Association between early hyperoxaemia exposure and intensive care unit mortality in intracerebral haemorrhage - an observational cohort analysis

Abstract

Abstract Background Supraphysiologic levels of oxygen could have potential adverse effects on the brain. These effects may be dose and time-dependent in brain injured patients. We therefore aimed to assess whether exposure to excess supplemental oxygen, measured as time-weighted mean exposure to hyperoxaemia, was associated with Intensive Care Unit (ICU) mortality in Intracerebral Haemorrhage (ICH).Methods In this single-centre retrospective cohort study we included all patients admitted to our ICU with a diagnosis of primary spontaneous ICH and an ICU length of stay over 24 hours. To provide a longitudinal measure of hyperoxaemia exposure we calculated the hyperoxaemia dose, defined as the area under the PaO2 time curve above the threshold PaO2 value of 13.3 kPa (100 mmHg) divided by the number of hours of potential exposure. To provide consistent potential exposure windows, nested subsets were created with progressively longer exposure periods (0–1 day, 0–2 days, 0–3 days, 0–4 days, 0–5 days, 0–6 days, 0–7 days). We used Cox regression to model the time-dependent association between hyperoxaemia dose and ICU mortality.Results Between September 2019 and July 2022, 275 patients met the inclusion criteria, with 24,588 ABG results available for analysis. Almost all patients (97.45%) were exposed to hyperoxaemia during their ICU admission. Cox regression modelling showed an association between hyperoxaemia dose and ICU mortality (Hazard Ratio (HR) 1.15, CI 1.05–1.25, p = 0.003). This association was observed in the 0–1 day exposure window in a step-function extended Cox model (HR 1.19, CI 1.06–1.35, p = 0.005) but not in any of the subsequent exposure periods.Conclusion In ICH patients admitted to ICU, early exposure to hyperoxaemia was associated with increased ICU mortality. Further prospective study is required to inform guidance on early systemic oxygen targets in ICH.