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

Abstract

ObjectivesThis study aimed to test the association between hypoxia level and outcomes according to shock status in traumatic brain injury (TBI) patients. MethodsAdult 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). ResultsOf 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. ConclusionsThere 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.