The influence of alfentanil on the intubating conditions after priming with vecuronium

The ability of alfentanil 15 micrograms kg-1 or 30 micrograms kg-1 to improve intubating conditions was studied in four groups of 25 ASA class 1 patients. Induction of anaesthesia was with thiopentone 5 mg kg-1. Neuromuscular blockade was induced with vecuronium using the priming principle. The priming dose, priming interval and intubating dose were 0.01 mg kg-1, 4 min, and 0.1 mg kg-1, respectively. Intubation was attempted 1 min after the intubating dose. Intubating conditions were judged unacceptable in about 30% of the patients belonging to the control groups. Alfentanil 15 micrograms kg-1, when administered 65 s before intubation, reduced the incidence of coughing and diaphragmatic movement (P less than 0.05) but did not reduce the incidence of overall unacceptable intubating conditions. Alfentanil 30 micrograms kg-1, however, reduced the incidence of vocal cord movement (P less than 0.005) as well as coughing and diaphragmatic movement (P less than 0.002). Alfentanil 30 micrograms kg-1 reduced the incidence of unacceptable intubating conditions from about 30% to 4% (P less than 0.02).     

Priming with vecuronium and atracurium--a comparison

Vecuronium (V) and atracurium (A) were compared in a randomised study in premedicated patients undergoing laparoscopy for gynecological pathology. Both groups contained ten patients. Anesthesia was induced with fentanyl (0.1 mg) and thiopentone (1 mg/kg initially and subsequently 4 mg/kg). A priming dose of vecuronium (20 micrograms/kg) or atracurium (100 micrograms/kg) was given one minute before the intubating dose (60 micrograms/kg for vecuronium and 300 micrograms/kg for atracurium). Ninety seconds thereafter intubation was performed. Maintenance of anesthesia consisted of isoflurane at an inspiratory concentration of 1% in a mixture of O2/N2O (50%/50%) with small supplements of fentanyl. Neuromuscular block was monitored with the Datex Relaxograph. Results show that neither drug offers major clinical advantages over the other: there is no difference in speed of onset (V:T190sec 14.6 +/- 4.3%; A:T190sec 23.5 +/- 6.5%; Mean +/- SEM) and duration of neuromuscular block (V:T150sec 34.2 +/- 3.5 min; A:T150sec 41.3 +/- 2.8 min; Mean +/- SEM) and intubation conditions are almost identical.     

Intubating conditions after vecuronium and atracurium given in divided doses (the priming technique)

Intubating conditions have been assessed at 60 s following administration of vecuronium 0.1 mg kg-1 or atracurium 0.5 mg kg-1 given either as a single dose after induction of anaesthesia with thiopentone or in divided doses; vecuronium 0.015 mg kg-1 followed 4 or 6 min later by 0.085 mg kg-1, or atracurium 0.075 mg kg-1 followed 4 or 6 min later by 0.425 mg kg-1. In the divided dose groups the smaller initial (priming) dose was given prior to induction of anaesthesia. Onset and duration of clinical relaxation were assessed using a peripheral nerve stimulator. The intubating conditions at 60 s improved significantly, with the use of relaxants in divided doses being acceptable in 80 and 70% of patients, respectively, with vecuronium and atracurium, but the conditions are not as good as those commonly found using suxamethonium. Priming at 6 min has no advantage over priming at 4 min. The onset of complete block was accelerated with priming, but the difference was not significant. The duration of clinical relaxation of vecuronium was significantly prolonged by giving it in divided doses. Unpleasant awareness of muscle weakness was observed in 15 patients, requiring early induction of anaesthesia in five of them.     

Vecuronium bromide: modification of its pharmacodynamics by etomidate, cimetidine and ranitidine

