Clinical study of large doses of vecuronium; duration of initial and additional doses

Neuromuscular blockade by large doses of vecuronium was investigated clinically and the duration of action of initial doses (0.2 mg.kg-1 and 0.3 mg.kg-1) and additional doses (0.01 mg.kg-1 and 0.02 mg.kg-1) were measured under enflurane-nitrous oxide anesthesia using a neuromuscular transmission monitoring system (Accelograph). In group A (initial dose = 0.2 mg.kg-1, additional dose = 0.02 mg.kg-1), the time of spontaneous recovery to 25% of control twitch height (T25) and 50% of control (T50) were 63.1 and 82.0 minutes respectively. The T50 interval of the two adjacent added doses (given at the time point of 50% recovery from the previous dose) was 31.1 minutes. Reversal time from TOF ratio = 25% to 75% after administration of edrophonium was 6.1 minutes. In group B (initial = 0.3 mg.kg-1, add. = 0.01 mg.kg-1), T25, T50, T50 interval and reversal time were 122.6, 159.4, 39.2 and 4.6 minutes respectively. In group C (initial = 0.3 mg.kg-1, add. = 0.02 mg.kg-1), above values were 119.2, 145.8, 48.4 and 6.7 minutes respectively. In this study there was no obvious side effect associated with administration of large doses of vecuronium. These methods will be very useful for long surgical procedures.     

Augmentation of vecuronium-induced neuromuscular block during sevoflurane anaesthesia: comparison with balanced anaesthesia using propofol or midazolam

We have quantified the potentiating effects of 1.7% sevoflurane (n = 12) on vecuronium-induced neuromuscular block and compared the results with those obtained during balanced anaesthesia with propofol (n = 12) or midazolam (n = 12) in 36 patients. Neuromuscular function was monitored using an accelerograph and the train-of-four responses of the adductor pollicis muscle to ulnar nerve stimulation. Vecuronium 0.1 mg kg-1 was administered as an intubating dose, and maintenance doses of 0.02 mg kg-1 were administered on three occasions when T1/T0 had recovered to 25%. Thereafter, spontaneous recovery was monitored until complete. Times to 25% recovery of T1/T0 (DUR25) after an intubating dose of vecuronium did not differ between groups (mean 44.2 (SD 18.7) min for sevoflurane, 38.3 (7.5) min for propofol and 35.5 (9.5) min for midazolam). DUR25 values after each maintenance dose were 29.8 (9.5) min, 30.3 (10.4) min and 31.6 (10.7) min during sevoflurane anaesthesia, and were significantly longer than values for propofol (21.7 (6.0) min, 21.5 (5.8) min and 21.9 (5.8) min) and midazolam (20.0 (5.9) min, 19.3 (7.7) min and 19.8 (8.0) min) (P < 0.05) in each case). Recovery index25-75% and interval from T1/T0 = 25% to T4/T1 = 0.7 after the final dose of vecuronium were significantly prolonged by sevoflurane (28.3 (13.2) min and 42.7 (16.4) min) compared with propofol (17.6 (6.1) min and 26.6 (9.8) min) or midazolam (16.3 (9.4) min and 26.0 (10.2) min) (P < 0.05 in each case).      

Comparative study of vecuronium and atracurium at low doses in minor pediatric surgery under combined anesthesia]

To compare, the time of onset and time of recovery of muscular blockade after use of half doses of vecuronium and atracurium, we studied 18 children ASA I who were proposed for short lasting pediatric surgery and combined anesthesia. Patients were divided into two groups: group V (n = 10) was treated with a single dose of 0.05 mg/kg of vecuronium and group A (n = 8) with 0.25 mg/kg of atracurium. Assessment of muscular relaxation was performed by measuring the electromyographic responses to a train of four stimuli applied to the cubital nerve at the level of the hypothenar eminence. We administered 0.02 mg/kg of atropine, 5 to 10 mg/kg of thiopental, and the muscular relaxing dose together with orotracheal intubation when the first stimulus of the train of four stimuli was blocked at 90% of its initial value (T90). Maintenance of the anesthetic level was performed with 50% of N2O-O2 without inhalational anesthetics. A caudal blockade was induced by 1 ml/kg of bupivacaine at 0.25%. We measured the following parameters of muscular relaxation: T90, T10 (time at which the 10% of the first stimulus reappears), T25 (time of clinical efficacy) and IR (index of recovery). Only 60% of patients (6 out of the 10 patients of vecuronium group and 5 out of the 8 subjects of atracurium group) achieved the T90. This occurred 2.5 +/- 0.7 min after vecuronium and 3.2 +/- 0.6 min after atracurium. T10 was 13.7 +/- 4.1 min for vecuronium and 13.3 +/- 4.1 min from atracurium. T25 occurred 18.2 +/- 6.5 min after vecuronium and 19.4 +/- 2.1 min for atracurium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical use of vecuronium during celioscopy

