Transfusion of blood during cardiac surgery is associated with higher long-term mortality in low-risk patients

Numerous reports have emphasized the need for reduction in transfusions of allogeneic red blood cells (RBC) due to increased morbidity and mortality. Nevertheless, transfusion rates are still high in several cardiac surgery institutions. Reports on long-term survival after cardiac surgery and RBC transfusion are few.

Data from the Western Denmark Heart Registry (WDHR) were used to identify all (25,117) adult cardiac surgery performed in four centres during 1999-2010. Patients with multiple entries (1049), re-do cardiac surgery (985), special/complex procedures (2329), dying within 30 days (668) and not eligible for follow-up (85) were excluded leaving a cohort of 20,001. Registration in the WDHR is mandatory. WDHR and the unique Danish Civil Registration System with continuous sequential updates of the Danish population ensure that all patients and outcomes are accounted for.

Kaplan-Meier survival plot for low-risk patients (EuroSCORE 0-4), undergoing simple cardiac surgery showed a significantly lower estimated survival after >4500 days (0.637 vs. 0.745) when receiving perioperative RBC transfusion (P<0.0001). The difference was less evident in patients with EuroSCORE 5-9 (0.373 vs. 0.4436, P<0.0001), while high-risk patients showed no difference. Adjusted risk ratio, after RBC transfusion, containing among others age, sex, EuroSCORE and diabetes, was 1.83 (95% CI (confidence interval) 1.67-2.01). The survival rate was independent of up till six units of RBC.

Long-term follow-up of low-risk patients undergoing simple cardiac surgery demonstrates a more than 10% higher mortality when receiving perioperative RBC transfusion. Even transfusion of 1-2 units seems to carry a risk of that magnitude.