Anemia and brain oxygen after severe traumatic brain injury
Oddo, Mauro ; Levine, Joshua ; Kumar, Monisha ; Iglesias, Katia ; Frangos, Suzanne ; Maloney-Wilensky, Eileen ; Le Roux, Peter
In: Intensive Care Medicine, 2012, vol. 38, no. 9, p. 1497-1504
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- Purpose: To investigate the relationship between hemoglobin (Hgb) and brain tissue oxygen tension (PbtO2) after severe traumatic brain injury (TBI) and to examine its impact on outcome. Methods: This was a retrospective analysis of a prospective cohort of severe TBI patients whose PbtO2 was monitored. The relationship between Hgb—categorized into four quartiles (≤9; 9-10; 10.1-11; >11g/dl)—and PbtO2 was analyzed using mixed-effects models. Anemia with compromised PbtO2 was defined as episodes of Hgb≤9g/dl with simultaneous PbtO2<20mmHg. Outcome was assessed at 30days using the Glasgow outcome score (GOS), dichotomized as favorable (GOS 4-5) vs. unfavorable (GOS 1-3). Results: We analyzed 474 simultaneous Hgb and PbtO2 samples from 80 patients (mean age 44±20years, median GCS 4 (3-7)). Using Hgb>11g/dl as the reference level, and controlling for important physiologic covariates (CPP, PaO2, PaCO2), Hgb≤9g/dl was the only Hgb level that was associated with lower PbtO2 (coefficient −6.53 (95% CI −9.13; −3.94), p<0.001). Anemia with simultaneous PbtO2<20mmHg, but not anemia alone, increased the risk of unfavorable outcome (odds ratio 6.24 (95% CI 1.61; 24.22), p=0.008), controlling for age, GCS, Marshall CT grade, and APACHE II score. Conclusions: In this cohort of severe TBI patients whose PbtO2 was monitored, a Hgb level no greater than 9g/dl was associated with compromised PbtO2. Anemia with simultaneous compromised PbtO2, but not anemia alone, was a risk factor for unfavorable outcome, irrespective of injury severity