Effect of age of transfused red blood cells on neurologic outcome following traumatic brain injury (ABLE-tbi Study): a nested study of the Age of Blood Evaluation (ABLE) trial

Background: Anemia is common in critically ill patients with traumatic brain injury, and often requires red blood cell transfusion. Studies suggest that prolonged storage causes lesions of the red blood cells, including a decreased ability to carry oxygen. Considering the susceptibility of the brain to hypoxemia, victims of traumatic brain injury may thus be more vulnerable to exposure to older red blood cells. Methods: Our study aimed to ascertain whether the administration of fresh red blood cells (seven days or less) results in a better neurologic outcome compared with standard red blood cells in critically ill patients with traumatic brain injury requiring transfusion. The Age of Blood Evaluation in traumatic brain injury (ABLE-tbi) study was a nested study within the ABLE study(ISRCTN44878718). Our primary outcome was the extended Glasgow Outcome Scale (GOSe) at six months. Results: In the ABLE study, 217 subjects suffered a traumatic brain injury: 110 in the fresh group, and 107 in the standard group. In the fresh group, 68 (73.1%) of the patients had an unfavourable neurologic outcome (GOSe ≤ 4) compared with 60 (64.5%) in the standard group (P= 0.21). Using a sliding dichotomy approach, we observed no overall effect of fresh red blood cells on neurologic outcome (odds ratio [OR], 1.34; 95% confidence interval [CI], 0.72 to 2.50; P= 0.35) but observed differences across prognostic bands with a decreased odds of unfavourable outcome in patients with the best prognosis at baseline (OR, 0.33; 95% CI, 0.11 to 0.96; P= 0.04) but an increased odds in those with intermediate and worst baseline prognosis (OR, 5.88; 95% CI,1.66 to 20.81; P= 0.006; and OR, 1.67; 95% CI, 0.53 to 5.30; P= 0.38, respectively). Conclusion: Overall, transfusion of fresh red blood cells was not associated with a better neurologic outcome at six months in critically ill patients with traumatic brain injury. Nevertheless, we cannot exclude a differential effect according to the patient baseline prognosis. Trial registration: ABLE study (ISRCTN44878718); registered 22 August, 2008.