The appropriate hemoglobin (Hb) level threshold for the early phase (i.e. from Emergency Department to ICU admission) in patients with severe traumatic brain injury (TBI) is still unknown. Therefore, we aimed to examine the association between Hb levels during the early phase and neurological outcomes in patients with severe TBI using data from the Brain Hypothermia (B-HYPO) Study Group.

We performed a post-hoc analysis of the B-HYPO study (a prospective, multicenter, randomized controlled trial on patients with severe TBI who received either mild therapeutic hypothermia [MTH; 32.0 °C–34.0 °C] or fever control [35.5 °C–37.0 °C]). We calculated Hb levels during early phase by the formula: (admission Hb + Hb on day 1) / 2. The primary outcome was the association between during early phase Hb levels and 6-month neurological outcome after the TBI based on the Glasgow Outcome Scale scores (a measure of functional recovery defined as moderate disability or good recovery).

We reviewed data from 130 patients and found favorable neurological outcomes in 48.5% of them. We found significant differences between the favorable and unfavorable neurological outcome groups in terms of their Hb levels on admission and on day 1. But, we found no Hb level differences after day 3 (including 1 day after rewarming). Our multivariable analysis showed that Hb levels during early phase were significantly associated with favorable neurological outcomes (odds ratio, 1.387; 95% confidence interval, 1.057–1.858; P = 0.018).

High early phase Hb levels are associated with favorable neurological outcomes after severe TBI.