Intraoperative Neuromuscular Monitoring Site and Residual Paralysis

Survey of Anesthesiology 06/2013; 57(3):156-157. DOI: 10.1097/


Residual paralysis is common after general anesthesia involving administration of neuromuscular blocking drugs (NMBDs). Management of NMBDs and reversal is frequently guided by train-of-four (TOF) monitoring. We hypothesized that monitoring of eye muscles is associated with more frequent residual paralysis than monitoring at the adductor pollicis.

This prospective cohort study enrolled 180 patients scheduled for elective surgery with anticipated use of NMBDs. Collected variables included monitoring site, age, gender, weight, body mass index, American Society of Anesthesiologists physical status class, type and duration of surgery, type of NMBDs, last and total dose administered, TOF count at time of reversal, dose of neostigmine, and time interval between last dose of NMBDs to quantitative measurement. Upon postanesthesia care unit admission, we measured TOF ratios by acceleromyography at the adductor pollicis. Residual paralysis was defined as a TOF ratio less than 90%. Multivariable logistic regression was used to account for unbalances between the two groups and to adjust for covariates.

150 patients received NMBDs and were included in the analysis. Patients with intraoperative TOF monitoring of eye muscles had significantly greater incidence of residual paralysis than patients monitored at the adductor pollicis (P < 0.01). Residual paralysis was observed in 51/99 (52%) and 11/51 (22%) of patients, respectively. The crude odds ratio was 3.9 (95% CI: 1.8-8.4), and the adjusted odds ratio was 5.5 (95% CI: 2.1-14.5).

Patients having qualitative TOF monitoring of eye muscles had a greater than 5-fold higher risk of postoperative residual paralysis than those monitored at the adductor pollicis.

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    ABSTRACT: Purpose: Over the past three decades, many studies have shown a high proportion of patients in the recovery room with residual neuromuscular blockade after anesthesia. The purpose of this Continuing Professional Development module is to present the physiological consequences of residual paralysis, estimate the extent of the problem, and suggest solutions to prevent its occurrence. Principal findings: Residual paralysis is defined as a train-of-four ratio (TOFR) < 0.9 at the adductor pollicis. While tidal volume and, to a lesser extent, vital capacity are well preserved as the intensity of blockade increases, the probability of airway obstruction, impaired swallowing, and pulmonary aspiration increases markedly as TOFR decreases. In recent studies, incidences of residual paralysis from 4-57% have been reported, but surveys indicate that anesthesiologists estimate the incidence of the problem at 1% or less. The decision to administer neostigmine or sugammadex should be based on the degree of spontaneous recovery at the adductor pollicis muscle (thumb), not on recovery at the corrugator supercilii (eyebrow). The most important drawback of neostigmine is its inability to reverse profound blockade, which is a consequence of its ceiling effect. When spontaneous recovery reaches the point where TOFR > 0.4 or four equal twitch responses are seen, reduced doses of neostigmine may be given. The dose of sugammadex required in a given situation depends on the intensity of blockade. Conclusion: Careful monitoring and delaying the administration of neostigmine until four twitches are observed at the adductor pollicis can decrease the incidence of residual paralysis. The clinical and pharmacoeconomic effects of unrestricted sugammadex use are unknown at this time.
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