occurred in six patients after all four twitches had returned in the diaphragm, but the rate of recovery of twitch height in the diaphragm was more rapid than in adductor pollicis in every patient.

Adult↗

PubMed2004

[Influence of epidural lidocaine injection on vecuronium-induced neuromuscular blockade].

BACKGROUND: We investigated vecuronium-induced neuromuscular blockade in patients with continuous epidural lidocaine injection and those without epidural lidocaine. METHODS: Lower thoracic epidural injection of lidocaine was commenced at a rate of 2-3 mg x kg(-1) x h(-1) following its bolus injection (1.5-2 mg x kg(-1)) only in epidural group. Neuromuscular function was monitored by acceleromyographic train-of-four (TOF) responses of the adductor pollicis muscle to ulnar nerve stimulation after induction of general anesthesia. RESULTS: Neuromuscular block was obtained by vecuronium 0.1 mg x kg(-1) as an intubating dose and was maintained 5-10% of baseline first twitch (T 1) of TOF responses by continuous vecuronium administration. The maximum depression of T 1 response and onset time obtained by vecuronium 0.1 mg x kg(-1) were not different between the groups, but mean clinical duration from administration of the first dose to T 1 recovery to 5% of baseline was significantly prolonged in group with epidural lidocaine (49.5 min), compared to that without lidocaine (32.3 min). Furthermore, maintenance dose of vecuronium obtained in the group with epidural lidocaine (0.034 mg x kg(-1) x h(-1)) was significantly smaller than that in the group without lidocaine (0.060 mg x kg(-1) x h(-1)). CONCLUSIONS: Based on our results, we conclude that lidocaine injected continuously into the epidural space potentiates vecuronium-induced neuromuscular block.

Adult↗

PubMed1995

Double burst monitoring during surgical degrees of neuromuscular blockade: a comparison with train-of-four.

UNLABELLED: With double burst stimulation (DBS) it is possible to monitor more profound degrees of neuromuscular blockade than with train-of-four stimulation (TOF). It may therefore be indicated to change between DBS and TOF stimulation during moderate to profound degrees of neuromuscular blockade. Consequently, the aim of the study was to evaluate and compare the twitch height of the first twitch (D1) in DBS and the twitch height of the first twitch (T1) in TOF stimulation during moderate to profound degrees of neuromuscular blockade. Thirty-three patients scheduled for gynaecological laparotomy under general anaesthesia were studied. Mechanomyography was used for neuromuscular monitoring. The T1 twitch height before atracurium was administered served as the control twitch height (T1 control). T1 control was considered as 100%. A constant degree of neuromuscular blockade was maintained at a T1 twitch height at a point between 4 and 11% of T1 control, using a continuous infusion of atracurium. Sequences of 16 DBS and 16 TOF stimulations were given. Two different DBS patterns were examined: DBS3,350/50, (3 stimuli at 50 Hz followed 0.75 sec later by 3 stimuli at 50 Hz), and DBS3,380/40, (3 stimuli at 80 Hz followed 0.75 sec later by 3 stimuli at 40 Hz). The data were analysed by the method described by Bland and Altman. The D1 repeatability coefficients of 1.72% for DBS3,350/50 and 1.20% for DBS3,380/40 were significantly greater than the repeatability coefficient of 1.02% for T1 (p <0.05). The D1 bias of 16.7% for DBS3,350/50 was significantly less than the D1 bias of 25.7% for DBS3,380/40 (p <0.05). The limits of agreement between D1 and T1 were 0.1 to 33.3% for DBS3,350/50 and 2.9 to 48.5% for DBS3,380/40. IN CONCLUSION: The repeatability of responses to DBS and TOF stimulations during moderate to profound degrees of neuromuscular blockade where only one twitch is consistently present is satisfactory. The responses to DBS were greater than responses to TOF as indicated by a positive bias of DBS. The limits of agreement between DBS and TOF responses were so wide that they cannot be used interchangeably.

Adult↗

PubMed1990

Effect of neuromuscular blockade on fetal oxidative metabolism.

Because fetal neuromuscular blockade has been used during cord blood sampling procedures to prevent fetal movement, we studied the effect of pancuronium bromide on fetal arterial concentrations of glucose, lactate, and oxygen and their umbilical uptake in 6 chronically prepared fetal sheep. We observed a significant increase in the arterial concentrations and decrease in the umbilical uptakes. We suggest that cord blood sampling procedures for fetal assessment of oxidative metabolism not be performed after fetal neuromuscular blockade so that data obtained might best reflect the unperturbed physiological condition of the fetus.

