April 8, 1997
Keeping surgery patients warm is a simple and inexpensive way to significantlyreduce the risk of heart complications, the leading cause of post-operative death, a JohnsHopkins study suggests.
Maintaining a surgical patient's normal body temperature has been shown to reduceinfections, speed healing and shorten hospital stays, but this is the first prospective clinicaltrial 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 MedicalAssociation and discussed in an accompanying editorial.
Most patients experience hypothermia, or lowered body temperature, during majorsurgery because of anesthesia, chilly operating rooms, open body cavities, intravenousfluids and blood infusions. While cool operating rooms keep surgeons comfortable andprovide patients with some benefits such as slowing metabolism, hypothermia also boostspatients' stress hormones, constricts blood vessels and raises blood pressure. Thiscardiovascular 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 orother risk factors for coronary disease. Body temperature was kept near normal withwarming methods in 142 patients, while 158 patients received routine care which resulted inmild hypothermia.
Results suggest a 55 percent risk reduction in cardiac complications when nearnormal body temperature is maintained, particularly immediately after surgery. Heart attack, cardiac arrest or unstable angina occurred in 1.4 percent of the warmer groupcompared to 6.3 percent in the group whose body temperatures were kept at traditionallevels.
Also, ventricular tachycardia, or an abnormally fast heart beat, occurred in 2 percentof the warmer group versus 8 percent in the cooler group. A similar number of patients inboth groups had a rapid heart beat during surgery, but heart beat irregularities after surgerywere more common in the lower body-temperature group.
"An estimated 25 million Americans have risk factors for heart disease, and ourfindings show they will benefit from active warming during surgery," says Frank.
Body temperature was kept near normal by warming intravenous fluids andsurrounding patients with a blanket that fills with warm air during and after surgery.Routine body-temperature care also included warming intravenous fluids, but patients werecovered only with paper drapes during surgery and cotton blankets after surgery.
Other Hopkins authors of the study, supported by the National Institutes of Healthand 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 Centerparticipated in the study.
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