Pressure–Volume Curve during Capnoperitoneum in Cats

SIMPLE SUMMARY: Keyhole surgery has become a very popular form of surgery in human and veterinary medicine because of its advantages in patient recovery and smaller incision sites. The disadvantages are side effects of high intra-abdominal pressures on the circulation system. Veterinary surgeons initially adapted guidelines from human medicine with pressure limits of 15 mmHg, although little is known about pressure limits in smaller sized patients and differences in species. Most surgeons already use smaller pressure limits but very few studies exist and guidelines are often based on personal experience. This study analyzes the pressure relationship in the abdomen during keyhole surgery for neutering in 59 cats by measuring the volume inflated and the pressure from 0 to 15 mmHg and compares it to previous study results in dogs. This study shows that, similar to dogs, the intra-abdominal pressure and the insufflated volume rise until a threshold of 6.44 mmHg is reached. After this point, the volume gain decreases and pressure rises exponentially with each additional insufflation. This means insufflation over 7 mmHg in cats will result in minimal gain and should be avoided. ABSTRACT: Laparoscopy is a growing field in veterinary medicine, although guidelines are lacking. The objective of this study was to evaluate the pressure–volume curve during capnoperitoneum in cats. A total of 59 female cats were scheduled for routine laparoscopy. Pressure and volume data were recorded and processed, and the yield point of the curve was calculated using a method based on a capacitor discharging function. For the remaining 40 cats, a linear-like pressure–volume curve was observed until a yield point with a mean cutoff pressure (COP) of 6.44 ± 1.7 mmHg (SD) (range, 2.72–13.00 mmHg) and a mean cutoff volume (COV) of 387 ± 144.35 mL (SD) (range, 178.84–968.43 mL) was reached. The mean mL/kg CO(2) value in cats was 208 ± 34.69 mL/kg (range, 100.00–288.46 mL/kg). The COV correlated with COP and body weight but not with body condition score (BCS). COP correlated only with the COV. This study suggests that feline patients have a pressure–volume curve similar to that of canine patients, and the same pressure limit recommendations can be used for both species. After a yield point of 6.44 mmHg is reached, the increment in volume decreases exponentially as the intra-abdominal pressure (IAP) increases.