A 35-year-old patient requires intubation for emergency surgery. Succinylcholine is administered. Which of the following is a characteristic sign that occurs immediately after succinylcholine administration but before paralysis sets in?

Explanation

## Succinylcholine: Fasciculations and Clinical Sequence **Key Point:** Fasciculations are visible, uncoordinated muscle contractions that occur immediately after succinylcholine administration, before the onset of paralysis. ### Timeline of Succinylcholine Effect ```mermaid flowchart LR A["Succinylcholine IV"]:::action --> B["Fasciculations visible<br/>0–5 sec"]:::outcome B --> C["Onset of paralysis<br/>30–40 sec"]:::outcome C --> D["Flaccid paralysis<br/>5–10 min duration"]:::outcome D --> E["Recovery via plasma<br/>pseudocholinesterase"]:::action ``` ### What Are Fasciculations? - Visible, involuntary muscle twitches - Caused by sustained depolarisation of muscle membrane - Uncoordinated and asynchronous contractions - Occur in face, neck, chest, and limbs - Last 5–10 seconds - Precede flaccid paralysis ### Clinical Consequences of Fasciculations | Consequence | Mechanism | Clinical Significance | | --- | --- | --- | | Hyperkalaemia | Muscle cell depolarisation → K^+^ efflux | Risk of cardiac dysrhythmias, especially in burns, crush injuries, renal failure | | Myoglobinuria | Muscle damage from fasciculations | Risk of acute kidney injury | | Postoperative myalgia | Muscle damage and inflammation | Pain in 40–70% of patients (reduced by pre-treatment with non-depolarising agent) | | Increased ICP | Muscle contraction → cerebral blood flow ↑ | Contraindicated in head injury | | Increased gastric pressure | Abdominal muscle contraction | Risk of aspiration | **High-Yield:** Fasciculations are PATHOGNOMONIC for succinylcholine and occur BEFORE paralysis. They are a visual hallmark of depolarising agent administration. **Clinical Pearl:** Pre-treatment with a small dose of non-depolarising agent (e.g., 0.01 mg/kg vecuronium) 3–5 minutes before succinylcholine can prevent fasciculations and reduce postoperative myalgia. **Mnemonic:** **FASCICULATIONS = Succinylcholine** - **F**asciculations (visible muscle twitches) - **A**cetylcholine mimic (depolarising agent) - **S**uccinylcholine (the drug) - **C**haracteristic sign (before paralysis) - **I**mmediate onset (within seconds) - **C**linical consequence (hyperkalaemia, myalgia) - **U**ncoordinated contractions - **L**asts 5–10 seconds - **A**lways precedes flaccid paralysis - **T**riggering agent for malignant hyperthermia - **I**nitial sign after IV administration - **O**bservable in all skeletal muscles - **N**on-depolarising agents do NOT cause this - **S**ustained depolarisation is the mechanism