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

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 nomioxia (p < 0.0001). Mortality/disability rates were 47.1%/57.1% in shock status and 20.5%/31 A% in non-shock status (p < 0.0001). AORs (95% as) 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 (139-2.45) in those with mild hypoxia. AORs (95% CIs) for worsened disability/mortality was 1.58 (120-2.09)/133 (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. (C) 2018 Elsevier Inc. All rights reserved.