Original Article

Reduction in Homologous Blood Transfusions Using a Low Prime Circuit

The New York Hospital-Cornell Medical Center, New York, New York

^* Address correspondence to: William J. DeBois, BS, CCP The New York Hospital 525 East 68th Street New York, NY 10021

Abstract

Due to a low estimated blood volume, small adults (weight less than 70 kg) undergoing cardiopulmonary bypass (CPB) are at highest risk for low hematocrit and homologous blood transfusion (HBT). To determine whether reductions in HBT could be achieved we compared the use of a low prime circuit (1400 ml) with our standard (2200 ml) cardiopulmonary bypass (CPB) circuit.

Eighty consecutive adult patients (>age 18, <70 kg) undergoing non-emergent CPB were randomly divided into two groups. Group LP (n=40) was the low prime group and group SP (n=40) was the standard prime group. In Group LP, either of two “low prime” hollow fiber membrane oxygenators with a 3/8 X 3/8 inch A-V loop were utilized. Alternately, in Group SP, a larger membrane oxygenator with a 3/8 X 1/2 A-V loop was utilized. Circuits and CPB management were otherwise identical. Excluded from the study were those patients who had bleeding disorders, reoperations, ejection fractions of less than 30% and history of cerebral vascular insufficiency.

Patients were closely matched for age, BSA, gender, preoperative risk and procedure. Mean weight (kg) was less in Group LP (59.2 vs 62.2, P<0.02). Pre-CPB hematocrits (HCT) were similar in both groups. Initial on CPB HCT was higher in Group LP (19.8 vs 18.4, P<0.04). Group LP had a higher frequency of initial on CPB HCTs of 20% or greater (55% vs 33% , P<0.04). Group LP had a lower packed red blood cell (PRBC) transfusion rate on CPB (0.4 vs 0.9 units, P<0.03). Group LP had higher percentage of patients that did not require transfusion on CPB (78% vs 55%, P<0.03). Despite fewer transfusions, Group LP had a higher post CPB HCT (20.6 vs 19.3, P<0.04). A trend was noted with a lower total PRBC transfusion rate in Group LP (1.9 vs 2.4, P=.10). During the entire length of stay, fewer Group LP patients required any homologous transfusion (26/40 versus 34/40, P <0.04). Chest drainage, 24 hour HCT and discharge HCT were similar in both groups. Transfusion of platelets, fresh frozen plasma and cryoprecipitate was similar in both groups. There were no deaths in either group.

Patients with low blood volume are at high risk of homologous transfusion when undergoing CPB. A significant reduction in prime volume appears to be safe, simple and reduces HBTs in these individuals. Prime reduction should be part of a comprehensive multi-modality blood conservation program.