Large doses of vecuronium and plasma histamine concentrations

The authors studied 20 surgical patients to determine the effect of large doses of vecuronium on plasma histamine concentrations. Patients were unpremedicated and anaesthetized with nitrous oxide and halothane via a mask. Tracheal intubation was performed without the use of muscle relaxants. Fifteen min later and before surgery had begun, vecuronium, in doses of 0.1 and 0.2 mg.kg-1 (n = 10 for each dose), was administered as an IV bolus. Arterial blood samples were obtained prior to and 2, 5, and 10 min after vecuronium administration and analyzed for plasma histamine by a radioenzymatic method. Arterial blood pressure and heart rate were measured continuously. In one patient who received 0.1 mg.kg-1 of vecuronium, plasma histamine concentrations at 2 min were 275 per cent of the control histamine value but fell below control at 10 min. This increase in plasma histamine was not associated with clinically important changes in blood pressure or heart rate. As a group, study patients had no significant changes in plasma histamine concentrations with either dose of vecuronium. In addition, mean plasma histamine values for each sampling interval did not differ between the two patient groups. Mean arterial blood pressure (MAP) decreased significantly at 10 min in patients receiving vecuronium 0.1 mg.kg-1, and at 2 and 10 min in patients receiving 0.2 mg.kg-1 of vecuronium. However, these decreases in MAP were not clinically important. Changes in plasma histamine concentrations did not correlate with corresponding changes in MAP. Heart rate did not change significantly in any patient during the study.(ABSTRACT TRUNCATED AT 250 WORDS)