Felis ISSN 2398-2950

Local anesthesia: overview

Contributor(s): John Dodam, Sheilah Robertson, Enzo Vettorato, Claire Waters

Definition, advantages and disadvantages

Definition
  • Local anesthesia or loco-regional anesthesia is a technique to induce a reversible absence of sensation (anesthesia) in a part of the body (local).
  • Depending on the loco-regional anesthetic technique used, local anesthetic drugs decrease transduction or transmission of a noxious stimulus to the spinal cord and to the brain.

Advantages of local anesthetic techniques

  • Cheap and relatively easy to perform.
  • Produce intraoperative antinociception and, depending on the drugs used and duration of the surgery, postoperative analgesia Analgesia: overview.
  • Might decrease postoperative opioid consumption.
  • Allow performing surgical procedures under sedation Sedation or sedative protocol or lighter plane of anesthesia, therefore decreasing the potential cardio-respiratory effects associated with general anesthesia.
    Minimal systemic side-effects have been reported, if not overdosed or accidently injected intravenously. However hypotension is common after spinal or epidural anesthesia.

Disadvantages of local anesthetic techniques

  • Failure of the block: if the animal is not anesthetized it is advisable assessing the quality and the extension of the block using pin-prick technique or hemostatic forceps before starting the surgery.
  • Toxic doses can produce neurological and cardiovascular signs especially if injected intravenously.
  • Depending on the type of surgery and animal's demeanour, the administration of sedative or general anesthetic in conjunction with local anesthetic technique might be necessary.
  • If the animal is sedated, intraoperative movement can occur even if the local anesthetic technique is 100% successful.
  • Systemic hypotension might occur especially after spinal or epidural anesthesia; blood pressure monitoring is therefore highly advisable.
  • Particular care must be exercised if clotting disorders, hypovolemia or sepsis are present, or if neoplasia are very close to the injection area.

Selection criteria

  • Size and temperament of the animal.
  • Clinical conditions of the animal.
  • Type of surgical procedure.
  • Technical skill of the clinician with the loco-regional technique.
  • Type of surgery.
  • Equipment available.
Print off the owner factsheet All about anaesthesia All about anaesthesia to give to your client.

Classes of local blocks

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Factors affecting duration and latency

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Further Reading

Publications

Refereed papers
  • Recent references fromVetMedResource and PubMed.
  • Haro P et al(2013) Ultrasound-guided dorsal approach for femoral nerve blockade in cats: an imaging study. J Feline Med Surg15, 91-98 PubMed.
  • Haro P et al(2012) Ultrasound-guided block of the feline sciatic nerve. J Feline Med Surg14, 545-552 PubMed.
  • McMillan M W et al(2012) Effect of intratesticular lidocaine on isoflurane requirements in dogs undergoing routine castration. JSAP 53, 393-397 PubMed.
  • Aprea F et al(2011) Severe cardiovascular depression in a cat following a mandibular nerve block with bupivacaine. Vet Anaesth Analg 38, 614-618 PubMed.
  • Mosing M et al(2010)Clinical evaluation of the anesthetic sparing effect of brachial plexus block in cats. Vet Anaesth Analg37, 154-161PubMed.
  • Trumpatori B J et al(2010)Evaluation of a midhumeral block of the radial, ulnar,  musculocutaneous and medial (RUMM Block) nerves for analgesia of the distal aspect of the thoracic limb in dogs. Vet Surg39, 785-796PubMed.

Other sources of information

  • Campoy L, Read M (2013)Small animal locoregional anesthesia and analgesia.Wiley-Blackwell.
  • Muir W W, Hubbell J A E & Skarda R (1989)Handbook of Veterinary Anesthesia. Mosby Press (Useful source of diagrams).
  • Vickers M D, Morgan M & Spencer P S J (1991)Drugs in Anesthetic Practice. Butterworth Heinemann (Good on the pharmacology of local anesthetic agents).


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