Matching early arterial oxygenation to long-term outcome in severe traumatic brain injury: target values

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OBJECTIVE

The aim of this study was to examine the relationship between early arterial oxygenation thresholds and long-term outcome after severe traumatic brain injury (TBI).

METHODS

In a post hoc analysis of a randomized trial, adults with severe TBI were classified based on exposure to different levels of arterial oxygenation as measured using the average of arterial partial pressure of oxygen (PaO2) values obtained within 24 hours of admission. Potentially important PaO2 thresholds were defined a priori. The primary outcome was Glasgow Outcome Scale–Extended (GOSE) score at 6 months. Secondary outcomes were cognitive outcomes measured using a battery of 9 neuropsychological tests administered at 6 months, and 6-month mortality.

RESULTS

In adjusted analyses, oxygenation thresholds of 150 and 200 mm Hg were associated with better functional outcome at 6 months (adjusted OR for better functional outcome on GOSE 1.82 [95% CI 1.12–2.94] and 1.59 [95% CI 1.06–2.37], respectively) and improved cognitive outcome at 6 months (adjusted beta coefficients for better cognitive percentile across 9 neuropsychological tests: 6.9 [95% CI 1.3–12.5] and 6.8 [95% CI 2.4–11.3], respectively). There was no significant association between oxygenation level and 6-month mortality except at a PaO2 threshold of 200 mm Hg (OR for death 0.36, 95% CI 0.18–0.71). Higher or lower oxygenation thresholds were not associated with functional or cognitive outcome.

CONCLUSIONS

In this observational study, the relationship between early arterial oxygenation and long-term functional and cognitive TBI outcomes appears to be U-shaped. Mild levels of hyperoxemia within the first 24 hours after injury were associated with better long-term functional and cognitive outcomes. These findings highlight the importance of examining balanced oxygen supplementation as a potential strategy to improve TBI outcomes in future research.

ABBREVIATIONS AIS = Abbreviated Injury Scale; COBRIT = Citicoline Brain Injury Treatment Trial; GCS = Glasgow Coma Scale; GOSE = Glasgow Outcome Scale–Extended; ISS = Injury Severity Score; PaO2 = arterial partial pressure of oxygen; TBI = traumatic brain injury.

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  • Supplemental Figs S1 and S2 and Table (PDF 544 KB)

Article Information

Correspondence Aziz S. Alali: University of Washington, Harborview Medical Center, Seattle, WA. aalali@uw.edu.

INCLUDE WHEN CITING Published online February 8, 2019; DOI: 10.3171/2018.10.JNS18964.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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    Stacked bar chart of GOSE score distribution at 6 months for different levels of arterial oxygenation. Hypoxemia is defined as any PaO2 < 60 mm Hg over the first 24 hours.

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    Adjusted relationship between arterial oxygenation level and GOSE score at 6 months. Adjusted covariates were age, GCS motor score, pupillary reactivity and asymmetry, hypotension, CT findings, mechanism of injury, and whether multisystem injuries were present. Hypoxemia is defined as any PaO2 < 60 mm Hg over the first 24 hours.

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    Adjusted relationship between arterial oxygenation level and 6-month mortality. Adjusted covariates were age, GCS motor score, pupillary reactivity and asymmetry, hypotension, CT findings, mechanism of injury, and whether multisystem injuries were present. Hypoxemia is defined as any PaO2 < 60 mm Hg over the first 24 hours.

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