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.     

Neuromuscular and cardiovascular effects of mivacurium chloride in surgical patients receiving nitrous oxide-narcotic or nitrous oxide-isoflurane anaesthesia

The neuromuscular and cardiovascular effects of mivacurium chloride were studied during nitrous oxide-oxygen narcotic (fentanyl) (n = 90) and nitrous oxide-oxygen isoflurane (ISO) anaesthesia (n = 45). In addition, a separate group (n = 9) received succinylcholine during fentanyl anaesthesia to compare its neuromuscular effects with mivacurium. Mivacurium was initially administered as a single bolus in doses from 0.03 mg.kg-1 to 0.25 mg.kg-1 to study the dose-response relationships, as well as the cardiovascular effects of mivacurium. Neuromuscular block (NMB) was measured by recording the twitch response of the adductor pollicis muscle following ulnar nerve stimulation (0.15 Hz, 0.2 ms supramaximal voltage). The ED95 values for mivacurium were estimated to be 0.073 mg.kg-1 and 0.053 mg.kg-1 in the fentanyl and ISO groups respectively. The duration of block (time from injection to 95 per cent recovery) for a dose of 0.05 mg.kg-1 mivacurium was 15.3 +/- 1.0 min and 21.5 +/- 1.3 min for fentanyl and ISO anaesthesia, respectively. The recovery index (25-75 per cent) between initial bolus dose (6.1 +/- 0.5 min), repeat bolus doses (7.6 +/- 0.6 min), mivacurium infusion (6.7 +/- 0.7 min) and succinylcholine infusion (6.8 +/- 1.8 min) were not significantly different. There was minimal change in mean arterial pressure (MAP) or heart rate (HR) following bolus doses of mivacurium up to 0.15 mg.kg-1. Bolus administration of 0.20 mg.kg-1 or 0.25 mg.kg-1 of mivacurium decreased MAP from 78.2 +/- 2.5 to 64.0 +/- 3.2 mmHg (range 12-59 per cent of control) (P less than 0.05). The same doses when administered slowly over 30 sec produced minimal change in MAP or HR.     

Effects of propofol and isoflurane on the neuromuscular block induced by atracurium]

Speed of onset, duration of action and recovery time for a bolus injection of atracurium were measured in two groups of patients. In group I anaesthesia considered of propofol, fentanyl, nitrous oxide and oxygen mixture. The induction dose of propofol was 2 mg/kg-1 followed by an infusion of 9.0 mg/kg-1/h-1 for first half hour and 4.5 mg/Kg-1/h-1 subsequently. In group II anaesthesia consisted of isoflurane, fentanyl, nitrous oxide and oxygen mixture. Isoflurane was given upon clinical needs. Speed of onset, duration of action, and recovery time for atracurium were measured in the two groups. No statistically significant differences between speed of onset and duration of action between the two groups were found. The recovery period from T1 = 10% to T1 = 70% twitch response was considerably longer with isoflurane (25 min +/- 6) than with propofol (18 min +/- 3) (p less than 0.01). Results obtained suggest that for adequate relaxation during tracheal intubation smaller doses of atracurium are not needed during isoflurane than propofol administration. Because of the longer recovery period of residual neuromuscular blockade during isoflurane anaesthesia decreasing doses of atracurium and careful monitoring of twitch depression tension are also suggested.     

Accelerated onset of non-depolarizing neuromuscular blocking drugs: pancuronium, atracurium and vecuronium. A comparison with succinylcholine

The time of onset and degree of neuromuscular blockade (NMB) in 80 anaesthetized patients, following either a single bolus injection of pancuronium 0.95 mg kg-1, atracurium 0.53 mg kg-1 or vecuronium 0.07 mg kg-1, or divided doses of pancuronium 0.15 mg kg-1, atracurium 0.07 mg kg-1 or vecuronium 0.01 mg kg-1 administered 3 min or 5 min before the second dose of pancuronium 0.08 mg kg-1, atracurium 0.46 mg kg-1 or vecuronium 0.06 mg kg-1, were determined and compared to the same parameters measured following succinylcholine administration (1 mg kg-1). The time to maximum NMB (100%) following the administration of succinylcholine was 58.1 +/- 5.3 s, whereas the time to maximum NMB (100%) following a single bolus injection of either pancuronium, atracurium or vecuronium was 130.6 +/- 22.2, 93.0 +/- 6.4, 127.5 +/- 13.0 s, respectively. These values for time to maximum NMB are significantly longer than the time required for succinylcholine to achieve maximal blockade. The time to attain maximum NMB following divided doses of pancuronium, atracurium or vecuronium separated by 3 min decreased significantly to 77.9 +/- 4.3, 77.5 +/- 7.6, 89.0 +/- 8.6 s, respectively. However, when the two doses of drug were separated by 5 min, only small, non-significant further decreases occurred in the time required to achieve maximum blockade. Although the time to maximum NMB following divided doses of pancuronium, atracurium or vecuronium is significantly longer than that for succinylcholine, divided dosing significantly decreases the time required to reach maximal NMB.     

