Failure of metronidazole to alter a vecuronium neuromuscular blockade in humans

Pharmacodynamic behaviour of vecuronium in primary hyperparathyroidism

This study evaluated the potency and time course of action of vecuronium in patients with primary hyperparathyroidism (HPT) and marked hypercalcaemia during nitrous oxide-opioid anaesthesia. Twenty ASA physical status I and II patients were studied by measuring the force of contraction of the adductor pollicis in response to stimulation of the ulnar nerve: ten control patients and ten patients with HPT and ionized calcium concentration over 2.80 mEq.L-1. After induction of anaesthesia with thiopentone and maintenance with N2O/O2 and fentanyl, vecuronium was administered to determine cumulative dose-response curves. When maximum block had been obtained, twitch height was maintained at 10% of baseline value over 20 min by adjusting the infusion rate of a syringe-pump containing vecuronium and vecuronium plasma concentration (EC90ss) was determined. During spontaneous recovery, after termination of infusion, the recovery index, the time from 25 to 75% recovery, was measured. The dose to produce 90% block was greater in the HPT than in control group: 69 (24) vs 54 (18) micrograms.kg-1 (P < 0.02). The calculated ED50 was also greater in HPT: 42 (4) vs 31 (5) micrograms.kg-1 in controls (P < 0.001). (Values are given as mean and coefficient of variation). The slope of the dose-response curve, the dose necessary to maintain 90% block, and the EC90ss did not differ. The RI25-75 was slower in the HPT group although the difference did not reach statistical significance. It is concluded that hyperparathyroidism with hypercalcaemia increases vecuronium requirement; only during the onset of neuromuscular blockade.

Continuous vecuronium infusion for prolonged muscle relaxation in children

Facilitation of mechanical ventilation of the lungs using an infusion of vecuronium in 11 infants and children and four neonates in an intensive care unit is described. A loading dose of vecuronium of 0.1 mg.kg-1 was followed by an infusion at an initial rate of 0.1 mg.kg-1.hr-1. The infusion rate was adjusted to maintain a neuromuscular block of approximately 90% as assessed by the presence of one response to a train-of-four stimulation. The duration of the infusions varied from 9.5 to 179 hr. The mean dose of vecuronium administered was 0.14 mg.kg-1.hr-1 (+/- 0.05, SD) in the children and 0.11 mg.kg-1.hr-1 (+/- 0.05) in the neonates. Mean recovery times from the time of stopping the infusion until absence of apparent fade in response to tetanic stimulation were 51.7 (+/- 17.6) and 46.8 (+/- 16.5) min for the children and neonates respectively. No adverse cardiovascular or toxic effects were noted. This technique of vecuronium infusion to facilitate mechanical ventilation of the lungs is feasible and satisfactory in clinical use.

Impairment of the antagonism of vecuronium-induced paralysis and intra-operative disopyramide administration

A 63-year-old male was admitted to hospital for a cholecystectomy, vagotomy and gastro-enterostomy. Muscle paralysis was induced with 70 micrograms/kg vecuronium, followed by increments of 20 micrograms/kg when the initial twitch height returned to 25% of control. The patient received 3 doses of 10 mg disopyramide intravenously, on account of supraventricular ectopic beats, followed by an infusion of 25 mg/hour. Paralysis was reversed using 0.75 mg atropine and 2.5 mg neostigmine once the twitch height had returned spontaneously to 25% of its initial value. Fifteen minutes later, twitch height had returned to control value and the train-of-four was above 85%, but the responses to tetanic stimulation at 100 Hz and 50 Hz remained severely depressed (10% and 45%, respectively). The patient's trachea was extubated after 20 minutes, but residual fade was still observed. This impairment of neuromuscular transmission, detected only with high frequency stimulation, was present with a measured concomitant plasma level of disopyramide of 5.1 micrograms/ml.