Minimally invasive surgery with endoscopic techniques has been gaining popularity in companion animal medicine.1–4 Laparoscopic approaches for canine and feline patients for routine and complex surgical procedures are well described.2,5–9 Minimally invasive surgical procedures modified for use in some exotic small mammals, particularly domestic rabbits, have also been described.4,10–12 Laboratory rabbits have also been used in research for pediatric laparoscopic surgical techniques.13,14 Despite the widespread use of laparoscopy in rabbits, the veterinary medical literature is lacking a detailed assessment of optimal IAPs for use in this species.
When creating pneumoperitoneum for laparoscopic surgery, it is critical to understand which IAP will provide the greatest increase in working space while minimizing adverse effects on cardiorespiratory function and local tissue perfusion.15–18 Working space refers to the volume of abdominal space created by insufflation to allow for visual access and instrument handling during laparoscopic procedures. It is dependent on fixed factors (eg, patient size, gastrointestinal contents, and presence of organomegaly) as well as factors that can be adjusted (eg, IAP, patient ventilation, and muscle tone effects of the anesthetic protocol).19 These factors need to be taken into account when evaluating the effect of a variable such as IAP on the working space.
Working space has been investigated in pigs and cats,19,20 but to the authors’ knowledge, there are currently no recommendations for optimal working space in rabbits. In 1 study,20 working space in cats was assessed by changes in abdominal width, height, and circumference at various IAPs. Significant increases in abdominal circumference were identified with IAP increases from 4 to 8 mm Hg and from 8 to 15 mm Hg.20 Nevertheless, the authors concluded that an IAP of 15 mm Hg, compared with 8 mm Hg, did not provide a sufficient clinically important difference in working space to justify its use and found that the higher pressure was associated with increased mean arterial blood pressure and Paco2. A study19 of pigs used CT to measure the intra-abdominal volume at pressures of 0, 5, 10, and 15 mm Hg.19 The CT-measured volume increased by approximately 93% between pressures of 5 and 10 mm Hg and by approximately 19% between pressures of 10 and 15 mm Hg; therefore, the increase in working space in pigs was deemed beneficial with an increase in IAP up to, but not beyond, 10 mm Hg.
The objective of the study reported here was to evaluate the effect of changes in IAP (from 4 to 12 mm Hg) created with CO2 insufflation on the working space in rabbits as assessed by measurement with abdominal CT. These pressures were selected in accordance with recommendations for other companion animal species, as well as previous reports that described laparoscopic procedures used in rabbits.4,10–12 On the basis of the previously described studies in cats and pigs,19,20 we hypothesized that the working space for laparoscopic procedures would increase with increases in IAP, although not necessarily in a linear manner.
Supported by the Ontario Veterinary College Pet Trust. The funding agency did not contribute to the design, data collection, analysis, or writing of this manuscript.
The authors declare that there were no conflicts of interest.
The authors thank John Phillips for assistance and expertise in use of 3-D imaging software to determine pneumoperitoneal volumes.
End-tidal partial pressure of CO2
Charles River Laboratories, Saint-Constant, QC, Canada.
Sandoz Canada Inc, Boucherville, QC, Canada.
Vetergesic, Sogeval UK Ltd, Sheriff Hutton, England.
BD Canada, Mississauga, ON, Canada.
Plasmalyte-A, Baxter Healthcare, Deerfield, Ill.
Pharmascience Inc, Montreal, QC, Canada.
IsoFlo, Zoetis Canada Inc, Kirkland, QC, Canada.
Nellcor, Covidien Canada, Saint-Laurent, QC, Canada.
2500A VET, Nonin Medical Inc, Plymouth, Minn.
Ultrasonic Doppler 811-B, Parks Medical Electronics Inc, Aloha, Ore.
Bair Hugger, 3M, London, ON, Canada.
R, version 3.4.1, R Core Team, R Foundation for Statistical Computing, Vienna, Austria.
GE Bright Speed, GE Healthcare, Milwaukee, Wis.
Stryker, Kalamazoo, Mich.
Karl Storz Endoscopy America Inc, El Segundo, Calif.
PDS II, Ethicon, Johnson & Johnson Medical Products, Markham, ON, Canada.
VersaOne, Covidien Canada, Saint-Laurent, QC, Canada.
Metacam, 20 mg/mL injectable, Boehringer Ingelheim, Burlington, ON, Canada.
Metacam, 1.5 mg/mL oral suspension, Boehringer Ingelheim, Burlington, ON, Canada.
Materialise Mimics, version 19, Materialise, Leuven, Belgium.
3-matic, version 11, Materialise, Leuven, Belgium.
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