The use of neuromuscular blocking agents (muscle relaxants) by anesthesiologists—for example, for tracheal intubation, maintenance of anesthesia, and ensuring optimal surgical conditions—occurs almost daily. However, very often we administer muscle relaxants “blindly,” calculating a certain mg/kg dose for each individual patient. Yet patients differ, just as muscle relaxants do. Each patient responds individually to one type of neuromuscular blocker or another, and a mg/kg dose is often unreliable [1].

We can observe that, without neuromuscular monitoring, during intubation a patient may cough, raise their arms, and so on. Or during surgery, surgeons may ask to “relax” the patient further. Even during extubation, the anesthesiologist may assess the recovery of neuromuscular function using clinical signs (asking the patient to stick out their tongue, squeeze a hand, lift their head, etc.). None of these clinical signs guarantees the absence of residual neuromuscular blockade [2]. This complication is one of the most dangerous and can lead to desaturation, re-intubation, or even postoperative aspiration pneumonia [3].

Using quantitative train-of-four (TOF) neuromuscular monitoring, residual neuromuscular blockade after tracheal extubation can be excluded with 100% certainty. The most authoritative anesthesia associations (the Association of Anaesthetists of Great Britain and Ireland, the European Society of Anaesthesiology, and the American Society of Anesthesiologists) state in their guidelines that quantitative neuromuscular monitoring (TOF) is mandatory when neuromuscular blocking agents are used, and that the likelihood of residual blockade should be excluded before extubation when TOF indicators meet the criteria: TOFC 4 and TOFR > 0.9 [4–5].

TOF monitoring makes it possible to objectively assess the degree of neuromuscular blockade during surgery and determine the depth of blockade required for a specific type of procedure. A surgeon’s subjective statement during an operation that the patient is not sufficiently “relaxed” can be objectively evaluated using this monitoring method, helping to determine whether an additional dose of a neuromuscular blocker is needed. This is particularly important given that rocuronium and its antidote, sugammadex, are still not widely available; an excessive dose of a neuromuscular blocker toward the end of surgery may lead to residual neuromuscular blockade after extubation.

1. Maybauer DM et al. Anaesthesia 2007;62: 12-17

2. Donati: Can J Anesthesiology 2013;60:714-29

3. Bulka et al. Anesthesiology 2016;125: 647-55

4. AA Klein et al. Anaesthesia 2021;76: 1212-1223  

5.  Fuchs-Buder T et al. Eur J Anaesthesiol. 2023;40(2):82

6. Thilen SR et al. Anesthesiology. 2023;138(1):13

7. Moira H Bruintjes et al.