gender and blood transfusions

Eric Tesdahl, PhD
Senior Biostatistician
November 23, 2016

Blood bagIt is a fairly well-known fact in the cardiac community that women have higher morbidity and mortality associated with coronary artery bypass (CABG) procedures. The reasons traditionally given for this disparity include women’s relatively smaller vasculature, higher incidence of anemia, and smaller circulating  blood volume. Early in 2016, we in the Medical Department were discussing this phenomenon and decided to design a study that could use the robust data from our SpecialtyCare Operative Procedural Registry (SCOPE™) to find something in the intraoperative space that might be leading to these very different post-operative outcomes for men and women. Given the links between RBC transfusions in CABG surgery and a number of post-operative outcomes, we decided to focus on gender differences in the frequency and extent of RBC transfusion. We hypothesized that women are at increased risk for RBC transfusions due to lower pre-op hematocrit (Hct) and blood volume, but that other factors may also contribute.

Last week, I presented our findings at the American Heart Association’s 2016 Scientific Sessions in New Orleans. “Gender Differences in Intraoperative Blood Transfusions” reviews 54,122 coronary artery bypass procedures gathered from 189 surgical facilities in our SCOPE™ database. It was published this week in the journal, Circulation.

Our findings were somewhat surprising to us. If you simply compare the transfusion rate for men and women you see a three-fold difference in RBC transfusion rate; 13.7% of men in our sample received a transfusion, compared with 45.1% of women. While multivariable analysis did confirm many of the traditional explanations for gender differences, we found that even after adjusting for 12 confounding factors, women continue to have a 30% increased risk of intraoperative RBC transfusion that has yet to be explained in the literature.

To narrow the gap in gender-based outcomes after cardiac surgery, healthcare providers and researchers must continue to look for reasons behind the disparity and consider strategies aimed at gender differences that may minimize unnecessary transfusions. Given the significant complications and costs associated with RBC transfusion (e.g., higher infection rates, increased length of stay, blood acquisition), future study on the impact of gender on transfusion practice in cardiac surgery is warranted.

Editor’s note:  Visit our Resource Library for more original research on perfusion, intraoperative neuromonitoring, and related surgical services.