Many studies have suggested that propofol in combination with remifentanil may provide adequate conditions for tracheal intubation without the use of muscle relaxants. Other hypnotic drugs have not been thoroughly investigated in this regard. The goal of our study was to evaluate the effect of thiopental, propofol or etomidate on tracheal intubating conditions and hemodynamic changes using remifentanil in the absence of muscle relaxants.

A total of 45 healthy adults were divided randomly into three groups. After iv lidocaine 1.5 mg/kg, thiopental 5 mg/kg (thiopental group) or propofol 2.5 mg/kg (propofol group), or etomidate 0.4 mg/kg (etomidate group) were injected. After the injection of study drugs, remifentanil 2 mcg/kg was administered. Ninety seconds after the administration of remifentanil, laryngoscopy and intubation were attempted. Intubating conditions were assessed and the mean arterial pressure and the heart rate was measured.

There were no significant differences in intubating conditions between patients in the three groups. The heart rate was significantly lower in the propofol and etomidate group patients when compared to the thiopental group patients after anesthetic induction. The mean arterial pressure was significantly lower in the propofol group patients when compared to the thiopental and etomidate group patients. Both heart rate and mean arterial pressure after tracheal intubation were significantly elevated in etomidate group patinets when compared to their preintubation value.

The use of thiopental 5 mg/kg, propofol 2.5 mg/kg, and etomidate 0.4 mg/kg did not differ in effect under intubating conditions for tracheal intubation using remifentanil in the absence of muscle relaxants. Thiopental provided the best hemodynamic conditions.