Intensive care implications of epidemic thunderstorm asthma

Objective: To investigate the environmental precipitants, treatment and outcome of critically ill patients affected by the largest and most lethal reported epidemic of thunderstorm asthma. Design, setting and participants: Retrospective multicentre observational study. Meteorological, airborne particulate and pollen data, and a case series of 35 patients admitted to 15 intensive care units (ICUs) due to the thunderstorm asthma event of 21–22 November 2016, in Victoria, Australia, were analysed and compared with 1062 total ICU-admitted Australian patients with asthma in 2016. Main outcome measures: Characteristics and outcomes of total ICU versus patients with thunderstorm asthma, the association between airborne particulate counts and storm arrival, and ICU resource utilisation. Results: All 35 patients had an asthma diagnosis; 13 (37%) had a cardiac or respiratory arrest, five (14%) died. Compared with total Australian ICU-admitted patients with asthma in 2016, patients with thunderstorm asthma had a higher mortality (15% v 1.3%, P < 0.001), were more likely to be male (63% v 34%, P < 0.001), to be mechanically ventilated, and had shorter ICU length of stay in survivors (median, 31.8 hours [interquartile range (IQR), 14.8–43.6 hours] v 40.7 hours [IQR, 22.3–75.1 hours]; P = 0.025). Patients with cardiac arrest were more likely to be born in Asian or subcontinental countries (5/10 [50%] v 4/25 [16%]; relative risk, 3.13; 95% CI, 1.05–9.31). A temporal link was demonstrated between airborne particulate counts and arrival of the storm. The event used 15% of the public ICU beds in the region. Conclusion: Arrival of a triggering storm is associated with an increase in respirable airborne particles. Affected critically ill patients are young, have a high mortality, a short duration of bronchospasm, and a prior diagnosis of asthma is common.