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Retrobulbar block: 4-point


Synonym(s): Peribulbar, nerve block

Introduction

  • Note from the Editor:
    • The naming of the techniques used to deposit local anesthesia behind the globe is a little controversial!
      • At present, different authors use different names for the various techniques.
      • We have chosen to use the names shown, for these techniques, but have included the alternative names in the synonyms section (below the title).
      • The authors and editor feel that the naming of these techniques is of secondary importance to the correct performance of them.
      • Full details of when and how to perform these techniques are given in the articles.
  • Peribulbar/retrobulbar injection of local anesthetic desensitises the structures of the eye and paralyses the external ocular muscles, providing a globe which is anesthetised, immobile and central.

Uses

  • Analgesia for Enucleation Enucleation, which is usually undertaken in standing and either 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 cerebrospinal fluid (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

Time required

Preparation

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

Procedure

  • 5-7 min to perform injections.

Decision taking

Criteria for choosing test

  • Used for peri-operative analgesia for enucleation surgery which is performed standing in cattle.

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 ethmoid turbinates; similarly, aspiration helps check for cerebrospinal fluid withdrawal which is also important as intrathecal injection can prove fatal.

Requirements

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Preparation

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Technique

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Aftercare

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Outcomes

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Further Reading

Publications

Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Edmondson M A (2016) Local, regional, and spinal anesthesia in ruminants. Vet Clin North Am Food Anim Pract 32 (3), 535-552 PubMed.
  • Pearce S G et al (2003) Comparison of the retrobulbar and Peterson nerve block techniques via magnetic resonance imaging in bovine cadavers. JAVMA 223 (6), 852-855 PubMed.

Other sources of information

  • Valverde A & Sinclair M (2015) Ruminant and Swine Local Anesthetic and Analgesic Techniques. In: Veterinary Anesthesia and Analgesia. Blackwell Publishing, UK.
  • Clarke K & Trim C (2014) Anaesthesia of Cattle. In: Veterinary Anaesthesia. 11th edn. Elsevier.