[1][2] Today residual neuromuscular blockade is defined as a train of four ratio[3] of less than 0.9 when measuring the response to ulnar nerve stimulation at the adductor pollicis muscle using mechanomyography or electromyography.

[5] Neuromuscular function monitoring and the use of the appropriate dosage of sugammadex to reverse blockade produced by rocuronium can reduce the incidence of postoperative residual curarization.

[citation needed] Multiple studies have demonstrated that incomplete reversal of NMBDs is an important risk factor for postoperative morbidity and mortality.

[7] Classified into two main groups: •Depolarizing NMBDs: produces skeletal muscle relaxation by binding directly with nAChRs to cause prolonged depolarization.

•Non-depolarizing NMBDs: competitive antagonists (competing with acetylcholine [ACh] for the binding sites at the nAChRs), preventing the initiation of action potential.

This type of block occurs when the desensitizing phase sets in and the muscle is no longer responsive to acetylcholine and full neuromuscular blockade is achieved.

[14] Subjective monitoring refers to the clinical evaluation of assessing the TOFC or degree of fade by using methods such as physically touching the patient and feeling movement or visibly observing a twitch in response to neurostimulation provided by a peripheral nerve stimulator.

"[15] Due to the difficulty detecting fade subjectively (TOF ratios between 0.4 and 0.9) when using peripheral nerve stimulators, clinicians are unable to reliably exclude residual neuromuscular blockade.

However, TOF ratios >4 can be measured accurately by using quantitative monitoring methods such as electromyography (EMG), kinemyography (KMG), phonomyography (PMG), and acceleromyography (AMG).

However, peripheral nerve stimulators can only subjectively determine the depth of block (train-of-four count) and cannot provide accurate information needed for the timing and dosing of reversal agents as well as ensure full recovery (TOF fade).