Curarization of the myasthenia patient by atracurium

The use of atracurium, a new intermediate duration of action non depolarizing muscle relaxant, is described in a myasthenic patient undergoing abdominal surgery. The effective dose to 95% twitch suppression is 0.15 mg.kg-1. Following the first dose, the time from maximum twitch depression to 25% recovery is 32 min, and 33 min following the second dose. The recovery index (25-75% recovery time) and the 5-90% recovery time are respectively 33 and 83 min. The train-of-four ratio is greater than 0.7 within 90 min after the reinjection. The significance of the behaviour of atracurium is discussed. In reduced dosage and with careful neuromuscular monitoring, atracurium appears to be a reasonable and safe choice of myasthenic patients to provide surgical relaxation.     

Maintenance of surgical muscle relaxation by repeat doses of vecuronium and atracurium at three different dose levels.

The time-course of the neuromuscular effects of vecuronium (n = 25) and atracurium (n = 25) has been compared at three different levels of maintenance dose in anaesthetized patients. Following intubation with vecuronium 0.1 mg kg-1 or atracurium 0.5 mg kg-1, surgical muscle relaxation was maintained by using increments of equipotent maintenance doses equivalent to 0.5, 1.0 and 1.5 x ED95 for each drug. Repeat doses were administered each time the twitch height, depressed by the previous dose, returned to 25% of its control value. The apparent increase in the duration of action, i.e. the difference between the duration of the last and the first maintenance dose, did not reach statistical significance and approximated 3 +/- 2, 6 +/- 4, 11 +/- 5 and 3 +/- 2, 8 +/- 13, 5 +/- 7 min following the low, medium and high maintenance doses of vecuronium and atracurium, respectively.     

Experimental pharmacology of atracurium dibesylate

Atracurium dibesylate is a new non depolarizing muscle relaxant, metabolized by a non enzymic pathway, the Hofmann elimination. The potency of atracurium in animals was similar to d-tubocurarine and six times less than that of pancuronium. In the cat, the ED50 was 130 micrograms . kg-1; an intravenous dose of 250 micrograms . kg-1 atracurium was sufficient to cause complete neuromuscular block; its duration was 29 min. Single twitch block was readily antagonized by neostigmine 50-100 micrograms . kg-1 or edrophonium 200 micrograms . kg-1. Halothane potentiated the block given by atracurium. Dose ratio for 50% vagal block (ED50) and 50% neuromuscular block was 24; atracurium had weak ganglioplegic effects. 2,000 micrograms . kg-1 atracurium (eight times the neuromuscular blocking dose) reduced mean aortic pressure, heart rate, cardiac output and peripheral resistance. Such effects could be prevented by giving histamine receptor blockers prior to injecting atracurium.     

L''atracurium chez le sujet âgé

The effects of age on the pharmacodynamics of atracurium have been studied in twenty-four consenting adult patients undergoing elective surgery. They were divided in three groups according to their age (mean +/- SEM): group 1 (n = 8; 26 +/- 3 yr), group 2 (n = 8; 53 +/- 2 yr) and group 3 (n = 8; 76 +/- 2 yr). Anaesthesia was induced with methohexitone (1 mg . kg-1) and fentanyl (5 micrograms . kg-1), and maintained with 66% N2O plus fentanyl on demand. Ventilation was controlled and adjusted to produce normocapnia. The isometric contraction of the adductor pollicis muscle in response to supramaximal cubital nerve stimulation delivered at 0.1 Hz was measured with a force displacement transducer. A loading dose of atracurium (0.3 mg . kg-1) was given before tracheal intubation. Thereafter, twitch height (TH) was maintained at 10% of its baseline reading by adjusting the flow of a Harvard syringe containing 0.5 mg . ml-1 of atracurium in saline. The amount of atracurium required to maintain a stable twitch height, calculated for a 60 min period, was 14.7 +/- 1 mg . m-2 . h-1 for group 1, 13.6 +/- 1.5 mg . m-2 . BSA-1 for group 2 and 15 +/- 2.1 mg . m-2 . BSA-1 for group 3. At the end of the infusion period, the TH25-75 recovery rates were not statistically different in the three groups: 15.4 +/- 1.9 min for group 1, 14.8 +/- 1.1 min for group 2 and 14.5 +/- 1.6 min for group 3.(ABSTRACT TRUNCATED AT 250 WORDS)     

Assessment of the postoperative residual curarisation using the train of four stimulation with acceleromyography.