In order to determine if vecuronium can be used for short operations, 40 women were studied during laparoscopy, randomly assigned to four groups: suxamethonium 1 mg X kg-1 in a single bolus followed by an infusion (group A), vecuronium 0.05 mg X kg-1 (group B), vecuronium 0.06 mg X kg-1 (group C) and vecuronium 0.07 mg X kg-1 (group D). Mean duration of operation was 22-25 min. Tracheal intubation can be performed in good conditions in all patients in group A and D, in 5/10 in group B and in 7/10 in group C. During laparoscopy, muscular relaxation was considered excellent in all patients in group A and D, 5/10 sufficient and 5/10 excellent in group C, 5/10 insufficient and 5/10 sufficient in group B. There were 7 reinjections in group B, 2 in group C and 1 in group A. The delay between the end of the procedure and extubation was the same in group A and C (7 min). This delay was significantly higher in group D (9 min). The delay between extubation and positive head lift test was significantly higher in group D. We conclude that the time course of action of vecuronium 0.06 mg X kg-1 is that required for a pelvic laparoscopy of 22-25 min; however, the conditions of intubation are not always perfect. Intubation is easier with a 0.07 mg X kg-1 dose; this dose induces a slight delay for extubation and positive head lift test. In all cases, the patient must be closely watched in a recovery ward.     

Antagonism of rapacuronium using edrophonium or neostigmine: pharmacodynamics and pharmacokinetics

We have studied the pharmacodynamics and pharmacokinetics of rapacuronium (Org 9487) in 70 healthy patients. Neuromuscular transmission was monitored using TOF stimulation of the ulnar nerve and mechanomyography of the adductor pollicis muscle. Half of the patients were given a single dose of rapacuronium 1.5 mg kg-1 and the remainder rapacuronium 1.5 mg kg-1 with three incremental doses of 0.5 mg kg-1, each given when T1/T0 had recovered to 25%. In all patients, neuromuscular block was antagonized using neostigmine 0.05 mg kg-1 or edrophonium 1.0 mg kg-1 (allocated randomly), 2 min after the final dose of rapacuronium. All patients developed complete block after rapacuronium 1.5 mg kg-1. Mean onset time was 66 (SD 24) s. In patients who received an antagonist 2 min after the first dose of rapacuronium, time to recovery of T1/T0 to 25% was similar after neostigmine (9.8 (3.8) min) and edrophonium (10.3 (4.3) min): in patients who received incremental doses of rapacuronium, spontaneous recovery of T1/T0 to 25% after the first dose was 18.9 (4.7) min. In those who received an antagonist 2 min after the first dose of rapacuronium, times to recovery of T4/T1 to 0.7 were also similar after neostigmine (23.7 (7.7) min) and edrophonium (29.1 (10.7) min). After three incremental doses of rapacuronium, there was a longer time to recovery of T1/T0 = 25% after neostigmine compared with edrophonium (5.1 (1.0) vs 3.3 (1.3) min; P < 0.05) but more rapid recovery to T1/T0 = 75% (10.1 (2.9) vs 16.8 (10.1) min; P < 0.05) and T4/T1 = 0.7 (19.8 (6.3) vs 35.1 (10.4) min; P < 0.05). A three-compartment pharmacokinetic model was justified. Typical values for clearance and initial volume of distribution (V1) were 4.4 ml kg-1 min-1 and 94.8 ml kg-1, respectively. In females, clearance was decreased by 38.5% compared with males and V1 was decreased by 25% in patients aged more than 65 yr.      

