Clinical evaluation of the efficacy of two different analgesic protocols during prescrotal orchiectomy in dogs

Orchiectomy is a common surgical procedure in small animal practice. In spite of the relative technical simplicity of execution, orchiectomy requires a serious approach to perioperative analgesic management. Neuroaxial (epidural) and loco-regional (infiltration of the incision line and testicular parenchyma) techniques of anaesthesia have been reported to improve the quality of sedation and/or general anaesthesia (1). The purpose of this study was to evaluate the analgesic efficacy of administration of ropivacaine hydrochloride by ultrasound-guided injection into the spermatic cord, together with infiltration of the same anaesthetic into the prescrotal incisional line (4). Fifty privately-owned dogs presented for clinical orchiectomy were randomly divided into two groups of 25 each (ROP group and Control group). The dogs were approximately 2 - 4 y of age and 15-25 kg body weight. They received the same combination of drugs for sedative-analgesic purposes: 3 mcg/kg of dexmedetomidine + 0,25 mg/kg of methadone (2,3). Subjects in the ROP group were administered only ropivacaine, injected into the tissue around the spermatic cord at the level of its starting point from the superficial inguinal ring, and also injected into the incision line (0,2 ml/kg of ropivacaine 0,5% at each injection site). In the Control Group (25 dogs), 20 min after sedation, propofol were administered i.v. to induce general anaesthesia. Parameters taken into consideration were haemodynamic stability, the need for additional administration of hypnotic and/or analgesic drugs in the intraoperative period, and the need for analgesics in the postoperative period. Dogs in the ROP group showed a greater hemodynamic stability intraoperatively (considering heart rate, electrocardiogram, pulse oximetry and blood pressure) compared with the Control group, and did not react on surgical stimulation. Dogs in the ROP group and in Control group had no requirement for hypnotics during the procedure. Immediately after surgery, evaluation of pain by the Glasgow pain scale demonstrated that both group did not present signs of pain. In the postoperative period at home, owners reported no signs of pain or discomfort in two group. The loco-regional approach used in this study has been shown to be effective in minimizing responses to the surgical stimulus, and ensured adequate analgesia in the both the intraoperative and postoperative period. This method allows the procedure to be performed under deep sedation and therefore avoids the use of general anaesthesia. REFERENCES: 1) Almeida RM, Escobar A, Maguilnik S et al., 2010 ‘Comparison of analgesia provided by lidocaine, lidocaine-morphine or lidocaine-tramadol delivered epidurally in dogs following orchiectomy’ , Vet Anaesth Analg. 37(6):542-9. 2) Cardoso CG, Marques DR, da Silva TH, de Mattos-Junior E, 2014 ‘Cardiorespiratory, sedative and antinociceptive effects of dexmedetomidine alone or in combination with methadone, morphine or tramadol in dogs’Vet Anaesth Analg. 41(6):636-43. 3) Ingvast-Larsson C, Holgersson A, Bondesson U, Lagerstedt AS, Olsson K., 2010, ‘Clinical pharmacology of methadone in dogs’, Vet Anaesth Analg.37(1):48-56. 4) Kushnir Y, Toledano N, Cohen L, Bdolah-Abram T, Shilo-Benjamini Y., 2017, ‘Intratesticular and incisional line infiltration with ropivacaine for castration in