After obtaining their informed consent, 60 patients (ASA groups I or II), 18 to 60 years of age were randomly allocated to six groups of 10 persons each. Anesthesia was induced in groups 1, 4, 5 and 6 with 2-3 mg kg-1 thiopentone and in groups 2 and 3 with 0.2-0.3 mg kg-1 etomidate. 20 min before induction, patients in groups 3 and 5 received 5 mg kg-1 cimetidine, and patients in group 6 received 1.25 mg kg-1 ranitidine. Induction of anesthesia was supplemented by 0.002 mg kg-1 fentanyl and 0.01 mg kg-1 lormetazepam. After beginning neuromuscular monitoring, 0.08 mg kg-1 vecuronium was injected and the intubation accomplished when the first twitch of the train of four (TOF) was suppressed of a rate greater than 90%. The anesthesia was maintained with supplemental doses of 0.002 mg kg-1 fentanyl and 0.01 mg kg-1 lormetazepam, if necessary, and the use of a nitrous oxide/oxygen mixture (2.4:1.6 l min-1). A train of four supramaximal nerve stimuli was applied to the ulnar nerve proximal to the wrist and the twitch responses were electrically recorded on the hypothenar musculature (Relaxograph, Datex). The frequency of the train was 2 Hz with an interval of 20 s between trains. The time from the injection of vecuronium to several degrees of neuromuscular recovery was statistically significantly prolonged after 5 mg kg-1 cimetidine (groups 3 and 5) in comparison to the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Conditions of intubation with vecuronium using a priming principle

Different protocols based on the priming principle have been proposed so as to enable rapid tracheal intubation with vecuronium. The conditions of such an intubation have been assessed in 47 ASA I or ASA II patients, with an empty stomach, using a priming dose of 0.01 mg X kg-1, followed by a second injection of 0.1 mg X kg-1 after a short interval of 4 min. An intubation score was defined using a nerve stimulator (Relaxograph Datex), by measuring the twitch in comparison with a reference value, as well as time before intubation for four groups of patients. Good intubation scores with a twitch approaching 50% was obtained in all and, in the same way, for a fifth group of patients, intubated in an arbitrary manner 60 s after the second dose of vecuronium. These results can be compared with those obtained by other authors using a different protocol. Nevertheless, this method does not match perfectly that of suxamethonium. Taking into account the side-effects and above all the inhalation risk existing after a priming dose, is it opportune to use this technique for the anaesthesia of a patient with a full stomach?     

Clinical study on the priming principle of muscle relaxants: comparison of pancuronium with vecuronium]

The priming principle of non-depolarizing muscle relaxants was treated in this study. The subjects were 48 patients. We administered divided doses (p) and single dose (s) using pancuronium (P) and vecuronium (V), and compared the 4 groups (Pp, Ps, Vp, Vs). Pp and Vp groups received intravenous injection of 0.02 mg.kg-1 first, and 0.08 mg.kg-1 after 5 minutes. Ps and Vs groups received intravenous injection of 0.1 mg.kg-1. Relaxograph was used for monitoring muscle relaxation. First-twitch (T1) and train-of-four ratio (TR) were recorded, and the time intervals required to decrease T1 to 25% (T1-25) and 5% (T1-5) were determined. T1-25 (sec) was 126.2, 153.1, 82.7, and 132.7 in Pp, Ps, Vp, and Vs group, respectively; and T1-5 (sec) was 192.8, 229.8, 112.7, and 165.2 in Pp, Ps, Vp, and Vs group, respectively. As these values suggest, there were no significant differences between Pp and Ps group, while significant differences were noted between Vp and Vs group. The following conclusions were obtained. Clinical usefulness of the priming principle was not shown with pancuronium, but was noted with vecuronium. However, the action of vecuronium appeared rapidly after single dose, and some patients complained of dyspnea during priming. Consequently, the priming principle was not considered to be clinically beneficial.     

Neuromuscular recovery after laparoscopy

Vecuronium bromide, 0.045 mg X kg-1, was compared with pancuronium, 0.07 mg X kg-1, when used to provide muscle relaxation for tracheal intubation and abdominal relaxation for outpatient gynecologic laparoscopy. Both drugs provided adequate intubating conditions within 5 min and satisfactory abdominal relaxation. Because spontaneous recovery from vecuronium was more rapid, either with inhalational or nitrous oxide-narcotic techniques, pharmacological reversal with edrophonium and atropine was either not necessary or more easily accomplished after vecuronium, as shown by the train-of-four. All patients receiving pancuronium required reversal of the blockade, and in a few patients reversal was difficult. Tests of muscle power and coordination performed 30 and 60 min postoperatively showed no difference between the drugs. There were no postoperative complications related to muscle relaxants and all patients met our discharge criteria the day of surgery. Given the conditions observed at the end of the procedure, we would choose vecuronium for muscular relaxation in laparoscopic surgery.     

