Harmful effects of early hyperoxaemia in patients admitted to general wards: an observational cohort study in South Korea

Objectives

We evaluated the association between hyperoxaemia induced by a non-invasive oxygen supply for 3 days after emergency department (ED) arrival and the clinical outcomes at day 5 after ED arrival.

Design

Observational cohort study.

Setting and patients

Consecutive ED patients ≥16 years of age with available arterial blood gas analysis results who were admitted to our hospital were enrolled from January 2010 to December 2016.

Interventions

The highest (PaO_2MAX), average (PaO_2AVG) and median (PaO_2MED) PaO₂ (arterial oxygen pressure) values within 72 hours and the area under the curve divided by the time elapsed between ED admittance and the last PaO₂ result (AUC₇₂) were used to assess hyperoxaemia. The AUC₇₂ values were calculated using the trapezoid rule.

Outcomes

The primary outcome was the 90-day in-hospital mortality rate. The secondary outcomes were intensive care unit (ICU) transfer and respiratory failure at day 5 after ED arrival, as well as new-onset cardiovascular, coagulation, hepatic and renal dysfunction at day 5 after ED arrival.

Results

Among the 10 141 patients, the mortality rate was 5.8%. The adjusted ORs of in-hospital mortality for PaO_2MAX, PaO_2AVG, PaO_2MED and AUC₇₂ were 0.79 (95% CI 0.61 to 1.02; p=0.0715), 0.92 (95% CI 0.69 to 1.24; p=0.5863), 0.82 (95% CI 0.61 to 1.11; p=0.2005) and 1.53 (95% CI 1.25 to 1.88; p<0.0001). All of the hyperoxaemia variables showed significant positive correlations with ICU transfer at day 5 after ED arrival (p<0.05). AUC₇₂ was positively correlated with respiratory failure, as well as cardiovascular, hepatic and renal dysfunction (p<0.05). PaO_2MAX was positively correlated with cardiovascular dysfunction. PaO_2MAX and AUC₇₂ were negatively correlated with coagulation dysfunction (p<0.05).

Conclusions

Hyperoxaemia during the first 3 days in patients outside the ICU is associated with in-hospital mortality and ICU transfer at day 5 after arrival at the ED.

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