The aim of this study was to measure the incidence of patients with train of four ratio < 0.9 in the immediate postoperative period using acceleromyography. At arrival in recovery room, 257 patients were enrolled. Train of four ratio was assessed at the adductor pollicis using TOF-GUARD INMT apparatus. Patients were divided in two groups according to TOF ratio < (group 1) or > (group 2) to 0.9. Demographic variables, dose (mg), dose/weight ratio (mg.kg-1) of atracurium and surgery duration (min) were registered. There was no difference in demographic variables, duration of surgery (100.90 +/- 67.38/94.83 +/- 62.42 min), number of incidence reversal of neuromuscular block. Patients in group 1 (n = 72) received a higher dose (54.58 +/- 38.03/41.43 +/- 19.47 mg) of atracurium compared to group 2 (n = 176). Thirty percent of patients presented a train of four ratio < 0.7 and 13% < 0.9. TOF-GUARD INMT was easy to use.     

Atracurium: neuromuscular blockade in repeated administration

The neuromuscular blocking action of repeated injections of atracurium and vecuronium was studied in 74 surgical patients during balanced anaesthesia (methohexitone or etomidate, intubation after suxamethonium, fentanyl, droperidol, N2O). The initial bolus dose (ID) of atracurium was 0.25 mg/kg and of vecuronium 0.05 mg/kg followed by repeated increments (RD) of atracurium 0.1 mg/kg and vecuronium 0.0125 mg/kg when neuromuscular function (EMG) had recovered to about 30% of pre-relaxant control. Dose-response relationships revealed atracurium to be about 1/5 as potent as vecuronium; the ED50 of atracurium was 0.13 +/- 0.03 mg/kg and of vecuronium 0.023 +/- 0.007 mg/kg. The ID of both relaxants produced a neuromuscular blockade of about 90% within 4 min. The duration from the time of injection to 30% recovery was slightly longer in atracurium 26 +/- 9 min. In all patients the RD produced within 3.5 min satisfactory muscle relaxation with a neuromuscular block of about 85%. The mean duration of atracurium (18 min) was 5-10 min longer than of vecuronium (12 min). To maintain good surgical relaxation (more than 70% blockade) atracurium 0.32 mg/kg X h and vecuronium 0.056 mg/kg X h were required. No cumulation could be measured after repeated injections. The recovery time of atracurium and vecuronium at the end of anaesthesia was 10-12 min. Neither cardiovascular side-effects nor signs of histamine release were observed after both relaxants in our particular dose range. It is concluded, that atracurium is a favourable blocker for anaesthetic practice: The time of onset is approximately the same compared with vecuronium. The duration of action, however, is slightly longer but still truly intermediate long.(ABSTRACT TRUNCATED AT 250 WORDS)     

Can nicardipine potentiate vecuronium induced neuromuscular blockade?]

The effects of intravenous nicardipine on the neuromuscular blockade produced by single bolus injection of vecuronium were studied in surgical patients undergoing tracheal intubation. We measured the mechanical response of the abductor pollicis muscle to stimulation of the ulnar nerve in a train-of-four sequence at 2 Hz and recorded the amplitudes of the first response (T1). Anesthesia was induced with thiopental 5 mg.kg-1 with or without nicardipine 10 micrograms.kg-1 followed by injection of vecuronium in a dose of either 0.1 or 0.15 mg.kg-1. Onset and duration of neuromuscular blockade were judged by percent depression of T1. The time intervals for 90% and 100% depression in T1 seen in patients who had received vecuronium 0.1 mg.kg-1 with nicardipine (n = 10) were 157.0 +/- 30.8 sec and 192.3 +/- 31.2 sec (mean +/- SD), respectively. These values were significantly shorter than those observed in patients without nicardipine administration (n = 10, P less than 0.05), and were not significantly different from the values in patients who had received vecuronium 0.15 mg.kg-1 (n = 10). On the other hand, the time for 25% recovery in T1 was uninfluenced by nicardipine. Present study indicates that nicardipine pretreatment possibly shortens the onset time after minor or moderate dose of vecuronium.     

