Hypobaric intrathecal anaesthesia for partial hemipelvectomy in a dog

OBJECTIVE: To report the intrathecal use of a hypobaric anaesthetic solution for partial hemipelvectomy in a nine-year-old, neutered female, Golden Retriever dog, weighing 34 kg. METHODS: Under inhalational anaesthesia, with the dog lying in lateral recumbency and the surgical side uppermost, 1.9 ml of a hypobaric solution containing 3.42 mg of bupivacaine and 0.66 mg of morphine were administered in the subarachnoid space at L5-6 level 30 minutes before surgery. Following the intrathecal injection the dog was maintained for five minutes in a 10 degrees head-down position, then for three minutes in a 10 degrees head-up position. RESULTS: Apart from a transient increase in heart and respiratory rates during resection of the sartorius muscle, which was treated with a plasma Target Controlled Infusion (TCI) of fentanyl, spinal anaesthesia provided cardiovascular stability and excellent relaxation of the surgical site. Neither motor blockade nor proprioceptive deficit were apparent in the contra-lateral hind limb at recovery, 200 minutes after injection. Postoperatively, rescue analgesia was not required in the 48 hours following surgery. CLINICAL SIGNIFICANCE: In dogs, the use of intrathecal hypobaric bupivacaine and morphine as a part of a balanced anaesthetic protocol should be considered during unilateral major orthopaedic surgeries of the pelvis and hind limb, as it allowed a reduction in the dose administered compared to isobaric solutions, providing selective spinal anaesthesia, excellent long-lasting analgesia, and rapid recovery of ambulation.