Humidified gas prevents hypothermia induced by laparoscopic insufflation - A randomized controlled study in a pig model

Background: This experimental study evaluated whether humidification of warmed insufflated CO2 during laparoscopic procedures would resolve the problem of laparoscopy-induced hypothermia. Methods: Changes in core temperature were quantified over a 3-h period of high-flow CO2 insufflation in a randomized, controlled trial of five pigs. Each animal was anesthetized and studied on three occasions under standardized conditions, acting as its own control by insufflation with no gas compared with insufflation by cool dry gas and heated humidified gas. Results. Core temperatures after insufflation with heated humidified gas were no different from that of controls. After insufflation with cool dry gas, core temperature dropped by 1.8 degrees C, which was significantly more than the 0.6 degrees C drop experienced by control animals and those insufflated with heated humidified gas (p < 0.01). Calculations of the heat expended in evaporation of water were also performed. The temperature drop due to water evaporation alone in pigs insufflated with cool dry gas was calculated to be 1.5 degrees C. This compares favorably with the measured 1.2 degrees C temperature difference between these animals and the control group. Conclusions: The majority of heat lost during laparoscopic insufflation is due to water evaporation, and laparoscopic hypothermia may be prevented by using heated and humidified gas insufflation.