"Hospitals may be less prepared to identify and respond to cardiac arrest during the night shift, when overall staffing is typically at its lowest," said Mary Ann Peberdy, M.D., lead author of the study and assistant professor of internal medicine and emergency medicine at Virginia Commonwealth University Health System in Richmond, Va.
Cardiac arrest is the abrupt loss of heart function. The most common cause of cardiac arrest is an abnormal heart rhythm known as ventricular fibrillation (VF). VF can be treated with a defibrillator, which can correct the abnormal heart rhythm.
The American Heart Association estimates that about 95 percent of cardiac arrest victims die before reaching the hospital. In cities where cardiopulmonary resuscitation and defibrillation are provided within three to five minutes, survival rates are as high as 49 percent to 74 percent.
"However, little is known about survival of patients who are already in the hospital when they suffer from cardiac arrest," Peberdy said.
Researchers used records from 250 hospitals participating in the National Registry of Cardiopulmonary Resuscitation (NRCPR). They evaluated 17,991 cardiac arrests that occurred in hospitalized adults between January 2000 and June 2002.
The patients' average age was 68. Seventy-two percent were white, 21 percent were black, 5 percent were Hispanic, and 2 percent were of other ethnic/racial origin.
Peberdy categorized the cardiac arrest events by when they occurred during the most common work shifts: day (7 a.m.-3 p.m.), evening (3 p.m.-11 p.m.) and night (11 p.m.-7 a.m.). They used a statistical analysis called ANOVA, or ANalysis Of VAriance to compare rates of cardiac arrest and time of shift. There was no statistically significant difference in the occurrence of cardiac arrest by shift. In addition, neither age nor ethnicity/race corresponded to the shift in which cardiac arrest occurred.
However, patients whose cardiac arrest occurred at night had a lower survival rate (41 percent) than those whose event occurred during the day (49 percent) or evening (48 percent). The survival was the same for those treated in the intensive care unit (ICU) or a non-ICU area.
Eighteen percent of those who had cardiac arrest in the day or evening survived until discharge, while only 13 percent of those with cardiac arrest during the night survived to discharge.
The researchers also found that cardiac arrest was recorded on hospital monitors and/or witnessed much less often at night - in 82 percent of events compared to 89 percent during both the day and evening shifts.
"This study draws attention to process issues in in-hospital cardiac arrest responses," Peberdy said. "We hope the information will lead to more hospitals evaluating their staff training and response to cardiac arrest at all times during the day and especially at night, and developing better mechanisms for identifying cardiac arrest in the hospital."
Co-author is Joseph P. Ornato, M.D.