Changes in core temperature during peritoneal insufflation: comparison of two CO2 humidification devices in pigs.

BACKGROUND: Various modifications of the physical status of CO2 have been used to reduce hypothermia caused by flow of insufflating gas. This animal study aimed to investigate the effects on core temperature, of insufflation with CO2 using two different humidification devices: unheated, humidified CO2 using the Modified-Aeroneb system (Nektar, San Carlos, CA) and warmed, humidified CO2 using the HME-Booster (Medisize, Hillegom, The Netherlands). METHODS: We undertook a prospective four-session study on a homogeneous group of four pigs. After general anesthesia, all animals were treated successively with the following protocols in a randomized order at 8-d intervals: Control (no pneumoperitoneum), Standard (unheated, unhumidified CO2), Modified-Aeroneb (unheated, humidified CO2 by cold nebulization), HME-Booster (heated, humidified CO2). The core temperature of the animals was recorded every 10 min. RESULTS: The temperature decrease is significantly influenced by time (P=0.0001; ANOVA), by the insufflation method (P=0.01), and by the interaction between time and the insufflation method (P=0.0001). The method of contrasts showed the following results:--The temperature decrease in the Standard group and HME-Booster group became greater than in the Control group after 40 min (P=0.02)--The temperature decrease in the Modified-Aeroneb group became greater than in the Control group after 100 min (P=0.04)--The temperature decrease in the Modified-Aeroneb group was less than in the HME-Booster group after 40 min (P=0.04) and less than in the Standard group after 60 min (P=0.01)--The temperature decrease in the Standard group was greater than in the HME-Booster group after 160 min (P=0.005). CONCLUSIONS: Compared with the HME-Booster system, the Modified-Aeroneb is at least as effective in limiting the drop in core temperature during laparoscopic insufflation.

An evaluation of gas humidifying devices as a means of intraperitoneal local anesthetic administration for laparoscopic surgery.

BACKGROUND: Intraperitoneal local anesthetic administration has been reported to provide perioperative analgesia during laparoscopic procedures. The aim of this in vitro study was to assess the efficiency of commercially available humidification devices to deliver ropivacaine and to determine the effects of modifying the device's position between the insufflator and the Veress needle on the amount of ropivacaine delivered. METHODS: In the first experiment, four humidification devices filled with ropivacaine (0.20% and 0.75%) were placed at the outlet of a laparoscopic insufflation system delivering a constant carbon dioxide flow. A catheter was connected to the humidifier's outlet and the other end submerged in a calibrated vial containing 25 mL of 50% methanol in water. The concentration of ropivacaine collected in the methanol-water solution was measured using high performance liquid chromatography. In the second experiment, the clinical situation was imitated by placing 3 m of silicone tubing between the humidifier and the collection vial to evaluate its influence on the amount of ropivacaine delivered. Only one humidifier was tested in the second experiment because the other three tested humidification devices did not efficiently deliver ropivacaine. RESULTS: The evaporation-based humidifiers delivered very small or nonmeasurable quantities of ropivacaine. In contrast, the microvibration-based aerosol humidification device delivered significant amounts (89.1%-94.3%) of the drug. The insertion of silicone tubing between the humidifier and the collecting vial reduced the amount of delivered ropivacaine to 62.3%. CONCLUSIONS: The microvibration-based aerosol humidification device may be used to deliver local anesthetics during laparoscopic procedures. Further research is necessary to confirm these results in clinical practice and to provide effective humidification that does not blur the surgeon's view.