Résumé : We studied the cardiovascular effects of hemodialysis in five critically ill patients with ultrafiltration using, alternately, bicarbonate and acetate in the dialysate. After 3 hr of dialysis with acetate, significant decreases in both arterial pressure and stroke volume resulted in lowered left ventricular stroke work (P less than 0.025). This effect persisted 30 min after the end of the dialysis (P less than 0.025). Differences in the patients' cardiac preload were ruled out by similar pulmonary artery balloon-occluded pressures during both types of dialysis. These observations suggest that dialysis with acetate can result in myocardial depression. The use of bicarbonate dialysate is thus advisable for acute hemodialysis in critically ill patients.