Combined i.v. bolus and infusion of pancuronium bromide.

An i.v. bolus and concomitant infusion of pancuronium is proposed for use in prolonged anaesthesia. Plasma concentrations of pancuronium were measured in 16 patients receiving this regime. The desired steady-state concentration of 0.2 fig ml" was achieved in most instances at approximately 45 min. Following the bolus, the neuromuscular twitch response decreased to low values or was abolished completely. Thereafter the response remained relatively constant or increased in intensity consistent with the mean steady-state plasma concentrations of 0.214 y.g ml" (SEM 0.012) maintained by the infusion. When the infusion was stopped, the mean twitch height was 23% of control and increased thereafter at approximately 1 % per min, while plasma concentrations decreased by half in 69 min. One patient with renal artery stenoses exhibited complete neuromuscular blockade at a steady-state plasma concentration of 0.29 (zgml"; following cessation of infusion the twitch response was detected after 30 min (plasma concentration 0.20 (ig ml"") and recovery was uneventful. Plasma clearance and apparent volume of distribution of pancuronium used to calculate the dosage regime were found not to differ significantly from those reported for a single dose. Following cessation of infusion, plasma concentrations declined in either a monoor bi-exponential form depending on the ratio of the hybrid disposition rate constants (P/a). In all instances a twocompartment open model was used to describe the time course of the plasma concentrations.