Transfusion of 1 and 2 Units of Red Blood Cells is Associated with Increased Morbidity and Mortality

BACKGROUND:

This study examined the relationship between
transfusion of 1 or 2 units of red blood cells (RBCs) and the risk of
morbidity and mortality after isolated on-pump coronary artery bypass
grafting (CABG).

METHODS:

A total of 22,785 consecutive
patients underwent isolated on-pump CABG between January 1, 2008, and
December 31, 2011 in Michigan. We excluded 5,950 patients who received
three or more RBC units. Twenty-one preoperative variables significantly
associated with transfusion by univariate analysis were included in a
logistic regression model predicting transfusion, and propensity scores
were calculated. Transfusion and the propensity score covariate were
included in additional logistic regression models predicting mortality
and each of 11 postoperative outcomes.

RESULTS:

Operative
mortality for the study cohort of 16,835 patients was 0.8% overall,
0.5% for the 10,884 patients with no transfusion, and 1.3% for the 5,951
patients who received transfusion of 1 or 2 units (odds ratio 2.44;
confidence interval 1.74 to 3.42; p < 0.0001). The association between transfusion and mortality lessened after propensity adjustment but remained highly significant (odds ratio 1.86; confidence interval 1.21 to 2.87; p = 0.005). Of the 11 postoperative outcomes studied, all but sternal wound infection and need for dialysis were also significantly associated with transfusion.

CONCLUSIONS:

Transfusion
of as little as 1 or 2 units of RBCs is common and is significantly
associated with increased morbidity and mortality after on-pump CABG.
The relationship persists after adjustment for preoperative risk
factors. These results suggest that aggressive attempts at blood
conservation and avoidance of even small amounts of RBC transfusion may
improve outcomes after CABG.