The effects of pulsatile perfusion on microcirculation and renal function in high-risk patients were evaluated in this study. Pulsatile roller pumps with a pulsatile control module and membrane oxygenator were used in a clinical setting. 40 patients undergoing elective cardiac surgery with a high risk of either having chronically obstructive pulmonary disease or chronic renal failure were randomly included in the study to be perfused using pulsatile or continuous flows. Blood samples were collected at induction of anesthesia, at the time of aortic clamping and declamping and 1 and 24 h following cessation of the bypass. Urea and creatinine concentrations in blood were measured and systemic vascular resistance was calculated. Urine output, crystalloid and colloid infusions were recorded. We observed that pulsatile roller pump perfusion and the extracorporeal circuit used in the clinical study improved microcirculation and renal function in high-risk patients undergoing cardiopulmonary bypass. Copyright (C) 2005 S. Karger AG, Basel.