Animals↗

PubMed1987

Relationship between posttetanic count and response to carinal stimulation during vecuronium-induced neuromuscular blockade.

The correlation between degree of peripheral neuromuscular blockade and response to carinal stimulation was evaluated in two groups of 25 patients: one group was anaesthetized with thiopental, N2O and halothane, and the other group received thiopental, N2O and fentanyl. The degree of peripheral blockade was evaluated using train-of-four (TOF) and posttetanic twitch (PTC) stimulation of the ulnar nerve. The degree of diaphragmatic paralysis was evaluated indirectly by stimulating the carina and observing the corresponding muscular response, which was graded as severe, mild or absent. During halothane anaesthesia a PTC of 0 always indicated that no response to carinal stimulation could be elicited. On the appearance of the first response to posttetanic twitch stimulation (PTC = 1), 2% of the patients showed a mild response to carinal stimulation. At the first response to TOF stimulation, 48% of the patients reacted with a mild response. During thiopental, N2O, fentanyl anaesthesia one of 25 patients showed a mild response to carinal stimulation at a PTC of 0. When PTC was 1, 20% of the patients reacted mildly to the stimulation. At the first response to TOF stimulation, 92% showed a response to carinal stimulation; 24% of these responses were severe, necessitating intervention. It is concluded that the TOF response elicited peripherally is a late sign of neuromuscular recovery of the diaphragm, and that the method of counting posttetanic twitches is superior to the TOF response in evaluating early recovery of this muscle. Further, to ensure total diaphragmatic paralysis, the neuromuscular blockade of the peripheral muscles should be so intense that no response to posttetanic twitch stimulation (PTC = 0) can be elicited.

Adolescent↗

PubMed1995

Oral clonidine does not alter vecuronium neuromuscular blockade in anaesthetized patients.

Since clonidine, an alpha 2-agonist, inhibits the release of norepinephrine or acetylcholine which can decrease nondepolarizing muscle relaxant-induced neuromuscular blockade, the authors examined whether clonidine given as an oral preanaesthetic medication would alter the onset, duration or recovery of a vecuronium neuromuscular blockade in lightly anaesthetized patients. Thirty-eight patients (aged 20-73 yr) randomly received oral clonidine either approximately 5 micrograms.kg-1 (n = 21) or none (n = 17), 90 min before arrival in the operating room. We measured acceleration of thumb contraction with ulnar nerve stimulation at the wrist to assess neuromuscular blockade. The onset time (the time from injection to decrease to 5% of baseline twitch height), duration (the time interval between injection and return of the first twitch to 25% of the baseline value), and recovery index (the time interval of the first twitch from 25% to 75% of the baseline value) of neuromuscular blockade from a single bolus of vecuronium 0.1 mg.kg-1 i.v. were determined and compared between the clonidine-treated and control patients during lower abdominal or extremity surgery under epidural plus general anaesthesia with fentanyl and nitrous oxide in oxygen. No differences were noted between the control and clonidine groups in onset time (100 +/- 6 sec (mean +/- SE) vs 101 +/- 6 sec), duration (44.5 +/- 2.7 min vs 42.9 +/- 2.7 min), or recovery index (21.6 +/- 2.8 min vs 19.1 +/- 1.9 min) of neuromuscular blockade from vecuronium, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗

PubMed1985

Partial neuromuscular blockade and cardiovascular responses to static exercise in man.

In human subjects sustained static contractions of the quadriceps femoris in one leg were performed with the same absolute and the same relative intensity before and after partial neuromuscular blockade with either decamethonium or tubocurarine which reduced strength to about 50% of the control value. During the contractions performed with the same absolute force, the magnitude of the cardiovascular responses (heart rate and blood pressure) was greater during neuromuscular blockade than during control contractions. During the contractions involving the same relative force the magnitude of the cardiovascular responses was almost the same with and without neuromuscular blockade. These findings were independent of the drug used. The metabolic part of the exercise pressor reflex was assessed by the application of an arterial cuff 1/2 min before cessation of exercise and for the following 3 min of rest. Although heart rate and blood pressure decreased after cessation of exercise, application of the tourniquet resulted in higher post-exercise values and this effect was seen both with and without neuromuscular blockade. Muscle biopsies from the subjects' m. vastus lateralis were analysed for fast- and slow-twitch fibre composition showing 27-66% slow-twitch fibres. No correlation was found between cardiovascular responses to static exercise, with or without neuromuscular blockade, and fibre type predominance. The results suggest that the involvement of fast- or slow-twitch muscle fibres does not play a dominant role in the cardiovascular responses to static exercise in man. Both central command and reflex neural mechanisms are of importance, and it appears that these two control mechanisms are redundant and that neural occlusion may be operative. However, when partial neuromuscular blockade induces a disproportion between an increase in central command and a constant or decreasing muscle tension and metabolism, the larger signal arising from central command determines the magnitude of the cardiovascular responses.

