Hemodynamic response to ganglionic blockade with pentolinium during N2O-halothane anesthesia in man

Hemodynamic and blood-gas variables were studied before and after pentolinium tartrate administration in six patients anesthetized with nitrous oxide-halothane and maintained at PaCO2 35-40 torr. Measurements were made prior to induction of anesthesia; before and 10, 20, and 60 minutes after administration of pentolinium (0.3 mg/kg); 15 minutes after return of arterial blood pressure to control values. Mean arterial blood pressure (MAP) was significantly decreased at 20 (P less than 0.02) and 60 (P less than 0.001) minutes, in association with significant decreases in systemic vascular resistance (SVR) (P less than 0.05 and P less than 0.005). At 60 minutes MAP was significantly lower than that at 10 minutes (P less than 0.01). Cardiac output (CO) was increased (P less than 0.05) after 10 minutes secondary to a significant increase in heart rate. Neither variable changes significantly thereafter. CO and HR were significantly lower (P less than 0.01) 60 minutes after pentolinium than at 10 minutes; both returned to 10-minute values after intravenous administration of atropine. Changes in stroke volume (SV) and mean right atrial pressure (MRAP) were not significant. Whole-body O2 uptake (VO2) was not significantly altered by pentolinium. However, a substantial diminution of myocardial O2 consumption (MVO2) was deduced from a significant decrease in the heart rate-arterial systolic pressure produce (HR X ASP). Fifteen minutes after return of MAP to control levels, SVR was 11.5 per cent lower, while CO was still significantly higher (P less than 0.02) than control values. Following ganglionic blockade with pentolinium during halothane-N2O anesthesia, HR is a valuable index of changes in CO, while the HR X ASP index may be utilized to evaluate changes in MVO2. Assessment of myocardial performance during controlled hypotension is possible by the use of routinely available measurements.