Anesthesiology
-
Comparative Study
Sympathetic responses to induction of anesthesia in humans with propofol or etomidate.
Anesthetic induction with propofol commonly results in hypotension. This study explored potential mechanisms contributing to hypotension by recording cardiovascular responses including sympathetic neural activity from patients during induction of anesthesia with propofol (2.5 mg.kg-1 plus 200 micrograms.kg-1.min-1) or, for comparison, etomidate (0.3 mg.kg-1 plus 15 micrograms.kg-1.min-1). Twenty-five consenting, nonpremedicated, ASA physical status 1 and 2, surgical patients were evaluated. ⋯ Both cardiac and sympathetic baroslopes were maintained with etomidate but were significantly reduced with propofol, especially in response to hypotension. These findings suggest that propofol-induced hypotension is mediated by an inhibition of the sympathetic nervous system and impairment of baroreflex regulatory mechanisms. Etomidate, conversely, maintains hemodynamic stability through preservation of both sympathetic outflow and autonomic reflexes.