[Effect of etomidate and thiopental on the onset of rocuronium action].

HYPOTHESIS

Differences in the hemodynamic effects of induction agents may cause them to affect the onset of action of rocuronium differently.

OBJECTIVES

To compare the onset of action of rocuronium after induction with etomidate and thiopental.

PATIENTS AND METHODS

Forty adult ASA I patients received 3 micrograms.kg-1. Three minutes later anesthesia was induced randomly with either 5 mg.kg-1 of thiopental (group I, n = 20) or 0.3 mg.kg-1 of etomidate (group II, n = 20). Rocuronium 0.6 mg.kg-1 was administered over 5 s. Baseline blood pressure and heart rate were measured just before delivery of rocuronium and just before intubation. Onset of action was defined as the time from injection of rocuronium until achievement of a blockade > or = 95% of the first electromyographic response in a trian-of-four stimulus of the short adductor of the thumb. We also studied intubation conditions.

RESULTS

Etomidate was associated with a smaller decrease in systolic arterial pressure than was thiopental. Onset of action was 81 +/- 29 s in group I versus 72 +/- 23 s in group II (NS). Similar intubation conditions were observed in both groups.

CONCLUSIONS

These results suggest that the induction drug does not affect rocuronium's onset of action.