Anesthesiology APPLIED Exam › Neuroanesthesia and neuromuscular

Neuromuscular blockade, monitoring and reversal

T1Neuroanesthesia and neuromuscular·1098 words · ~6 min read·v0.1✓ Sourced · 5DRAFT

Why examiners ask this

Neuromuscular blockade is the drug class the examiner can attach to any stem, and the 2023 ASA practice guideline gave them a clean standard to test against: quantitative monitoring at the adductor pollicis and reversal to a train-of-four ratio of 0.9. It stresses application of knowledge (pharmacology of the blockers and reversal agents), judgment (which drug, which dose, when), and organization, because the candidate who cannot state a monitoring plan in one sentence looks unsafe. It also hides inside other topics: myasthenia, renal failure, magnesium, and the patient who is weak in the PACU.

The 60-second answer

I use a non-depolarizing relaxant only when the surgery or the airway needs it, I monitor it quantitatively from induction to extubation, and I reverse to a measured train-of-four ratio of at least 0.9 before I take the tube out.¹ For intubation I give rocuronium 0.6 mg/kg, or up to 1.2 mg/kg for a rapid sequence,² and I redose to the surgeon's need while keeping one or two twitches. At the end I check the depth with a quantitative monitor at the thumb: with deep block (post-tetanic count 1–2) I give sugammadex 4 mg/kg, once two twitches return 2 mg/kg,³ and I reserve neostigmine 0.03–0.07 mg/kg, maximum 5 mg, with glycopyrrolate⁴ for minimal block, a measured ratio of at least 0.4.¹ I wait for the ratio to read 0.9 and the patient to sustain a head lift before extubation, because residual weakness is what sends these patients back to the OR.

Decision points and the "why"

Quantitative over qualitative monitoring — a clinician feeling the thumb cannot detect fade once the ratio is above about 0.4, so a peripheral nerve stimulator alone misses the band where aspiration and hypoxemia occur. I use acceleromyography or electromyography at the adductor pollicis; the ASA 2023 guideline recommends quantitative over qualitative monitoring and against clinical assessment alone.¹
The adductor pollicis, not the orbicularis oculi — the eye recovers earlier than the diaphragm and the thumb; monitoring the face overestimates recovery. I may use the face to time intubation, because the laryngeal muscles track it, but the guideline recommends against eye muscles, so I switch to the thumb before reversal.¹
Sugammadex versus neostigmine — sugammadex encapsulates rocuronium and vecuronium and reverses any depth within about 3 minutes; neostigmine has a ceiling, cannot reverse deep block, and generally reaches a ratio of 0.9 within 10–20 minutes.⁴ The guideline recommends sugammadex over neostigmine at deep, moderate and shallow depths and calls neostigmine a reasonable alternative at minimal depth, a ratio of 0.4 to 0.9.¹
Dose sugammadex to the measured depth — 2 mg/kg at two twitches, 4 mg/kg at a post-tetanic count of 1–2, 16 mg/kg for immediate reversal after a 1.2 mg/kg rocuronium dose.³ Under-dosing produces recurarization.
Renal failure changes the drug, not the plan — rocuronium and vecuronium accumulate, so I use cisatracurium, which clears by Hofmann elimination, and I still monitor to 0.9. Sugammadex is not recommended for a creatinine clearance below 30 mL/min;³ neostigmine is my reversal there.
Potentiators — volatile agents, magnesium, aminoglycosides, hypothermia, acidosis and hypokalemia all prolong block. I reduce the dose and lengthen my expectations rather than being surprised at the end.
Succinylcholine for the short case — a single 1–1.5 mg/kg dose lasts 5–10 minutes; I avoid it after the acute phase of burns, trauma and denervation, in prolonged immobility and in myopathies because of hyperkalemia, and I know that phase II block after large or repeated doses looks like a non-depolarizing block on the monitor.⁵

The complication they will inject

I extubate and the patient is weak in the PACU: uncoordinated, tachypneic, with a saturation falling to 88%. I treat it as residual block until proven otherwise. I support ventilation with bag and mask, sit the patient up, give 100% oxygen, and put the quantitative monitor back on. If the ratio is below 0.9 and I used neostigmine, I give sugammadex 2–4 mg/kg; if I already gave sugammadex, I give more, because recurarization after an inadequate dose is the usual cause. I check temperature, potassium, magnesium and acid-base, and I look for the other causes of weakness: opioids, a missed myasthenic history, pseudocholinesterase deficiency after succinylcholine. If the patient cannot protect the airway, I reintubate and reverse at leisure rather than gamble on a borderline patient who is aspirating.

Pitfalls that cost points

Saying "I would reverse with neostigmine" without stating the twitch count you require first.
Quoting a train-of-four ratio of 0.7 as adequate; the standard is 0.9 and the guideline is explicit.
Giving sugammadex and then a usual dose of rocuronium for an unexpected reintubation; onset is delayed and duration shortened, so the dose has to be 1.2 mg/kg or a different class, and after 16 mg/kg a 24-hour wait is suggested.³
Forgetting that neostigmine given at full recovery causes paradoxical weakness.
Mentioning the clinical tests (head lift, grip) as proof of reversal; they are insensitive and only supplement the monitor.¹

Rapid-why

Q: Why does fade occur with non-depolarizers but not with succinylcholine? A: Non-depolarizers block presynaptic nicotinic receptors that mobilize acetylcholine during repeated stimulation; succinylcholine does not, so phase I block shows equal twitches.

Q: Why do I give glycopyrrolate with neostigmine? A: Neostigmine raises acetylcholine at muscarinic receptors as well, causing bradycardia, bronchospasm and secretions; glycopyrrolate matches its onset better than atropine.

Q: Can sugammadex reverse succinylcholine or cisatracurium? A: No. It binds the steroidal relaxants rocuronium and vecuronium only; benzylisoquinoliniums need neostigmine or time.

Q: What happens to hormonal contraception after sugammadex? A: It binds progesterone; I counsel a non-hormonal backup method for 7 days.³

Numbers to know

Item	Value
Rocuronium intubating / RSI dose	0.6 mg/kg / 1.2 mg/kg
Succinylcholine	1–1.5 mg/kg IV; 3–4 mg/kg IM, max 150 mg⁵
Sugammadex	2 mg/kg at TOF 2; 4 mg/kg at PTC 1–2; 16 mg/kg immediate³
Neostigmine	0.03–0.07 mg/kg, max 5 mg,⁴ with glycopyrrolate 0.01 mg/kg
Extubation threshold	TOF ratio ≥0.9, measured quantitatively¹
Cisatracurium	0.15–0.2 mg/kg, Hofmann elimination

Sources

1.New Practice Guidelines for Neuromuscular Blockade · APSF, 2023 · apsf.orgReproduces the recommendations of the 2023 ASA Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade; the Anesthesiology full text was not reachable.
2.Rocuronium bromide injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
3.BRIDION (sugammadex) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
4.Neostigmine methylsulfate injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov
5.QUELICIN (succinylcholine chloride) injection prescribing information · FDA / DailyMed · dailymed.nlm.nih.gov

Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.