Mechanisms of renal dysfunction during positive end-expiratory pressure ventilation.

Twenty-seven anesthetized dogs were studied to determine the effects of intrarenal blood flow distribution, hepatic congestion, and cardiac output (Q) and/or intravascular volume on renal function during ventilation with positive end-expiratory pressure (PEEP) of 10 cmH2O. In 10 dogs intrarenal blood flow distribution, as determined by the radioactive-microsphere technique, remained unchanged although PEEP caused a significant antidiuresis and antinatriuresis. The selective release of hepatic congestion during PEEP in eight animals by means of a vena cava to jugular venous shunt circuit did not restore renal function. Nine dogs were transfused with 25 ml/kg of autologous blood during PEEP. Although Q remained at only 70% of control, renal blood flow and renal function (glomerular filtration rate, urinary sodium excretion, urine output, osmolar clearance, and free water clearance) were restored to control values. Our results suggest that the impairment in renal function during PEEP is not caused by changes in intrarenal blood flow distribution, Q, or hepatic congestion, but rather by a decrease in intravascular volume.