Effect of gonadectomy on pain assessment in dogs undergoing orthopaedic stifle surgery

Abstract

ObjectiveTo compare pain perception between gonadectomized and intact dogs. Study designBlinded, prospective, cohort study. AnimalsA group of 74 client-owned dogs. MethodsDogs were divided into four groups: group 1—female/neutered (F/N), group 2—female/intact (F/I), group 3—male/neutered (M/N) and group 4—male/intact (M/I). Premedication consisted of intramuscularly administered acepromazine (0.05 mg kg−1) and morphine (0.2 mg kg−1), and subcutaneously administered carprofen (4 mg kg−1). Anaesthesia was induced with propofol (1 mg kg−1 intravenously and supplementary doses to effect) and maintained with isoflurane in 100% oxygen. Intraoperative analgesia was achieved with fentanyl infusion (0.1 μg kg−1 minute−1). Pain assessments [using the University of Melbourne Pain Scale (UMPS) and an algometer at the incision site (IS), parallel to the incision site (NIS), and on the contralateral healthy limb] were performed preoperatively, and at 1, 2, 4, 6, 9 and 20 hours after extubation. The time-standardised area under the curve (AUCst) for measurements was calculated and compared by performing a one-way multivariate analysis of variance (manova). Statistical significance was set at p < 0.05. ResultsPostoperatively, F/N exhibited higher pain than F/I, with estimated marginal means (95% confidence intervals) AUCstISGroup1 909 (672–1146) versus AUCstISGroup2 1385 (1094–1675) (p = 0.014), AUCstNISGroup1 1122 (823–1420) versus AUCstNISGroup2 1668 (1302–2033) (p = 0.024) and AUCstUMPSGroup1 5.30 (4.58–6.02) versus AUCstUMPSGroup2 4.1 (3.2–5.0) (p = 0.041). Similarly, M/N showed higher pain than M/I with AUCstISGroup3 686 (384–987) versus AUCstISGroup4 1107 (871–1345) (p = 0.031) and AUCstNISGroup3 856 (476–1235) versus AUCstNISGroup4 1407 (1109–1706) (p = 0.026), and AUCstUMPSGroup3 6.0 (5.1–6.9) versus AUCstUMPSGroup4 4.4 (3.7–5.2) (p = 0.008). Conclusions and clinical relevance:Gonadectomy affects pain sensitivity in dogs undergoing stifle surgery. Neutering status should be taken into consideration when planning individualized anaesthetic/analgesic protocols.