The hemodynamic consequences of high-dose methohexital anesthesia in humans

The hemodynamic, electroencephalographic (EEG), and metabolic effects of a high-dose methohexital anesthetic were examined in eight neurosurgical patients. The patients were studied at rest and at 15-min intervals during a 60-min infusion of the drug, given at a rate of 0.40 mg . kg-1 . min-1 (total dose 24 mg/kg). Ventilation was controlled with oxygen:air (FIO2 = 0.50), and fluid was infused at a rate sufficient to maintain pulmonary capillary wedge (PCW) pressures at control values (8 +/- 2 mmHg, mean +/- SD). Serum methohexital concentrations increased progressively, reaching values of 11.7 +/- 2.9 micrograms/ml at t = 30 min and 18.1 +/- 10.8 micrograms/ml at t = 60 min. Characteristic barbiturate-induced EEG changes were noted, with isoelectricity achieved at t = 28 +/- 13 min. Methohexital infusion resulted in significant reductions in arterial pressure (84% of control at t = 60 min), systemic vascular resistances (83% of control at t = 60 min), right and left ventricular stroke work indices (65% and 68% of control, respectively at t = 60 min), and total body O2 consumption (76% of control at t = 60 min). In addition, a progressive dose-related decrease in stroke volume index was noted (50.1 +/- 90 ml X beat-1 X m-2 at t = 0, 40.1 +/- 10.2 ml X beat-1 X m-2 at t = 60 [80% of control]). This occurred in spite of unchanged ventricular filling pressures.(ABSTRACT TRUNCATED AT 250 WORDS)