Felis ISSN 2398-2950

Muscle relaxant: overview

Contributor(s): Sheilah Robertson, Claire Waters, Marieke de Vries

Introduction

  • General anesthesia is a triad consisting of narcosis (drug induced sleep), analgesia and muscle relaxation.
  • Muscle relaxation allows: precision surgery to be performed (eg intra-ocular surgery); prevents unexpected reflex movement; reduces traction needed to expose deep structures and therefore reduces tissue damage and post-operative discomfort; facilitates mechanical ventilation of lungs.
  • Movement during anesthesia is usually of 3 types:
    • Involuntary movement resulting from local (spinal) reflexes in response to noxious stimuli;
    • Tonus resulting from slow asynchronous discharge from ventral horn in spinal cord;
    • Muscular contraction as a myogenic response to direct traction (largely beyond pharmacological control).
If the movement is purposeful or in response to a painful stimulus, reassess the level of anesthesia.

1. General anesthesia

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2. Drugs acting within spinal cord

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3. Local anesthetic agents

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4. Neuromuscular blocking agents (NMBAs)

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Pharmacology – non-depolarizing NMBAs

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Pharmacology – depolarizing NMBA

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Further Reading

Publications

Referred papers

  • Recent references from VetMed Resource and PubMed.
  • Martin-Flores M et al (2016) Prevention of laryngospasm with rocuronium in cats: a dose-finding study. Vet Anaesth Analg 43(5), 511-518 PubMed.
  • Moreno-Sala A et al (2013) Use of neuromuscular blockade with rocuronium bromide for intubation in cats. Vet Anaesth Analg 40(4), 351-358 PubMed.
  • Auer U, Mosing M (2006) A clinical study of the effects of rocuronium in isoflurane-anaesthetized cats. Vet Anaesth Analg 33(4), 224-228 PubMed.
  • Appiah-Ankam J, Hunter JM (2004) Pharmacology of neuromuscular blocking drugs. Contin Educ Anaesth Crit Care & Pain 4(1), 2–7.
  • Corletto F, Brearley JC (2003) Clinical use of mivacurium in the cat. Vet Anaesth Analg 30(2), 93-94 PubMed.
  • Martinez E A (1999) Newer neuromuscular blockers, is the practitioner ready for muscle relaxants? Vet Clin North Am Small Anim Pract 29(3), 811-817 PubMed.
  • Forsyth S F et al (1990) Effect of gentamicin administration on the neuromuscular blockade induced by atracurium in cats. Am J Vet Res 51(10), 1675-1678 PubMed.
  • Ilkiw J E et al (1990) Atracurium administration, as an infusion, to induce neuromuscular blockade in clinically normal and temporarily immune-suppressed cats. JAVMA 197(9), 1153-1156 PubMed.

Other sources of information

  • Flaherty D & Auckburally A (2016) Neuromuscular blocking agents. In: BSAVA Manual of Canine and Feline Anaesthesia and Analgesia. 3rd edn. Eds. Duke-Novakovski T, de Vries M, Seymour CJ BSAVA, Quedgeley (UK). Chapter 16.


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