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Neuromuscular Block Management: Evidence-Based Principles and Practice

GasNovice Neuromonitoring

Introduction & Current Landscape

• Residual neuromuscular block (RNMB) remains a frequent source of postoperative morbidity despite modern drugs and monitors. Contemporary series still report RNMB (train-of-four (TOF) ratio < 0.9) in 2–40 % of patients, depending on monitoring practices. Quantitative monitoring coupled with appropriate antagonism virtually eliminates RNMB and reduces pulmonary complications.

Depth of Block–Unified Definitions

Depth	Quantitative criteria	Typical clinical use
Complete	Post-tetanic count (PTC) = 0	Radical airway surgery, profound immobility
Deep	PTC ≥ 1, TOF count 0	Low-pressure laparoscopy, robotic pelvic work
Moderate	TOF count 1–3	Most intra-abdominal & thoracic surgery
Shallow	TOF ratio < 0.4	Approaching reversal–avoid extubation
Minimal	TOF ratio 0.4–0.9	Safe for neostigmine; still at risk of airway collapse
Acceptable recovery	TOF ratio > 0.9 (> 0.95 with acceleromyography)	Extubation threshold

Monitoring Modalities

Technology	Principle	Advantages	Pitfalls
Acceleromyography (AMG)	Thumb acceleration (ulnar n.)	Widely available, inexpensive	Requires stabilisation & normalisation; overestimates recovery
Electromyography (EMG)	Compound muscle action potential	Accurate when hand inaccessible; no need for preload	Higher cost; skin prep crucial
Mechanomyography (MMG)	Isometric force (research gold standard)	Reference method	Bulky; rarely used clinically
Kinaemyography (KMG)	Piezo-electric thumb flex sensor	Portable	Susceptible to movement artefact

• Best site: ulnar nerve→adductor pollicis. Facial-nerve responses recover early and mislead.

Evidence-based Guidelines (2021-2024)

• Association of Anaesthetists (UK) 2021: quantitative monitoring mandatory whenever neuromuscular blocking drugs (NMBDs) are used, from baseline to TOF > 0.9.
• ASA Practice Guideline 2023: strong recommendation for objective monitoring; adductor pollicis preferred; clinical tests alone unacceptable.
• ESAIC Guideline 2023: advocates deep block only when clear surgical benefit; quantitative monitoring at adductor pollicis to exclude RNMB.
• South Africa (SAJAA 2023): local surveys show <40 % routine quantitative use; guideline alignment with international standards encouraged to reduce postoperative pulmonary complications (POPC).

Clinical Consequences of RNMB

Severity	Manifestations	Approximate incidence without quantitative monitoring
Mild (TOF 0.7-0.9)	Upper-airway obstruction, impaired swallow	20-50 %
Moderate (TOF 0.4-0.7)	Hypoxaemia, aspiration, delayed PACU stay	5-15 %
Severe (TOF < 0.4)	Reintubation, unplanned ICU, POPC	<3 %

• A prospective BJA 2024 study with universal EMG and sugammadex showed a residual block rate of 2.2 %, illustrating the value of guideline adherence.

Optimising Depth During Surgery

• Low-pressure laparoscopy: Deep block improves surgical workspace and allows pneumoperitoneum 8–10 mm Hg; meta-analyses show small but significant improvements in rating scores and early pain, with no proven morbidity benefit.
• Standard procedures: Moderate block (TOF count 1-3) suffices.
• Tailor dosing with real-time PTC/TOF feedback; avoid repeated blind boluses.

