Following administration of 0.6 mg kg−1 rocuronium, the pharmacokinetics and the pharmacodynamics were studied in six obese and six control (normal weight) patients receiving balanced anaesthesia. Twelve gynaecological patients were allocated into two groups, according to body mass index (normal weight: body mass index: 20–24, obese weight: body mass index > 28). Venous plasma concentrations were determined by high-pressure liquid chromatography before administration of rocuronium, at 1, 2, 4, 6, 8,10, 15, 20, 25, 30, 35, 40, 48, 60, 75, 120, 180, 240, 300, 360 and 420 min after administration of rocuronium and at recovery of single twitch to 25% and 75% of control twitch height. Onset time was shorter (NS) in the obese compared with normal weight (obese weight: 65 ± 16, normal weight: 100 ± 39 s, mean±SD). Duration 25% (obese weight: 29.5 ± 5.3, normal weight: 28.4±5.3 min) and spontaneous recovery time (obese weight: 12.6 ± 2.7, normal weight: 12.5 ± 2.3 min) did not show any differences between the two groups. The pharmacokinetics of rocuronium were comparable in the two groups. The volume of distribution at steady state Vss (mL kg−1) was 208 ± 56 in normal weight and 169 ± 37 in obese weight. Distribution (T1/2α) and elimination half-life (T1/2β) as well as mean residence time were 15.6 ± 3.7, 70.3 ± 23.9 and 53.2 ± 9.8 min in normal weight and 16.9 ± 3.8, 75.5 ± 25.5 and 51.1 ± 18.9 min in obese weight,respectively. Also, no differences were observed in plasma clearance (3.89 ± 0.58 in normal weight and 3.62 ± 1.42 mL kg−1 min−1 obese weight). This study indicates that the pharmoacodynamics and pharmacokinetics of rocuronium are in female patients not altered by obesity.

A case of recurarization in the recovery room is reported. Accumulation of atracurium in the intravenous line led to recurarization after flushing the line in the recovery room. A respiratory arrest with severe desaturation and bradycardia occurred. Circumstances leading to this event and the mechanisms enabling a neuromuscular blockade to occur, following the administration of a small dose of relaxant, are discussed.

In order to compare the neuromuscular effects following rocuronium 0.6 mg kg−1 and atracurium 0.5 mg kg−1 30 children aged from 18 to 67 months were studied under the same anaesthetic conditions. After induction of anaesthesia with etomidate and fentanyl, neuromuscular blockade was monitored by recording the electromyographic response of the adductor pollicis muscle to a supramaximal train-of-four (TOF) stimulation of the ulnar nerve at 2 Hz for 2 s at 20-s intervals. Intubation was performed when more than 90% muscle relaxation was achieved, thereafter anaesthesia was maintained with 70% nitrous oxide in oxygen and isoflurane 0.5% end-tidal. Mean onset of action was significantly faster following rocuronium (86±44.9 s) (mean±SD) compared with atracurium (126.3±61.0 s). Clinical duration with rocuronium was 22.8±5.31 min and thus significantly shorter than that of atracurium, which was 31.5±6.01 min. A statistically significant difference between rocuronium and atracurium also had been found for recovery of T1 to 50%, 75% and 90% as well as for the time taken to a TOF ratio of 70%. The recovery index for rocuronium and atracurium was not significantly different with 9.2±3.43 min and 10.9±2.65 min, respectively. Thus, rocuronium may be more advantageous than atracurium for short-lasting surgical procedures in young children.

The influence of acute moderate haemodilution on the relation between dose and response for rocuronium was evaluated in 60 adult patients, ASA grade I, undergoing elective plastic surgery. The patients were randomly allocated to either the control or the haemodilution group. Following the induction of general anaesthesia, the status of acute moderate haemodilution in the haemodilution group was achieved by draining venous blood, and intravenous infusion of lactated Ringer's solution, 6% dextran or gelofusine, during which the levels of haemoatocrit and haemoglobin dropped from 44% to 27.5% and from 148.3 to 91.3 g L−1, respectively. Neuromuscular function was assessed mechanomyographically with train-of-four stimulation at the wrist every 12 s and the percentage depression of T1 response was used as the study parameter. The relation between dose and response for rocuronium in the two groups was determined by the cumulative dose–response technique. The results showed that the dose–response curve for rocuronium during acute moderate haemodilution was shifted in a parallel fashion to the left and the potency of rocuronium was increased. There were significant differences in ED50, ED90 and ED95 between the two groups. The ED50, ED90 and ED95 of rocuronium in the haemodilution group was decreased by 28.2%, 35.4% and 38.8%, respectively, compared with the control group.

The dose-response and concentration-response relation of rocuronium infusion was studied in 20 adult surgical patients during propofol-nitrous oxide and isoflurane (1 MAC) -nitrous oxide anaesthesia. Neuromuscular block was kept constant, initially at 90% and then at 50% with a closed-loop feedback controller. At 90% block the steady-state infusion of rocuronium was 0.55 ± 0.16 mg kg−1 h−1 and the corresponding concentration 1714 ± 281 ng mL−1 in patients receiving propofol. At 50% block the corresponding infusion rate was 0.27 ± 0.11 mg kg−1 h−1 and the concentration 1077 ± 244 ng mL−1, respectively. At 50% block isoflurane reduced the rate of infusion by 52% (P < 0.005) and the concentration by 59% (P < 0.001); at 90% block both the mean infusion rate and the concentration of rocuronium were reduced by 35% (P <0.005). The mean rocuronium clearance at 50% block was unaffected by the type of anaesthesia; it was 4.1 ± 1.6 and 4.9 ± 2.7 mL kg−1 min−1 in the groups receiving propofol and isoflurane anaesthesia, respectively. We conclude that isoflurane reduces the infusion requirements of rocuronium by changing the pharmacodynamic behaviour.

