Repeated resistance to non-depolarizing neuromuscular blocking drugs in a patient with multiple myeloma.

were taken from this mixture at nine intervals for up to 128 min. Each sample was immediately acidified, stored at — 20 °C and subsequently transferred to Groningen for analysis. All samples revealed vecuronium without any of its breakdown products. Unlike the 3-hydroxy metabolite, neither of the two other metabolites of vecuronium (17-hydroxy and 3,17-dihydroxy vecuronium) have been detected previously in biological material [2]. The 17-hydroxy vecuronium in this patient's blood may suggest an alternative metabolic pathway. However, this statement must be taken with caution, as her original samples were not acidified, and a sample of blood had not been collected before she received vecuronium. Finally, the sensitivity and selectivity of the analytical methods may have been at least partly responsible for 17-hydroxy vecuronium not having been demonstrated earlier in human material. It is, nevertheless, of interest that 1 yr earlier, the same patient had required a general anaesthetic. According to the anaesthetic chart, she had been given vecuronium 4 mg and, about 5 min later, pancuronium 4 mg. Although there was no comment on the record as to why the two agents were administered in such short order, it is very likely that on that occasion also, no effect was seen with vecuronium. Final confirmation of her resistance to vecuronium and the detection of 17-hydroxy metabolite obviously can only be obtained if this particular patient requires a general anaesthetic again. Anaesthetists confronted with apparent resistance to vecuronium which cannot be explained on more classical grounds should ask for plasma vecuronium analysis for the patient in question.