Circadian variation and outcome of in-hospital cardiopulmonary resuscitation.

OBJECTIVE: Assessment of contemporary in-hospital cardiopulmonary resuscitation outcomes.
METHODS: The study was designed as a retrospective, single-institution, registry investigation of all adult patients for whom a cardiopulmonary resuscitation (CPR) was attempted between October 1, 2002 and September 30, 2004. Hospital, patient's, arrest and outcome variables were included based on the "Utstein Style" of reviewing, reporting, and conducting research on in-hospital resuscitation.
RESULTS: 202 patients (94 women, age 70 +/- 15 years) received in-hospital CPR during the study period. One hundred-two events were primary respiratory arrests. Overall, 67% (95% CI 59%-72%) of patients were successfully resuscitated and 38% (95% CI 31%-45%) survived to hospital discharge. Of the patients with initial respiratory depression followed by circulatory collapse, 57% (95% CI 47%-66%) were alive at the end of hospitalization, while 20% (95% CI 13.3%-28.8%) of patients with cardiac arrest survived to hospital discharge (OR=5.2, 95% CI=2.8-9.5, P<0.0001). A circadian variation in the occurrence of primary cardiac arrests was noted with a nadir between midnight and 0600 hours. Though there were fewer events during overnight hours, CPR for patients with a primary cardiac arrest occurring at this time was less likely to be successful (OR = 2.5, 95% CI=1.01-6.1, p=0.04). This did not result in a difference in survival to discharge (OR=2.6, 95% CI=0.7-9.4, p=0.14).
CONCLUSION: Primary cardiac arrest has a significantly worse in-hospital outcome when compared to an initial respiratory event. The finding of a circadian variation in both the incidence and outcome of in-hospital primary cardiac arrest is intriguing and warrants further study.