Reversal Strategy (Adults, Ideal Body Weight)

Depth at decision	Sugammadex dose	Neostigmine + glycopyrrolate	Expected recovery (min)
PTC 0-1 (complete)	16 mg kg⁻¹	Wait; neostigmine ineffective	2–3
PTC ≥ 1, TOF 0	4 mg kg⁻¹	Wait until TOF count ≥ 4	3–5
TOF count ≥ 2	2 mg kg⁻¹	Wait if TOF ratio < 0.4	3–4
TOF ratio 0.4–0.9	2 mg kg⁻¹	30 µg kg⁻¹ (max 5 mg)	3 vs >10
TOF ratio > 0.9	Not required	Not required	–

• Key points
  • Give neostigmine only in minimal block; excess dosing beyond TOF 0.9 paradoxically impairs upper-airway tone.
  • Sugammadex is contraindicated in severe renal failure (CrCl < 30 mL min⁻¹) and temporarily reduces contraceptive efficacy (advise alternative for 7 days).
  • Document calibrated TOF > 0.9 (> 0.95 with AMG) before extubation.

Practical Workflow

• Before induction
  1. Check monitor calibration and baseline TOF ratio.
  2. Agree target depth and reversal agent on WHO checklist.
• Intra-operative
  • Re-ssess every 15 min (or continuously with EMG).
  • Use PTC to guide redosing during deep block.
  • Avoid “timed” redoses; titrate to count.
• Emergence
  • Stop volatile/propofol, warm patient, correct acidosis/electrolytes.
  • Ensure TOF > 0.9 (> 0.95 AMG) and sustained head lift or bite pressure if desired.
• Post-operative
  • Continue oxygen and head-up tilt until able to swallow.
  • Monitor SpO₂ and respiratory rate for ≥30 min; delayed events still occur if extubation criteria were borderline.

Special Situations

• Obesity & pregnancy: lean body weight for sugammadex; deep block avoids high insufflation pressures in bariatric laparoscopy.
• Paediatrics: EMG preferable (small thumb mass); sugammadex 2–4 mg kg⁻¹ highly effective.
• Resource-limited settings (South Africa): if quantitative devices are scarce, prioritise high-risk lists (thoracic, obstetric, bariatric) and implement audit-feedback programmes to improve uptake.

Sugammadex Vs Neostigmine – TOF-based Recovery Profile

Parameter	Sugammadex	Neostigmine (+ anticholinergic)	Key Implication
Depth that can be safely reversed	Deep block to PTC ≥ 1 (rocuronium/vecuronium only)	Minimal block (TOF ratio ≥ 0.4)	Quantitative monitor essential to avoid premature neostigmine
Median time to TOF ≥ 0.9	2–3 min (2 mg kg⁻¹ at TOF ≥ 2)	8–18 min (50 µg kg⁻¹ at TOF 4)	Faster, predictable extubation with sugammadex
Incidence of residual block (PACU TOF < 0.9)	0–4 %	10–40 %	RNMB markedly lower with sugammadex
Post-operative pulmonary complications (PPCs)	2–3 %	5–6 %	Large cohort & meta-analysis suggest ~40 % relative risk reduction, but effect size varies
Side-effect profile	Rare bradycardia; avoids PONV, cholinergic crisis; temporary ↓ progesterone efficacy	Bradycardia, PONV, bronchospasm, paradoxical weakness if overdosed	Consider sugammadex in high-risk airway & cardiac patients
Limitations	Cost; ineffective for benzylisoquinoliniums; avoid CrCl < 30 mL min⁻¹	Ceiling effect; unpredictable if hypothermic or deeply blocked	Economic & renal factors guide local policy

