RENAL-FUNCTION DURING CARDIOPULMONARY BYPASS - INFLUENCE OF PUMP FLOWAND SYSTEMIC BLOOD-PRESSURE

The influence of systemic blood flow (pump flow) and arterial blood pr essure on renal function was studied during hypothermic cardiopulmonar y bypass (CPB) in 14 male patients where the pump flow rate was varied between 1.45 and 2.20 l . min-1 m-2. Renal blood flow (RBF) was measu red in the left renal vein with retrograde thermodilution technique an d urinary flow and circulatory variables were measured with an on-line computer set-up. During CPB the RBF comprised 12 - 13% of the systemi c blood flow and was positively related to systemic blood pressure (r = 0.71; P < 0.001) and pump flow rate (r = 0.69; P < 0.001). These fin dings indicate that the renal autoregulation was not operative during the hypothermic CPB period. According to multiple regression analysis, RBF was primarily determined by the pump flow rate and systemic blood pressure was of secondary importance. Urinary flow increased during h ypothermic CPB and became closely related to blood pressure and pump f low. According to multiple regression analysis, urinary flow was prima rily determined by systemic blood pressure.