Détermination de la courbe dose-effet du dibésylate d''atracurium chez l''homme adulte anesthésié

The mechanical response of the adductor pollicis to a 0.15 Hz stimulation of the ulnar nerve was studied in 35 unpremedicated adult patients (mean age 38 yr) under general anaesthesia using thiopentone, fentanyl and a N2O/O2 mixture under mechanical ventilation. PaCO2, pH, K, Ca, Mg plasma levels and temperature were in the normal range. Each patient received a single bolus of atracurium dibesylate: 0.10 mg . kg-1 (n = 11), 0.15 mg . kg-1 (n = 10), 0.20 mg . kg-1 (n = 11) or 0.30 mg . kg-1 (n = 4). The dose-response curve was constructed using the log-probit method for 0.10, 0.15, 0.20 mg . kg-1 doses, giving neuromuscular blocks greater than 0% and less than 0.20 mg . kg-1. The 0.20 mg . kg-1 dose had an onset time of 6.1 +/- 0.6 min, duration 0-90% of 34.3 +/- 3.2 min and a recovery index 25-75% of 10.9 +/- 1.0 min. The 0.3 mg . kg-1 dose resulted in onset time of 4.7 +/- 1.3 min, duration of 39.9 +/- 3.7 min and a recovery index of 10.7 +/- 1.8 min. Thus atracurium dibesylate seemed to be an agent of intermediate potency. Onset time was approximately the same as that for other non-depolarizing neuromuscular blocking drugs, but duration of action and recovery index were quite shorter, except for vecuronium bromide.     

Tetanus-induced changes in apparent recovery after bolus doses of atracurium or vecuronium.

The current study evaluated the duration and magnitude of post-tetanic effects in 56 patients recovering from a bolus dose of nondepolarizing relaxant to assess the impact of tetanus on monitoring in a common clinical setting. After induction of general anesthesia (thiopental, fentanyl, oxygen, nitrous oxide, and isoflurane), a baseline response to train-of-four (TOF) stimulation was recorded using an adductor pollicis force transducer, and the ratio of the fourth response (T4) to the first (T1) was calculated. Patients then received a bolus dose of either atracurium 0.50 mg.kg-1 (n = 28) or vecuronium 0.10 mg.kg-1 (n = 28). TOF was recorded at 12-s intervals between 25% and 75% recovery of T1 (time25-75%, first data set); then, block was reestablished with the same agent (atracurium 0.10 or vecuronium 0.02 mg.kg-1), and monitoring of time25-75% was repeated (second data set). Subjects were randomized such that none, one, or both sets had TOF monitoring interrupted by a 5-s, 50-Hz tetanic stimulus at 50% recovery (TET). For each drug, 7 patients were assigned to each of the four possible sequences: no tetanus (NOTET) set followed by NOTET set; NOTET-TET; TET-NOTET; and TET-TET. After either drug, the TET data sets demonstrated significant acceleration of recovery of T1 from 50% to 75% (time50-75%) of its baseline height (P less than 0.05 by paired t test). After atracurium, time50-75% was shortened by the tetanic stimulation from a control of 6.3 +/- 1.1 to 5.0 +/- 1.3 min (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

A single bolus dose of vecuronium for rapid endotracheal intubation]

The changes in EMG evoked by train-of-four (TOF) stimulation of ulnar nerve were recorded to determine proper single bolus dose of vecuronium for endotracheal intubation in surgical patients. Onset and duration of neuromuscular block were judged by percent depression of EMG. Mean time intervals for 90% depression in TOF seen in 0.10 mg.kg-1 vecuronium group (n = 10), 0.15 mg.kg-1 vecuronium group (n = 10) and 0.20 mg.kg-1 vecuronium group (n = 10), were 181.1 sec, 135.0 sec and 120.0 sec, respectively. Similarly, mean time intervals for 100% depression for each vecuronium group were 240.0 sec, 177.5 sec and 160.0 sec, respectively. Onset time intervals in both 0.15 mg.kg-1 and 0.20 mg.kg-1 groups were significantly shorter than that in 0.10 mg.kg-1 group (P less than 0.05). On the other hand, mean time intervals for 25% recovery in EMG were 53.6 min in 0.10 mg.kg-1 group, 63.3 min in 0.15 mg.kg-1 group and 104.3 min in 0.20 mg.kg-1 group. No statistically significant difference was observed in recovery time between 0.10 mg.kg-1 and 0.15 mg.kg-1 group. These results indicate that the appropriate dose of vecuronium for rapid intubation is considered to be 0.15 mg.kg-1. This dose is allowable for surgical procedures of short duration.     

