Warming to 39 C necessary to reverse hypothermia effect in monocytes

Last Updated: 2015-03-13

By Larry Hand

NEW YORK (Reuters Health) - Warming human monocytes to a febrile-range temperature, rather than normal body temperature, may reverse the effects of hypothermia, according to a new study.

"The findings of this study suggest that once a patient becomes hypothermic, for example during an elective surgery, warming to a normal body temperature of 37 (degrees Celsius) does not reverse the hypothermia-induced changes in the monocyte inflammatory response," Dr. Adrian T. Billeter, of the department of surgery at the University of Louisville in Kentucky, told Reuters Health by email.

"According to our results, only warming to supra-normal temperatures, i.e. febrile-range temperatures, appears to normalize the monocyte inflammatory response. Hence, patients should be warmed to supra-normal body temperatures in case they get hypothermic," he said.

Intraoperative hypothermia still occurs in about 7% of all elective colorectal procedures and in up to 31% of patients who require postoperative intensive care, Dr. Billeter and colleagues note in Annals of Surgery, online February 25.

The team conducted an in vitro study of primary human monocytes isolated from healthy volunteers. They exposed the monocytes to 32 C for three or six hours, then warmed them to either 37 C or 39 C for 33 or 36 hours, respectively.

Warming to 37 C did not normalize monocyte cytokine secretion within 36 hours, the researchers found, but warming to 39 C partially reversed the hypothermia effects on monocytes.

Specifically, the team found that:

-- Warming to 39 C suppresses the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha), but has a greater effect after three hours of hypothermia compared with six hours of hypothermia on TNF-alpha.

-- Warming to either 37 C or 39 C increases anti-inflammatory cytokine interleukin-10 (IL-10) levels.

-- Warming to either temperature suppresses the proinflammatory microRNA-155 and microRNA-101, but has a greater effect at 39 C.

"These findings may explain the findings of some previous studies that (found that) hypothermia is an important risk factor for subsequent infectious but also cardiovascular complications," Dr. Billeter said. "A deranged and unbalanced inflammatory response could be the cause, or at least contribute to, postoperative infectious or cardiovascular complications. It should be tested in clinical trials whether warming to supra-normal temperatures could reduce these complications and ultimately reduce the adverse outcome of hypothermic patients."

In terms of clinical use today, Dr. Billeter said, "These findings could be used to treat patients with infections and sepsis. It appears that febrile-range temperatures may have beneficial effects on the monocyte inflammatory response. Warming patients to 39 (degrees Celsius) should be investigated as an additional treatment in patients with sepsis or other infections."

This research was funded by the John W. and Barbara Price Trust Fund and the Joint Royal College of Surgeons of Edinburgh/James and Emmeline Ferguson Research Fellowship. No authors reported any conflicts of interest.

SOURCE: http://bit.ly/1EbL2um

Ann Surg 2015.