Atrial fibrillation and mortality in critically ill patients undergoing emergent fixed-wing air ambulance transport: a retrospective cohort study

Abstract

ObjectiveTo examine if atrial fibrillation at the time of emergency transport to tertiary care hospital by air ambulance is associated with increased mortality risk.DesignRetrospective cohort study. Logistic regression and Cox regression were used to assess associations of condition with outcome (mortality). Propensity score matching (1:1) was used to identify the comparison cases.SettingOne tertiary care centre in sparsely populated northern SwedenParticipantsCritical care cases undergoing emergent fixed-wing air transport in the northern healthcare region of Sweden was included. 2143 cases were included in the study between 2000-2016.Primary and secondary outcomes measuresThe primary outcome was mortality risk at 90-days post transport in cases with atrial fibrillation during the fixed-wing air ambulance transport. The secondary outcome measures were vasopressor and impaired oxygenation was associated with mortality at 90-days post transport.ResultsAtrial fibrillation showed a higher 90-day post transport mortality risk estimate in the multivariate analysis of all cases, hazard ratio (HR) 1.70 (95% CI 1.08-2.67, p=0.022). In a propensity matched analysis, no increased mortality risk for atrial fibrillation was observed at the same time interval with hazard ratio 1.22 (0.65-2.27, p=0.536). In the secondary analysis, vasopressor use was associated with atrial fibrillation at the time of transport whereas impaired oxygenation was not associated with an increased risk of atrial fibrillation.ConclusionNo increased mortality risk at 90 days was seen for cases with atrial fibrillation at time of transport in this cohort using a propensity score matched approach.Article summaryStrengths and limitationsExplores the scarcely studied topic of mortality risk and atrial fibrillation at time of transport with fixed-wing air ambulanceQuasi-experimental approach with propensity score matching to handle selection biasNo co-morbidity and disease severity data which risk confounding resultsA single transport system was studied which limits generalizability