Neuromuscular monitoring explained

In anesthesia, neuromuscular blocking agents may be required to facilitate endotracheal intubation and provide optimal surgical conditions. When neuromuscular blocking agents are administered, neuromuscular function of the patient must be monitored.[1] Neuromuscular function monitoring is a technique that involves the electrical stimulation of a motor nerve and monitoring the response of the muscle supplied by that nerve.[2] It may be used from the induction of to recovery from neuromuscular blockade. Importantly, it is used to confirm adequacy of recovery after the administration of neuromuscular blocking agents.[3] The response of the muscles to electrical stimulation of the nerves can be recorded subjectively (qualitative) or objectively (quantitatively). Quantitative techniques include electromyography, acceleromyography, kinemyography, phonomygraphy and mechanomyography. Neuromuscular monitoring is recommended when neuromuscular-blocking drugs have been part of the general anesthesia and the doctor wishes to avoid postoperative residual curarization (PORC) in the patient, that is, the residual paralysis of muscles stemming from these drugs.

When train of four monitoring is "used continuously, each set (train) of stimuli normally is repeated every 10th to 12th second. Each stimulus in the train causes the muscle to contract, and 'fade' in the response provides the basis for evaluation." These sets are called trains because their shape bears the resemblance of a train.[4] In train of four monitoring, "peripheral nerve stimulation can ensure proper medication dosing and thus decrease the incidence of side effects" by "assessing the depth of neuromuscular blockade".[5]

Before the patient is fully awake, voluntary muscle testing is not possible and indirect clinical tests, such as apparent muscle tone and pulmonary compliance, can be affected by factors other than PORC. Direct neuromuscular monitoring avoids these problems and allows the doctor to remedy PORC before it becomes a source of patient distress.[6] [7] [8] [9] [10]

Patterns of nerve stimulation

Various nerve stimulation patterns may be used in neuromuscular function monitoring and the response to these stimulation patterns is used to assess the depth of neuromuscular blockade.

Some patterns of stimulation used today include, single twitch (ST), train-of four (TOF),[11] double burst stimulation (DBS), tetanic stimulation

and the post tetanic count.[12]

Monitoring the response of the muscle to nerve stimulation

The response of the muscle to stimulation of the nerve supplying it can be assessed by subjective (visual or tactile) techniques or quantitative (objective) devices that provide a numeric value relating to the depth of neuromuscular blockade.

Quantitative (objective) neuromuscular monitors

Quantitative neuromuscular monitors can be subdivided into monitors that measure the electrical response, the compound evoked muscle action potential, and those that monitor the contractile response to stimulation. The measurement of the electrical response to muscle stimulation is called electromyography. The mechanical response to stimulation of the muscle can be measured by mechanomyography, kinemyography and acceleromyography[13]

Consensus Statement on Perioperative Use of Neuromuscular Monitoring

In 2018 recommendations by an international panel of experts on neuromuscular monitoring to assist anaesthesia care providers and professional organisations that develop practice advisories and guidelines regarding the minimum standards for monitoring patients that receive neuromuscular blockade (NMB) during anaesthesia. The recommendations include the following:

  1. "Quantitative (objective) NMB monitoring should be used whenever non-depolarising neuromuscular blocking drug is administered."
  2. "Subjective or clinical tests of NMB are not predictive of adequate neuromuscular recovery and are not sensitive to detect residual weakness; their use should be abandoned in favour of quantitative (objective) monitoring."
  3. "Professional organisations should develop practice standards and guidelines detailing how best to monitor and manage perioperative administration of NMBDs."
  4. "Terms that describe the levels of NMB should be standardised. New proposed definitions are published in the consensus statement based on quantitative NMB monitoring criteria."[14]

Anaesthetic organisations with guidelines or professional standards on neuromuscular monitoring

The Association of Anaesthetists of Great Britain and Ireland published recommendations for standards of monitoring during anaesthesia and recovery in 2015.[15] These included that a peripheral nerve stimulator is mandatory for all patients receiving neuromuscular blocking drugs and that they should be applied and used from induction (to confirm adequate muscle relaxation before intubation) until recovery from blockade and return of consciousness. They state that a more reliable guarantee of return of safe motor function is a train of four ratio of greater than 0.9. A quantitative neuromuscular monitor is required to accurately assess the train of four ratio.[16]

The Australian and New Zealand College of Anaesthetists also publishes professional standards and guidelines on monitoring during anaesthesia. In respect to neuromuscular function monitoring - They state " Neuromuscular function monitoring, preferably quantitative, must be available for every patient in whom neuromuscular blockade is induced and should be used whenever the anaesthetist is considering extubation following the use of non-depolarising neuromuscular blockade."[17]

