The intubating conditions and neuromuscular blocking profile following 600 micrograms.kg-1 rocuronium (Org 9426) have been investigated in patients under various experimental conditions. They were compared with conditions following 1.5 mg.kg-1 suxamethonium, preceded by a precurarising dose (10 mg) of gallamine, and with those in a control group in the absence of a muscle relaxant. Rocuronium produced good to excellent intubating conditions at 60 as well as at 90 s after administration, even though there was only a partial blockade of the adductor pollicis muscle. Intubating conditions following suxamethonium were comparable with those after rocuronium. Half of the control patients could be intubated. The clinical duration and the recovery time of 600 micrograms.kg-1 of rocuronium were 24(4) and 9(3) min (mean(s.d.)), respectively. Rocuronium may have a major advantage over existing non-depolarising muscle relaxants due to the early presence of excellent intubating conditions. The results indicate that rocuronium may replace suxamethonium in procedures in which rapid sequence induction is required.

The Relaxometer is a computer-controlled system developed for reliable clinical experimental measurements on neuromuscular block. This system is based on an adapted personal computer (Atari 1040 ST) with a monochrome monitor (Atari SM 124), and a microcomputer-driven slave unit (stimulator). There are several stimulation patterns available: single twitch at 0.1 and 1 Hz, single train-of-four, continuous train-of-four every 12 seconds, and tetanic stimulation at 50 Hz for 5 seconds followed by posttetanic count. The system is equipped with a temperature module for continuous monitoring of the skin/muscle temperature and a rechargeable battery to allow uninterrupted measurements if the apparatus is disconnected from the line power. All acquired data, computer-calculated parameters (onset time, duration time, recovery index, train-of-four ratio, tetanic fade, and posttetanic count), and the mechanomyogram are presented on screen continuously, are stored on floppy disk, and can be printed in a well-organized format.

The pharmacokinetics of atracurium, laudanosine and the quaternary alcohol were studied in patients with normal and impaired renal function following intravenous administration of atracurium. Anaesthesia consisted of thiopental, fentanyl, halothane and nitrous oxide in oxygen. Plasma and urine concentrations of the parent compound and its degradation products were measured by high performance liquid chromatography. Renal failure was defined as a creatinine clearance of less than 5 ml/min; it caused no significant differences in the pharmacokinetics of atracurium but did result in a different pharmacokinetic profile of laudanosine, with a 3-fold increase in the mean ( +/- SD) terminal half-life (176 +/- 84 and 516 +/- 262 minutes for patients with normal and impaired renal function, respectively). Moreover, the half-life of the quaternary alcohol increased from 27.1 +/- 8.3 minutes in patients with normal renal function to 42.5 +/- 8.3 minutes in those with impaired renal function (mean +/- SD). Renal elimination of unchanged atracurium accounted for 11% of the administered dose and at least 27% of the total degradation of atracurium occurred via ester hydrolysis. The neuromuscular function was monitored by measuring the twitch tension of the adductor pollicis muscle elicited by stimulation of the ulnar nerve at 0.1 Hz. The total duration of neuromuscular blockade (51.8 +/- 11.5 minutes) and the recovery index (9.6 +/- 2.0 minutes) are shortened in patients with impaired renal function, compared with those with normal renal function (64.1 +/- 7.2 and 16.7 +/- 4.1 minutes, respectively), indicating that sensitivity to the neuromuscular blocking action of atracurium may be altered by renal failure.

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