Effect of Time of Day on Prehospital Care and Outcomes after Out-of-Hospital Cardiac Arrest
Background—Over 300,000 out-of-hospital cardiac arrests (OHCA) occur each year in the United States. The relationship between time of day and OHCA outcomes in the prehospital setting is unknown. Any such association may have important implications for Emergency Medical Services (EMS) resource allocation.
Methods and Results—We performed a retrospective review of cardiac arrest data from a large, urban EMS system. Included were OHCA occurring in adults from January 2008 to February 2012. Excluded were traumatic arrests and cases where resuscitation measures were not performed. Day was defined as 8:00am to 7:59pm, and night as 8:00pm to 7:59am. A relative risk regression model was used to evaluate the association between time of day and prehospital return of spontaneous circulation (ROSC) and 30-day survival, adjusting for clinically relevant predictors of survival. Among the 4,789 included cases, 1,962 (41.0%) occurred at night. Mean age was 63.8 (SD 17.4) years; 54.5% were male. Patients with an OHCA occurring at night did not have significantly lower rates of prehospital ROSC compared to daytime arrests (11.6% vs. 12.8%, p=0.20). However, rates of 30-day survival were significantly lower at night (8.56% vs. 10.9%, p=0.02). After adjusting for demographics, presenting rhythm, field termination, duration of call, dispatch-to-scene interval, automated external defibrillator application, bystander cardiopulmonary resuscitation, and location, 30-day survival remained significantly higher following daytime OHCA, with a relative risk of 1.10 (95% CI 1.02-1.18).
Conclusions—Rates of 30-day survival were significantly higher for OHCA occurring during the day compared to night, even after adjustment for patient, event, and prehospital care differences.
- emergency medicine
- emergency department
- heart arrest
- cardiac arrest
- cardiopulmonary resuscitation
- emergency medical services
- Received February 17, 2013.
- Accepted March 6, 2013.