Influence of Peri-Operative Hypothermia on Surgical Site Infection in Prolonged Gastroenterological Surgery.

Background: There have been several recent studies on the correlation between intra-operative hypothermia and the occurrence of surgical site infection (SSI). Differences in the depth and timing of hypothermia and the surgical procedure may have led to conflicting results.

Methods: Patients undergoing gastroenterologic surgery with a duration of >3 h were analyzed. Hypothermia was defined as a core temperature <36°C and was classified as mild (35.5-35.9°C), moderate (35.0-35.4°C), or severe (<35.0°C). Hypothermia also was classified as early-nadir (<36°C within two h of anesthesia induction) and late-nadir (after that time). Risk factors for SSIs were analyzed according to these classifications.

Results: Among 1,409 patients, 528 (37.5%) had hypothermia, which was classified as mild in 358, moderate in 137, and severe in 33. Early-nadir and late-nadir hypothermia was found in 23.7% and 13.8%, respectively. There was no significant difference in the incidence of SSIs between patients with and without hypothermia (relative risk 1.00; 95% confidence interval [CI] 0.80-1.25; p = 0.997). However, there was a significantly greater incidence of SSIs in patients with severe hypothermia (33.3%) than in those with normothermia (19.2%; p = 0.045) or mild hypothermia (17.0%; p = 0.021). The incidence of SSIs also was significantly greater in patients with late-nadir than in those with early-nadir hypothermia (23.7% vs. 16.5%; p = 0.041). The incidence of organ/space SSIs was significantly greater in patients with late-nadir hypothermia (19.6%) than in patients with normothermia (12.7%; p = 0.012). In multivariable analysis, neither severe hypothermia (odds ratio 1.24; 95% CI 0.56-2.77] nor late-nadir hypothermia (OR 0.71; 95% CI 0.46-1.01) was an independent risk factor for SSIs.

Conclusions: Severe and late-nadir hypothermia were associated with a greater incidence of SSIs and organ/space SSIs. However, neither of these patterns was identified as an independent risk factor for SSIs, possibly because of the small number of patients.