Prediction of the maintenance dose of vecuronium for continuous infusion]

The purpose of this study is to examine how to predict the optimal maintenance dose of vecuronium for continuous infusion, knowing the recovery time from the block induced by the first bolus injection. All patients studied were undergoing surgical procedures and were anesthetized using thiopental, vecuronium, 50% nitrous oxide and 2% enflurane in oxygen. Mechanical twitch responses of adductor pollicis muscle caused by the stimulation of the ulnar nerve supramaximally were monitored. Vecuronium concentrations in the plasma were measured using high performance liquid chromatography. The experiments consisted of two phases. Phase 1.: To demonstrate the relationship between the recovery time (T0-T25) and the maintenance dose. Thirty patients were studied in this phase. A bolus injection was given as the first dose (1.5 mg.kg-1). During the recovery from the first block, recovery time (T1) was measured and the second dose (2 mg) was injected at the T25 (25% control twitch height). After waiting the recovery until the T25, the third dose (2 mg) was injected. The duration (T2) (min) between the second and the third injection was measured. The maintenance dose-recovery time curve was obtained. Y = 52.70.exp (-17.50 X) + 1224.53.exp (-224.27X), X = recovery time (min), Y = maintenance dose (mg.hr-1). Phase 2.: Thirty patients were studied in this phase. Patients received infusions after the bolus injection. The infusion rates were obtained from the maintenance dose-recovery time curve.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vecuronium in dystrophia myotonica (Curschmann-Steinert)

An emergency laparotomy was performed in a 31-year-old female (body wt 48 kg) with known myotonic dystrophy. Premedication with dantrolene (1 mg/kg i.v.) was used to prevent a myotonic response. Muscle relaxation was monitored electromyographically. Following induction with fentanyl (0.3 mg) and thiopental (200 mg), muscle relaxation was achieved with 2 mg vecuronium titrated for about 3 min until the T1-response was reduced to 10%. The recovery time was normal. A repetitive dose of 0.5 mg vecuronium was necessary after 20 min, when the T1 reached 60%. Extubation and the early postoperative period were uneventful. Because of the unknown predisposition of our patient for the development of malignant hyperthermia, anesthesia was performed with trigger-free anesthetics.     

Resistance to vecuronium in burned children

We compared the time-course of action of vecuronium in 16 burned children undergoing excision and autograft surgery with that of ten unburned children. Standardized anaesthesia was induced with thiopentone 4-6 mg kg-1 and fentanyl 1 microgram.kg-1 and maintained with endtidal 1-1.5% isoflurane in N2O/O2. Neuromuscular responses were monitored by acceleromyography (TOF-Guard, Organon Teknika/Biometer) with supramaximal train-of-four (TOF) stimuli delivered every 15s. Vecuronium 0.1 mg kg-1 was administered intravenously. Onset was recorded as the time, in seconds, between the initial bolus of vecuronium and a decline in the first twitch of TOF (T1) to 5% of control. The times for the recovery of T1-25%, 50% and 75% of control, recovery index and the recovery of TOF 25% and 50% were recorded. Onset of action was found slower in burned patients (189 +/- 70 s) than in control (98 +/- 20 s) (P < 0.01). Recovery times of T1(25), T1(50), T1(75), TOF25 and TOF50 were significantly shorter in burned patients indicative of decreased sensitivity to vecuronium (P < 0.01).     

