Original Articles

The Relationship between Intra-Operative Transfusions and Nadir Hematocrit on Post-Operative Outcomes after Cardiac Surgery

^* Westchester Medical Center, New York Medical College, Valhalla, New York.
^† Division of Cardiac Surgery, Massachusetts General Hospital, Boston, Massachusetts.
^‡ INOVA Health Systems, Fairfax, Virginia.
^§ St. John Providence Health System Detroit Hospitals, Detroit, Michigan.
^¶ Department of Cardiac Surgery, University of Michigan, Ann Arbor, Michigan.
^∥ Specialty Care, Nashville, Tennessee.
^** Division of Cardiothoracic Surgery, Department of Surgery, Henry Ford Hospital, Heart and Vascular Institute, Detroit, Michigan.
^†† PERForm Registry and the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative

Address correspondence to: Donald S. Likosky, PhD, Section Head, Section of Health Services Research and Quality, Department of Cardiac Surgery (5346 CVC), University of Michigan Medical School, Ann Arbor, MI 48109-5864. E-mail: likosky@umich.edu

Received: 7 July 2016
Accepted: 14 October 2016

Abstract

Uncertainty exists regarding the optimal strategy for the management of anemia in the setting of cardiac surgery. We sought to improve our understanding of the role of intra-operative hematocrit (HCT) and transfusions on peri-operative outcomes following cardiac surgery. A total of 18,886 patients undergoing on-pump cardiac surgery were identified from a multi-institutional registry including surgical and perfusion data. Patients were divided into four groups based on their intra-operative nadir HCT (<21 or ≥21) and whether or not they received intra-operative red blood cell (+RBC or −RBC) transfusions. Outcomes were adjusted for the Society of Thoracic Surgeons predicted risk of mortality (PROM), pre-operative HCT, and medical center. Regardless of nadir HCT cohort, those who received a transfusion had higher PROM relative to patients who did not receive a transfusion. The mean PROM was significantly higher among those HCT ≥21 + RBC (5.3%) vs. HCT ≥ 21 − RBC (1.9%), p < .001. Similarly, the PROM was significantly higher among HCT <21 + RBC (5.1%) vs. those HCT <21 − RBC (3.1%), p < .001. Adjusted outcomes demonstrated an increased impact of RBC transfusions on adverse outcomes irrespective of nadir HCT including stroke (p < .001), renal failure (p < .001), prolonged ventilation (p < .001), and mortality (p < .001). This study demonstrates that transfusions have a more profound effect on post-operative cardiac surgery outcomes than anemia.