A prospective randomized study comparing volume-standardized modified and conventional ultrafiltration in pediatric cardiac surgery

Background: Modified ultrafiltration has been touted as superior to convent ional ultrafiltration for attenuating the consequences of hemodilution afte r cardiac surgery with cardiopulmonary bypass in children. We conducted a p rospective randomized study to test the hypothesis that modified and conven tional ultrafiltration have similar clinical effects when a standardized vo lume of fluid is removed. Methods: From October 1998 to September 1999, 110 children weighing 15 kg o r less (median weight 6.1 kg, median age 6.3 months) undergoing surgery wit h cardiopulmonary bypass for functionally biventricular congenital heart di sease were randomized to conventional (n = 67) or arteriovenous modified ul trafiltration (n = 43) for hemoconcentration. The volume of fluid removed w ith both method,, was standardized as a percentage of effective fluid balan ce (the sum of prime volume and volume added during cardiopulmonary bypass rr nus urine output): in patients weighing less than 10 kg, 50% of effectiv e 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 group s. Results: There were no significant differences between groups in age, weigh t, or duration of cardiopulmonary bypass. The total volume of fluid added i n the prime and during bypass was greater in patients undergoing convention al ultrafiltration than in those receiving modified ultrafiltration (205 +/ - 123 vs 162 +/- 74 mL/kg P =.05), although the difference was due primaril y to a greater indexed priming volume in patients having conventional ultra filtration. There was no difference in the percentage of effective fluid ba lance that was removed in the 2 groups. Accordingly, the volume of ultrafil trate was greater in patients receiving conventional than modified ultrafil tration (95 +/- 63 vs 68 +/- 28 mL/kg,-; P =.01). Preoperative and postoper ative 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% i n those having modified ultrafiltration. By repeated-measures analysis of v ariance, patients receiving modified and conventional ultrafiltration did n ot 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 differenc es between groups in duration of mechanical ventilation, stay in the intens ive care unit, or hospitalization. Conclusions: When a standardized volume of fluid is removed, hematocrit, he modynamics, ventricular function, requirement for blood products, and posto perative resource use do not differ between pediatric patients receiving co nventional and modified ultrafiltration for hemoconcentration after cardiac surgery.