equis - Articles
Forelimb: perineural analgesia
Introduction
- By removing sensitization to source of pain, lameness is abolished or lessened.
- Technique is conducted sequentially, working from distal to proximal.
Uses
- Localization of pain causing lameness or poor performance.
- Valuable adjunct to lameness diagnostic work-up.
- Direct diagnostic imaging, diagnosis and prognosis.
- Peri-operative analgesia Anesthesia: analgesia - overview.
Advantages
- Systematic procedure.
- Minimally invasive.
- Regional localization of source(s) of pain is a valuable adjunct to lameness or poor-performance work-ups.
- Majority of perineural analgesia techniques are easy to perform.
Disadvantages
- Local anesthetic solution may diffuse from deposition site and desensitize adjacent structures, eg joints, bursae, tendon sheaths, or more proximal nerves. Perineural analgesia is not as specific as once thought.
- Accurate technique and choice of volume of local anesthetic solution are essential.
- Careful interpretation of results often requires experience.
- Can be time consuming if multiple blocks are to be performed in multiple limbs.
- Anesthetic solution irritates tissues and can cause low grade inflammation → may sometimes confound scintigraphic imaging techniques for up to 2 weeks.
- Procedure complicated by fractious horses.
- There is a risk of introducing bacteria, and therefore infection.
Technical problems
- Desensitization may not occur in the desired or intended regions.
- Inadvertent administration of local anesthetic solution into a synovial structure or blood vessel → misinterpretation of results and sterility concerns.
- Full (100%) resolution of lameness is ideal, however this is not always achieved and an improvement of 70-80% is generally considered a positive response.
- Diagnostic analgesia will not improve lameness associated with mechanical gait deficits.
- In horse with multilimb lameness, all blocks should be performed before the first positive block wears off (90-120 min for mepivacaine Mepivacaine).
- The more proximal nerve blocks are more technically difficult because the nerves do not lie directly subcutaneously; therefore precise placement of the local anesthetic is difficult; loss of skin sensation is also variable.
Alternative techniques
- Gait evaluation Musculoskeletal: gait evaluation.
- Examination of horse at rest Musculoskeletal: physical examination - adult, including thorough hoof and foot examination.
- Manipulative tests Musculoskeletal: manipulative tests.
- Intrasynovial anesthesia Forelimb: joint anesthesia.
- Radiography Forelimb: radiography.
- Ultrasonography Ultrasonography: musculoskeletal .
- Scintigraphy Bone: scintigraphy.
- Thermography Thermography.
- Computed tomography (CT) Computed tomography.
- Magnetic resonance imaging (MRI) Magnetic resonance imaging.
Time required
Preparation
- 5-10 min.
Procedure
- 15-30 min for each block to be administered, take effect and tested.
Decision taking
Criteria for choosing test
- Degree of lameness and history - if lameness is severe and a fracture Musculoskeletal: fracture - first aid is suspected do not administer nerve blocks. Diagnostic imaging is indicated instead.
- Presence of cellulitis, infectious skin disease or tissue inflammation over the injection site contraindicates injection.
- In horses with multi-limb lameness, always start by blocking the lamest limb.
- Local anesthetic solution:
- Lidocaine (2%) Lidocaine: shortest duration of action (30-45 min), greater tissue irritation.
- Mepivacaine Mepivacaine: duration of action 90-120 min, less tissue irritation, most commonly used local anesthetic solution of diagnostic analgesia.
- Bupivacaine hydrochloride Bupivacaine hydrochloride (0.5%): longest duration of action (4-6 h), most commonly used for peri-operative analgesia.
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.
- Pezzanite L, Contino E & Kackak C (2018) Lameness originating from the proximal metacarpus/tarsus: A review of local analgesic techniques and clinical diagnostic findings. Equine Vet Educ (In press) WileyOnline.
- Paz C F, Magalhaes J F et al (2016) Mechanical nociceptive thresholds of dorsal laminae in horses after local anaesthesia of the palmar digital nerves or dorsal branches of the digital nerve. Vet J 214, 102-108 PubMed.
- Malton R & Nagy A (2015) Diffusion of radiodense contrast medium after a mid-pastern ring block. Equine Vet Educ 28 (1), 40-46 VetMedResource.
- Nagy A & Malton R (2015) Diffusion of radiodense contrast medium after perineural injection of the palmar digital nerves. Equine Vet Educ 27 (12), 648-654 VetMedResource.
- Michou J & Leece E (2012) Sedation and analgesia in the standing horse 2. Local anaesthesia and analgesia techniques. In Pract 34 (10), 578-587 VetMedResource.
- Nagy A, Bodo G & Dyson S J (2012) Diffusion of contrast medium after four different techniques for analgesia of the proximal metacarpal region: An in vivo and in vitro study. Equine Vet J 44 (6), 668-673 PubMed.
- Nagy A, Bodo G, Dyson S J, Szabo F & Barr A R S (2009) Diffusion of contrast medium after perineural injection of the palmar nerves: An in vivo and in vitro study. Equine Vet J 41 (4), 379-383 PubMed.
- Castro F A, Schumacher J S, Pauwels F & Blackford J T (2005) A new approach for perineural injection of the lateral palmar nerve in the horse. Vet Surg 34 (6), 539-542 PubMed.
- Schumacher J, Schumacher J, Schramme M C, DeGraves F J, Smith R & Coker M (2004) Diagnostic analgesia of the equine forefoot. Equine Vet Educ 16 (3), 159-165 VetMedResource.
- Lopez-Sanroman F J, Cruz J M, Santos M, Mazzini R A, Tabanera A & Tendillo F J (2003) Evaluation of the local analgesic effect of ketamine in the palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses. Am J Vet Res 64 (4), 475-478 PubMed.
- Jones E (2003) The palmar digital nerve block. UK Vet 8 (5), 6-7.
- McGuigan M P & Wilson A M (2001) The effect of bilateral palmar digital nerve analgesia on the compressive force experienced by the navicular bone in horses with navicular disease. Equine Vet J 33 (2), 166-171 PubMed.
- Schumacher J et al (2000) Effects of analgesia of the distal interphalangeal joint or palmar digital nerves on lameness caused by solar pain in horses. Vet Surgery 29, 54-58 PubMed.
- Drevemo S, Johnston C, Roepstorff L & Gustas P (1999) Nerve block and intra-articular anaesthesia of the forelimb in the sound horse. Equine Vet J Suppl 30, 266-269 PubMed .
Other sources of information
- Moyer W, Schumacher J & Schumacher J (2011) Eds Equine Joint Injection and Regional Anesthesia. In: Academic Veterinary Solutions. Chadds Ford, USA.
- Redding W R (2006) Critical Evaluation and Review of Local Anaesthetic techniques for the Lower Limb. In: Handbook of Presentations & Free Communications. BEVA Congress 2006. BEVA, UK. pp 28-30.
- Singer E R (2006) Critical Evaluation and Review of Local Anaesthetic techniques for the Upper Forelimb. In: Handbook of Presentations & Free Communications. BEVA Congress 2006. BEVA, UK. pp 31-32.
- Bassage L H & Ross M W (2003) Perineural Analgesia in the Forelimb. In: Diagnosis & Management of Lameness in the Horse. Eds: Ross M W & Dyson S J. Saunders, USA. pp 100-107.