Renal blood flow velocity in acute renal failure following cardiopulmonary bypass surgery

Diminished renal perfusion is believed to be the main factor precipitating acute renal failure (ARF) following cardiopulmonary bypass surgery (CPB). We aimed to assess renal perfusion in patients following CPB surgery using Doppler ultrasound measurements. The Pulsatility index (PI) of the renal and intrarenal arteries was calculated as an index of renal perfusion. Two groups of patients were studied. Group 1 consisted of children with complex cardiac malformations who developed ARF following CPB. Group 2 consisted of children with atrial septal defects who were studied before and after CPB, but who did not develop ARF. In group 1, there were significant correlations between PI of the renal artery and standard deviation score of systolic blood pressure (SDS) (correlation coefficient = -0.588, p < 0.0001), and PI and urine output (UOP) (correlation coefficient = -0.46, p = 0.001). In the survivors, PI of the renal artery dropped significantly at the onset of recovery from ARF (6.27-2.15, p = 0.007). In group 2, PI of renal and intrarenal arteries remained unchanged on day 1 and day 4 post-CPB surgery in comparison with preoperative values. PI of the renal artery may aid the prediction of onset and recovery from ARF following CPB surgery, and help modify treatment in these critically ill patients.