Why do patients develop in-hospital cardiac arrest? A prospective clinical observational study (WHY-IHCA)

No previous study has described in-hospital cardiac arrest (IHCA) aetiologies prospectively through a protocolised investigation. In this study, we investigated IHCA aetiologies in both IHCA patients achieving return of spontaneous circulation (ROSC) as well as IHCA patients not achieving ROSC. Adult IHCA patients were included at Aarhus University Hospital in Denmark. In patients with ROSC, the investigation consisted of blood tests including toxicology, echocardiography, and whole-body computed tomography (CT). In patients without ROSC, the investigation consisted of blood tests including toxicology and whole-body CT- and magnetic resonance imaging (MRI). The primary outcome was the IHCA aetiology as determined by a four-person expert panel using pre-defined main- and subcategories. Secondary outcomes included the presumed cause as determined by cardiac arrest team leaders as well as the discrepancy between presumed and expert panel causes. 150 patients were included, and 71 (47%) achieved ROSC. Expert panel aetiologies (with between-expert ranges) were determined as cardiac in 29% (27-29%) and pulmonary in 30% (25-32%) of cases. Myocardial ischaemia and hypoxia were the most prevalent specific subcategories in 11% (10-15%) and 21% (14-23%) of cases, respectively. The cause was deemed unknown in 7% (0-14%) of cases, and presumed causes were deemed unknown in 26% of cases. Agreement between presumed and expert panel causes was low (Kappa: 0.16-0.42 across experts). The predominant aetiologies of IHCA are pulmonary and cardiac. A protocolised investigation, including post-mortem investigations, aided in disclosing IHCA aetiologies. Presumed causes are often unknown and often differ from expert panel causes.