EFFECTS OF HYPOTENSION DUE TO HEMORRHAGE AND OF BLOOD TRANSFUSION ON RENAL FUNCTION IN DOGS

Abstract

In anesthetized dogs, hypotension due to bleeding decreases renal blood flow and glomerular nitration rate. Transfusion of withdrawn blood returns renal blood flow to normal levels, and causes a temporary increase of urine flow above normal levels. Dogs with denervated kidneys respond to transfusion by a slow and incomplete restoration of inulin and diodrast clearance. Profound, prolonged and repeated hypotension due to bleeding prevents the restoration to normal of renal blood flow and function after transfusion, apparently because of vasoconstriction due to humorally circulating vasoconstrictor substances liberated during the onset of shock. Diodrast clearance loses its value as a measure of renal plasma flow (a) during and after severe hypotension, and (b) during restoration of arterial pressure by transfusion. (1) In the former case, clearance is decreased by decreased renal extraction of diodrast, presumably the result of partitioning of renal blood flow through areas of lower vascular resistance; (2) after transfusion, clearance may be increased out of proportion to renal plasma flow by excretion of diodrast accumulated in tubules during hypotension. The equilibrium of diodrast between renal plasma and interstitial fluid may explain the incompleteness of renal diodrast extraction under normal conditions. It is suggested that high spinal anesthesia may interfere with recovery of renal circulation in cases of shock.