Onset of vecuronium-induced neuromuscular block after a long priming interval

Purpose. We examined whether a new application of the priming principle, i.e., having the priming dose of vecuronium administered before the insertion of the epidural catheter, would hasten the onset of the neuromuscular block induced by the intubating dose of vecuronium. Methods. Forty-five adult female patients scheduled for general anesthesia combined with epidural anesthesia were studied. In group A (n = 15), the priming dose of vecuronium, 0.01 mg·kg⁻¹, was administered before insertion of the epidural catheter. The intubating dose of vecuronium, 0.09 mg·kg⁻¹, was given after the insertion of the epidural catheter. In group B (n = 15), the priming dose of vecuronium, 0.01 mg·kg⁻¹, was given 4 min before the intubating dose of vecuronium, 0.09 mg·kg⁻¹. In the control group (n = 15), no priming dose was given, and only the intubating dose of vecuronium, 0.10 mg·kg⁻¹, was administered. In all three groups, general anesthesia was induced with propofol 2.5 mg·kg⁻¹, and the trachea was intubated when T1/control value (control twitch height in response to train-of-four stimuli) was less than 0.1. Results. In group A, the priming dose was given 16 ± 3 min (mean ± SD) before the administration of the intubating dose. The times to onset of neuromuscular block in groups A and B, and the control group were: 145 ± 30, 184 ± 45, and 219 ± 23 s, respectively (P < 0.05 among the three groups). In all three groups, intubating conditions (graded on a four-point scale) were excellent (P = 0.59). Before the induction of anesthesia, symptoms of paralysis were observed in 5, 4, and 0 patients in groups A and B and the control group, respectively (P < 0.05 between group A or B vs control group). Conclusions. If the priming dose of vecuronium is given after a long priming interval (16 ± 3 min), the time to onset of the neuromuscular block caused by the intubating dose of vecuronium is markedly shorter than when the conventional priming interval of 4 min is employed. Received: March 5, 2001 / Accepted: October 4, 2001     

The dose effect of ephedrine on the onset time of vecuronium

A small dose of ephedrine decreases the onset time of rocuronium and cisatracurium; however, ephedrine might be associated with adverse hemodynamic effects. The appropriate dose of ephedrine has not been determined. We, therefore, studied 120 patients anesthetized with fentanyl 2 microg/kg and propofol 2-2.5 mg/kg who were randomly divided to receive either ephedrine (30, 70, or 110 microg/kg) or saline. During propofol anesthesia, the neuromuscular block was monitored by mechanomyography by using submaximal current of train-of-four stimulation every 10 s. To determine cardiac output, a transcutaneous Doppler probe was placed externally at the suprasternal notch. Tracheal intubation was performed by a blinded investigator at 2 min after vecuronium. Neuromuscular block, intubating conditions, and hemodynamic effects were measured during the induction of anesthesia. Both ephedrine 70 and 110 microg/kg improved intubating conditions at 2 min after vecuronium; however, 110 microg/kg was associated with adverse hemodynamic effects. We conclude that ephedrine 70 microg/kg given before the induction of anesthesia improved intubating conditions at 2 min after vecuronium, probably by increased cardiac output without significant adverse hemodynamic effects. IMPLICATIONS:Ephedrine 70 microg/kg given before the induction of anesthesia improved tracheal intubating conditions at 2 min after vecuronium by increased cardiac output without significant adverse hemodynamic effects.     

Accelerated onset and delayed recovery of d-tubocurarine blockade with pancuronium in infants and children

The effect of age on the onset and duration of action of a d-tubocurarine (DTC) neuromuscular blockade with and without pancuronium priming in children was examined. Sixty ASA physical status I or II patients in three age ranges (0-1 yr, 1-3 yr and 3-10 yr) were anaesthetized with thiopentone, halothane and nitrous oxide. Each patient received either a single paralyzing dose of DTC 0.4 mg.kg-1, or DTC 0.36 mg.kg-1 preceded three minutes earlier by pancuronium 0.007 mg.kg-1. Evoked force of contraction of the adductor pollicis was measured using train-of-four stimulation applied every 12 sec. Time to 90 per cent first twitch depression after a single dose of DTC increased with increasing age (r = 0.65, p less than 0.01), and was 1.6 min (SEM +/- 0.3) in the 0-1 yr group, 1.9 +/- 0.3 min (1-3 yr), and 5.2 +/- 1.2 min (3-10 yr). Time to ten per cent spontaneous recovery after single dose DTC was shorter in older individuals (r = 0.40, p less than 0.05), being 36.4 +/- 5.1 min in infants 0-1 yr, 30.6 +/- 4.6 min (1-3 yr), and 24.0 +/- 2.7 min (3-10 yr). Priming with pancuronium accelerated the onset significantly in all age groups with 90 per cent T1 depression occurring at 0.7 +/- 0.1 min (0-1 yr), 0.9 +/- 0.1 min (1-3 yr), and 2.1 +/- 0.6 min (3-10 yr). However, priming delayed recovery, especially in infants.(ABSTRACT TRUNCATED AT 250 WORDS)     

