Assessing Whether Quantitative Neuromuscular Blockade Monitoring Should Be the Standard of Care

Educational Objectives

The goal of this program is to improve quantitative monitoring of neuromuscular blockade. After hearing and assimilating this program, the clinician will be better able to:

1. Use mechanomyography in monitoring of neuromuscular blockade.
2. Compare use of acceleromyography with electromyography in monitoring of neuromuscular blockade.

Summary

Basics of neuromuscular blockade monitoring: divided into 2 main categories, qualitative and quantitative monitoring; qualitative monitoring involves the subjective assessment of the strength of muscle contraction in response to stimulation by peripheral nerve stimulator, using visual or tactile means; quantitative monitoring involves objective measurement of train-of-four ratio using a device that measures, analyzes, and displays data in real time

Qualitative monitoring: utilizes clinical signs to make sure that the patient has regained strength before extubation; other qualitative test is a peripheral nerve stimulator (PNS); the 2 most common ways of using PNS is by the use of train-of-four stimulation by train-of-four count, and by tetanic stimulation with posttetanic count

Train-of-four count: involves 4 single twitches at 2 hertz (Hz), and then subjective assessment of the presence of fade from the first twitch to the last, indicating a deeper level of blockade; tetanic stimulus provides tetanus for 50 Hz for 5 sec, followed 3 sec later by 20 single twitches; presence of only 1 twitch after the tetanic stimulus is a sign of deep blockade; it takes ≈30 min for a patient to spontaneously recover their first twitch; this is subjective and is prone to error

Quantitative monitoring: mechanomyography (MMG) is primarily used in research setting and requires application of 200 to 300 g of pretension to the thumb; it is the gold-standard, as it directly measures the force generated by the skeletal muscle; new commercially available devices do not directly measure the force generated by the skeletal muscle like MMG, but instead measure the acceleration or electrical activity at the muscle, and the most common are acceleromyography (AMG), electromyography (EMG), and, less commonly, kinemyography

Acceleromyography: the most common type of quantitative monitor and is based on Newton's second law of motion; it uses the electrical signals measured in the thumb to calculate the force of contraction; these signals are then digitized, processed, and electronically displayed in real-time displaying train-of-four count; with 4 twitches, train-of-four ratio is calculated

Electromyography: the second-most common monitor that measures combined muscle action potentials across the neuromuscular unit; the amplitude of the C-max is directly proportional to the number of activated muscle fibers and thus, the force of contraction; it also displays train-of-four count and with 4 twitches, it calculates train-of-four ratio

Expert guidelines: the French Society of Anesthesiology recommended instrumental monitoring in 2000, which was agreed upon by the Czech Society of Anesthesia in 2010; the Australia and New Zealand College of Anesthetists in 2017 specifically endorsed quantitative monitoring; in 2020, Canada also agreed upon quantitative monitoring as the best, but mandated the use of monitoring device; the most specific recommendation from the Association of Anesthetists of Great Britain and Ireland in 2021 stated that quantitative neuromuscular monitoring should be used whenever neuromuscular blocking drugs are administered, throughout all phases of anesthesia from before initiation of neuromuscular blockade until the confirmation of recovery with the train-of-four ratio to >0.9; a questionnaire study on 108 Brazilian anesthesiologists reported that 73% chose to reverse if the time since the last neuromuscular blocking drug was short, 71% reversed it if the breathing pattern was inadequate, 53% were less likely to use reversal agents if >1 hr had elapsed after a single intubating dose of rocuronium; 64% of Americans and 52% of Europeans reported that the estimated incidence of clinically significant postoperative residual neuromuscular paralysis was <1%

