Restrictive Transfusion Strategy after Cardiac Surgery: Role of Central Venous Oxygen Saturation Trigger: A Randomized Controlled Trial

Background

Recent guidelines on transfusion in cardiac surgery suggest that hemoglobin might not be the only criterion to trigger transfusion. Central venous oxygen saturation (Svo₂), which is related to the balance between tissue oxygen delivery and consumption, may help the decision process of transfusion. We designed a randomized study to test whether central Svo₂–guided transfusion could reduce transfusion incidence after cardiac surgery.

Methods

This single center, single-blinded, randomized controlled trial was conducted on adult patients after cardiac surgery in the intensive care unit (ICU) of a tertiary university hospital. Patients were screened preoperatively and were assigned randomly to two study groups (control or Svo₂) if they developed anemia (hemoglobin less than 9 g/dl), without active bleeding, during their ICU stay. Patients were transfused at each anemia episode during their ICU stay except the Svo₂ patients who were transfused only if the pretransfusion central Svo₂ was less than or equal to 65%. The primary outcome was the proportion of patients transfused in the ICU. The main secondary endpoints were (1) number of erythrocyte units transfused in the ICU and at study discharge, and (2) the proportion of patients transfused at study discharge.

Results

Among 484 screened patients, 100 were randomized, with 50 in each group. All control patients were transfused in the ICU with a total of 94 transfused erythrocyte units. In the Svo₂ group, 34 (68%) patients were transfused (odds ratio, 0.031 [95% CI, 0 to 0.153]; P < 0.001 vs. controls), with a total of 65 erythrocyte units. At study discharge, eight patients of the Svo₂ group remained nontransfused and the cumulative count of erythrocyte units was 96 in the Svo₂ group and 126 in the control group.

Conclusions

A restrictive transfusion strategy adjusted with central Svo₂ may allow a significant reduction in the incidence of transfusion.