The association between early arterial oxygenation and mortality in ventilated patients with acute ischaemic stroke

BACKGROUND: There are conflicting data that suggest that hyperoxia may be associated with either worse or better outcomes in patients suffering a stroke. OBJECTIVES: To investigate the association between PaO(2) in the first 24 hours in the intensive care unit and mortality among ventilated patients with acute ischaemic stroke. DESIGN: Retrospective cohort study. SETTING: Data were extracted from the Australian and New Zealand Intensive Care Society Adult Patient Database. PARTICIPANTS: Adults ventilated for ischaemic stroke in 129 ICUs in Australia and New Zealand, 2000-2009. MAIN OUTCOME MEASURES: The primary outcome was the odds ratio for in hospital mortality associated with "worst" PaO(2) considered as a categorical variable, with data divided into deciles and compared with the mortality of the 10th decile. For patients on an FiO(2) of _50% at any time in the first 24 hours, "worst" PaO(2) was defined as the PaO(2) associated with the highest alveolar-arterial (A-a) gradient. For patients on an FiO(2) of <50%, it was defined as the lowest PaO(2). Secondary outcomes were ICU and hospital length of stay and the proportion of patients in each decile discharged home. RESULTS: Of the 2643 patients eligible for study inclusion, 1507 (57%) died in hospital. The median "worst" PaO(2) was 117mmHg (interquartile range, 87-196mmHg). There was no association between worst PaO(2) and mortality, length of stay or likelihood of discharge home. CONCLUSIONS: We found no association between worst arterial oxygen tension in the first 24 hours in ICU and outcome in ventilated patients with ischaemic stroke.