Anesthetic modulation of the cardiovascular response to microlaryngoscopy. A comparison of propofol and methohexital with special reference to leg blood flow, catecholamines and recovery.

The modulating effects of propofol versus methohexital on the cardiovascular response to microlaryngoscopy were studied in 35 patients divided into four equal groups (one patient participated twice). Heart rate (HR), mean arterial blood pressure (MAP, cardiac output (CO; impedance cardiography), leg blood flow (LBF; occlusion plethysmography) and concentrations of arterial catecholamines were measured. After administration of atropine and fentanyl (2 micrograms.kg-1), anesthesia was induced by either an injection of propofol (2.0 mg.kg-1) followed by a low (6 mg.kg-1.h-1; n = 9) or a high (12 mg.kg-1.h-1; n = 9) dose propofol infusion or an injection of methohexital (1.5 mg.kg-1) followed by a low (5 mg.kg-1.h-1; n = 9) or a high (10 mg.kg-1.h-1; n = 9) dose methohexital infusion. The low methohexital infusion dose was insufficient to control MAP, which increased 41% during microlaryngoscopy compared to the awake state. The HR increased in all groups but the increase was most prominent in the low dose methohexital group. There were no statistically significant changes in CO in any group, whereas LBF increased consistently in all groups except in patients anesthetized with the low dose of methohexital. The increases of LBF in the propofol groups were intermediate and not dose dependent. The methohexital low dose group showed increases in norepinephrine levels compared to awake values and in epinephrine levels compared to the other groups. Propofol seems to differ from methohexital in modulation of peripheral vascular tone.(ABSTRACT TRUNCATED AT 250 WORDS)