**Core Concept**
Malignant hyperthermia (MH) is a rare, life-threatening metabolic crisis triggered by volatile anesthetics or depolarizing muscle relaxants, particularly in susceptible individuals with a genetic defect in the ryanodine receptor (RyR1) on the sarcoplasmic reticulum. It involves uncontrolled release of calcium from sarcoplasmic reticulum, leading to uncontrolled muscle contraction, hypermetabolism, and rapid rise in body temperature.

**Why the Correct Answer is Right**
Suxamethonium (suxamethone) is a depolarizing neuromuscular blocker that acts by blocking acetylcholine receptors at the neuromuscular junction. It is a well-established trigger of malignant hyperthermia due to its mechanism of action involving depolarization of muscle membranes, which can activate the ryanodine receptor pathway. This leads to uncontrolled calcium release and muscle hypermetabolism, especially in genetically predisposed patients. Suxamethonium is contraindicated in patients with a history of MH or family history of the condition.

**Why Each Wrong Option is Incorrect**
Option A: Cisatracurium is a non-depolarizing, non-competitive neuromuscular blocker with no known direct link to MH. It is not a trigger of malignant hyperthermia and is generally considered safe in MH-prone patients.
Option C: Propofol is a sedative-hypnotic agent that does not trigger MH. It is not associated with the pathophysiology of MH and is not a known precipitant.
Option D: Thiopentone (a barbiturate) is a general anesthetic with no known association with MH; it does not activate ryanodine receptors or induce hypermetabolism in this context.

**Clinical Pearl / High-Yield Fact**
Suxamethonium is the most common neuromuscular blocker associated with malignant hyperthermia. Always perform a **malignant hyperthermia susceptibility screening** in high-risk patients and avoid suxamethonium in such cases. If MH is suspected, **stop all triggering agents immediately** and administer dantrolene.

✓ Correct Answer: B. Suxamethonium