The effect of anesthesia on hemodynamics and renal function in the rat

Although many renal physiologic studies in the rat have utilized pentobarbital anesthetized animals, there has been no systematic evaluation of the effects of barbiturate anesthesia on renal function. We therefore compared systemic hemodynamic and renal function parameters in conscious (C) and pentobarbital anesthetized (A) rats. Cardiac index and renal blood flow as assessed by microspheres were greater in C rats while systemic and renal vascular resistance were less in C rats. Although basal glomerular filtration rate was similar in both groups of animals, glomerular filtration rate following hypotonic volume expansion was greater in C than A rats. During hypotonic volume expansion, distal delivery as estimated by the sum of free water and sodium clearances was greater in C rats. In contrast, function of the distal nephron as assessed by maximum fractional free water clearance during hypotonic volume expansion and by solute free water reabsorption at maximum levels of osmolar clearance were comparable in C and A rats. Collecting duct water permeability as assessed by the response to exogenous vasopressin was similar in C and A rats. Following an exogenous sodium chloride load, C rats excreted 16% more of the sodium. No differences in measured whole blood or plasma volume were present when C and A rats were compared.We conclude that pentobarbital does not impair basal glomerular filtration rate, distal nephron function or the water permeability response of the collecting duct. Pentobarbital does result in alterations in systemic and renal hemodynamics which may contribute to the failure of A rats to normally excrete a saline load.