Carbon Dioxide Pneumoperitoneum and Laparoscopic Ovariectomy in the Domestic Rabbit (Oryctolagus cuniculus)
Laparoscopic surgeries are increasingly popular in exotic companion mammals, but information about their benefits or disadvantages is limited. The aims of this thesis are: 1) to assess the working space achieved with carbon dioxide pneumoperitoneum in rabbits; 2) to evaluate the cardiorespiratory effects of pneumoperitoneum; and 3) to compare intra-operative and post-operative outcomes between laparoscopic and open ovariectomy in rabbits. For the first two cross-over studies, six female New Zealand White rabbits were randomly assigned to sequences of intra-abdominal pressures (IAP). Computed tomography (CT) was used to measure working space after insufflation to 4, 8, and 12 mm Hg. From 4 to 8 mmHg, there was a 19% increase in working space, whereas from 8 to 12 mm Hg the increase was only 6.9%. The order of IAPs affected working space. To assess the effect of pneumoperitoneum on cardiorespiratory parameters, the following outcomes were measured at 0, 4, and 8 mm Hg: blood pressures (ABP); cardiac output, cardiac and stroke volume indices (CI, SVI); heart rate; end-tidal CO2 (ETCO2); blood gases (PaCO2, PaO2); peak inspiratory pressure (PIP); and peripheral oxygen saturation (SpO2). Heart rate, SpO2, and ABP were unaffected by IAP. For PaO2, an interaction effect was seen between IAP and pressure sequence. PaCO2 increased at 8 mm Hg, and ETCO2 and PIP were greater with each IAP. IAP decreased cardiac output and CI. Intra-operative and post-operative outcomes between laparoscopic (LapOVE) and open ovariectomy (OVE) were compared in female New Zealand White rabbits randomly allocated to surgical treatments (n=6 per group). Surgical and anaesthetic time were longer and incision length was shorter for LapOVE versus OVE. There were no significant differences in post-operative outcomes between the treatments, including ethograms evaluated by a blinded observer. Surgical complications associated with LapOVE included intestinal perforation, subcutaneous emphysema, and seroma formation. Incisional dehiscence occurred in both groups. In summary, pneumoperitoneal pressures should be limited to 8 mm Hg in rabbits. When performing ovariectomy in rabbits, laparoscopy may not provide as marked of an advantage over open approaches as in other mammals. However, further evaluation of laparoscopic techniques is warranted for this species.