The role of anesthesia and catecholamines in the renal response to mild hemorrhage.

The role of the sympathoadrenal system in the renal response to mild hemorrhage was investigated in animals anesthetized with either sodium pentobarbital (Group I) or alpha-chloralose (Group II). Significantly greater decreases in renal blood flow (RBF) and increases in renal vascular resistance (RVR) were seen after hemorrhage in Group II than in Group I. Concomitant with these changes were increases both in circulating catecholamines and plasma renin activities. In Group II, however, the rise in plasma epinephrine was also significantly higher than in Group I. Additional studies were performed in pentobarbital anesthetized dogs either chemically denervated with 6-hydroxydopamine (Group III) or treated with the prostaglandin synthetase inhibitor indomethacin (Group IV). In Group III, following hemorrhage, changes in renal hemodynamics and circulating catecholamines were similar to those of Group I. In Group IV, although blood pressure was better maintained during hemorrhage than in the other groups, RVR increased to the same extent as in Group II, although increases in circulating catecholamines were comparable to those observed in Group I. Whereas pentobarbital anesthesia attenuated the sympathoadrenal response to mild hemorrhage, indomethacin appeared to sensitize the animals to adrenergic discharge by removing the modulatory effect of the prostaglandin system.