Barriers to acceptance of quantitative monitoring: most studies found by the speaker reported incidence of residual blockade between 40% and 60%; a meta-analysis conducted in 2007 noted that the incidence of residual neuromuscular weakness following the use of intermediate-acting neuromuscular blocking drugs was 41%; residual curarization and its incidence at tracheal extubation (RECITE) study done in Canada in 2015 found that the incidence of residual blockade was about 64% at extubation and 57% in postanesthesia care unit (PACU); similar study conducted in America reported that 65% of patients had residual weakness, of which 31% had train-of-four ratios of <0.6; a systematic review also reported that the overall incidence of residual blockade ranged from 0% to 90%; the incidence of residual blockade was lower with sugammadex

Currently accepted definition of adequate recovery: this is a train-of-four ratio ≥0.9 measured at the adductor pollicis muscle to restore the functional integrity of the muscles for airway protection; in 1979, train-of-four ratio of 0.7 was deemed appropriate; but subsequently, multiple studies have shown that patients have significant weakness between 0.7 and 0.9; adductor pollicis muscle is exquisitely sensitive to neuromuscular blockade, is the first to be affected and the last to recover, whereas diaphragm is resistant; few of the upper airway muscles have similar recovery timeline as adductor pollicis muscle; though orbicularis oculi is close in recovery timeline to the adductor pollicis, it is not used as it is hard to differentiate between the corrugator supercilii and orbicularis oculi, resulting in overestimation of patient's degree of recovery

Reasons for using train-of-four ratio for measuring adequate recovery: patients can generate normal tidal volumes at train-of-four ratios between 0.2 and 0.4, and start lifting their heads and squeezing a hand at 0.3 to 0.4; swallowing, maintenance of patent airway, or clenching of teeth begin at ≥0.8

Use of PNS: the most important difference between PNS and a quantitative monitor occurs when the train-of-four count is 4; experts describe 3 different levels of blockade as shallow, minimal, and acceptable recovery; many studies reported that experienced clinicians cannot reliably detect a fade with peripheral nerve stimulator at train-of-four ratios between 0.4 and 0.9, but detect accurately when it reaches ≤0.4; it is important to differentiate between shallow or minimal block because significant adverse events occur between the train-of-four ratios 0.7 and 0.9

Volunteer studies: reported weakness and impaired hypoxic ventilatory drive at train-of-four ratio of 0.7; there was swallowing dysfunction, increased risk for aspiration, decreased pharyngeal function, and partial upper airway obstruction at train-of-four ratio of 0.8 and even at 0.9, but there was still reduced upper esophageal sphincter tone

High-risk patients: patients with respiratory disease, neuromuscular disease, sleep apnea, old age, and obesity might develop severe postoperative complications when they have residual blockade; a study compared the quantitative (PNS) with qualitative monitoring (AMG) and adverse events in PACU, and concluded that significant respiratory events do occur and shows a reduction in these events when quantitative monitoring is used; another study reported that the incidence of pneumonia in patients receiving a paralytic agent was 1.79 times that of propensity-matched patients without a neuromuscular blocking drug; the incidence of pneumonia in patients without reversal agents was 2.26 times higher compared with those who received neostigmine

Residual weakness and patients standpoint: can cause airway obstruction, collapse, increased oxygen requirements, lower quality of recovery, increased length of stay in PACU and hospital stay, unplanned ICU admissions, increased risk for morbidity and mortality, and financial burden; residual blockade is likely to be short-lived; the typical dose of rocuronium lasts about 21 min in an anesthetized adult, but varies substantially ranging from 15 to 85 min; other source claims that it is between 33 and 137 min

Sugammadex: reverses fast and is effective at any depth of blockade when rocuronium and vecuronium are used; rocuronium and vecuronium are the most commonly used intermediate-acting neuromuscular blocking drugs in the United States

