Prediction of infusion rates of rocuronium using the bolus test dose technique.

Twenty-four patients were given a loading dose of rocuronium 1.0 mg.kg-1 intravenously followed by boluses of 20 mg (n = 19) and 10 mg (n = 24) after return of T1 of the train-of-four to 5% of control. Neuromuscular function was assessed using a Relaxograph. The time was recorded for the return of T1 to 5% after the administration of the boluses and subsequently an infusion of rocuronium was started. The aim was to maintain T1 between 3% and 7% of control for at least 40 min without a change of infusion rate. The correlations between the duration of the test doses and the infusion rates were -0.94 (10 mg) and -0.86 (20 mg). The predictive accuracy of the 10 mg bolus was assessed in a further 10 patients. At the termination of the infusion three patients had a T1% that was outside the desired range of 3-7%. A 10 mg bolus that lasts 6 min indicates a need for an infusion of at least 60 mg.h-1, 8 min (50 mg.h-1), 10 min (40 mg.h-1), 15 min (30 mg.h-1), 24 min (20 mg.h-1) and 34 min (15 mg.h-1).