Am J Emerg Med. 2018 Dec 20;Epub ahead of print

# Effect of hypoxia on mortality and disability in traumatic brain injury according to shock status: A cross-sectional analysis.

Seo D, Shin S, Song K, Ro Y, Hong K, Park J

OBJECTIVES: This study aimed to test the association between hypoxia level and outcomes according to shock status in traumatic brain injury (TBI) patients.

METHODS: Adult TBI patients transported by emergency medical services in 10 provinces were enrolled. Hypoxia was a main exposure; three groups by oxygen saturation (SaO2, non-hypoxia (≥94%), mild hypoxia (90 ≤ SaO2 < 94%)), and severe hypoxia (<90%). Shock status (<systolic blood pressure 90 mmHg) was an interactive exposure. The outcomes were hospital mortality and worsened disability (a 2-point increase of Glasgow Outcome Scale). Multivariable logistic regression was used to calculate the adjusted odds (AORs) with 95% Confidence intervals (CIs).

RESULTS: Of the 6125 patients, the mortality/disability rates were 49.4%/69.0% in severe hypoxia, 30.7%/46.9% in mild hypoxia, and 18.5%/27.5% in normoxia (p < 0.0001). Mortality/disability rates were 47.1%/57.1% in shock status and 20.5%/31.4% in non-shock status (p < 0.0001). AORs (95% CIs) for worsened disability/mortality compared with normoxia (reference) were 3.23 (2.47-4.21)/2.24 (1.70-2.96) in patients with severe hypoxia and 2.11 (1.63-2.74)/1.84 (1.39-2.45) in those with mild hypoxia. AORs (95% CIs) for worsened disability/mortality was 1.58 (1.20-2.09)/1.33 (1.01-1.76) by severe hypoxia than normoxia in patient with only non-shock status in the interaction analysis.

CONCLUSIONS: There was a trend toward worsened outcomes with mild and severe hypoxia in patient with and without shock, however, the only met statistical significance for patients with both severe hypoxia and non-shock status.