Abstract of Research Presented at the
Society of Thoracic Surgeons (STS) Annual Meeting

Adult Cardiac Session: General 

The Unintended Consequences of Over Reducing Cardiopulmonary Bypass Circuit Prime Volume
B. C. Sun , T. A. Dickinson2, D. S. Likosky3 , D. Wells2 , S. Weinstein2
1Minneapolis Heart Institute, MN, 2SpecialtyCare, Nashville, TN, 3University of Michigan Health System, Ann Arbor

COMMERCIAL RELATIONSHIPS D. S. Likosky: Consultant/Advisory Board, AmSECT; Research Grant, Agency for Healthcare Research and Quality, National Institutes of Health; S. Weinstein: Employment, SpecialtyCare; D. Wells: Consultant/Advisory Board, SpecialtyCare; Employment, SpecialtyCare; Ownership Interest, SpecialtyCare

Purpose: The Society of Thoracic Surgeons blood conservation guidelines recommend minimizing cardiopulmonary bypass (CPB) circuit prime volume (PV) as an integral, evidence-based (Class I, Level A) blood conservation strategy. We used a large, multiinstitutional database to evaluate the effectiveness of restricting CPB prime volume on intraoperative red blood cell (RBC) transfusion.

Methods: We reviewed 51,100 isolated coronary artery bypass grafting (CABG) procedures performed among 190 institutions between April 2012 and May 2015. We categorized net prime volume (NPV) as total prime volume minus autologous priming and evaluated three groups: <500 mL, 500-999 mL, and ≥1 L. The primary outcome was transfusion of at least one unit of intraoperative RBCs. Logistic regression was used to model the odds of transfusion. We report odds ratios for transfusion after adjusting for age, gender, acuity, reoperation, estimated blood volume (EBV), first hematocrit in the operating room, nadir hematocrit on CPB, and year. We tested for an interaction by gender.

Results: Nearly one-quarter of patients (n=11,351, 22.2%) received an intraoperative RBC transfusion. Relative to an NPV between 500-999 mL, patients exposed to NPV <500 mL had a 1.26-fold increased adjusted odds of transfusion, while those exposed to a net prime ≥1 L had a 1.61-fold increased odds of transfusion. Women had similar average CPB NPV to men (864 mL vs 858 mL, P = .12), although a higher odds of transfusion (OR 5.26, P < .001). There was a statistical interaction by gender, P = .037. Relative to patients with NPV between 500-999 mL, men exposed to an NPV ≥1 L had a 1.52-fold increased adjusted odds of transfusion and a 1.36-fold increase when exposed to net prime of <500 mL (both P < .001). Women had a 1.72-fold increased adjusted odds of transfusion when exposed to net prime of ≥1 L (P < .001), but a nonsignificant 1.11-fold increase when exposed to net prime <500 mL (P = .12).

Conclusions: Efforts to minimize CPB NPV below 500 mL do not protect patients from intraoperative RBC transfusion and may actually increase exposure. Perfusion net prime volume can impact both patient morbidity and the economic impact associated with blood utilization. Further studies on the influence of gender on blood transfusion are warranted. 

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