Adult↗

PubMed2003

Closed-circuit anesthesia prolongs the neuromuscular blockade of rocuronium.

BACKGROUND: Volatile anesthetics are known to potentiate the neuromuscular blocking effect of nondepolarizing muscle relaxants. The influences of anesthetic techniques, closed-circuit anesthesia (CCA) and high flow semi-closed anesthesia (SCA), on the neuromuscular blockade of rocuronium has not yet been studied in detail. This study was purposed to compare the effects of isoflurane conveyed in minimal flow (CCA) and in high flow (SCA) on the neuromuscular blockade of rocuronium. METHODS: Fifty females scheduled for elective laparoscopic gynecological surgery were enrolled for study and randomly assigned to receive either CCA (n = 25) or SCA (n = 25). Anesthesia was induced with fentanyl 2 micrograms/kg, thiopental 5 mg/kg and rocuronium 0.6 mg/kg. Two percent isoflurane in high O2 flow (3 l/min) was given for 10 min to all patients initially to wash isoflurane in the functional residual capacity of both lungs and the breathing circuit. After the wash in, for CCA group, the O2 flow was reduced to 300 ml/min with isoflurane vaporizer setting adjusted to 3-5% for anesthesia maintenance, while for SCA group, anesthesia was maintained with 1.5-2% isoflurane in 3 l/min O2 flow throughout the surgery. Electromyogram was used to determine neuromuscular blockade. Rocuronium (0.15 mg/kg) was given to maintain muscle relaxation when T1 reached 25% of control. We maintained the anesthetic depth until the recordings of T1 twitch response which reached 75% was completed. Onset time, duration, recovery index and intubating conditions were recorded. The hemodynamic parameters and the inhaled/exhaled concentrations were also measured every 15 min after skin incision in both groups. RESULTS: The onset time and intubating conditions were similar in both groups. In comparison with SCA group, longer clinical durations (54.1 +/- 14.4 vs. 45.4 +/- 9.2 min, P < 0.05), longer durations of maintained dose (41.1 +/- 11.1 vs. 30.2 +/- 8.6 min, P < 0.01) and longer recovery index (34.2 +/- 10.7 vs. 20.9 +/- 5.4 min, P < 0.0001) were observed in CCA group. CONCLUSIONS: We conclude that CCA may further prolong the neuromuscular blocking effect of rocuronium than SCA.

Adolescent↗

PubMed1995

Comparison of tactile and mechanomyographical assessment of response to double burst and train-of-four stimulation during moderate and profound neuromuscular blockade.

It is common clinical practice to estimate the degree of neuromuscular blockade by tactile evaluation of twitch responses. The aim of the present study was to evaluate the use of tactile responses of adductor pollicis to double-burst stimulation (DBS) and train-of-four (TOF) peripheral nerve stimulation for monitoring moderate and profound levels of neuromuscular blockade. The study comprised 44 women scheduled for gynaecological laparotomy and anaesthetised with midazolam, fentanyl, thiopentone, halothane, nitrous oxide and atracurium. The tactile responses of the adductor pollicis were compared with mechanomyographical measurements in the contra lateral arm during recovery from neuromuscular blockade. The observers (anaesthetic nurses) of the tactile responses were blinded with regard to the stimulation pattern and the mechanomyographical measurements. The time from injection of the initial dose of atracurium until tactile reappearance of the first twitch in DBS (D1), was 24.6 (0-39.8) min, median (range). This was more rapid than the time until tactile reappearance of the first twitch in TOF (T1) 32.8 (18.2-43.4) min (P < 0.05). The median time from tactile reappearance of D1 until T1 recovered to 15% of the control twitch height was longer than the median time from tactile reappearance of T1 (14.6 versus 10.5 min) (P < 0.05). One or two responses to DBS or TOF were often felt before any responses had been detected mechanomyographically in the contralateral arm. When three or four responses to TOF were felt, responses were always detected mechanomyographically. It is concluded that tactile evaluation of responses ot DBS stimulation can estimate deeper levels of blockade than tactile evaluation of responses to TOF.

