Hospital patients suffering cardiac arrest at night or on weekend are far less likely to survive than those who suffer one during weekdays or weekday evenings, according to a U.S. study quoted by media reports Wednesday.

Although the study was not set up to pinpoint exactly why this is happening, it's likely that different staffing patterns, access to procedures, and other systemic issues may explain the difference in outcomes.

"Hospitals simply don't work the same at night as they do during the day," explained study author Dr. Mary Ann Peberdy, an associate professor of internal medicine and emergency medicine at Virginia Commonwealth University in Richmond.

The immediate cause of poor survival on nights and weekends may be one of timing: either there is a delay getting critical procedures or a delay in diagnosing the cardiac arrest in the first place.

"We're literally talking about a difference in seconds, which makes a significant impact," said Beth Mancini, associate dean of Undergraduate Nursing Programs at the University of Texas at Arlington. "It's time for hospitals to look critically at their processes."

Mancini is one of the "mothers" of the database used in this study, which is published in the Feb. 20 issue of the Journal of the American Medical Association.

According to the Institute of Medicine, up to 98,000 preventable in-hospital deaths occur every year in the United States, and the rate of medical errors is higher at night.

Previous, smaller studies have reported that heart attacks treated on a Saturday or Sunday are more deadly than those attended to during the week. 

Meanwhile, Canadian researchers have also found that strokes treated on weekend are deadlier than those that are treated on a weekday.

The current study, the most comprehensive of its kind, analyzed survival rates for 86,748 adults who had suffered cardiac arrest events in one of 507 hospitals participating in the American Heart Association's National Registry of Cardiopulmonary Resuscitation.

Other process issues may also be at fault. In one hospital, Mancini said, certain doors are locked at night, taking it longer to get a patient to a defibrillator. Even physician fatigue at the end of a shift could play a role.

"This paper really needs to go to hospitals, and the people who run them," Peberdy said.

(Xinhua News Agency February 20, 2008)