Succinylcholine: indications and contraindications
Stem
A 34-year-old man, 85 kg, fell from a roof four days ago and is now paraplegic at T6. He is scheduled for posterior spinal fixation. He ate breakfast two hours ago before the case was moved up, his potassium this morning was 4.3, and the resident has drawn up succinylcholine for a rapid-sequence induction.
Question
Will you use succinylcholine for this induction, and when do you use it at all?
Ideal answer
HeadlineNo. Four days after a cord injury, receptors have proliferated below the lesion and potassium could jump to lethal levels; I stop the syringe and give rocuronium.
- Rocuronium 1.2 mg/kg, near succinylcholine's onset, sugammadex 16 mg/kg ready, the labeled reversal dose about 3 minutes after it.1
- Tell the resident why. Labeled contraindications: known or suspected MH susceptibility, myopathies such as Duchenne, and the period after major burns, multiple trauma, extensive denervation or upper motor neuron injury.2
- Treat prolonged immobilization the same, because it also upregulates extrajunctional receptors.
- Keep succinylcholine 1–1.5 mg/kg for its niche:3 RSI (quote 1.5 mg/kg) where rocuronium cannot be used, laryngospasm unbroken by positive pressure, short procedures such as ECT.
Watch for: intubating conditions in about a minute, recovery from 4–7 minutes, function back under 10 minutes at intubating doses.2,4
Breaking down the answer
- Hyperkalemia mechanism — normally potassium rises up to about 0.5 mEq/L.3 With denervation, burns or immobility, immature and alpha-7 receptors spread across the membrane and stay open longer, so the rise can exceed 5 mEq/L and cause arrest.
- The time window — risk is minimal in the first 24–48 hours, peaks at 7–10 days, and upregulation can last up to 2 years;4 the label states the exact onset and duration are undetermined.2
- Pre-existing hyperkalemia — in renal failure the rise is the usual 0.5 mEq/L; I use it below about 5.5 without acidosis (a potassium of 5.8 is a no), because the problem is the starting value.
- Children — the FDA boxed warning describes acute rhabdomyolysis with hyperkalemia, ventricular dysrhythmias and death in apparently healthy children, often boys with unrecognized Duchenne;2 no routine use in children, emergencies only: laryngospasm or the full stomach.
- Pseudocholinesterase deficiency — homozygous atypical patients (about 1 in 2,500) stay paralyzed for hours;2 sedated and ventilated until train-of-four shows full recovery, then dibucaine number and family referral.
- Open globe, full stomach — succinylcholine only if rocuronium is not an option, per the label's benefit-risk advice.2 Masseter spasm: abort elective surgery, CK, urine myoglobin, monitor for MH.
- Bradycardia — muscarinic, common in children after a first dose, worst with a second within minutes;4 anticholinergic pretreatment reduces it,2 so atropine 0.02 mg/kg before a repeat dose.
Follow-up question
Before you can stop him, the resident pushes the succinylcholine. Two minutes later the ECG shows peaked T waves, then a wide-complex rhythm. What do you do?
Follow-up answer
HeadlineSuccinylcholine-induced hyperkalemia from upregulated receptors; I say so out loud and call for help.
Calcium chloride 1 g IV to stabilize the membrane, then insulin 10 units with 25 g dextrose, and hyperventilation to shift potassium into cells. Pulseless: CPR and ACLS for a prolonged period, because hyperkalemic arrest responds to sustained resuscitation. I send potassium and a blood gas, repeat them as treatment continues and watch the QRS narrow. Surgery waits until he is stable, and I disclose the event and file a safety report.
Pitfalls that cost points
- Saying renal failure is an absolute contraindication.
- Calling the rise in intragastric, intraocular and intracranial pressure a contraindication; it is small and transient, and aspiration is the larger threat.
Rapid-fire
Q: Why the fasciculations? A: Depolarization causes disorganized contraction before the end plate becomes inexcitable; it produces myalgia and a small potassium rise.
Q: What is a phase II block? A: After large or repeated doses (the label describes the transition after accumulated doses of 2–4 mg/kg) the block takes on non-depolarizing characteristics, with fade and post-tetanic potentiation.2
Q: Why does a myasthenic need more succinylcholine? A: Fewer functional receptors resist depolarization; they need about 2 mg/kg, and they are very sensitive to non-depolarizers.
Q: Why is a burn patient safe in the first 24 hours? A: Upregulation takes time; risk is minimal in the first two days, then rises to a peak at 7–10 days and persists while the receptors remain upregulated.4
Numbers to know
| Item | Value |
|---|---|
| Intubating dose | 1–1.5 mg/kg IV; IM 3–4 mg/kg, max 150 mg2 |
| Onset / recovery | ~1 min / begins at 4–7 min2,4 |
| Normal K+ rise | Up to ~0.5 mEq/L3 |
| Upregulation risk window | Minimal <48 h, peak 7–10 days, up to 2 years4 |
| Rocuronium RSI dose | 1.2 mg/kg; sugammadex 16 mg/kg for immediate reversal1 |
| Laryngospasm dose | 0.1–0.5 mg/kg IV |
Links
- Rapid sequence induction and full stomach, hyperkalemia, Malignant hyperthermia, Muscular dystrophies and myotonias, burns, Spinal cord injury and autonomic hyperreflexia
- MHAUS guidance on masseter muscle rigidity
Sources
- 1.Bridion (sugammadex) prescribing information · FDA label (via Drugs.com) · drugs.com
- 2.Quelicin (succinylcholine chloride injection) prescribing information · FDA label (via Drugs.com) · drugs.com
- 3.Succinylcholine Chloride · StatPearls · statpearls.com
- 4.Succinylcholine · OpenAnesthesia (IARS), 2024 · openanesthesia.org
Facts on this page were checked against these sources on Oct 14, 2026. Guidelines change; confirm doses against current institutional protocols.