Laparoscopy involves insufflation of the abdomen with CO2 to create a working space that allows for maneuvering of an endoscope and instruments.1 Laparoscopic procedures in dogs cause less surgical stress and postoperative pain and improve postoperative recovery, compared with traditional open approaches.2–4 Because of these benefits, laparoscopy is commonly performed in veterinary medicine.5,6
Insufflation with STCO2 for laparoscopy is performed at a temperature of 22°C and 0% relative humidity.7–9 Core body temperature of dogs ranges from 37.5° to 39.2°C,10 which is ≥ 15°C higher than that of the insufflated CO2. The use of STCO2 insufflation is a major cause of hypothermia in human patients undergoing laparoscopic procedures, which is the result of heat loss attributable to evaporation of liquid from the peritoneal surface at a rate of decrease of 0.3°C in core body temperature for every 50 L of insufflated CO2.9 Effects of the use of STCO2 on core body temperature in dogs are unknown.
Perioperative hypothermia in dogs is defined as a body temperature < 36.5°C.11 Perioperative hypothermia has detrimental effects that can lead to patient morbidity, including cardiac, hepatic, and renal dysfunction; coagulopathies; increases in transfusion requirements; impairments of humoral and cellular immunity that affect wound healing; prolongation of recovery; and alterations of drug metabolism.11,12 Inadvertent perianesthetic hypothermia is one of the most common complications associated with anesthesia.12 In 1 study11 of approximately 1,500 dogs undergoing general anesthesia for surgical or diagnostic procedures, 84% were classified as hypothermic at the time of anesthetic recovery.
Investigation of the hemostatic effects of hypothermia in humans revealed hypocoagulability in clinical patients and impairment of in vitro hemostasis (as measured with thromboelastography).13 Even mild perioperative hypothermia (decrease in core body temperature of 1° to 3°C) resulted in increased bleeding times during surgery, higher rates of blood loss, and an increased need for blood transfusion in people undergoing surgery.14 Similar to results for humans, intraoperative hemorrhage may be exacerbated by perioperative hypothermia in dogs, which can lead to complications such as the need for a blood transfusion, hypoxia, and even death.15
Strategies to prevent perioperative hypothermia are needed to ensure safe outcomes for patients undergoing laparoscopy. Use of WHCO2 (37°C and 97% relative humidity) for creation of pneumoperitoneum has been evaluated extensively for laparoscopic surgery in humans through evaluation of core body temperature, postoperative pain, recovery time, postoperative nausea, urine output, lens fogging, and hemodynamic data.16–21 In 50 morbidly obese patients undergoing gastric bypass surgery, use of WHCO2 resulted in a higher intraoperative core body temperature and less postoperative shivering, compared with results for use of STCO2.17 In contrast, clinical trials of adult humans found no differences in intraoperative core body temperature between CO2 treatments.18,19,21 A study20 of pigs (body weight, 30 to 35 kg) to compare insufflation devices found that WHCO2 used for pneumoperitoneum and duration of the procedure impacted heat loss, with heat loss for WHCO2 being significantly less than that for STCO2 only at ≥ 50 minutes. Variation in the peritoneal surface area in dogs, compared with that in humans,22 may allow thermoregulatory protection for dogs when WHCO2 is used.
Apart from the potential thermoregulatory benefits, WHCO2 creates a less irritant environment, which results in reduced patient discomfort in humans.17,21,23,24 Studies23,24 of rats have revealed that insufflation with WHCO2 during laparoscopy reduces peritoneal injury and adhesion formation as detected with scanning electron microscopy. It is the preservation of peritoneal tissues from desiccation that is thought to mediate a reduction in the systemic inflammatory response as indicated by a reduction in the concentrations of circulating CRP and IL-6.a Both CRP and IL-6 are inflammatory mediators used as biomarkers to assess the presence and degree of tissue damage. These substances are sensitive indicators of surgical trauma and inflammation in dogs.25
Advanced laparoscopic procedures (eg, cholecystectomy, ureteronephrectomy, and adrenalectomy) are being performed in veterinary medicine, which requires prolonged periods of pneumoperitoneum. However, to our knowledge, the effects of WHCO2 in dogs undergoing laparoscopy have not been investigated. Evaluation of the use of WHCO2 is necessary to optimize postoperative recovery and outcome.
The objective of the study reported here was to evaluate the effect of insufflation with WHCO2 to create pneumoperitoneum on cardiorespiratory variables, core body temperature, the systemic inflammatory response, coagulation, peritoneal morphology, and signs of postoperative pain in healthy mature dogs undergoing laparoscopy. Our hypothesis was that the use of WHCO2 would result in better thermoregulation, a reduced inflammatory response, better cardiovascular function, and signs of less pain than for the use of STCO2.
Supported by the OVC Pet Trust and Lexicon Medical.
The authors have no conflicts of interest to declare.
The authors thank William Sears and Gabrielle Monteith for assistance with the statistical analysis.
Arterial oxygen concentration
Central venous oxygen concentration
Central venous pressure
Diastolic arterial blood pressure
End-tidal concentration of isoflurane
Lithium dilution cardiac output
Maximum amplitude of blood clot
Mean arterial blood pressure
End-tidal partial pressure of CO2
Systolic arterial blood pressure
Stroke volume index
Systemic vascular resistance
Warmed humidified CO2
Ott DE. Reduction of the inflammatory response using wet CO2 during laparoscopy (abstr). J Am Assoc Gynecol Laparosc 2002;9:542.
Microsoft Excel, version 14.7, Microsoft Corp, Redmond, Wash.
BD, Franklin Lakes, NJ.
Sandoz, Boucherville, QC, Canada.
Fresenius Kabi, Toronto, ON, Canada.
Zoetis Inc, Parsippany, NJ.
S/5 anesthesia monitor, GE Healthcare, Madison, Wis.
DOT-34 NRC 300/375 M1014, Datex-Ohmeda Division, Helsinki, Finland.
S/5 Aespire 7900 ventilator, GE Healthcare, Madison, Wis.
Bair-hugger, 3M, Saint Paul, Minn.
Acklands Grainger, ON, Canada.
Baxter Corp, Mississauga, ON, Canada.
Mila International Inc, Florence, Ky.
LiDCO Ltd, London, England.
Flow-through cell electrode assembly, LiDCO Ltd, London, England.
ABL90 flex blood gas analyzer, Radiometer, Brea, Calif.
0.15 mmol/mL, LiDCO Ltd, London, England.
6-mm laparoscopic cannula, Karl Storz Endoscopy, Goleta, Calif.
Insuflo, provided by Lexicon Medical, Saint Paul, Minn.
Endoflator, Karl Storz Endoscopy, Goleta, Calif.
Laparoscope, Karl Storz Endoscopy, Goleta, Calif.
TEG 5000 thrombelastograph hemostasis analyzer system, Haemonetics, Braintree, Mass.
Kaolin, Haemonetics, Braintree, Mass.
5-mm round cup biopsy forceps, Karl Storz Endoscopy, Goleta, Calif.
Emitech K550 sputter-coater, Ashford, Kent, England.
Hitachi S-570 scanning electron microscope, Hitachi High Technologies Inc, Tokyo, Japan.
Pfizer, New York, NY.
Metacam, Boehringer Ingelheim, Burlington, ON, Canada.
PROC GLM, SAS, version 9, SAS Institute Inc, Cary, NC.
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