Train-of-four fade of non depolarizing muscle relaxants: an insight into the mechanism of precurarization

This study was carried out to assess the prejunctional effect of non depolarizing muscle relaxants during the onset of neuromuscular blockade using the train-of-four ratio (TR). The prejunctional effect was compared with previous results concerning the ability of the relaxants to prevent suxamethonium-induced fasciculations. Fifty-three adult patients were relaxed with small incremental doses of either alcuronium (0.03 mg.kg-1), atracurium (0.04 mg.kg-1), pancuronium (0.01 mg.kg-1), d-tubocurarine (0.05 mg.kg-1) or vecuronium (0.01 mg.kg-1) during anaesthesia with thiopentone, fentanyl and nitrous oxide in oxygen. The muscle relaxant was given after recovery from an initial suxamethonium blockade needed for tracheal intubation. The evoked integrated EMG response to supramaximal train-of-four (2 Hz) stimulation was recorded every 20 s. TR % was calculated at different first twitch (T1) levels during the onset of neuromuscular blockade. Significant changes occurred at the 100% and 90% T1 levels, alcuronium having the lowest mean TR values. Atracurium, pancuronium and vecuronium gave similar TR values. Results with d-tubocurarine placed it between alcuronium and the others. These train-of-four ratio results were compared with the ability of non depolarizing muscle relaxants to prevent fasciculations. In conclusion, the stronger the train-of-four fade, the greater was the ability of the relaxant to prevent suxamethonium-induced fasciculations. This supports the theory that the blockade of prejunctional cholinergic receptors is the mechanism of action of precurarization.     

Administration of vecuronium, atracurium and pancuronium in divided doses: effect on onset and duration of action

The time to onset of neuromuscular block (as assessed by single twitch stimulation at 0.1 Hz) and the duration to 25% recovery of twitch height were measured after administration of vecuronium 0.1 mg kg-1, atracurium 0.5 mg kg-1 or pancuronium 0.1 mg kg-1, administered either as a single bolus or in divided doses, 10% being administered 4 min prior to the remaining 90%. The patients were anaesthetized with thiopentone, nitrous oxide in oxygen and i.v. fentanyl. There was no significant difference between the single- and divided-dose groups, either in the onset times (2.8 and 2.9 min for vecuronium, 2.7 and 2.4 min for atracurium and 3.3 min each for pancuronium for single- and divided-dose groups, respectively) or the duration to 25% recovery of twitch height (35 and 29 min for vecuronium, 45 and 39 min for atracurium and 87 and 93 min for pancuronium for single- and divided-dose groups, respectively).     

A comparative evaluation of intubating doses of atracurium,d-tubocurarine,pancuronium and vecuronium in children

To determine the onset and recovery times and haemodynamic effects of intubating doses of atracurium (0.4 mg.kg-1), d-tubocurarine (0.8 mg.kg-1), pancuronium (0.12 mg.kg-1), and vecuronium (0.07 mg.kg-1), sixty-seven children aged one to eight years were studied under halothane and nitrous oxide anaesthesia. The time to maximum twitch depression and the time to recovery to T1/Tc 25 per cent were recorded with an integrated evoked EMG recorder. The heart rate and systolic blood pressure were recorded for five minutes after drug administration and prior to intubation. There was no difference in onset times between drugs. The recovery time to T1/Tc 25 per cent following vecuronium (25.5 +/- 6.3 min) was shorter than following atracurium (37.5 +/- 7.0 min). Recovery times for d-tubocurarine and pancuronium were greater than sixty minutes. Elevation of heart rate occurred after administration of pancuronium (+29.8 per cent to +38.6 per cent) and d-tubocurarine (+31 per cent to +34.9 per cent), but no change was observed after atracurium or vecuronium. Elevation of blood pressure was greatest following pancuronium (+10.8 to +14.8 per cent). No significant change was observed following atracurium or vecuronium. A transient lowering of blood pressure (-9.3 per cent) occurred following d-tubocurarine.     

