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Reversal of neuromuscular block — neostigmine and sugammadex
Neostigmine raises acetylcholine and so works only when partial recovery is already present; sugammadex traps rocuronium or vecuronium and reverses even a deep block, at a dose set by the depth of block.
Why it matters in the exam
Exam questions test the sugammadex doses by depth of block, why glycopyrrolate or atropine is given with neostigmine, which relaxants sugammadex does not reverse, and its interaction with the contraceptive pill. They also ask what residual paralysis is, why it is dangerous and how its absence is proven.
Residual paralysis — a TOF ratio below 0.9 — weakens the pharyngeal muscles and increases aspiration, hypoxaemia and distress on waking. The 2023 ASA guideline recommends quantitative monitoring whenever a non-depolarising relaxant is used, and sugammadex for reversal of deep, moderate or shallow rocuronium and vecuronium block; neostigmine is reasonable only for minimal block.
Exam questions often show a patient who looks awake after surgery but breathes shallowly, struggles to swallow or starts to desaturate in recovery — this is the picture of residual paralysis. The answer is not only a drug but a measurement: a quantitative device that shows an exact TOF ratio. Remember too that the choice between sugammadex and neostigmine depends on the relaxant given — benzylisoquinolinium relaxants are not trapped, so with them one waits for recovery and uses neostigmine. In a patient with severe renal failure the sugammadex–rocuronium complex is cleared slowly, so the choice should be weighed with care and paralysis should still be monitored after reversal.
Key points
- Sugammadex traps rocuronium and vecuronium; 2, 4 or 16 mg/kg by depth of block.
- Neostigmine works only with partial recovery, together with glycopyrrolate or atropine.
- A TOF ratio of at least 0.9 = adequate recovery; measured quantitatively.
- Sugammadex reduces the efficacy of the pill — additional contraception for 7 days.
- No drug reverses succinylcholine; wait.
Summary table
| Monitoring state | Sugammadex | Neostigmine |
|---|---|---|
| Deep block: no TOF response, 1–2 post-tetanic responses | 4 mg/kg | Not effective — wait |
| Moderate block: 2 or more TOF responses | 2 mg/kg | Not recommended until minimal block |
| Minimal block: TOF ratio 0.4 to below 0.9 | 2 mg/kg | 0.04–0.05 mg/kg with glycopyrrolate |
| Immediate reversal after rocuronium 1.2 mg/kg | 16 mg/kg | Not possible |
| Relaxants that are not reversed | Succinylcholine, cisatracurium, atracurium | Prolongs a succinylcholine block |
Free exam questions
בסיום ניתוח חובר Quantitative nerve stimulator למטופל על מנת להעריך את המינון המומלץ של תרופות להיפוך שיתוק שרירים. מה מהבאים נכון? (TOF- train of four) (the question as examined, in Hebrew)
- א. אם למטופל TOF count 0 יש לתת 0.05 Neostigmine מ״ג לק״ג
- ב. אם למטופל TOF count 0 יש לתת 2 Sugammadex מ״ג לק״ג
- ג. אם למטופל TOF count 1-4 יש לתת 2 Sugammadex מ״ג לק״ג
- ד. אם למטופל TOF ratio>0.9 יש לתת 0.05 Neostigmine מ״ג לק״ג
מה המינון המומלץ של Neostigmine להיפוך שיתוק שרירים במטופל השוקל 70 ק״ג אשר בבדיקת NMT ( איכותית Qualitative ) נצפו 4 טוויצ׳ים ללא עדות ל- Fade ? (the question as examined, in Hebrew)
- א. 1.4 מ״ג
- ב. 2.1 מ״ג
- ג. 2.5 מ״ג
- ד. 5 מ״ג
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Sources
- ASA Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade, 2023 — Antagonism with sugammadex or neostigmine
- Miller's Anesthesia, 9th edition (2020) — Reversal (Antagonism) of Neuromuscular Blockade
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.