Adolescent↗

PubMed2003

Phonomyography as a novel method to determine neuromuscular blockade at the laryngeal adductor muscles: comparison with the cuff pressure method.

BACKGROUND: Neuromuscular blockade at the laryngeal adductor muscles may be measured using the cuff of a endotracheal tube placed between the vocal cords. Phonomyography is an alternative method of neuromuscular monitoring. In this study, phonomyography is applied to determine blockade at the larynx and compared with the cuff pressure method. METHODS: After the authors obtained approval from the ethics committee and informed consent, 28 patients were entered in the study. After induction of anesthesia, a endotracheal tube was inserted. Its cuff was placed in the trachea in routine fashion (n = 14) or between the vocal cords (n = 14). In all patients, a small condenser microphone was placed in the vestibular fold, just lateral to the tube, next to the laryngeal adductor muscles. The recurrent laryngeal nerve was stimulated supramaximally with single twitch stimulation (0.1 Hz) for onset, and train-of-four stimulation every 12 s during offset of neuromuscular blockade was produced by 0.1 mg/kg mivacurium. Onset and recovery of neuromuscular blockade measured by the two methods were compared using the test (P < 0.05), and a Bland-Altman test was performed to define agreement between the two methods. Onset and recovery of neuromuscular blockade measured by phonomyography with the cuff placed between the vocal cords or in the trachea were compared using the test (P < 0.05). RESULTS: Mean onset, maximum effect, and time to reach 25% and 75% of control twitch response for phonomyography cuff pressure method were 145 s (SD, 25) 156 s (SD, 33), 89% (SD, 4) 91% (SD, 4), 9 min (SD, 4) 10 min (SD, 3), and 27 min (SD, 4) 29 min (SD, 4), respectively, without being significantly different. Mean bias was -2%, with limits of agreement of -20 and +18% for all signals (cuff method minus phonomyography). There was no significant difference in onset and offset of neuromuscular blockade measured using phonomyography with the cuff placed between the vocal cords or in the trachea. CONCLUSIONS: Both methods can be used interchangeably to determine neuromuscular blockade of the laryngeal adductor muscles. Phonomyography allows measurement of laryngeal blockade with the endotracheal tube in the normal position.

Blood Pressure↗

PubMed1992

[Effects of magnesium and calcium on muscle contractility and neuromuscular blockade produced by muscle relaxants and aminoglycoside].

The muscle contractility and neuromuscular blockade of muscle relaxants are influenced by the electrolytes, especially magnesium ion(Mg2+) and calcium ion(Ca2+), in the extracellular fluid. The present study was designed to evaluate the effects of Mg2+ and Ca2+ on muscle contractility and on the blocking properties of d-tubocurarine, succinylcholine and aminoglycoside antibiotics, tobramycin in vitro, using rats' phrenic nerve-hemidiaphragm preparations. Mg2+ inhibited the twitch tensions in a concentration dependent manner. A low concentration of Ca2+ decreased the twitch tensions, but a high concentration of Ca2+ had no effect on them. Mg2+ potentiated the block produced by d-tubocurarine, succinylcholine and tobramycin depending on the concentration of Mg2+, and good regression lines were obtained. Ca2+, however, antagonized the neuromuscular blockade of the three drugs at any level of Mg2+ concentration. From these findings, it should be noticed that special care must be taken to prevent a profound neuromuscular blockade due to the drug interaction of each drug when a muscle relaxant or an aminoglycoside antibiotics is administered to a patient suffering from hypermagnesemia and/or hypocalcemia.

Aminoglycosides↗

PubMed1995

Stabilization of the neuromuscular response when switching between different modes of nerve stimulation at surgical degrees of neuromuscular blockade.