Rapid tracheal intubation with vecuronium: the priming principle

Following the administration of a single 0.1 mg/kg dose of vecuronium bromide, satisfactory conditions for tracheal intubation developed in 156 +/- 12 s (mean +/- SEM), and the clinical duration of the initial dose was 36 +/- 2 min. When the initial dose of vecuronium was administered in two increments, a 0.015 mg/kg "priming" dose, followed 6 min later by a 0.050 mg/kg "intubating" dose, intubation time decreased to 61 +/- 3 s and clinical duration to 21 +/- 1 min. The priming dose that had no unpleasant effect on premedicated, awake patients could be administered 3-4 min before, and the intubating dose 2 to 3 min after induction of anesthesia. With the described technique, comparable intubating conditions could be obtained just as rapidly with vecuronium as with succinylcholine chloride, without subjecting the patients to the side effects of and the complications occasionally encountered with succinylcholine. An added advantage of the use of a priming dose is that it will reveal undiagnosed, pathologic, or idiopathic increase of sensitivity to nondepolarizing muscle relaxants.     

Rapid induction sequence with vecuronium: should we intubate after 60 or 90 seconds?

The purpose of the study was to determine intubating conditions after administration of either succinylcholine or vecuronium in a rapid induction sequence. Patients received either succinylcholine 1.5 mg.kg-1 (Groups I and II) after d-tubocurarine 0.05 mg.kg-1 four minutes earlier, or vecuronium (Groups III and IV) in an initial dose of 0.01 mg.kg-1 followed four minutes later by 0.1 mg.kg-1. In Groups I and III an apnoeic delay of one minute was allowed before intubation whereas in Groups II and IV the delay was 90 sec. There was no significant difference in intubating conditions between Groups I and IV. Intubating conditions in Group III (vecuronium-delay of one minute) were statistically worse than in any of the three other groups. A delay of 90 sec after succinylcholine improved intubating conditions in male patients. Considering that intubating conditions obtained after 90 sec in patients given a priming sequence with vecuronium (Group IV) were not different from those obtained 60 sec after succinylcholine (Group I), the authors conclude that vecuronium is an acceptable alternative for rapid tracheal intubation. In the doses used in this study, intubating conditions 60 sec after vecuronium were unacceptable for rapid induction of anaesthesia.     

Rapid sequence induction using vecuronium

The purpose of this study was to determine the ideal priming and total dose of vecuronium when used as the relaxant during rapid sequence induction of anesthesia and tracheal intubation. Seventy patients were studied. Various priming and total dose schedules using vecuronium were compared with succinylcholine, 1.5 mg/kg. The mean onset times, intubating conditions, and mean duration times were compared. A priming dose of 10 micrograms/kg produced good intubation conditions with both 70 micrograms/kg and 150 micrograms/kg (total doses), but the mean onset times remained significantly longer than succinylcholine 1.5 mg/kg (P less than 0.05). A priming dose of 15 micrograms/kg of vecuronium with 100 micrograms/kg total dose, on the other hand, not only produced excellent intubating conditions but also resulted in a mean onset time not significantly different from succinylcholine, 1.5 mg/kg. This latter dose schedule of vecuronium is recommended for rapid sequence induction when succinylcholine is contraindicated. Vecuronium is preferable to pancuronium for rapid sequence induction because of its lack of cardiovascular side effects and short duration.     

Clinical use in adults of 2 new muscle relaxants: atracurium and vecuronium

115 general and urologic surgery adult patients, ASA class I-II, were divided in four groups according to initial bolus and relaxant used: group A atracurium 0.6 mg X kg-1, group B 0.5 mg X kg-1, group C vecuronium 0.1 mg X kg-1 and group D pancuronium 0.1 mg X kg-1. When the single twitch recovered to 25% of control height (T25), subgroups were individualized depending on whether repeat doses of 1/3 of initial bolus were given or not, and whether reversal was spontaneous or obtained by a standard dose of neostigmine 2.5 mg and atropine 1.25 mg. By ulnar nerve stimulation at the wrist, the force of thumb adduction was recorded on a polygraph; single twitch (tw), train of four (tof) and ratio tof 4/1 (Rtof) were measured. Anaesthesia was induced with thiopentone and fentanyl without premedication and maintained with fentanyl and N2O in oxygen; the trachea was intubated once the block was at its maximum. The onset time of maximal block was 5 min for groups A, B and C, and 7.9 min for group D. T25 was 39.9 +/- 8.5 min for group A, 34.4 +/- 9.7 min for group B, 28.9 +/- 9.9 min for group C and 70.7 +/- 25.9 min for group D. A Rtof equal to 75% was achieved in less than 65 min with atracurium and vecuronium, but much later with pancuronium. Reversal at T25 was efficient, but not really required, for atracurium and vecuronium, but necessary and useful for pancuronium.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of succinylcholine on vecuronium and pancuronium

