Comparison of the effects of etomidate, propofol, and thiopental on respiratory resistance after tracheal intubation

Background: Tracheal intubation frequently results in reversible bronchoconstriction. Propofol has been reported to minimize this response in healthy patients and in asthma patients, but may be unsuitable for hemodynamically unstable patients for whom etomidate may be preferable. The current study examined respiratory resistance after tracheal intubation after induction with either thiopental, etomidate, or propofol. A supratherapeutic dose of etomidate was used to test the hypothesis that the bronchoconstrictive response could be minimized by deep intravenous anesthesia. Methods: Seventy-seven studies were conducted in 75 patients. Anesthesia was induced with either 2.5 mg/kg propofol, 0.4 mg/kg etomidate, or 5 mg/kg thiopental. Respiratory resistance was measured at 2 min after induction. Results: Respiratory resistance at 2 min was 8.1 ± 3.4 cmH ₂O · l ^-1 · s (mean ± SD) for patients receiving propofol versus 11.3 ± 5.3 for patients receiving etomidate and 12.3 ± 7.9 for patients receiving thiopental (P ≤ 0.05 for propofol vs. either etomidate or thiopental). Conclusions: Respiratory resistance after tracheal intubation is lower after induction with propofol than after induction with thiopental or after induction with high-dose etomidate.