• Retrobulbar injection of local anesthetic desensitizes the structures of the eye and paralyzes the external ocular muscles, providing a globe which is anesthetized, immobile and central.

Uses

• Analgesia for Enucleation Enucleation, which is usually undertaken in standing, sedated or unsedated cattle that are well restrained in a crush Restraint techniques.

Advantages

• Provides excellent peri-operative analgesia.

Disadvantages

• Inadvertent injection of local anesthetic agent into a blood vessel could lead to sudden death.
• Inadvertent injection of local anesthetic agent into the CSF surrounding the optic nerve could lead to collapse, seizures and respiratory arrest (followed by cardiac arrest) due to brainstem anesthesia.
• Risk of globe trauma if performed incorrectly. Prior to enucleation this complication is less of a concern unless endophthalmitis is present, in which case it risks local spread of infection.
• Risk of trauma to local tissues.
• Risk of initiation of oculocardiac reflex.

Alternative techniques

• Retrobulbar nerve block: 4-point Retrobulbar nerve block: 4-point.
• Peterson nerve block Peterson nerve block.

Time required

Preparation

• 5 min to prepare syringes and anesthetic agents.
• Skin should be aseptically prepared at sites of injection using Chlorhexidine Chlorhexidine or povidone-iodine.

Procedure

• 5 min to perform injection.

Decision taking

Risk assessment

• Procedure carries some risk.
• Always aspirate prior to injection to ensure needle placement is not within a blood vessel or likely to result in injection into the brainstem.