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)     

Evolution du bloc neuromusculaire sous atracurium. Comparaison avec l''alcuronium

Using a standardized anaesthetic protocol, the continuous monitoring of the twitch height after a 0.1 Hz stimulus was used to follow the evolution of curarization following injection of either atracurium (0.6 mg . kg-1) or alcuronium (0.2 mg . kg-1). The maximum twitch height inhibition was always greater than 99% of the control value and occurred after 107 +/- 50 s with atracurium (n = 30) and 172 +/- 120 s for alcuronium (n = 30) (p less than 0.02). Although surgical stage of muscular relaxation (twitch height less than 25% of reference value) was the same for both drugs (55 +/- 15 min for alcuronium versus 52 +/- 10 min for atracurium; n = 30 for both groups), the clinical duration (spontaneous restoration of twitch height to 90% of the reference value) was significantly longer (p less than 0.005) for alcuronium: 89 +/- 20 min (n = 10) versus 62 +/- 9 min for atracurium (n = 10). The spontaneous return to normal of the train of four was also significantly longer (p less than 0.001) for alcuronium: 118 +/- 23 min (n = 10) versus 69 +/- 7 min for atracurium (n = 10). The recovery index (the time required for twitch height to rise from 25% to 75%) was three times quicker (p less than 0.01) for atracurium (10 +/- 3 min; n = 10) than for alcuronium (30 +/- 13 min; n = 10).(ABSTRACT TRUNCATED AT 250 WORDS)     

七氟烷对罗库溴铵、维库溴铵及阿曲库铵临床药效的影响

目的 以丙泊酚为对照,观察1.3 MAC的七氟烷对罗库溴铵、维库溴铵及阿曲库铵临床药效的影响.方法 选择60例择期腹部手术的病人随机分为6组,每组10人.七氟烷罗库溴铵组(sR组)、七氟烷维库溴铵组(SV组)及七氟烷阿曲库铵组(SA组)分别吸入1.3 MAC的七氟烷及静注芬太尼维持麻醉,丙泊酚罗库溴铵组(CR组)、丙泊酚维库溴铵组(CV组)及丙泊酚阿曲库铵组(CA组)以丙泊酚6 mg·kg-1·h-1～8 mg·kg～·h-1及芬太尼维持麻醉.监测起效时间、最大抑制程度、作用时间、维持速率、恢复时间、恢复指数.结果 七氟烷组与相应的对照组在最大抑制程度、恢复指数方面的无统计学差异,起效时间、作用时间、维持速率、恢复时间有统计学差异.结论 七氟烷能明显延长罗库溴铵、维库溴铵以及阿曲库铵的作用时间和恢复时间并减少其起效时间、维持剂量,但对最大抑制程度和恢复指数则无明显影响.     

Clinical study of interaction between rocuronium and some commonly used antimicrobial agents

The onset and duration of clinical relaxation and reversibility of rocuronium bromide (ORG 9426) 0.6 mg kg-1 were studied following administration of netilmicin 2 mg kg-1 (n = 10) or cefuroxime 20 mg kg-1 (n = 10) in patients undergoing urological surgery; and cefuroxime 20 mg kg-1 (n = 10) metronidazole 7.5 mg kg-1 (n = 10), metronidazole 7.5 mg kg-1 and cefuroxime 20 mg kg-1 (n = 10), or placebo (n = 10) in patients undergoing abdominal surgery under anaesthesia with thiopentone, nitrous oxide in oxygen, fentanyl and halothane. The antimicrobial agents were administered intravenously 5 min before rocuronium. Neuromuscular function was monitored using mechanomyography and train-of-four (TOF) mode of stimulation. Onset of neuromuscular block occurred in approximately 60 s with all patients achieving complete block. The mean clinical duration (+/- SD) was 50 +/- 10.7 and 44 +/- 6.7 min following netilmicin and cefuroxime respectively in patients undergoing urological surgery; and 49 +/- 13.7, 44 +/- 11.1, 48 +/- 11.1 and 38 +/- 7.3 min in the groups undergoing abdominal surgery receiving cefuroxime, metronidazole, cefuroxime and metronidazole combination and placebo respectively. There were no statistically significant differences between the groups in either the onset or the duration of clinical relaxation. Reversal of neuromuscular block with neostigmine carried out at spontaneous recovery of T1 (first response in the TOF) of 25% or more was easily achieved in all groups in 2-4 min. It is concluded that there is no significant interaction between rocuronium and single doses of the antimicrobial agents used in the present study.     