In 105 adult patients under halothane anesthesia, the neuromuscular blocking effects of vecuronium and pancuronium were determined with prior succinylcholine 1 mg.kg-1 administration and without. Force of the evoked twitch increased 123.7% of control after recovery from succinylcholine-induced block. Prior administration of succinylcholine was associated with a leftward shift of dose-response curve of vecuronium or pancuronium. Onset of the force reduction from initial dose (0.08 mg.kg-1) was faster and recovery from initial and maintenance doses (0.02 mg.kg-1) were slower. This potentiating effect persisted at least 2 hours.     

Facilitation of rapid endotracheal intubations with divided doses of nondepolarizing neuromuscular blocking drugs

The authors sought to determine whether prior administration of a small, subparalyzing dose of nondepolarizing muscle relaxant would shorten the onset time of an intubating dose of muscle relaxant. Initially, in 60 anesthetized patients, twitch response of adductor pollicis to ulnar nerve stimulation was studied after a small dose of pancuronium 0.015 mg . kg-1, metocurine 0.03 mg . kg-1, or d-tubocurarine 0.04 mg . kg-1, followed 3 min later by pancuronium 0.08 mg . kg-1 or atracurium 0.4 mg . kg-1 administered iv. After 60 s, the minimum neuromuscular block, in all patients was 79.0 +/- 5.0%. A 95% depression or twitch tension occurred between 59.1 +/- 5.3 and 86.1 +/- 5.9 s. In another 60 patients, intubating conditions under similar regimen were studied, except the small dose of muscle relaxant was given immediately prior to induction of anesthesia. At the end of 60 s, good to excellent intubating conditions were present in 100% of the patients following the second dose of pancuronium and in 83% of the patients following atracurium. In 17% of the patients, after atracurium intubating conditions were fair. When nondepolarizing neuromuscular blocking drugs are administered in divided doses, neuromuscular blockade adequate for endotracheal intubation is achieved in less than 90 s. This facilitates rapid endotracheal intubation in a time comparable to using succinylcholine, without undesirable effects of the depolarizing neuromuscular blocking drugs.     

Comparison of the action kinetics of alcuronium and vecuronium by electromyographic monitoring

Twenty-eight ASA I or ASA II adults undergoing microsurgery were anaesthetized according to a standard protocol using droperidol, phenoperidine and thiopentone followed by enflurane. The patients were randomly assigned to two homogeneous groups: the first group (n = 14) received 0.2 mg.kg-1 alcuronium, whereas the second group (n = 14) received 0.08 mg.kg-1 vecuronium. There was no reinjection of either drug and curarization tapered off spontaneously. Neuromuscular monitoring was begun once anaesthesia was stable and after intentional isovolaemic haemodilution. The type of stimulus used was the train-of-four, delivered by a Relaxograph monitor to the ulnar nerve. Muscle response was measured at the hypothenar eminence. The kinetic study considered the time interval required between the injection of the muscle relaxant and the appearance of the minimal value of the twitch (first response of the train-of-four = T1min). The times to recovery of the twitch height to 25, 75 and 100% of the reference value (T1/T0) and of the fourth response of the train-of-four to 25 and 75% of the ratio (T4/T1) were also recorded. Finally, the recovery indexes represented by the times required for T1/T0 and T4/T1 to rise from 25% to 75% respectively were studied. The maximal twitch height inhibition was significantly greater (p less than 0.001) in the vecuronium group (T1min = 0.36 +/- 1.33%) than in the alcuronium group (T1min = 4.36 +/- 5.08%); it occurred significantly more quickly (p less than 0.001) with vecuronium (139 +/- 48 s) than with alcuronium (316 +/- 133 s).(ABSTRACT TRUNCATED AT 250 WORDS)