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Am J Med. 2007 Feb;120(2):158-64.

Resuscitation in the hospital: circadian variation of cardiopulmonary arrest.

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Department of Internal Medicine, Mercer University School of Medicine/Medical Center of Central Georgia, Macon, Ga, USA.



Over 25 reports have found outpatient frequency of sudden cardiac death peaks between 6 am and noon; few studies, with inconsistent results, have examined circadian variation of death in hospitalized patients. This study assesses circadian variation in cardiopulmonary arrest of in-hospital patients across patient, hospital, and event variables and its effect on survival to discharge.


A retrospective, single institution registry included all admissions to the Medical Center of Central Georgia in which resuscitation was attempted between January 1987 and December 2000. The registry included 4692 admissions; only the first attempt was reported. Analyses of 1-, 2-, 4-, and 8-hour intervals were performed; 1- and 4-hour intervals are presented.


Significant circadian variation was found at 1 hour (P=.01), but not at 4-hour intervals. Significant circadian variation was found for initial rhythms that were perfusing (P=.03) and asystole (P=.01). A significantly higher percentage of unwitnessed events were found as asystole during the overnight hours (P=.002). Using simple logistic regression, time in 4-hour intervals and rhythm were each significantly related to patient survival until hospital discharge (P=.003 and P <.0001). In multivariate analysis, only rhythm remained significant.


Circadian variation of cardiopulmonary arrest in this hospital has several temporal versions and is related to survival. Late night variation in witnessed events and rhythm suggests a delay between onset of clinical death and discovery, which contributes to poorer outcomes.

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