Spontaneous recovery of residual neuromuscular blockade after atracurium or vecuronium during isoflurane anaesthesia

With atracurium and vecuronium, spontaneous recovery of residual neuromuscular blockade monitored electromyographically during 0.5% isoflurane anaesthesia was studied in 60 patients undergoing plastic surgery. After thiopentone, in random order, either atracurium 0.5 mg kg-1 or vecuronium 0.1 mg kg-1 was administered and isoflurane added to N2O and O2 mixture. Following spontaneous recovery of both the single twitch amplitude (T1) to 75% of the control value and the train-of-four ratio (TOF ratio) to 75%, incremental doses of the relaxant were given to maintain the T1 at less than 10%. Before the end of surgery, the blockade was again permitted to recover spontaneously. During the initial spontaneous recovery, the mean recovery time of T1 from 25% to 75% (the recovery index) with atracurium was longer (P less than 0.001) than that with vecuronium (13.2 min and 10.1 min, respectively) but, during the second recovery, the mean recovery index was shorter (P less than 0.05) with atracurium than with vecuronium (16.1 min and 19.8 min, respectively). The recovery time from T1 75% to TOF ratio 75%, indicating the recovery rate of residual neuromuscular blockade, with atracurium was about 15 min after both the initial and the second recoveries. With vecuronium, the respective recovery times were significantly (P less than 0.001) longer (25.6 min and 38.5 min, respectively). It is concluded that with vecuronium there is slower spontaneous recovery of residual neuromuscular blockade than with atracurium.     

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)     

The effects of nicardipine and verapamil on the recovery time of vecuronium-induced neuromuscular blockade]

The present study investigated the effects of intravenous therapeutic dose of either nicardipine or verapamil on the recovery from transient neuromuscular blockade produced by vecuronium in 21 adult patients scheduled for elective surgery. Neuromuscular function was evaluated by single twitch height (T1), an amplitude of activity of the ulnar nerve being evoked by an electrical stimulation (0.2 msec, 0.1 Hz) under N2O/O2 and halothane anesthesia. The patients given vecuronium were randomly assigned to one of 3 groups: a control group who received no Ca entry blocker, nicardipine group and verapamil group. Nicardipine (30 mcg.kg-1) or verapamil (50 mcg.kg-1) was injected when T1 reached to 10% of the control twitch height. The recovery time of vecuronium (the time between 25% and 75% recovery) was not different significantly among the control (9.4 +/- 3.7 min), nicardipine (8.5 +/- 3.1 min) and verapamil (9.8 +/- 4.3 min) groups. We conclude that a therapeutic dose of either nicardipine or verapamil could be safely given intravenously to the patients under vecuronium-induced neuromuscular blockade.     

Neuromuscular blockade following high-dose vecuronium administration

To determine the onset time, duration of action and recovery time of high-dose vecuronium, 70 patients were assigned to receive either 100, 150, 200 or 300 micrograms.kg-1 of vecuronium for muscle relaxation during elective surgery. Neuromuscular blockade was continuously quantitated by recording the EMG response to stimulation of the ulnar nerve. The onset time from the time of vecuronium administration to maximum blockade decreased from 4.6 +/- 1.1 to 2.4 +/- 0.5 min when the vecuronium doses increased from 100 to 300 micrograms.kg-1. Significant differences were observed in the onset time between the 100 micrograms.kg-1 dose and the other dose groups. Endotracheal intubating conditions were excellent in all patients except 3 in the 100 micrograms.kg-1 dose group. The duration of action from the time of injection to 25% recovery increased from 32 +/- 9 to 138 +/- 48 min in a dose dependent manner. The duration of action after increment doses of 40 or 50 micrograms.kg-1 up to 25% recovery of T1 did not vary significantly within the same dose group. With an initial dose of 150 micrograms.kg-1 and subsequent increment doses of 50 micrograms.kg-1 or less, the duration of action remained constant. The recovery time from 25 to 75% recovery was within 11 minutes when antagonists were administered. High-dose vecuronium may, therefore, be a useful alternative to SCC, when a rapid onset is required and to pancuronium, when a rapid recovery from neuromuscular blockade is requested.     

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)     

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.     

Does vecuronium accumulate in the renal transplant patient?

