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Local anesthesia: overview


Definition, advantages and disadvantages


  • 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.
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Classes of local blocks

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Factors affecting duration and latency

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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Haro P, Laredo F, Gil F et al (2013) Ultrasound-guided dorsal approach for femoral nerve blockade in cats: an imaging study. J Feline Med Surg 15 (2), 91-98 PubMed.
  • Haro P, Laredo F, Gil F et al (2012) Ultrasound-guided block of the feline sciatic nerve. J Feline Med Surg 14 (8), 545-552 PubMed.
  • McMillan M W, Seymour C J, Brearley J C (2012) Effect of intratesticular lidocaine on isoflurane requirements in dogs undergoing routine castration. JSAP 53 (7), 393-397 PubMed.
  • Aprea F, Vettorato E, Corletto F (2011) Severe cardiovascular depression in a cat following a mandibular nerve block with bupivacaine. Vet Anaesth Analg 38 (6), 614-618 PubMed.
  • Mosing M, Reich H, Moens Y (2010) Clinical evaluation of the anesthetic sparing effect of brachial plexus block in cats. Vet Anaesth Analg 37 (2), 154-161 PubMed.
  • Trumpatori B J, Carter J E, Hash 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 Surg 39 (7), 785-796 PubMed.

Other sources of information

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

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