Surgical Hypothermia Affects Even Warmed Patients

Despite forced-air warming, hypothermia is common and often prolonged in patients undergoing non-cardiac surgery, according to a new study.

Researchers at the Cleveland Clinic (CC; OH, USA) extracted data from the most recent visit of 143,157 patients who underwent non-cardiac inpatient surgery between April 1, 2005, and February 15, 2013. Patient records were only included if the anesthetic lasted at least one hour, forced-air warming was used, and time-weighted measurement of core temperature was taken in the esophagus. Estimates were obtained for one-degree temperature bands ranging from 34 °C to 37 °C.

The results showed that approximately one-third of the patients had a core temperature of 34 °C or lower for at least one hour; 8% were below 34 °C for more than three hours. The researcher found that esophageal temperatures below 35 °C as manifest in 5% of the patients significantly increased hospital length of stay and transfusion requirements, with the incidence of hypothermia greatest one hour after induction, and then progressively improving. The study was published online in the May 2014 issue of Clinical Anesthesiology.

“Hypothermia-related complications depend more on time-weighted core temperature than final intraoperative temperature. Even with forced-air warming, our results indicate that a fair fraction of patients still become hypothermic,” said lead author Prof. Daniel Sessler, MD. “In fact, almost 10% of patients were distinctly hypothermic and remained near 35 °C at the end of surgery. This is a degree of hypothermia that has been shown to cause major complications in randomized trials.”

Approximately 72,000 surgical patients around the world are warmed each day using forced-air warming convection and radiation to transfer heat from the movement of warm air across the surface of the patient’s skin. For more than 20 years, forced-air warming has been regarded as the standard of care to help prevent surgical site infections (SSIs) and other serious complications of unintended hypothermia, including increased blood loss, morbid myocardial events, and reduced resistance to surgical wound infections.

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