Neuromuscular Blockade Monitoring – Its importance, current application and guidelines

Postoperative residual paralysis or residual neuromuscular blockade is defined as a train-or-four (TOF) ratio of <0.9. Consequences of residual neuromuscular blockade include:

• Generalised muscle weakness
• Delayed recovery
• Reduced chemoreceptor responsiveness to hypoxia
• Increased risk of aspiration
• Pulmonary complications
• Accidental intraoperative awareness.

Research and guidelines indicate that quantitative neuromuscular monitoring and assessment is the only effective measure to ensure adequate return of neuromuscular function. Currently, anaesthetists use various methods in practice to test return of neuromuscular function after administration of chemical neuromuscular blockade and before tracheal extubation. Some of these methods include:

1. Pharmacological reversal (Suggamadex, Neostigmine + Glycopyrrolate)
2. Clinical criteria (sustained head-lift, hand grip and positive predictive values)
3. Neuromuscular transmission monitoring
4. Combination of the above.

Guidelines and research has demonstrated that clinical criteria and other signs such as spontaneous respiration, perceived adequacy of tidal breaths, coughing on tracheal tube, extremity movements to command does not exclude residual blockade. Similarly, qualitative peripheral nerve stimulation is unable to guarantee adequacy of neuromuscular blockade recovery. Tactile or visible ToF fade only indicates a recovery ratio of up to 0.4 or greater which has led guidelines to suggesting a change in monitoring from qualitative to quantitative ensuring complete assessment is conducted.
Guidelines outline that quantitative monitoring is essential and should be utilised when administering neuromuscular blockade drugs. The guidelines suggest that every operative environment where neuromuscular blockade drugs are used should be equipped with a quantitative neuromuscular monitoring device along with other essential equipment. This monitor should be activated during induction of anaesthesia but before administration of neuromuscular blockade to gain a baseline reading. This should then be continued until appropriate recovery from neuromuscular blockade has been achieved after completion of operation.

• Appropriate recovery has been defined as a ToF ratio of >0.9 before extubation is attempted.
• Quantitative (superior) = data that is measured (e.g. ToFScan)
• Qualitative (inferior) = data that is observed but not measured (objective)

Limitations:

• Unfortunately, when the hand is unavailable for monitoring due to anatomical or surgical reasons, the facial nerve can be used. This should be done with extreme caution as the risk of residual neuromuscular blockade is 5 times greater when using facial nerve monitoring.

Example in Australia of current risks + rate of residual neuromuscular paralysis
In an Australian, prospective, cohort study of 599 adult patients who received anaesthesia and neuromuscular blockade, 186 patients were identified as affected by residual neuromuscular blockade in the recovery unit. 97 experienced one or more adverse respiratory events, more commonly seen in the group who experienced residual neuromuscular blockade (P=0.033). AREs were associated with decreased level of consciousness, age, open abdominal surgery, <90 minutes of surgical intervention and a low core temperature. Preventable causes such as hypothermia, decreased level of consciousness and appropriate delay of extubation until appropriate quantitative + qualitative assessment is completed by the clinician. https://airr.anzca.edu.au/anzcacrisjspui/handle/11055/666.
Current clinical recommendations for monitoring:

1. Clinical judgement on length of monitoring is to be used when assessing fundamental physiological variables.
2. Healthcare facilities are responsible for providing adequate equipment to safely monitor patients during anaesthesia.
3. Some recommendations in the guidelines need to be exceeded based on patient variability, results and pre-anaesthesia consultation.
4. Equipment to monitor patients should be used in conjunction with careful clinical observation to avoid unfavourable circumstances which monitors may not detect.
5. Visual and audible alarms must be enabled on all monitoring equipment, disabling of these alarms are only accepted during extreme circumstances (such as during active cardiac bypass where the patient is aponeic and pulseless).

Current guidelines for neuromuscular blockade monitoring:

1. Quantitative neuromuscular monitoring should be used whenever neuromuscular blocking (NMB) drugs are administered, throughout all phases of anaesthesia from before initiation of neuromuscular blockade until recovery of the train-of-four ratio to > 0.9 has been confirmed.
2. Neuromuscular function monitor – Quantitative neuromuscular function monitoring should be available for every patient in whom neuromuscular blockade has been induced and should be used whenever the anaesthetist is considering extubation following the use of non-depolarising neuromuscular blockade.
   1. Essentially – hospitals/facilities need to supply adequate equipment for anaesthesiologists to safely monitor the patient against recommendations outlined by governing bodies.
3. Processed electroencephalogram (pEEG) monitoring should be used when total intravenous anaesthesia (TIVA) is administered together with a NMB drug. It should start before induction and continue at least until full recovery from the effects of the neuromuscular blockade has been confirmed. It should be considered during other anaesthetic techniques including inhalational anaesthesia and for the high-risk patient

ICU EDM Points LinkedIn Post:
There has been an update of recommendations for neuromuscular blockade monitoring:

• Studies have shown that healthy volunteers can sustain a head lift with a train-of-four ratio as low as 0.45. A train-of-four ratio greater than 0.9 is recommended prior to extubation.

Key Recommendations
Given the persistence of this problem, the ASA Committee on Practice Parameters convened a task force of anesthesiologists, epidemiology-trained methodologists and patient representatives. Together, they outlined the criteria that guided the systematic review, which comprised a search of the PubMed, EMBASE and SCOPUS databases for relevant studies published between 1990 and June 2022. The Cochrane Central Register of Controlled Trials was also queried. Eligible studies included randomised and non-randomized trials, comprising diagnostic, before-after/time series, cohort, and case–control designs.
As a result of the literature search, the expert panel made eight recommendations:

1. When neuromuscular blocking drugs are administered, the panel recommends against clinical assessment alone due to the insensitivity of the assessment (strong recommendation; moderate strength of evidence).
2. The guidelines recommend quantitative TOF monitoring over qualitative assessment (strong recommendation; moderate strength of evidence).
3. When using quantitative monitoring, the panel recommends confirming a TOF ratio of 0.9 or greater before extubation (strong recommendation; moderate strength of evidence).
4. The guidelines recommend use of the adductor pollicis muscle (hand) for neuromuscular monitoring (strong recommendation; moderate strength of evidence).
5. Similarly, the guidelines recommend against using eye muscles for neuromuscular monitoring (strong recommendation; moderate strength of evidence).
6. With respect to the comparative safety and efficacy of antagonist drugs, the panel recommends sugammadex over neostigmine at deep, moderate and shallow depths of neuromuscular blockade induced by rocuronium or vecuronium (strong recommendation; moderate strength of evidence).
7. Conversely, the panel suggests neostigmine is a reasonable alternative to sugammadex at minimal depths of neuromuscular blockade (conditional recommendation; low strength of evidence).
8. Finally, the panel recommends antagonism with neostigmine at minimal neuromuscular blockade depth when atracurium or cisatracurium is administered and qualitative assessment is used. In the absence of quantitative monitoring, however, at least 10 minutes should elapse from antagonism to extubation. On the other hand, when quantitative monitoring is employed, extubation can be done as soon as a TOF ratio of 0.9 or greater is confirmed before extubation (conditional recommendation; very low strength of evidence).