We chat about neuromuscular blockade, monitoring, and reversal in the ICU, including why sugammadex isn’t more widely used, with Sara J Hyland, PharmD, BCCCP, FCCP, researcher and clinical pharmacist in perioperative and emergency medicine.



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Takeaway lessons




* Aminosteroids (rocuronium, vecuronium) can be reversed by neostigmine + glycopyrrolate (the latter to mitigate peripheral cholinergic effects of neo), or sugammadex. Benzylisoquinoliniums (e.g. cisatracurium) can only be reversed by the neostigmine option.



* Neostigmine is an acetylcholinesterase inhibitor; in other words, it doesn’t directly antagonize the effect of the paralytic, it simply helps boost the supply of ACH at the neuromuscular junction to overcome it. This means its reversal effect is indirect and imperfect.



* Neo is completely ineffective when blockade is deep. In fact, it can have a paradoxical effect of prolonging paralysis when used in these situations. It should really only be used when the train-of-four is 4 twitches. It is also slower acting than sugammadex, and even given with glyco, has inevitable risk of cholinergic toxicity (e.g. bradycardia).



* Neo + glycopyrrolate costs around $30 for a dose, versus around $150-200 for a sugammadex approach. (This does not take into consideration broader system costs from a less effective and less efficient reversal method.) Overall cost with sporadic ICU use will always pale in comparison to high-volume perioperative use, though.



* Sugammadex is a direct binder of the rocuronium/vecuronium molecule, and can attract even already-bound compound from its receptor; hence, it can function at any level of blockade (even very deep).



* A large number of our patients who appear to have cleared their paralysis (seeming clinically “strong,” TOF 4) still have a significant continuing effect of neuromuscular blockade. This may contribute to failures of extubation and other complications. In one ICU study of random ICU patients, >40% had active neuromuscular blockade to a degree that would have precluded extubation by anesthesia standards.



* As a result, the international, guideline-directed gold standard for reversal of neuromuscular blockade is now using quantitative, objective neuromuscular monitoring (before and after reversal agents) to confirm resolution to a >90% TOF ratio.



* What’s that? Normal train-of-four devices (qualitative peripheral nerve stimulators) are inadequate; 4 out of 4 twitches may be present despite 70% of nicotinic ACH receptors still blocked. Better devices (with accelerometers, myometers, EMG, etc) can measure the actual twitch strength and compare the ratio of first to last twitch—i.e. does it fade or maintain strength? The fourth twitch should be >90% the strength of the first before extubation. (All four twitches must be present to even attempt this technique; other techniques can be used at levels of blockade deeper than this.)



* Although sugammadex will be effective at any degree of block, it is dosed differently at different levels, so pre-drug assessment is still important. (It may also reveal the option of using neostigmine, if desired.) Post-drug assessment is then needed to confirm adequate response.



* “Recurarization,” or recurrence of paralysis after reversal, is a known phenomenon. It is rare after sugammadex, and tends to occur when it was underdosed; the immediate effect may be good but the paralytic may outlast the reversal.