Peritoneal clearance of creatinine and inulin during dialysis in dogs: Effect of splanchnic vasodilators

Abstract

The peritoneal clearance of creatinine and inulin during isotonic peritoneal dialysis was studied in dogs before and after the administration of two vasodilators: isoproterenol and glucagon. One-liter exchanges with 15-min dwell times were used. Blood flow in the superior mesenteric artery was recorded with an electromagnetic flow probe and used as an index for total splanchnic flow. Intravenous isoproterenol (2.4 μg/min) increased blood flow by 88%, but did not alter peritoneal clearances. When isoproterenol was given i.p. (0.5 μg/ml dialysis fluid), blood flow increased by 81%, and inulin clearance rose by 26.8% (2.06 ± 0.18 to 2.61 ± 0.23 ml/min; P<0.05). Creatinine clearance increased by 17.5%, from 10.94 ± 0.32 to 12.85 ± 0.34 ml/min (P<0.05). When blood flow was returned to control levels with a clamp, clearances also returned to control levels. Glucagon given i.p. (1.0 μg/ml) had no effect on any measured variable. Glucagon given i.v. at 10 μg/min caused blood flow to rise by 81% and inulin clearance to rise by 25% from 1.88 ± 0.16 to 2.35 ± 0.19 ml/min (P<0.05). Creatinine clearance did not change. When blood flow was kept constant with a clamp, inulin clearance remained at control levels. Vasodilators seem to exercise two effects in augmenting clearance of small and middle-sized molecules: a direct permeability effect and a blood-flow related effect, possibly in increasing the surface area available for exchange and/or increasing permeability of the capillalry endothelium.