Quantitative Neuromuscular Monitoring in Anesthesia

By June 21, 2021Uncategorized

Residual paralysis is a prevalent yet under-recognized issue in perioperative medicine. Residual paralysis occurs when the effects of a neuromuscular blocking agent persist into the surgical recovery period. This complication has been associated with increased risk of critical respiratory events, postoperative pulmonary complications, coma, and patient death [1,2]. Additionally, certain populations are more susceptible to residual paralysis, particularly the elderly. A recent American study reported that up to 57.7 percent of older patients experience residual paralysis following surgery [3]. In order to mitigate associated risks, it is recommended that physicians perform perioperative quantitative neuromuscular monitoring on patients who are more susceptible to residual paralysis.

Quantitative neuromuscular monitoring involves transcutaneous stimulation using the train-of-four (TOF) or post-tetanic count (PTC) pattern, depending on the depth of the neuromuscular block. Following TOF stimulation, one can measure the number of elicited muscular contractions as well as the ratio of the fourth to the first twitch response. Quantitative measurements of twitch force, acceleration, velocity, or compound muscle action potential can be taken using mechanomyography, acceleromyography (AMG), kinemyography, and electromyography (EMG), respectively. Today, most clinics have access to an AMG monitoring device [4]. Importantly, AMGs require additional normalization to the control TOF ratio for increased accuracy, which can be achieved by measuring a baseline value before administration of a neuromuscular blocking drug [5]. Though EMG devices are less common, they are not affected by changes in muscle contractility nor temperature, making them the gold standard of quantitative neuromuscular monitoring according to Manfred et al. [4].

Once the patient has been subjected to quantitative neuromuscular measurements, physicians may use the resulting data to make pertinent clinical decisions. If the measurements indicate residual neuromuscular paralysis, then reversal of the neuromuscular block may be necessary. This can be accomplished by either waiting for the patient’s neuromuscular function to return spontaneously (which often involves prolonged recovery times and continuous monitoring) or through pharmacological intervention. Some of the most common neuromuscular block reversal agents are acetylcholinesterase inhibitors, which inhibit the breakdown of the muscle-stimulating neurotransmitter acetylcholine. Since this methodology requires a minimal threshold of acetylcholine already in the synaptic cleft to be effective, this option is only optimal in cases where minimal residual paralysis remains. If the persistent neuromuscular block is severe, more rigorous intervention may be needed: for example, the modified cyclodexterine sugammadex has been shown to sequester and encapsulate steroidal muscle relaxants for renal excretion, thus reducing their presence in muscle tissue and reversing paralytic effects [6,7]. Sugammadex is therefore useful in both moderate and extreme cases of residual neuromuscular paralysis.

In sum, quantitative neuromuscular measurements can be used to effectively identify postoperative residual paralysis, thus allowing physicians to make informed clinical decisions and improving patient outcomes. It is therefore of great clinical interest for anesthesia providers to perform quantitative neuromuscular monitoring following intensive surgical procedures, particularly in patients that are at a high-risk for persistent paralysis. Moreover, it is anticipated that this type of post-surgical monitoring will become increasingly integrated into standard care in the years to come.



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