L e t t e r s t o t h e e d i t o r Hypoxia and Traumatic Brain InjuryTO THE EDITOR: We read with interest the paper by Tolias, et al. (Tolias CM, Rurent M, Seiler R, et al: Normobar-ic hyperoxia-induced improvement in cerebral metabolism and reduction in intracranial pressure in patients with severe head injury: a prospective historical cohort-matched study. J Neurosurg 101: 435-444, September, 2004) in which the authors describe improvement in cerebral metabolism and reduction in intracranial pressure in patients with severe traumatic brain injury (TBI) treated for 24 hours with 100% fraction of inspired O 2 (FiO 2 ). AbstractObject. The effect of normobaric hyperoxia (fraction of inspired O 2 [FIO 2 ] concentration 100%) in the treatment of patients with traumatic brain injury (TBI) remains controversial. The aim of this study was to investigate the effects of normobaric hyperoxia on five cerebral metabolic indices, which have putative prognostic significance following TBI in humans.Methods. At two independent neurointensive care units, the authors performed a prospective study of 52 patients with severe TBI who were treated for 24 hours with 100% FIO 2 , starting within 6 hours of admission. Data for these patients were compared with data for a cohort of 112 patients who were treated in the past; patients in the historical control group matched the patients in our study according to their Glasgow Coma Scale scores after resuscitation and their intracranial pressure within the first 8 hours after admission. Patients were monitored with the aid of intracerebral microdialysis and tissue O 2 probes.Normobaric hyperoxia treatment resulted in a significant improvement in biochemical markers in the brain compared with the baseline measures for patients treated in our study (patients acting as their own controls) and also compared with findings from the historical control group. In the dialysate the glucose levels increased (369.02 Ϯ20.1 mol/L in the control group and 466.9 Ϯ 20.39 mol/L in the 100% O 2 group, p = 0.001), whereas the glutamate and lactate levels significantly decreased (p Ͻ 0.005). There were also reductions in the lactate/glucose and lactate/pyruvate ratios. Intracranial pressure in the treatment group was reduced significantly both during and after hyperoxia treatment compared with the control groups (15.03 Ϯ 0.8 mm Hg in the control group and 12.13 Ϯ 0.75 mm Hg in the 100% O 2 group, p Ͻ 0.005) with no changes in cerebral perfusion pressure. Outcomes of the patients in the treatment group improved.Conclusions. The results of the study support the hypothesis that normobaric hyperoxia in patients with severe TBI improves the indices of brain oxidative metabolism. Based on these data further mechanistic studies and a prospective randomized controlled trial are warranted. This is a major contribution to the growing body of evidence that supernormal amounts of O 2 delivered early to the patient with severe brain injury has the potential for improving metabolic derangement and potentially clinical outc...
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