Thoracic epidural anaesthesia vs intrathecal morphine in dogs undergoing major thoracic and abdominal surgery: clinical study.

BACKGROUND: There is scant clinical research on neuraxial analgesia in dogs undergoing major surgery. With this study we compared the perioperative analgesic effects of thoracic epidural anaesthesia (TEA) and intrathecal morphine (ITM) in dogs scheduled for thoracic or cranial abdominal surgery. The dogs received methadone and dexmedetomidine, were anaesthetized with propofol maintained with sevoflurane, and randomly assigned to receive either TEA (ropivacaine 0.5% at 0.2 mg/kg and morphine 0.1 mg/kg administered at T12-T13) or ITM (morphine 30 µg/kg administered at L6-L7). Intraoperative rescue analgesia (iRA) was fentanyl 1 µg/kg administered if heart rate or mean arterial pressure increased by 30% above the pre-stimulation level. Glasgow Pain Composite Scale score (GPCS) dictated the use of postoperative rescue analgesia (pRA) with methadone 0.2 mg/kg. RESULTS: There was a statistically significant difference in iRA, median time to first fentanyl bolus, median fentanyl dose after surgical opening, and median GPCS score at 30 minutes (min), 1 ,2, 4, 6, and 8 hours (h) between the two groups (p<0.001; p<0.001; p<0.001; p<0.01; p<0.01; p<0.001; p<0.01; p=0.01; p=0.01, respectively). Fewer TEA than ITM group dogs required iRA during surgical opening and pRA: 5% (1/18) and 2/18 (11%), respectively, in the TEA and 83% (16/18) and 10/18 (55%), respectively, in the ITM group. Side effects were urinary retention in 3/18 (16%) TEA group dogs and 2/18 (11%) ITM group dogs and prolonged sedation in 2/18 (11%) in ITM group dogs. TEA and ITM were effective in managing perioperative pain in dogs undergoing thoracic or cranial abdominal surgery.

Effects of intravenous dexmedetomidine infusion on local anaesthetic block: A spinal anaesthesia clinical model in dogs undergoing hind limb surgery.

The aim of this randomised, prospective clinical trial was to determine how the administration of a low dose of dexmedetomidine (DEX) by IV constant rate infusion, modified the duration of the nerve block in dogs undergoing spinal anaesthesia (SA) in a clinical setting. Forty-four dogs undergoing hind limb orthopaedic surgery in a day-surgery regime, maintained under anaesthesia with isoflurane plus SA, were randomly assigned to receive 1 µg/kg/h (IV) of DEX (group D) or not (group C). Spinal anaesthesia was performed with a hyperbaric solution of bupivacaine and morphine at the L5-6 interspace. Every mean arterial pressure (MAP) increase by 30% above the pre-skin incision value was considered an intraoperative analgesic failure and treated with a bolus of fentanyl as intraoperative rescue analgesia (iRA). Time free from iRA was analysed with a Kaplan-Maier survival curve. The ability to walk at 5 h from SA and the event of bradycardia (HR lower 60 beat per min) and hypotension (MAP value lower 60 mmHg) were recorded. The mean times at which iRA was required were 77.4 (3.2) in group C and 112.2 (8.6) in group D (Logrank test P = 0.038). In groups C and D hypotension incidence was 11/17 (65%) and 2/22 (9%), (P = 0.0004) and bradycardia 3/17 (18%) and 6/22 (27%) (P = 0.704), respectively. The ability to walk 5 h after SA was 14/14 (100%) and 13/14 (93%) in groups C and D, respectively. DEX infusion significantly prolonged the duration of the nociceptive nervous block without prolonging the motor block or increasing the bradycardia events.