Twenty ASA physical status Class III patients undergoing cadaver renal transplantation were studied. After 90 per cent T1 recovery, as determined by train-of-four measurement, from 1.0 mg.kg-1 succinylcholine to facilitate tracheal intubation, nine patients received atracurium 0.25 mg.kg-1 (Group I) and 11 patients received vecuronium 0.05 mg.kg-1 (Group II) intravenously. The following measurements were made: time to maximum block onset (first dose Max), injection to start of recovery (start REC1), injection to 25 per cent T1 twitch recovery (REC 251), injection to 75 per cent T1 (REC 75(1], injection to 90 per cent T1 (REC 90(1] and time from 25-75 per cent recovery T1 (REC 25-75(1]. Maximum blockade (Max block 1) was also measured. At 90 per cent T1 recovery, if time permitted, an identical dose of the appropriate relaxant was administered. Time from second dose to onset of maximum block (second dose Max) and 90 per cent recovery after second dose (REC 90(2] were then measured. At the conclusion of surgery, neuromuscular blockade was reversed with neostigmine 2.5 mg and glycopyrrolate 0.5 mg. One way ANOVA was performed to determine significance between the groups and a p less than 0.05 was considered significant. A paired t test was also performed between REC 90(1) and REC 90(2) for atracurium and vecuronium respectively. A p less than 0.05 was again considered significant. Measurement of first dose Max, start REC1, REC25(1), REC 75(1), REC 90(1), REC 25-75(1) and Max block 1 revealed no difference between the patients receiving an initial dose of atracurium and those receiving vecuronium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Neuromuscular blocking effects and train-of-four fade with cisatracurium: comparison with other nondepolarising relaxants

Neuromuscular blocking drugs exhibit different degrees of fade in response to train-of-four stimulation believed to represent their relative prejunctional effects. The present study was designed to compare the train-of-four fade after cisatracurium and compare this with other commonly used muscle relaxants. Train-of-four fade during onset and recovery of block were recorded after administration of cisatracurium 0.05 or 0.1 mg.kg-1, atracurium 0.5 mg.kg-1, vecuronium 0.08 mg.kg-1, mivacurium 0.15 mg.kg-1 or rocuronium 0.6 mg.kg-1 to patients anaesthetised with fentanyl, nitrous oxide and a propofol infusion. Neuromuscular monitoring was by stimulation of the ulnar nerve and recording the force of contraction of the adductor pollicis muscle. The onset and recovery of block were also measured. Train-of-four fade during onset of block was greater with the lower dose of cisatracurium compared with the higher dose of cisatracurium and all other relaxants. Train-of-four fade during recovery was similar. The median times (and ranges) for the onset of maximum block were 3.4 (2.1-5.6), 1.5 (1.2-2.3), 2.1 (1.2-2.6), 2.0 (1.5-2.7) and 1.0 (0.7-1.3) min for cisatracurium 0.1 mg.kg-1 and atracurium, mivacurium, vecuronium and rocuronium, respectively. The median times (and ranges) for the recovery of T1 to 25% of control and to a train-of-four ratio of 0.8 were 41 (21-50) and 65 (40-78); 43 (37-54) and 69 (58-79); 15 (11-20) and 25 (19-30); 31 (23-46) and 60 (45-117); and 33 (18-57) and 50 (28-76) min following cisatracurium, 0.1 mg.kg-1, atracurium, mivacurium, vecuronium and recuronium, respectively.     

Post-tetanic count and train-of-four responses during neuromuscular block produced by vecuronium and infusion of nicardipine

We have examined onset and recovery of neuromuscular block produced by vecuronium using either post-tetanic count (PTC), or the first twitch of the train-of-four (TOF) (T1/T0) and TOF ratio (T4/T1) during continuous infusion of nicardipine. Sixty adult patients were allocated to one of four groups of 15 patients each: nicardipine-PTC, nicardipine- TOF, control-PTC and control-TOF. In the nicardipine-PTC and nicardipine-TOF groups, nicardipine 0.03 mg kg-1 was given before vecuronium 0.1 mg kg-1 and a continuous infusion of nicardipine was started immediately at a rate of 2 micrograms kg-1 min-1. Mean time from administration of vecuronium to onset of neuromuscular block in the nicardipine-PTC and nicardipine-TOF groups was significantly shorter than in the control-PTC and control-TOF groups (166 (SD 39) vs 220 (28) s; P < 0.05). There was no significant difference in recovery of PTC between the nicardipine-PTC and control-PTC groups or in recovery of TOF ratio in the nicardipine-TOF and control-TOF groups. However, during recovery, T1/T0 in the nicardipine-TOF group was significantly less than that in the control-TOF group, 60-100 min after administration of vecuronium.