Pros and cons of using quantitative monitoring: with the train-of-four ratio >0.9, sugammadex can be avoided; sugammadex is expensive, its administration without monitoring can result in residual weakness in 9.4% to 16% of patients; reoccurrence of neuromuscular blockade can occur postoperatively if inappropriate dose of sugammadex is used; neuromuscular monitoring is expensive as the devices are more expensive than PNS and recurring costs for disposable electrode-sensor arrays; though it is expensive, judicious use of neuromuscular blocking drugs and their antagonist, may offset these costs; prolonged PACU stay, unplanned admissions, and re-intubations are more expensive; a recent study from Temple University on EMG-based quantitative monitoring found that the incidence of residual blockade was 60%, complication rate of patients with residual blockade was about 5.4% compared with only 1.8% in patients without residual blockade

Quantitative neuromuscular monitoring: disruptive to the workflow; however, newer improved devices are more reliable and convenient; newer monitors are reliable, tri-axial, and measure 3 dimensions of movement to account for the complex motion of the thumb; they also have preload devices that are incorporated into them; a study tested 3 different devices (PNS, AMG, and EMG) and found that quantitative monitors took only 19 sec longer to apply than PNS

Comparison of AMG and EMG devices: unlike EMG, AMG requires protection of the hand during tucked cases; AMG is also subject to reverse fade, indicating that the baseline train-of-four ratio on anesthetized but not paralyzed patients can exceed 100%; unlike newer AMD devices, one needs to do normalization process before proceeding with older AMD devices; both of them have high-level agreement with MMG

Disadvantages of EMG: expensive, may be affected by electrocautery, and is sensitive to temperature changes; C-max can increase 2% to 3% for every 1°C decrease in temperature; a study that compared AMG and EMG on the same arm at the adductor pollicis muscle at the same time reported that EMG had higher precision and greater repeatability than AMG

Newer advancements: cuff pressure modality that combines 2 monitors into one, but studies indicated that it overestimates the train-of-four ratio at the adductor pollicis muscle and needs further validation

Readings

Duţu M, Ivaşcu R, Tudorache O, et al. Neuromuscular monitoring: an update. Rom J Anaesth Intensive Care. 2018;25(1):55-60. doi:10.21454/rjaic.7518.251.nrm; Fortier LP, McKeen D, Turner K, et al. The RECITE Study: A Canadian Prospective, Multicenter Study of the Incidence and Severity of Residual Neuromuscular Blockade. Anesth Analg. 2015;121(2):366-372. doi:10.1213/ANE.0000000000000757; Hemmerling TM, Donati F. Neuromuscular blockade at the larynx, the diaphragm and the corrugator supercilii muscle: a review. Can J Anaesth. 2003;50(8):779-794. doi:10.1007/BF03019373; Lozano-García M, Sarlabous L, Moxham J, et al. Surface mechanomyography and electromyography provide non-invasive indices of inspiratory muscle force and activation in healthy subjects. Sci Rep. 2018;8(1):16921. Published 2018 Nov 16. doi:10.1038/s41598-018-35024-z; Martinsen T, Pettersen FJ, Kalvøy H, et al. Electrosurgery and Temperature Increase in Tissue with a Passive Metal Implant. Front Surg. 2019;6:8. doi:10.3389/fsurg.2019.00008; Murphy GS. Residual neuromuscular blockade: incidence, assessment, and relevance in the postoperative period. Minerva Anestesiol. 2006;72(3):97-109; Naguib M, Brull SJ, Johnson KB. Conceptual and technical insights into the basis of neuromuscular monitoring. Anaesthesia. 2017;72 Suppl 1:16-37. doi:10.1111/anae.13738; Suzuki T, Fukano N, Kitajima O, et al. Normalization of acceleromyographic train-of-four ratio by baseline value for detecting residual neuromuscular block. Br J Anaesth. 2006;96(1):44-47. doi:10.1093/bja/aei273.

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Morris was recorded at the Texas Society of Anesthesiologists 2022 Annual Meeting, held September 8-11, 2022, in Round Rock, TX, and presented by the Texas Society of Anesthesiologists. For more information on further CME activities from this presenter, please visit tsa.org. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 1.25 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 1.25 CE contact hours.

Lecture ID:

AN651602

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.