Background: Modified ultrafiltration has been touted as superior to conventional ultrafiltration for attenuating the consequences of hemodilution after cardiac surgery with cardiopulmonary bypass in children. We conducted a prospective randomized study to test the hypothesis that modified and conventional ultrafiltration have similar clinical effects when a standardized volume of fluid is removed.

Methods: From October 1998 to September 1999, 110 children weighing 15 kg or less (median weight 6.1 kg, median age 6.3 months) undergoing surgery with cardiopulmonary bypass for functionally biventricular congenital heart disease were randomized to conventional (n = 67) or arteriovenous modified ultrafiltration (n = 43) for hemoconcentration. The volume of fluid removed with both methods was standardized as a percentage of effective fluid balance (the sum of prime volume and volume added during cardiopulmonary bypass minus urine output): in patients weighing less than 10 kg, 50% of effective fluid balance was removed, whereas 60% was removed in patients weighing 10 to 15 kg. Hematocrit, hemodynamics, ventricular function, transfusion of blood products, and postoperative resource use were compared between groups.

Results: There were no significant differences between groups in age, weight, or duration of cardiopulmonary bypass. The total volume of fluid added in the prime and during bypass was greater in patients undergoing conventional ultrafiltration than in those receiving modified ultrafiltration (205 +/- 123 vs 162 +/- 74 mL/kg; P =.05), although the difference was due primarily to a greater indexed priming volume in patients having conventional ultrafiltration. There was no difference in the percentage of effective fluid balance that was removed in the 2 groups. Accordingly, the volume of ultrafiltrate was greater in patients receiving conventional than modified ultrafiltration (95 +/- 63 vs 68 +/- 28 mL/kg; P =.01). Preoperative and postoperative hematocrit levels were 35.6% +/- 6.6% and 36.3% +/- 5.6% in patients having conventional ultrafiltration and 34.4% +/- 6.7% and 38.7% +/- 7.5% in those having modified ultrafiltration. By repeated-measures analysis of variance, patients receiving modified and conventional ultrafiltration did not differ with respect to hematocrit value (P =.87), mean arterial pressure (P =.85), heart rate (P =.43), or left ventricular shortening fraction (P =.21) from baseline to the postbypass measurements. There were no differences between groups in duration of mechanical ventilation, stay in the intensive care unit, or hospitalization.

Conclusions: When a standardized volume of fluid is removed, hematocrit, hemodynamics, ventricular function, requirement for blood products, and postoperative resource use do not differ between pediatric patients receiving conventional and modified ultrafiltration for hemoconcentration after cardiac surgery.