title: Local insufflation of warm humidified CO₂increases open wound and core temperature during open colon surgery: a randomized clinical trial.
abstract: BACKGROUND
  The open surgical wound is exposed to cold and dry ambient air resulting in heat loss through radiation, evaporation, and convection. Also, general and neuraxial anesthesia decrease the patient's core temperature. Despite routine preventive measures mild intraoperative hypothermia is still common and contributes to postoperative morbidity and mortality. We hypothesized that local insufflation of warm fully humidified CO(2) would increase both the open surgical wound and core temperature.
  
  
  METHODS
  Eighty-three patients undergoing open colon surgery were equally and parallelly randomized to either standard warming measures including forced-air warming, warm fluids, and insulation of limbs and head, or to additional local wound insufflation of warm (37°C) humidified (100% relative humidity) CO(2) at a laminar flow (10 L/min) via a gas diffuser. Wound surface and core temperatures were followed with a heat-sensitive infrared camera and a tympanic thermometer.
  
  
  RESULTS
  The mean wound area temperature during surgery was 31.3°C in the warm humidified CO(2) group compared with 29.6°C in the control group (P < 0.001, 95% confidence interval [CI], 1.2°C to 2.3°C). Also, the mean wound edge temperature during surgery was 30.1°C compared with 28.5°C in the control group (P < 0.001, 95% CI, 0.2°C to 0.7°C). Mean core temperature before start of surgery was similar with 36.7°C ± 0.5°C in the warm humidified CO(2) group versus 36.6°C ± 0.5°C in the control group (95% CI, 0.4 to -0.1°C). At end of surgery, the 2 groups differed significantly with 36.9 ± 0.5°C in the warm humidified CO(2) group versus 36.3 ± 0.5°C in the control group (P < 0.001, 95% CI, 0.38°C to 0.82°C). Moreover, only 8 patients of 40 in the warm humidified CO(2) group had a core temperature <36.5°C (20%, 95% CI, 7 to 33%), whereas in the control group this was the case in 24 of 39 (62%, 95% CI, 46% to 78%, P = 0.001) patients (difference of the percentages between the groups 42%, 95% CI, 22% to 61%, P < 0.001). With a cutoff at <36.0°C none of the patients in the warm humidified CO(2) group compared with 7 patients (18%, 95% CI, 5% to 31%, P = 0.005) in the control group was hypothermic at end of surgery (difference of the percentages between the groups 18%, 95% CI, 6% to 30%, P = 0.005). The median (25th/75th percentile) operating time was 181.5 (147.5/288) minutes in the warm humidified CO(2) group versus 217 (149/288) minutes in the control group (P = 0.312). Clinical variables did not show any significant differences between the groups.
  
  
  CONCLUSIONS
  Insufflation of warm fully humidified CO(2) in an open surgical wound cavity increases surgical wound and core temperatures and helps to maintain normothermia.
authors.affiliation: Department of Molecular Medicine and Surgery, The Karolinska Institute, Stockholm, Sweden. joana.frey@ki.se
authors.forename: Joana M
authors.initials: JM
authors.lastname: Frey
authors.forename: Martin
authors.initials: M
authors.lastname: Janson
authors.forename: Monika
authors.initials: M
authors.lastname: Svanfeldt
authors.forename: Peter K
authors.initials: PK
authors.lastname: Svenarud
authors.forename: Jan A
authors.initials: JA
authors.lastname: van der Linden
mesh_terms: D058107:Abdominal Wound Closure Techniques; D000368:Aged; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology*; D002245:Carbon Dioxide / Q000008:administration & dosage*; D003106:Colon / Q000502:physiology / Q000601:surgery*; D017558:Elective Surgical Procedures / Q000379:methods; D005260:Female; D006358:Hot Temperature / Q000627:therapeutic use*; D006801:Humans; D006813:Humidity; D008297:Male; D008875:Middle Aged; D014945:Wound Healing / Q000187:drug effects / Q000502:physiology*
chemical_list: D002245:Carbon Dioxide