TRACS: Differing blood transfusion strategies yield similar complication, death rates in cardiac surgery patients

Hajjar L. JAMA. 2010;304:1559-1567.

Issue: December 2010

A liberal strategy for initiating perioperative blood transfusions resulted in statistically similar clinical complication and mortality rates compared with a more restrictive strategy, results from a study indicated. Regardless of treatment strategy, blood transfusions were associated with higher death and complication rates.

Some researchers have suggested the use of perioperative transfusion for the maintenance of hemoglobin levels of 10 g/dL and 30% hematocrit concentrations, according to the study. Other researchers have recently questioned these thresholds, however, as the risks of transfusion and the highly individualized nature of a patient’s response to anemia have become better understood.

A prior study of critically ill patients found that maintaining hemoglobin concentrations between 7 and 9 g/dL may result in fewer patient deaths than a more liberal strategy of sustaining hemoglobin between 10 and 12 g/dL. Ludhmila A. Hajjar, MD, PhD, and colleagues compared similar strategies in 502 patients undergoing elective cardiac surgery with cardiopulmonary bypass at a cardiac surgery referral center in Brazil.

Before surgery, patients were randomly assigned in a prospective fashion to two groups. Patients in the restrictive group received red blood cell transfusions if their hematocrit values were less than 24% at any point from the start of surgery until discharge from the ICU. For patients in the liberal group, the transfusion trigger was hematocrit levels of less than 30%.

Significantly more patients in the liberal group received red blood cell transfusions. In this group, 198 of 253 patients (78%) received a transfusion, compared with 118 of 249 (47%) patients in the restrictive group (P<.001).

Average hemoglobin concentrations were kept at 10.5 g/dL (95% CI, 10.4-10.6) in the liberal group vs. 9.1 g/dL (95% CI, 9.0-9.2) in the restrictive group (P<.001).

The researchers defined their composite endpoint as 30-day all-cause mortality and severe morbidity, including acute respiratory distress syndrome, cardiogenic shock or acute renal injury requiring dialysis or hemofiltration. In the liberal group, 10% of patients reached the endpoint vs. 11% of patients in the restrictive group (95% CI, –6% to 4%). There were no significant differences in cardiac complications, neurologic complications, infection or severe bleeding requiring reoperation.

In their conclusion, the researchers posited that the reported similarity in complication rates “occurred because the restrictive strategy did not result in reduced oxygen availability to the cells. This is supported by the lack of difference in lactate levels between the two groups during the study period”

Although neither transfusion strategy was associated with greater risk, the total number of transfused red blood cell units was an independent risk factor for complications or death at 30 days (HR for each additional unit transfused, 1.2; 95% CI, 1.1-1.4).

“These findings suggest that the primary strategy in patients undergoing cardiac surgery should be to avoid giving [red blood cell] transfusion solely to correct low hemoglobin levels. The increased risk of mortality related to the number of transfused [red blood cell] units supports a restrictive therapy in cardiac surgery,” the researchers wrote. “In addition, clinicians caring for patients after cardiac surgery should administer only one [red blood cell] unit at a time because this may result in less exposure to risks but similar benefits.”

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