Do blood transfusions improve outcomes related to mechanical ventilation?

Background: Correcting the decrease in oxygen delivery from anemia using al logeneic RBC transfusions has been hypothesized to help with increased oxyg en demands during weaning from mechanical ventilation. However, it is also possible that transfusions hinder the process because RBCs may not be able to adequately increase oxygen delivery. In this study, we determined whethe r a liberal RBC transfusion strategy improved outcomes related to mechanica l ventilation. Methods: Seven hundred thirteen patients receiving mechanical ventilation, representing a subgroup of patients from a larger trial, were randomized to either a restrictive transfusion strategy, receiving allogeneic RBC transf usions at a hemoglobin concentration of 7.0 g/dL land maintained between 7. 0 g/dL and to 9.0 g/dL), or to a liberal transfusion strategy, receiving RB Cs at 10.0 g/dL land maintained between 10.0 g/dL and 12.0 g/dL). The large r trial was designed to evaluate transfusion practice rather than weaning p er se. Results: Baseline characteristics in the restrictive-strategy group (n = 357) and the liberal-strategy group (n = 356) were comparable. The ave rage durations of mechanical ventilation were 8.3 +/- 8.1 days and 8.3 +/- 8.1 days (95% confidence interval [CI] around difference, - 0.79 to 1.68; p = 0.48), while ventilator-free days were 17.5 +/- 0.9 days and 16.1 +/- 11 .4 days (95% CI around difference, - 3.07 to 0.21; p = 0.09) in the restric tive-strategy group vs the liberal-strategy group, respectively. Eighty-two percent of the patients in the restrictive-strategy group were considered successfully weaned and extubated for at least 24 h, compared to 78% for th e liberal-strategy group (p = 0.19), The relative risk (RR) of extubation s uccess in the restrictive-strategy group compared to the liberal-strategy g roup, adjusted for the confounding effects of age, APACHE (acute physiology and chronic health evaluation) II score, and comorbid illness, was 1.07 (9 5% CI, 0.96 to 1.26; p = 0.43), The adjusted RR of extubation success assoc iated with restrictive transfusion in the 219 patients who received mechani cal ventilation for > 7 days was 1.1 (95% CI, 0.84 to 1.45; p = 0.47). Conclusion: In this study, there was no evidence that a liberal RBC transfu sion strategy decreased the duration of mechanical ventilation in a heterog eneous population of critically ill patients.