Effects of halothane and sodium nitroprusside on renal function and autoregulation

The effects of sodium nitroprusside and halothane on renal autoregulation and kidney function were studied in 14 mongrel dogs at mean arterial pressures of 120, 100, 80, 60 and 40 mm Hg. In group 1, stepwise decreases in mean arterial pressure were achieved by increasing the halothane concentration. In group II, mean arterial pressure was decreased by infusing sodium nitroprusside during halothane anaesthesia. In group I, renal blood flow decreased significantly at mean arterial pressures of 100, 80, 60 and 40 mm Hg. In group II, renal blood flow was well maintained at mean arterial pressures of 100 and 80 mm Hg, but decreased significantly at 60 and 40 mm Hg; at these low pressures flow was greater in group II than in group I. There were no significant differences between two groups in inulin clearance, inulin clearance/renal plasma flow, urine output, urine osmolarity and sodium excretion rate. Significantly larger fractions of cardiac output were distributed to the kidneys in group I.