Perioperative analgesic effects of a modified supratemporal retrobulbar block in dogs undergoing corneal and endocular surgery.

OBJECTIVES

To evaluate the perioperative efficacy of a modified supratemporal retrobulbar block in dogs undergoing ocular surgery.

MATERIALS AND

METHODS

In this prospective randomised clinical trial, dogs were premedicated with dexmedetomidine (1 mcg/kg im) and methadone (0.1 mg/kg im), induced with propofol to effect and maintained with isoflurane (FE'Iso 1.1%). In the retrobulbar group a mixture of lidocaine 2% (5.5 mL) and ropivacaine 0.75% (2 mL) was administered at 0.1 mL/kg, via a modified supratemporal technique using a Tuohy needle. No block was performed in the controls. When heart rate or mean arterial pressure increased above 30% of the pre-incisional values, fentanyl (1 mcg/kg iv) was administered. Propofol (1 mg/kg iv) was injected when anaesthesia was deemed too light. After a total of three administrations regardless of the type of drugs (fentanyl/propofol), a constant rate infusion of fentanyl (5 mcg/kg/h iv) was started. Quality of recovery (blindly assessed using a descriptive score scale), postoperative eye rubbing and complications were studied.

RESULTS

Eighteen dogs were included. The retrobulbar group (nine) dogs had significantly less risk of receiving fentanyl than controls (nine) (Relative risk:  0.142, 95% CI: 0.021 to 0.936) and a recovery score > 2 (RR: 0.058, 95% CI: 0.003 to 0.887). The median amount of fentanyl (mcg/kg) was statistically lower in the retrobulbar group than in the controls: 0 mcg/kg (range, 0 to 1) versus 2 mcg/kg (range, 0 to 8.49), respectively. Only controls showed eye rubbing.

CLINICAL SIGNIFICANCE: The modified supratemporal retrobulbar block reduced the intraoperative rescue analgesia and improved the quality of recovery.