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October 15, 2014
8:00 AM - 9:30 AM
Room Room 245
Incremental Measures of Transfused Red Blood Cell Units Are Associated with Acute Kidney Injury in Cardiac Surgery Patients
Vwaire J. Orhurhu, B.A., M.P.H., Khurram Owais, M.D., Jeffrey Hubbard, M.D., M.S., Amit Bardia, M.D., Anam Pal, M.D., Mario Montealegre, M.D., Emmanuel Akintoye, M.D., John Mitchell, M.D., Feroze Mahmood, M.D., Robina Matyal, M.D.
Harvard School of Public Health, Boston, Massachusetts, United States

Recent studies have reported adverse postoperative outcomes associated with red blood cell transfusion in patients undergoing cardiac surgery. In this study, we sought to examine the relationship between the quantity of red blood cells (RBC) units transfused and the risk of post-operative complications following cardiac surgery.


A total of 7599 consecutive patients who underwent cardiac surgery, including CABG and valvular surgeries, between January 2002 and December 2013 at a single center were included. Of these patients, 2296 could not meet the inclusion criteria for the study. A step-wise logistic regression was used to analyze twenty-four preoperative characteristics that could potentially act as confounders in our study. These included: weight, BMI, height, weight, gender, race, age, last preoperative creatinine level, perfusion time, hypertension, baseline hematocrit, surgery status, use of angiotensin converting enzyme inhibitor, diabetes, ejection fraction, congestive heart failure, and use of intra-aortic balloon pump. The adjusted association between RBC transfusion (1-2 units, 3-4 units, and >4 units) and six postoperative outcomes were reported in the form of odds ratio and a 95% confidence interval.


Patient characteristics are listed in Table 1. Acute Kidney Injury (AKI) occurred in 4.8% of the entire cohort of 5303 patients, 2.03% of the 2072 patients with no transfusion, 2.59% for the 1389 transfused with 1-2 units, 4.66% for the 1008 transfused with 3-4 units, and 16.28% for the 823 transfused with more than 4 units of RBCs. Compared to the group without blood transfusion, the adjusted odds of developing AKI were 1.67 (0.69-4.03, p= 0.259), 3.24 (1.34-7.84, p=0.009), and 5.42 (2.06-14.25, p=0.001) for 1-2 units, 3-4 units, and more than 4 units of transfused RBCs respectively. Of the five additional postoperative outcomes, renal failure, length of ICU stay and initial ventilation time were associated with blood cell transfusion in all RBC categories (Table 2). RBC transfusion greater than 4 units was, however, not associated with significantly higher odds of readmission after 30 days.


Transfusion of 1 – 2 units of RBC was common but not significantly associated with increased risk of AKI in patients undergoing cardiac surgery in our study. However, RBC transfusions greater than 3 units were significantly associated with relatively higher risk of AKI. These results suggest conservative measures and avoidance of aggressive RBCs transfusions may improve postoperative outcomes in patients undergoing cardiac surgery.
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