Atracurium for short surgical procedures: a comparison with succinylcholine

A comparison was made between atracurium and succinylcholine in 40 patients undergoing short gynaecological procedures of 30 minutes or less. Good intubating conditions were produced in 76.7 +/- 39.3 seconds (mean +/- S.D.) with succinylcholine 1 mg . kg-1 and 198 +/- 84 seconds with atracurium 400 micrograms . kg-1. Muscle relaxation was maintained with the initial dose of atracurium or with repeated boluses of succinylcholine. The mean time of surgery was 17.65 +/- 5.3 minutes in the atracurium group and 15.2 +/- 4.6 minutes in the succinylcholine group. Residual neuromuscular block with atracurium was reversed with neostigmine 0.036 mg . kg-1 and atropine 0.018 mg . kg-1. Recovery of neuromuscular function following reversal, assessed by return of all responses to train-of-four stimulation occurred in 5.05 +/- 4.6 minutes in the atracurium group but half the above doses of neostigmine and atropine were repeated in three patients. We conclude that a single dose of atracurium 400 micrograms . kg-1 is suitable for intubation and maintainance of muscle relaxation for short surgical procedures. However, the onset of action is slow, compared to succinylcholine. Residual neuromuscular block can be antagonised with standard doses of neostigmine, less than 20 minutes after the initial dose of relaxant. Atracurium appears to be a suitable alternative for short procedures where succinylcholine is unsuitable or contraindicated.     

Pharmacodynamics and safety of mivacurium in infants and children under halothane-nitrous oxide anesthesia

OBJECTIVES: To determine pharmacodynamic effects and safety of mivacurium in paediatric patients. STUDY DESIGN: Multicentric, prospective, open, non-randomized study. PATIENTS: Forty-eight three-month-old to eight-year-old physical class ASA I or II children. METHOD: Anaesthesia was induced and maintained with halothane and nitrous oxide. Tracheal intubation was performed without a neuromuscular blocking agent. Neuromuscular blockade was measured with a strain force transducer after train-of-four stimulation of the ulnar nerve at the wrist every ten seconds. A single bolus dose of mivacurium (0.2 mg.kg-1) was injected during 15 seconds in patients allocated into three groups. Group 1: three to 12-month-old infants (n = 15), group 2: one- to three-year-old children (n = 16) and group 3: three- to eight-year-old children (n = 17). Onset and recovery parameters were measured in each patient. Heart rate and noninvasive arterial blood pressure were recorded every minute for five minutes after mivacurium injection. RESULTS: Following halothane administration for 29 and 32 min, and a FEThalothane = 1 vol%, mivacurium (0.2 mg.kg-1) determined a 100% neuromusmcular blockade in all patients. The onset time was 71 +/- 34 s (mean +/- SD) in all patients and did not differ between groups. Time to 25% and 95% recovery of the first twitch and recovery index for all the patients were 12 +/- 3 min, 19 +/- 5 min and 4 +/- 2 min respectively and did not differ between groups. No prolonged paralysis was observed. No significant changes of HR and BP occurred. CONCLUSIONS: Following 0.2 mg.kg-1 of mivacurium in patients aged between three months to eight years, a complete blockade occurs with a rapid onset time and a short duration of action, without significant cardiovascular effect.     

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).     

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.     

Onset and duration of action of vecuronium in the elderly: comparison with adults

The onset and duration of action of vecuronium were studied in young adult (n = 30; mean age 34 +/- 11.1 (s.d.) yr), middle-aged (n = 20; mean age 60 +/- 5.8 yr) and elderly patients (n = 30; mean age 80 +/- 4.6 yr) anaesthetised with thiopentone, nitrous oxide in oxygen and halothane. Neuromuscular block was monitored by applying the train-of-four (TOF) stimulation at 2 Hz to the ulnar nerve every 12 s. Half the patients in each group received 0.08 and the other half 0.12 mg kg-1 of the relaxant. The time to return of T1 (first response in the TOF sequence) to 25% of control was 28 +/- 5.2 (s.d.), 34 +/- 7.1 and 39 +/- 10.2 min following 0.08 mg kg-1 dose (P less than 0.05 between the elderly and young adults) and 45 +/- 9.2, 48 +/- 6.2 and 69 +/- 19.2 min following 0.12 mg kg-1 dose, respectively, in the three age groups (P less than 0.05 between the elderly and the other two groups). The recovery indices (time for 25-75% recovery of T1) after the 0.08 mg kg-1 was 9.6 +/- 3.4, 13.6 +/- 5.1 and 17.4 +/- 6.1 min, respectively (P less than 0.05 between the elderly and young adults). There was no significant difference in any of the parameters between the young adults and the middle-aged. The onset of block at each dose was not significantly different between the three age groups; however, the time to maximum effect was significantly shorter with the higher dose in the young and the middle-aged, but not in the elderly. Regression analysis of the data between age and the duration of action and recovery index suggested a significant prolongation (P less than 0.05) of these parameters in the elderly.