April 8, 1997
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Keeping surgery patients warm is a simple and inexpensive way to significantly reduce the risk of heart complications, the leading cause of post-operative death, a Johns Hopkins study suggests.
Maintaining a surgical patient's normal body temperature has been shown to reduce infections, speed healing and shorten hospital stays, but this is the first prospective clinical trial to show it also reduces the chance of serious heart injury, says Steven M. Frank, M.D., lead author and an associate professor of anesthesiology and critical care medicine.
Results are published in the April 9 issue of the Journal of the American Medical Association and discussed in an accompanying editorial.
Most patients experience hypothermia, or lowered body temperature, during major surgery because of anesthesia, chilly operating rooms, open body cavities, intravenous fluids and blood infusions. While cool operating rooms keep surgeons comfortable and provide patients with some benefits such as slowing metabolism, hypothermia also boosts patients' stress hormones, constricts blood vessels and raises blood pressure. This cardiovascular stress may trigger serious heart problems.
Researchers studied 300 non-cardiac surgery patients who underwent abdominal, chest or vascular surgery. All patients were above age 60 with coronary artery disease or other risk factors for coronary disease. Body temperature was kept near normal with warming methods in 142 patients, while 158 patients received routine care which resulted in mild hypothermia.
Results suggest a 55 percent risk reduction in cardiac complications when near normal body temperature is maintained, particularly immediately after surgery. Heart attack, cardiac arrest or unstable angina occurred in 1.4 percent of the warmer group compared to 6.3 percent in the group whose body temperatures were kept at traditional levels.
Also, ventricular tachycardia, or an abnormally fast heart beat, occurred in 2 percent of the warmer group versus 8 percent in the cooler group. A similar number of patients in both groups had a rapid heart beat during surgery, but heart beat irregularities after surgery were more common in the lower body-temperature group.
"An estimated 25 million Americans have risk factors for heart disease, and our findings show they will benefit from active warming during surgery," says Frank.
Body temperature was kept near normal by warming intravenous fluids and surrounding patients with a blanket that fills with warm air during and after surgery. Routine body-temperature care also included warming intravenous fluids, but patients were covered only with paper drapes during surgery and cotton blankets after surgery.
Other Hopkins authors of the study, supported by the National Institutes of Health and Mallinckrodt Medical, Inc., were Lee A. Fleisher, M.D.,Michael J. Breslow, M.D., Krista F. Olson, B.S.E., and Susan Kelly, B.S.N. Vanderbilt University Medical Center participated in the study.