Severe Local Hypothermia from Laparoscopic Gas Evaporative Jet Cooling: A Mechanism To Explain Clinical Observations

BACKGROUND AND OBJECTIVES Explanations for laparoscopic-induced hypothermia fail to explain clinical observations. It is possible that water evaporation occurs from the jet stream of gas inflation resulting in tissue surface super-cooling leading to tissue damage and drying. METHODS Theoretical calculations based on thermal conductivity, mass transfer effects and heat flux considerations correlated closely with synthetic and tissue experiments. Thermocouple measurements at a rate of 15 data points per second were performed. RESULTS Cooling rates of 10 to 25 degrees centigrade per second for high flow rates were found based on gas flow rate and effective size of gas delivery site. These rapid temperature drops extended beyond a 2 cm2 diameter. CONCLUSIONS Evaporative cooling accounts for significant hypothermia. The cooling is dependent on the lack of water vapor in the gases currently used during laparoscopy. Cooling rates are independent of height from tissue and geometry of delivery port. Heating and hydrating the gas to a physiologic condition eliminates hypothermia and tissue dessication.