Canis ISSN: 2398-2942

Anesthesia: monitoring of neuromuscular blockade

Contributor(s): Elizabeth Leece, Alexander Valverde

Introduction

Uses

  • During neuromuscular blockade administration and recovery:
    • To assess degree and duration of neuromuscular blockade.
    • To allow a constant level of relaxation to be produced - optimizing operating conditions.
    • To identify individual sensitivity to neuromuscular blockade.
    • To indicate when redosing is necessary and avoid overdosing.
    • To indicate when neuromuscular blockade may be antagonized - lowering risk of desensitization block.

Advantages

  • Use of peripheral nerve stimulator:
    • Preferred and safer technique.
    • To monitor neuromuscular transmission by electrically stimulating the nerve via percutaneous or transcutaneous electrodes, and measuring either electrical or mechanical responses evoked in the target muscle.
  • Evoked mechanical responsescan be gauged in 3 ways:
    • By visually examining the number and strength of 'twitches' - straightforward and feasible but inaccurate.
    • By palpation - inaccurate.
    • By transducing the force of response into a measurable electrical signal - relies on the muscle and limb under test being immobilized in a fixation device - inconvenient, especially in dogs where breed differences in limb size and conformation precludes the use of a standard limb-fixation device.

Disadvantages

  • Interpreting nerve stimulation studies may be complicated because responses differ according to species, relaxant used and nerve/muscle unit under examination - under or overestimation of the degree of relaxation at the operation site may result.
  • Agreement between the three methods of quantifying block are not always similar and depend on whether the block is waxing or waning.
  • Most stimulation patterns cause pain in the conscious patient.
  • Improper nerve stimulation can create the impression of a block where none exists.
  • The operation site often limits the ease with which a given nerve may be stimulated.
  • When responses are measured by transduction, the equipment may prove bulky and interfere with surgery - proving impractical in small dogs.

Requirements

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Preparation

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Procedure

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Outcomes

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Further Reading

Publications

Refereed papers

Other sources of information

  • BSAVA Manual of Small Animal Anaesthesia and Analgesia(1999) Seymour C & Gleed R D (eds)
  • Cullen L K (1996)Muscle relaxants and neuromuscular block.In: Thurmon J C, Tranquilli W J, Benson G J (eds):Lumb & Jones' Veterinary Anesthesia, 3rd edn. Baltimore: Williams & Wilkins, pp 337-364.


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