Refinement of ovariohysterectomy in rabbits through reducing the surgical stress

Although animal welfare has been of great concern for many years, an increased scientific interest on prevention and reduction of animal suffering recently arose. Rabbits are very popular laboratory animals, farm animals and pets. Ovariohysterectomy (OHE) is a common surgical procedure in rabbits and is potentially painful unless appropriate analgesia is provided. Reduction of surgical stress and minimizing inflammatory response might significantly improve the welfare of laboratory animals [1]. Reduced pain associated with laparoscopic OHE has already been reported [2]. However, more rigorous comparisons of laparoscopic OHE versus so called open OHE by laparotomy have yet to establish a clear advantage [3]. The present study compared laparoscopic OHE with conventional open OHE and open OHE with pre-incisional local anaesthesia in rabbits. The aim was to indicate the most suitable approach for minimizing the surgical stress. Eighteen New Zealand white rabbits weighing 2.8±0.26 kg were divided into three groups of six animals each. Animals of group A underwent laparoscopic OHE, in rabbits of group B open OHE through a standardized 5-cm midline abdominal incision and in those of group C open OHE with a pre-incisional subcutaneous infusion of lidocaine 2% was performed. Blood samples were taken from each rabbit 30 minutes before induction of anesthesia (T0), after skin incision (T1), 90 minutes postoperatively (T2), and 24 hours postoperatively (T3). Cortisol and C-reactive protein (CRP) were measured in serum, and adrenocorticotropic hormone (ACTH), tumor necrosis factor-α (TNFα), adrenaline, noradrenaline and interleukin-6 (IL-6) in plasma. Shapiro-Wilk, and t or Mann-Whitney U-tests were used for statistical analysis. Rabbits undergoing laparoscopic OHE demonstrated less serum cortisol response immediately after skin incision (T1) compared with rabbits of group B [t (6)=2,617, p=0.035)]. Adrenaline was significantly lower 24 h (T3) after laparoscopy than after open surgery [t (7)=2,610, p=0.035)]. At the same time point during open surgery, TNF-α was significantly increased compared with laparoscopic surgery [t (5)=2,612, p=0.048)]. No significant difference was found for ACTH, noradrenaline, IL-6 and CRP levels between the groups. Our findings suggest that laparoscopic OHE causes less activation of the surgical stress system, as expressed by reduced secretion of cortisol and adrenaline. In addition, the laparoscopic technique seems to stimulate the inflammatory response to a lesser extent through reduced TNF-α secretion, compared with the open technique with or without local anesthesia. These findings combined with faster recovery and less postoperative pain after minimally invasive OHE indicate that this technique may improve animal welfare in rabbits. [1] Flecknell PL. Refinement of animal use-assessment and alleviation of pain and distress. Lab Anim. 1994; 28:222-231. [2] Devitt CM, Cox RE, Hailey JJ. Duration, complications, stress, and pain of open ovariohysterectomy versus a simple method of laparoscopic-assisted ovariohysterectomy in dogs. J Am Vet Med Assoc. 2005;227:921-927. [3] Davidson EB, Moll HD, Payton ME. Comparison of laparoscopic ovariohysterectomy and ovariohysterectomy in dogs. Vet Surg 2004;33:62–69.