Patients kept at a body temperature of 37 degrees C during major surgery had no fewer cardiac complications than patients kept at 35.5 degrees C, according to findings from the PROTECT trial presented April 4 at ACC.22 and simultaneously published in The Lancet. There were also no differences in the number of infections or required blood transfusions in patients kept at cooler body temperatures.

Researchers enrolled 5,050 patients who had surgery at 13 medical centers, mostly in China. Participants had various major noncardiac surgical procedures, with a minimum duration of two hours and an average duration of four hours. Half of the patients were randomly assigned to receive routine care, with a target body temperature of 35.5 degrees C, while half received aggressive warming, with a target body temperature of 37 degrees C.

For patients assigned to routine care, nursing staff put a warming cover in position but did not activate it until the patient's body temperature decreased to less than 35.5 degrees C, resulting in an average group body temperature of 35.6 degrees C. With the more aggressive warming protocol, nurses covered patients with a heated blanket for 30 minutes before surgery and then used two forced-air heaters to keep patients warmed to a mean of 37.1 degrees C during surgery.

Results showed no significant differences between groups for the trial's primary endpoint – a composite of troponin elevation due to ischemia, nonfatal cardiac arrest or death from any cause within 30 days after surgery. In addition, there were no significant differences between groups in terms of serious wound infections, length of hospitalization, hospital readmissions or the need for blood transfusions.

"This study shows that it is reasonable to keep patients warm, but we saw no evidence whatsoever that it makes a difference if they're just above or just below 36 degrees C," said Daniel I. Sessler, MD, the trial's lead author. "Also, the results show that 36 degrees C should not be considered the threshold for defining mild hypothermia since there was no harm at 35.5 degrees C."

Keywords: ACC Annual Scientific Session, ACC22, Hypothermia, Intraoperative Complications, Preoperative Care

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