Indications for ultrafiltration in the cardiac surgical patient

Ultrafiltration is an extracorporeal technique that employs the principle of convective solute transport across a semipermeable membrane and by which plasma water is removed from blood. Ultrafiltration has been employed in 74 cardiac surgical patients intraoperatively, preoperatively, and postoperatively. In 55 patients with clinical evidence of excess body water, the ultrafilter was employed at the start of cardiopulmonary bypass. The amount of ultrafiltrate removed was 2,914 +/- 1,662 ml (SD), and the fluid balance was -219 +/- 1,298 ml (SD). In 17 patients the ultrafilter was inserted during bypass because of excess reservoir volumes, low hematocrit, or prolonged bypass time. The amount of ultrafiltrate removed was 1,450 +/- 898 ml (SD), and the fluid balance was 1,296 +/- 2,161 ml (SD). One patient with cardiopulmonary failure and nutritional depletion underwent slow continuous ultrafiltration preoperatively along with intravenous alimentation, producing a positive nitrogen balance and improvement in cardiorespiratory failure. One patient underwent slow continuous ultrafiltration for severe, diuretic-resistant congestive heart failure postoperatively. After 9 days of ultrafiltration, there was an 8 kg weight loss, an improvement in congestive heart failure, and a return of the response to diuretics. From this experience my colleagues and I have developed the following indications for ultrafiltration in the cardiac surgical patient: during cardiopulmonary bypass to prevent further fluid accumulation in the patient with clinical evidence of excess body water; during bypass to prevent excess fluid balance in a patient whose bypass time will be greater than 2 hours; during bypass when the pump reservoir volumes are excessive and/or the hematocrit is less than 18%; preoperatively or postoperatively to increase caloric intake in the fluid-overloaded patient; and preoperatively or postoperatively to reverse severe congestive heart failure in the diuretic-resistant patient.