Warming to 39°C but Not to 37°C Ameliorates the Effects on the Monocyte Response by Hypothermia.

Objective: To investigate whether warming to normal body temperature or to febrile range temperature (39°C) is able to reverse the detrimental effects of hypothermia. Background: Unintentional intraoperative hypothermia is a well-described risk factor for surgical site infections but also sepsis. We have previously shown that hypothermia prolongs the proinflammatory response whereas normothermia and especially febrile range temperature enhance the antiinflammatory response. Methods: Primary human monocytes were isolated from healthy volunteers. After stimulation with LPS (Lipopolysaccharide), the monocytes were exposed to 32°C for 3 hours or 6 hours and then warmed at either 37°C or 39°C for the remaining 33 hours or 36 hours, respectively. Tumor necrosis factor α, interleukin 10, and the expression of miR-155 and miR-101 were assessed at 24 hours and 36 hours. Results: Warming to 37°C does not normalize monocyte cytokine secretion within 36 hours, whereas warming to 39°C partially reverses the effects of hypothermia on monocyte function. Both miR-155 and miR-101 were suppressed after the warming episode. However, 39°C had a stronger suppressive effect than 37°C. The duration of hypothermia and the warming temperature seem to be critical for a full reversibility of the effects of hypothermia. Conclusion: Warming to normal body temperature (37°C) does not restore normal monocyte function in vitro. These data suggest that hypothermic patients should be warmed to febrile range temperatures. Furthermore, febrile range temperatures should be investigated as a means to modulate the inflammatory response in patients with systemic infections. [ABSTRACT FROM AUTHOR]