During general anesthesia, different modes of nerve stimulation are used for estimation of the degree of neuromuscular blockade. When switching between the different modes, it is important to know whether the preceding mode influences the responses to the succeeding mode, and if so, for how long. The object of our study was to determine the number of stimulations required for stabilization of the muscular response when switching between double-burst stimulation (DBS) applied every 20 sec, train-of-four (TOF) applied every 12 sec, and posttetanic count (PTC) at surgical degrees of neuromuscular blockade. A total of 33 women were anesthetized with fentanyl, thiopental, halothane, and nitrous oxide. A constant degree of neuromuscular blockade was maintained at a twitch height of 4 to 11% of the control twitch height using a continuous infusion of atracurium. The ulnar nerve was stimulated supramaximally at the wrist, and the contraction in the adductor pollicis was measured mechanomyographically. At surgical degrees of neuromuscular blockade, only the first twitch response to TOF stimulation (T1) and the first twitch response to DBS stimulation (D1) are consistently present. When switching from DBS to TOF, 4 to 7 stimulations (56 to 92 sec) were required for stabilization of the T1 response. When switching from TOF to DBS, 3 stimulations (36 to 52 sec) were required for stabilization of the D1 response, and, finally, when switching from PTC to DBS, 5 to 11 stimulations (81 to 201 sec) were required for stabilization of the D1 response. Stabilization of D1 was faster following TOF than following PTC (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1990

Does perioperative tactile evaluation of the train-of-four response influence the frequency of postoperative residual neuromuscular blockade?

The authors conducted a randomized controlled clinical trial to evaluate the usefulness of perioperative manual evaluation of the response to train-of-four (TOF) nerve stimulation. A total of 80 patients were divided into four groups of 20 each. For two groups (one given vecuronium and one pancuronium), the anesthetists assessed the degree of neuromuscular blockade during operation and during recovery from neuromuscular blockade by manual evaluation of the response to TOF nerve stimulation. In the other two groups, one of which received vecuronium and the other pancuronium, the anesthetists evaluated the degree of neuromuscular blockade solely by clinical criteria. The use of a nerve stimulator was found to have no effect on the dose of relaxant given during anesthesia, on the need for supplementary doses of anticholinesterase in the recovery room, on the time from end of surgery to end of anesthesia, or on the incidence of postoperative residual neuromuscular blockade evaluated clinically. The median (and range of) TOF ratios recorded in the recovery room were 0.75 (0.33-0.96) and 0.79 (0.10-0.97) in the vecuronium groups monitored with and without a nerve stimulator, respectively. These ratios were significantly higher than those found in the pancuronium groups, which wre 0.66 (0.06-0.90) and 0.63 (0.29-0.95), respectively. However, no difference was found between the vecuronium and pancuronium groups in the number of patients showing clinical signs of residual neuromuscular blockade, as evaluated by the 5-s head-lift test.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMedDate not supplied

Management of pharmacologically induced neuromuscular blockade using peripheral nerve stimulation.

Currently, many critically ill patients are treated with neuromuscular blocking agents to facilitate endotracheal intubation, mechanical ventilation, and manage confused, combative, head injured, and status epileptus patients. To prevent persistent pharmacologically induced paralysis, the aide of a peripheral nerve stimulator and clinical indicators may help determine the minimal effective drug dose to facilitate safe neuromuscular blockade. The purpose of this article is to provide nursing clinicians the essential knowledge to manage patients with neuromuscular blockade effectively using peripheral nerve stimulation monitoring.

Drug Monitoring↗

PubMed1990

Practical points in understanding neuromuscular blockade.

The physiology of the neuromuscular junction has a significant impact on the pharmacology of neuromuscular blockade and associated reversal. Depolarizing and nondepolarizing agents for blockade and enzyme inhibitors for reversal of blockade are discussed. Clinical applications are also reviewed.

Humans↗

PubMed1991

Edrophonium priming alters the course of neuromuscular recovery from a pipecuronium neuromuscular blockade.

