Alteration of renal hemodynamics by thiopental, diazepam, and ketamine in conscious dogs.

Renal hemodynamic changes associated with thiopental, diazepam, and ketamine were studied in conscious dogs after previous surgical placement of an aortic catheter and a Doppler ultrasonic flow probe on the left renal artery. Thiopental, 10 mg/kg, changed blood pressure minimally whereas 20 mg/kg significantly decreased blood pressure by 5% to 10%. Renal blood flow initially increased significantly, then returned to control levels after both doses. Renal resistance was not significantly altered by 10 mg/kg of thiopental whereas 20 mg/kg significantly reduced resistance by 10%. Diazepam, 1 and 2 mg/kg, caused transient increases in arterial pressure of approximately 10%. Renal blood flow significantly decreased 5% to 10% from control levels with both doses. Renal resistance did not change with the 1-mg/kg dose of diazepam, but 2 mg/kg of diazepam increased it by 8% to 12%. Ketamine, 2.5 and 5 mg/kg, elevated arterial pressure 20% to 40%. Renal blood flow increased significantly by 10% to 15% with both doses of ketamine. This effect lasted longer with the large dose. Renal resistance was significantly elevated by the 2.5-mg/kg dose of ketamine, whereas 5 mg/kg did not alter this variable. In conclusion, each of these drugs maintains renal blood flow reasonably well in an unanesthetized animal. However, ketamine appears to be more beneficial than thiopental, which in turn, is superior to diazepam in this regard. Little dose-response effect was evident for any of the drugs. Furthermore, it should be noted that changes in arterial pressure can be misleading when perfusion of this vascular bed is considered.