The facial nerve is monitored intra-operatively using electromyography to identify and prevent damage during the excision of an acoustic neurinoma. In order to determine whether a profound level of peripheral neuromuscular blockade could be achieved without compromising facial electromyographic monitoring, 11 patients undergoing resection of acoustic neuroinoma were studied. After induction of anaesthesia, an infusion of atracurium was administered to reduce the integrated electrically evoked muscle potential (EEMP) of the hypothenar eminence by 70–100%. The facial nerve was directly stimulated in the surgical field and the facial evoked muscle potentials (EMPs) were recorded. Even under complete peripheral neuromuscular blockade (i.e. no electrically evoked muscle potential measurable over the hypothenar eminence, no palpable hypothenar muscle response) it was possible to evoke facial muscle electromyographic responses by stimulation of the facial nerve.

Pipecuronium bromide, a long acting non-depolarizing neuromuscular blocking agent was administered to four groups of 10 patients using the priming technique.The effects of the combination of two different priming doses (0.01 or 0.015 mg kg−1) given at two different time intervals (3 or 4 min) before the ‘main’ intubating dose (0.07 or 0.065 mg kg−1) were investigated. Onset times were recorded and the intubation conditions were scored and compared with a group of patients receiving the same total amount of pipecuronium(0.08 mg kg−1) in a single bolus injection. Intubating conditions at 90 s after administration of the intubating dose were found to be significantly improved in all primed groups but the onset times, evaluated using the response of the adductor pollicis muscle to a single twitch stimulation, were similar to that observed after the single bolus injection. The optimal priming combination is considered to be 0.01 mg kg−1 of pipecuronium followed 3 to 4 min later by 0.07 mg kg−1.

A 21-year-old female weighing 55 kg was anaesthetized for facial reconstruction. After an initial bolus of pancuronium 5 mg and top-up doses of 2 mg at 135 min and 1 mg at 290 min and 335 min, no further relaxant was given for 130 min at which time neuromuscular transmission appeared fully recovered with a full train-of-four twitches and a sustained response to 50 Hz stimulation of the posterior tibial nerve. Subsequently, a single dose of mivacurium 8 mg(2 X ED95) produced extended paralysis with no response to train-of-four stimulation for 85 min. The prolonged effect of mivacurium may have been because of inhibition of plasma cholinesterase by pancuronium. The serum cholinesterase activity 12 h after surgery was 0.38 units mL−1 (normal range 0.65–1.0 units mL−1). There was no evidence of atypical choylinesterase.

A survey was conducted among British, French and German anaesthetists to evaluate possible national differences in the peri-operative use of muscle relaxants and their reversal agents. The same non-depolarizing relaxants are used in all three countries, with the exception of d-tubocurarine, which is only available in Great Britain, and alcuronium which is mainly used in Germany. The French anaesthetists seem to use significantly less succinylcholine than their peers in Great Britain or Germany for both elective and emergency intubation. Monitoring of neuromuscular blockade still relies mainly on ‘clinical judgement’. Reversal of non-depolarizing muscle relaxants is performed routinely in Great Britain, while a substantial number of French anaesthetists avoid the use of a reversal. Dose regimes for neostigmine vary largely, with German anaesthetists administering the lowest, and British anaesthetists administering the highest doses. Side effects of reversal agents are reported by colleagues from all three countries in too high a percentage to justify uncritical administration of these drugs. In Germany there seems to be a noteworthy lack of recovery facilities.

The effect of the duration of stabilization of control responses on the onset and duration of clinical relaxation of suxamethonium 1 mg kg−1 and rocuronium 0.6 mg kg−1 were investigated in 90 patients. The control responses were allowed to stabilize for 1, 5, 10, 15 or 20 min prior to administration of rocuronium and for 1, 5, 10 or 15 min prior to suxamethonium. The mean onset time for rocuronium decreased from 150 to 46 s as the duration of stabilization increased from 1 to 20 min (P < 0.001) although the maximal effect was observed within the first 5 min. The average duration of clinical relaxation also increased from 25 to 40 min (P < 0.001). No effect was observed for either variable in the case of suxamethonium.

The most suitable time for tracheal intubation, following vecuronium 0.1 mg kg−1, was estimated in 120 patients. The trachea was intubated at cessation of the visually observed response of the orbicularis oculi muscle to facial nerve stimulation (group 1; n = 30), or of the manually detected response of the adductor pollicis to ulnar nerve stimulation (group 2; n = 30), or after waiting 3 min (group 3; n = 30), or 4 min (group 4; n = 30). There were no significant differences in intubation scores between the four groups of patients. Loss of response to train-of-four stimulation occurred significantly sooner in group 1 (orbicularis oculi) than in group 2 (adductor pollicis) P = 0.021). However, intubating conditions were poor in four patients (14%) in group 1, compared with none in group 2 and one in groups 3 and 4, respectively. Thus, contrary to expectations, the cessation of the response of the orbicularis oculi muscle did not guarantee good or even satisfactory intubating conditions. The results suggest that in fit adult patients it is as good to wait 3 min after injection of vecuronium 0.1 mg kg−1 before tracheal intubation, as to use a nerve stimulator.