Warmth After Surgery Can Save Lives

Mothers everywhere exhort their children, "Bundle up, or you'll catch your death of cold." Apparently the prescription applies in the recovery room, too. A new study shows that keeping people warm after surgery can save lives.

 Despite their bright lights, operating rooms are kept at a cool 65@ to 70@F. Doctors and nurses do their work sheathed in gowns that retain heat, but patients are naked, apart from paper-thin drapes and perhaps a skimpy blanket. Chill air bathes their organs.

 Anesthesia puts the hypothalamus -- the brain's thermostat -- to sleep, depriving patients of the body's innate safeguards against cold. Patients can no longer shiver to generate warmth, and their blood vessels no longer constrict to retain heat. Their bodies are cooled by the surrounding air.

 In effect, warm-blooded people become temporarily cold-blooded, like reptiles, says Steven M. Frank of the Johns Hopkins Medical Institutions in Baltimore.

 People aren't designed to be cold-blooded. A drop in body temperature of just 3.5@F induces hypothermia, Frank says. In the operating room, however, hypothermia has little effect. Anesthesia prevents the release of stress hormones known as catecholamines, which constrict veins, raise blood pressure, and tax the heart.

 Once the anesthesia wears off, in the chilly recovery room, the hypothalamus awakens. At a body temperature 4@F below normal, it boosts catecholamine concentrations 200 to 700 times, sending the heart into overdrive.

 Eight million people at risk of heart problems in the United States undergo surgery each year. About 50,000 of these patients survive their operation only to die within days of heart attack or other cardiac complications, the most common causes of postoperative deaths.

 Frank and his colleagues studied 270 people over age 60 at risk of heart complications. They compared 143 who were covered with thin cotton blankets during and after surgery with 127 whose temperatures were kept normal using blankets with tiny jets that bathe the patient in warm air.

 Keeping people warm did not measurably affect the complication rate during surgery. Statistical analysis showed, however, that it reduced by 55 percent the incidence of heart complications within 24 hours after surgery, the researchers say. Just two of the warmed patients suffered angina pain, death of heart tissue, or cardiac arrest -- compared to 10 patients who weren't warmed.

"We've shown that prevention of hypothermia is a simple, inexpensive way to reduce the incidence of cardiac deaths," Frank says.

 The report appears in the April 9 Journal of the American Medical Association.

 The research runs counter to the long-cherished notion that a small drop in body temperature during and after surgery is either inconsequential or protects the patient by slowing metabolism and reducing the body's demand for blood and oxygen. The report buttresses earlier studies showing that postoperative cold may have tragic consequences.

"We, as a profession, had never really paid attention to the minor 1 or 2 degree drops in temperature that we see during surgery. But small declines we never thought were a problem do have effects we never dreamed of," says Frederick W. Cheney, an anesthesiologist at the University of Washington School of Medicine in Seattle.

 Cheney, who wrote an editorial accompanying the report, raised one issue that concerns him. None of the studies has been duplicated by other researchers. If doctors respond to the new report by routinely warming patients, such studies may never be done, depriving doctors of information about other possible effects -- even though their new diligence may save lives.

"He's right," Frank observes. Yet Frank argues that the individual studies, taken together, demonstrate conclusively the value of warming patients. "The pieces fit together," he says.