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Peterson block
Synonym(s): Local anesthesia
Introduction
Uses
- Nerve supply to the eye and surrounding structures is complex and this technique requires skill and anatomical knowledge.
- This block involves local anesthesia of the cranial nerves supplying sensory and motor function to the eye and some of its surrounding structures.
- This block produces anesthesia of the eye and orbit, with immobilization of the globe and produces almost complete anesthesia of the lateral aspect of the head except for the eyelids.
- The Peterson block is usually combined with the auriculopalpebral block Auriculopalpebral block (motor only) to provide complete paralysis of the eyelids to facilitate surgery.
Uses
- Desensitization of the eye and orbit for eye surgery such as enucleation and foreign body removal.
- With additional modification, such as the addition of an auriculopalpebral block to abolish motor activity, surgery of the eyelids is possible (e.g. mass removal).
- The Peterson technique may also be necessary for some horn procedures in adult bovids.
Advantages
- Safer than the Retrobulbar block Retrobulbar block as there is less risk of globe penetration and hemorrhage.
- Additionally, potential catastrophic injection of the meninges surrounding the optic nerve is minimized using this technique.
- More effective than alternative techniques if performed correctly.
- Less edema and inflammation with this block than with infiltration of local anesthetics into the eyelids and orbit.
- The nerves blocked include the ophthalmic and maxillary branches of the trigeminal nerve.
- The mandibular division should not be affected as this branches off before the other two divisions of the trigeminal nerve exit via the foramen orbitorotundum.
- If enough local anesthetic is deposited in the pterygopalatine fossa, it is also possible to block the optic nerve.
- This is also dependent upon the final positioning of the needle and proximity of local anesthetic deposition to the optic foramen.
- The optic nerve should not be affected if this technique is correctly performed.
Disadvantages
- Technically more challenging to perform than other blocks anesthetizing the same or similar area.
Alternative techniques
- Retrobulbar block.
Time required
Preparation
- Sedation Sedating cattle may be required in some difficult cases to allow the nerve block to be carried out: 5 - 15 min for injection and time to peak effect of sedative drug.
Procedure
- 5 min depending on temperament of animal and skill of clinician.
- Effective in 10 - 15 min.
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 Prac 32, 535-552 PubMed.
Other sources of information
- Grimm K A, Lamont L A, Tranquilli W J et al (2015) Veterinary Anesthesia and Analgesia: Lumb and Jones. 5th edn. Wiley and Blackwell, USA.