Renal function during consciousness and anesthesia in sheep: effects of renal vasodilation by papaverine and acetylcholine.

Adult ewes were studied to determine the effects of barbiturate anesthesia on renal function and the natriuretic response to renal vasodilation by papaverine and acetylcholine. During a period of consciousness, renal blood flow, glomerular filtration rate, urinary Na excretion (UNaV) and arterial blood pressure were monitored. Renal blood flow was maximally increased by renal arterial infusion of papaverine or acetylcholine and changes in renal function were observed. The sheep were subsequently anesthetized and the experimental protocol was repeated. Barbiturate anesthesia resulted in statistically significant increases in glomerular filtration rate, UNaV and blood pressure. Calculated fractional Na excretion also increased significantly. During consciousness, maximal renal vasodilation by papaverine or acetylcholine did not increase UNaV or fractional Na excretion. During anesthesia, both papaverine and acetylcholine produced large increases in both UNaV and fractional Na excretion. These data indicate that renal vasodilation per se is not a sufficient condition to increase UNaV and suggest that barbiturate anesthetics can alter renal function in such a manner as to render drugs, which are not natriuretic during consciousness, effective natriuretic agents during anesthesia.