This study was designed to investigate the effect of divided administration of edrophonium on the course of neuromuscular recovery from a pipecuronium neuromuscular blockade. During thiopentone-nitrous oxide-halothane anaesthesia 48 patients were given pipecuronium 70 micrograms.kg-1. Patients were randomly assigned to one of four groups (n = 12 in each) to receive either edrophonium 1 mg.kg-1 (Groups I and II) or edrophonium 0.75 mg.kg-1 (Groups III and IV). In Groups I and III (single-dose groups), edrophonium was administered as a single bolus dose. In Groups II and IV (divided-dose groups) edrophonium was administered as an initial dose of 0.25 mg.kg-1 followed three minutes later by either 0.75 or 0.50 mg.kg-1 respectively. Reversal was attempted at 20% spontaneous recovery of twitch height. Administration of edrophonium in divided doses (Groups II and IV) accelerated the reversal of the pipecuronium neuromuscular blockade. At ten minutes post-reversal, train-of-four (TOF) ratio recovery reached 0.75 or more in 12 (100%) and in ten (83%) patients in Groups II and IV respectively. Similarly, times to attain a TOF of 0.75 (SEM) were shorter in the divided-dose groups than in the single-dose groups (P less than 0.05), being 354.5 (38.7) and 398.3 (49.1) sec in Groups II and IV vs 705.4 (66.6) and 651.2 (54.3) sec in Groups I and III respectively. Time was counted from the first administration of edrophonium. It is concluded that administration of edrophonium in divided doses produced a faster reversal of residual pipecuronium-induced neuromuscular blockade than single bolus administration. Also, administration in divided doses reduced the requirements of edrophonium needed for reversal of pipecuronium neuromuscular blockade.

Adult↗

PubMed1994

Vecuronium neuromuscular blockade reflects liver function during hepatic autotransplantation in pigs.

BACKGROUND: Rapid assessment of hepatic function early after reperfusion of the liver graft is of great importance, because it may allow for prompt detection of incipient hepatic graft failure. The current study was undertaken to determine whether the continuous recording of neuromuscular transmission could be used as an on-line assessment of hepatic function during liver transplantation when a muscle relaxant with high hepatic uptake is used. METHODS: We quantified and compared the effect of liver exclusion and graft reperfusion on the level of vecuronium-induced neuromuscular blockade in nine pigs studied twice within 3 days. During the 1st day (control session), an intravenous infusion of vecuronium was administered to maintain a constant 90-95% twitch depression during 180 min. The twitch response was then allowed to recover spontaneously to 75% of its prerelaxant value. Neuromuscular transmission was continuously measured on the right anterior leg using an acceleration transducer. During the same time period, the metabolic rate of 14C-labeled aminopyrine (a well-established quantitative test of the liver microsomal function) was determined by measuring the excretion of 14CO2 in expired air after administration of an intravenous bolus of 14C-labeled aminopyrine. Two days later, the pigs underwent a hepatic autotransplantation, during which vecuronium was administered to maintain a constant 90-95% twitch depression. After reperfusion of the liver graft, the vecuronium infusion rate was maintained at its anhepatic level, and the recovery index of the neuromuscular blockade (the time from 25% to 75% recovery of twitch height) was calculated. The aminopyrine breath test was performed during the last 30 min of the anhepatic phase, and during 3 h after reperfusion of the liver graft. RESULTS: During control studies, the mean infusion rate of vecuronium was 1.30 +/- 0.33 mg.kg-1.h-1 and the recovery index was 3.4 +/- 0.5 min. During liver dissection, the infusion rate of vecuronium was similar to the control value (1.18 +/- 0.16 mg.kg-1.h-1), then considerably decreased to 0.05 +/- 0.03 mg.kg-1.h-1 during the anhepatic phase. After reperfusion of the liver graft, the recovery index was markedly prolonged to 35.5 +/- 15.8 min, indicating a prolongation of the recovery of neuromuscular blockade by a factor of 10.4. Excretion of 14CO2 was equal to zero during the anhepatic phase and then increased to 0.19 +/- 0.11% during the 1st h after reperfusion of the liver graft, an excretion rate corresponding to 11.2% of control conditions. The relationship between individual changes in the recovery index of the neuromuscular blockade and 14CO2 excretion in expired air after reperfusion of the liver graft showed a strong significant correlation (r2 = 0.71). CONCLUSIONS: These results indicate that, compared with the control studies, there is a similar decrease in the recovery rate of vecuronium-induced neuromuscular blockade and in the metabolic rate of 14C-labeled aminopyrine during the progressive recovery of hepatic function immediately after unclamping of the liver vessels. Metabolism of 14C-labeled aminopyrine increased progressively during the reperfusion phase. Therefore, recording of neuromuscular transmission during liver transplantation could serve as a continuous and easy to perform assessment of liver graft function provided that a muscle relaxant with a high hepatic uptake is used for neuromuscular blockade.

Aminopyrine↗