Surgical humidification explained
Surgical humidification is the conditioning of insufflation gas with water vapour (humidity) and heat during surgery. Surgical humidification is used to reduce the risk of tissue drying and evaporative cooling.
Laparoscopic surgery humidification
During laparoscopy (laparoscopic surgery or minimally invasive surgery), it is necessary to insufflate the abdominal cavity (i.e. inflate the abdomen like a balloon) with medical-grade carbon dioxide (CO2) to create a viewing and working space for the surgery. The CO2 may be unconditioned, or conditioned with heat, or with humidification and heat. During insufflation, the peritoneum (an extensive delicate membrane that lines the abdominal cavity and covers most of the abdominal organs) is exposed to the CO2.
Unconditioned medical-grade CO2 has virtually no moisture[1] and enters the abdomen at room temperature (19 to 21 °C).[2] The condition of the gas is dry and cold compared to that of the natural physiological state of the peritoneum which is immersed in fluid at body temperature (37 °C). Experimental and clinical investigations have demonstrated that insufflation with unconditioned CO2 causes evaporation of the fluid and drying of the peritoneum, resulting in inflammation and damage to its cells.[3] [4] [5] Clinically, peritoneal injury caused by drying has been linked to post-operative pain,[6] [7] [8] evaporative cooling resulting in a decrease in core temperature and increased risk of intra-operative hypothermia,[9] [10] [11] [12] as well as adhesion formation.[13]
In addition, animal studies have revealed that surgical humidification reduces peritoneal tumor implantation and tumor load [14] [15] suggesting a possible benefit in cancer patients undergoing abdominal surgery.
Conditioning the CO2 with only heat causes tissue drying.[16] Warmer gas has a greater capacity for evaporation as the gas can hold more water vapor, therefore the tissues will dry faster than when unconditioned gas is used, potentially leading to increased adverse consequences.[17] [18] [19] Conditioning the CO2 with humidity, in combination with heat, has been shown to decrease peritoneal damage by reducing the capacity of CO2 to carry moisture away from the tissue. Temperature loss during surgery, due to tissue drying, can be prevented by adequately humidifying and heating the CO2.[20]
Open (abdominal) surgery humidification
During open surgery the surgeon exposes the peritoneal cavity to the ambient air. Exposure to ambient air results in evaporation and cooling. Current studies have shown that the use of surgical humidification during open abdominal surgery (laparotomy) have warmer core body temperatures and reduced risk of operative hypothermia.[21] [22] As with any operation, maintaining patient normothermia is a critical process to prevent surgical site infections, additional respiratory distress and surgical bleeding.[23] [24]
Respiratory humidification during surgery
Anesthesia causes vasodilatation, which increases blood flow to the surface of the body and thus increases heat loss from the body. During anesthesia, blood flow to the surface may maintain skin temperature (which is normally lower than the core temperature), even while the core temperature is falling.[25] Barring preventive interventions, hypothermia occurs in more than half of all surgical patients undergoing anesthesia.[26]
The risk of a loss of body temperature and hypothermia increase with the duration of surgery, especially for surgery that lasts more than one hour. Surgical hypothermia, defined as a core temperature below 36.0 °C, is associated with increased risk of infectious and non-infections complications,[27] longer post-operative ICU and overall hospital recovery, and more frequent requirement of transfusions.[28] [29] Elderly persons, especially those with lower muscle and body mass are at greater risk of hypothermia.[30]
Respiratory humidification during surgery helps maintain body temperature and normal function of the respiratory mucosa.[31] [32] In the same way that some animals pant to lose excess body heat, heat is lost through the lungs during mechanical or assisted ventilation. Heated humidification of respiratory gases during surgery has been demonstrated to reduce the fall in core body temperature, especially in surgeries lasting longer than one hour. The lungs can be insufflated with respiratory gases that are heated to near body temperature and humidified to 90 to 100% relative humidity(RH). Normally, air in the lungs is at core body temperature and at close to 100% RH. Especially when cold dry gases (such as anhydrous compressed gas from oxygen tanks) are used, it cool and can dry the airway. The body then utilizes energy to evaporate sufficient water from the lungs to maintain lung gas temperature and humidity. It is generally estimated that 10 percent of the loss of body heat during surgery is from the respiratory tract.[33] Especially in open surgery (rather than endoscopic/robotic surgery), respiratory humidification can be used in concert with forced air warming blankets or gowns, warmed IV, and irrigation fluids to prevent hypothermia.