Further reading

Notes and References

  1. Ortega R, Brull SJ, Prielipp R, Gutierrez A, De La Cruz R, Conley CM . Monitoring Neuromuscular Function . The New England Journal of Medicine . 378 . 4 . e6 . January 2018 . 29365307 . 10.1056/NEJMvcm1603741 .
  2. Naguib M, Brull SJ, Johnson KB . Conceptual and technical insights into the basis of neuromuscular monitoring . Anaesthesia . 72 Suppl 1 . S1 . 16–37 . January 2017 . 28044330 . 10.1111/anae.13738 . free .
  3. Checketts MR, Alladi R, Ferguson K, Gemmell L, Handy JM, Klein AA, Love NJ, Misra U, Morris C, Nathanson MH, Rodney GE, Verma R, Pandit JJ . Recommendations for standards of monitoring during anaesthesia and recovery 2015: Association of Anaesthetists of Great Britain and Ireland . Anaesthesia . 71 . 1 . 85–93 . January 2016 . 26582586 . 5063182 . 10.1111/anae.13316 .
  4. Web site: Train-of-Four Stimulation. 2000. Churchill Livingstone. 10 September 2014. https://web.archive.org/web/20140911001731/http://web.squ.edu.om/med-Lib/MED_CD/E_CDs/anesthesia/site/content/v03/030470r00.HTM. 11 September 2014. dead.
  5. Web site: Saenz AD, Maillie S, Eiger G . Spencer DC . Peripheral Nerve Stimulator - Train of Four Monitoring. 12 July 2013. Medscape. 10 September 2014.
  6. Book: Viby-Mogensen, Jorgen . vanc . Chapter 39: Neuromuscular Monitoring . http://faculty.washington.edu/ramaiahr/Chapter_39_Neuromuscular_Monitoring.pdf . Miller's Anesthesia . 5th . Churchill Livingstone, Inc. .
  7. Harvey AM, Masland RL . Actions of durarizing preparations in the human. . Journal of Pharmacology and Experimental Therapeutics . 73 . 3 . 304–311 . 1941 .
  8. Botelho SY . Comparison of simultaneously recorded electrical and mechanical activity in myasthenia gravis patients and in partially curarized normal humans . The American Journal of Medicine . 19 . 5 . 693–6 . November 1955 . 13268466 . 10.1016/S0002-9343(55)80010-1.
  9. Christie TH, Churchill-Davidson HC . The St. Thomas's Hospital nerve stimulator in the diagnosis of prolonged apnoea . Lancet . 1 . 7024 . 776 . April 1958 . 13526270 . 10.1016/s0140-6736(58)91583-6.
  10. Engbaek J, Ostergaard D, Viby-Mogensen J . Double burst stimulation (DBS): a new pattern of nerve stimulation to identify residual neuromuscular block . British Journal of Anaesthesia . 62 . 3 . 274–8 . March 1989 . 2522790 . 10.1093/bja/62.3.274. free .
  11. ALI. HASSAN H.. UTTING. J.E.. GRAY. CECIL. November 1970. British Journal of Anaesthesia. 42. 11. 967–978. 10.1093/bja/42.11.967. 5488360. 0007-0912. Stimulus Frequency in the Detection of Neuromuscular Block in Humans. free.
  12. Monitoring Neuromuscular Function NEJM. New England Journal of Medicine. 378. 4. e6. en. 10.1056/nejmvcm1603741. 29365307. 2018. Ortega. Rafael. Brull. Sorin J.. Prielipp. Richard. Gutierrez. Alexander. de la Cruz. Rossemary. Conley. Christopher M..
  13. Brull. Sorin J.. Kopman. Aaron F.. January 2017. Current Status of Neuromuscular Reversal and Monitoring. Anesthesiology. 126. 1. 173–190. 10.1097/aln.0000000000001409. 27820709. 34444215 . 0003-3022.
  14. Naguib. Mohamed. Brull. Sorin J.. Kopman. Aaron F.. Hunter. Jennifer M.. Fülesdi. Béla. Arkes. Hal R.. Elstein. Arthur. Todd. Michael M.. Johnson. Ken B.. July 2018. Consensus Statement on Perioperative Use of Neuromuscular Monitoring. Anesthesia & Analgesia. 127. 1. 71–80. 10.1213/ane.0000000000002670. 29200077. 0003-2999. free.
  15. Checketts. M. R.. Alladi. R.. Ferguson. K.. Gemmell. L.. Handy. J. M.. Klein. A. A.. Love. N. J.. Misra. U.. Morris. C.. 2016. Recommendations for standards of monitoring during anaesthesia and recovery 2015 : Association of Anaesthetists of Great Britain and Ireland. Anaesthesia. en. 71. 1. 85–93. 10.1111/anae.13316. 1365-2044. 5063182. 26582586.
  16. Hemmerling. Thomas M.. Le. Nhien. January 2007. Brief review: Neuromuscular monitoring: an update for the clinician. Canadian Journal of Anesthesia. 54. 1. 58–72. 10.1007/bf03021901. 17197470. 0832-610X. free.
  17. Web site: Australian and New Zealand College of AnaesthetistsProfessional Standards 2017 PS18 Guidelines on monitoring during anaesthesia.

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