Neuromuscular monitoring: An assistant not an alternative.

Sir,

We came across an article 'Reversal agents: Do we need to administer with neuromuscular monitoring – an observational study' by Goyal et al. published in the March issue of IJA.[1]

The article had many shortcomings which would have needed proper justification. In an observational study, the investigator does not intervene and rather simply 'observes' and assesses the strength of the relationship between an exposure and disease variable.[2] Use of neostigmine in one group and its avoidance in the other precludes it from being an observational study. Nine patients from NMT group needed muscle relaxant, amounting to the requirement of neostigmine in 10.11% cases which is quite substantial, hence itself justifying the use of neostigmine even in the patients being monitored with neuromuscular monitoring. Furthermore, their exclusion cannot be justified and if they would have been considered for calculations, average time required for extubation in NMT group without the use of neostigmine would have been much prolonged (statistical significance remains to be seen).

As per latest guidelines, objective neuromuscular monitoring is advised, for providing anaesthesia in all the patients receiving neuromuscular blockade to prevent residual muscle paralysis.[3] This study could have been better served with the use of neuromuscular monitoring in both the groups, followed by administration of neostigmine after achievement of train-of-four (TOF) ratio >0.9. The difference in time of extubation observed after that would have provided the clearer picture regarding the use of neostigmine.

It has been observed that post-operative recovery of the TOF ratio to 0.9 does not exclude an impairment of neuromuscular transmission.[4] Hence, it cannot be considered as the sole criteria for extubation. Objective assessment combined with the subjective assessment would be the best approach while extubating the patient as residual muscle paralysis poses a significant threat in the post-anaesthetic care unit, as already mentioned in the article. In addition, though research has shown that neostigmine's use may cause genioglossus and pharyngeal muscle hypoactivity in rats, no such clinical experience has been reported in humans, till now.

Use of neuromuscular monitoring is for optimising the dosage of neuromuscular blocking agent as well as neostigmine (and glycopyrrolate) but total abolishment of neostigmine's use, even with the neuromuscular monitoring is not advisable. In conclusion, though the article can be considered a daring discourse, benefits of using neostigmine to reverse a neuromuscular blockade far outweighs its potential risks which have not been yet observed in the human population.

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Conflicts of interest

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