Notes and References
- United States Pharmacopoeia and the National Formulary Supplements. 2003. 26-NF 21. 3rd ed. United States Pharmacopeial Convention: 2003; NJ.
- Puttick. M. Scott-Coombes D . Dye J . Nduka C . Menzies-Gow N . Mansfield A . Darzi A . Comparison of immunologic and physiologic effects of CO2 pneumoperitoneum at room and body temperatures. Surg Endosc. 1999. 13 . 6. 572–575. 10.1007/s004649901043. 10347293. 21301841.
- Erikoglu. M. Yol S . Avunduk MC . Erdemli E . Can A . Electron-microscopic alterations of the peritoneum after both cold and heated carbon dioxide pneumoperitoneum. J Surg Res. 2005. 125 . 1. 73–77. 10.1016/j.jss.2004.11.029. 15836853.
- Peng. Y. Zheng M . Ye Q . Chen X . Yu B . Liu B . Heated and humidified CO2 prevents hypothermia, peritoneal injury, and intra-abdominal adhesions during prolonged laparoscopic insufflations. J Surg Res. 2009. 151 . 1. 40–47. 10.1016/j.jss.2008.03.039 . 18639246.
- Volz. J. Koster S . Spacek Z . Paweletz N . Characteristic alterations of the peritoneum after carbon dioxide pneumoperitoneum. Surg Endosc. 1999. 13 . 6. 611–614. 10.1007/s004649901052. 10347302. 22338506.
- Mouton. W G. Bessell JR . Otten KT . Maddern GJ . Pain after laparoscopy. Surg Endosc. 1999. 13 . 5. 445–448. 10.1007/s004649901011. 10227938. 21450398.
- Sajid. M. Mallick A . Rimpel J . Bokari S . Cheek E . Baig M . Effect of heated and humidified carbon dioxide on patients after laparoscopic procedures: a meta-analysis. Surg Laparosc Endosc Percutan Tech. 2008. 18 . 6. 539–546. 10.1097/SLE.0b013e3181886ff4. 19098656. 5927215.
- Wills. VL. Hunt DR . Pain after laparoscopic cholecystectomy. Br J Surg. 2000. 87 . 3. 539–546. 10.1046/j.1365-2168.2000.01374.x. 10718794. 313322. free.
- Bessel. J. Karatassas A . Patterson J . Jamieson G . Maddern G . Hypothermia induced by laparoscopic insufflation. A randomized study in a pig model.. Surg Endosc. 1995. 9 . 7. 791–796. 10.1007/bf00190083. 7482186. 11045850.
- Bessell. J. Ludbrook G . Millard S . Baxter P . Ubhi S . Maddern G . Humidified gas prevents hypothermia induced by laparoscopic insufflation: a randomized controlled study in a pig model. Surg Endosc. 1999. 13 . 2. 101–105. 10.1007/s004649900914. 9918606. 10775676.
- Noll. E. Schaeffer R . Joshi G . Diemunsch S . Koessler S . Diemunsch P . Heat loss during carbon dioxide insufflation: comparison of a nebulization based humidification device with a humidification and heating system. Surg Endosc. 26. 12. 3622–5. 2012. 10.1007/s00464-012-2385-2. 22722768. 22446856.
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- Binda. M. Molinas C . Hansen P . Koninckx P . Effect of desiccation and temperature during laparoscopy on Adhesion formation in mice. Fertil Steril. 2006. 86 . 166–175. 166–75. 10.1016/j.fertnstert.2005.11.079. 16730008.
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