Sugammadex: Recommended Doses in Common Situations

Clinical situation	Depth of block / monitor finding	Dose (mg kg⁻¹)	Basis & notes	Expected time to TOF ≥ 0.9
Routine reversal at end of surgery	TOF count ≥ 2	2 mg kg⁻¹ (actual body weight in adults)	FDA-labelled; works for rocuronium or vecuronium	2–3 min
Deep block	PTC ≥ 1, TOF 0	4 mg kg⁻¹	Give when surgical stimulation finishes but block persists	3–5 min
Immediate rescue (“can’t intubate, can’t ventilate”) after single rocuronium dose (≤1.2 mg kg⁻¹)	Any depth within 3 min of NMBD	16 mg kg⁻¹	Provides reversal in ~90 s; evidence only for rocuronium	1.5–2 min
Paediatrics ≥ 2 y	Same criteria as adults	2 or 4 mg kg⁻¹*	16 mg kg⁻¹ not licensed in children	2–4 min
Morbid obesity (BMI > 40 kg m⁻²)	Dose by actual or adjusted body weight†	2 or 4 mg kg⁻¹	ABW gives fastest reversal; IBW + 40 % acceptable where cost limiting	2–5 min
Repeat dosing after initial 2 mg kg⁻¹ if TOF < 0.9 after 5 min	Additional 2 mg kg⁻¹	Redosing seldom required (<5 %)	3 min
Re-paralysis with rocuronium after sugammadex	Wait ≥5 min, give 1.2 mg kg⁻¹ rocuronium	OR use non-steroidal NMBD	Block partly resistant for 4 h after sub-optimal wait
Severe renal impairment (eGFR < 30 mL min⁻¹)	—	Avoid routine use; consult renal/ICU	Sugammadex–complex relies on glomerular filtration	—

• *Limited data in infants < 2 y; small series suggest 2 mg kg⁻¹ effective but off-label.
• †Adjusted body weight = IBW + 0.4 × (TBW–IBW) when cost containment necessary.

Links

• Awareness
• Total intravenous anaesthesia (TIVA)
• Anaesthesia equipment

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References:

1. Rodney, G., Raju, P., & Brull, S. (2024). Neuromuscular block management: evidence-based principles and practice. BJA Education, 24(1), 13-22. https://doi.org/10.1016/j.bjae.2023.10.005
2. Raj, T. D. (2017). Data interpretation in anesthesia.. https://doi.org/10.1007/978-3-319-55862-2
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4. Recommendations for Standards of Monitoring during Anaesthesia and Recovery (6th ed.). Association of Anaesthetists, 2021. anaesthetists.org
5. ESAIC Task Force. Evidence-based guidelines for peri-operative management of neuromuscular blockade. ESAIC 2023. esaic.org
6. Sehlapelo M. The physics of neuromuscular monitors in anaesthesia. SAJAA 2023;29:136-142. sajaa.co.za
7. Anaesthetists’ knowledge and frequency of use of neuromuscular monitoring at Wits. SAJAA 2022;28:186-192. sajaa.co.za
8. Smith J et al. Residual neuromuscular block in the post-anaesthesia care unit: a prospective observational study. Br J Anaesth 2024;132:871-879. bjanaesthesia.org
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11. Zewdu M et al. Effect of sugammadex on patient morbidity and quality of recovery: a randomised trial. Br J Anaesth 2023;131:1122-1131. bjanaesthesia.org
12. Sen A, Lee JK. Sugammadex vs neostigmine in reversing neuromuscular block: a randomised trial. Anesth Analg 2021;133:1120-1128. pubmed.ncbi.nlm.nih.gov
13. Chen Y et al. Meta-analysis of recovery to TOF 0.9 with sugammadex or neostigmine. J Clin Med 2024;13:4128. mdpi.com
14. Neuromuscular Blockade: Summary of Recommendations. MPOG, 2024. mpog.org
15. StatPearls. Sugammadex. Updated 2024. ncbi.nlm.nih.gov
16. Zhang L et al. Actualversus ideal-body-weight dosing of sugammadex in obese adults: systematic review. BMC Anesthesiol 2021;21:181. bmcanesthesiol.biomedcentral.com
17. Goyal R. Sugammadex for our little ones: narrative review. Anesth Pain Med 2024;19:235-242. anesth-pain-med.org
18. Safety of Sugammadex in Pregnancy, Paediatrics, and Renal Failure. APSF Newsletter 2025;40:12-17. apsf.org
19. Image: Novice Anaesthesia. (2021). Infographics. Retrieved April 24, 2025, from https://www.gasnovice.com/infographics
20. . ICU One Pager. (2024). Retrieved June 5, 2024, from https://onepagericu.com/

Summaries:
ICU- OP_NMB

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