All the following cause malignant hyperpyrexia except –
**Core Concept**
Malignant hyperpyrexia, also known as malignant hyperthermia, is a rare but life-threatening medical emergency triggered by certain anesthetic agents. It is characterized by a rapid rise in body temperature, muscle rigidity, and autonomic dysfunction.
**Why the Correct Answer is Right**
Malignant hyperpyrexia is caused by a genetic mutation affecting the ryanodine receptor (RyR1) on skeletal muscle cells, leading to an abnormal release of calcium ions. This results in an intense and uncontrolled metabolic response, including muscle rigidity, hyperthermia, and autonomic dysfunction. The anesthetic agents implicated in malignant hyperpyrexia are typically volatile anesthetics, such as halothane, isoflurane, and sevoflurane, as well as depolarizing muscle relaxants like succinylcholine.
**Why Each Wrong Option is Incorrect**
* **Option A:** Incorrect because succinylcholine is a depolarizing muscle relaxant known to trigger malignant hyperpyrexia in susceptible individuals.
* **Option B:** Incorrect because isoflurane is a volatile anesthetic agent that can cause malignant hyperpyrexia in individuals with the genetic mutation.
* **Option C:** Incorrect because halothane is a volatile anesthetic agent that has been implicated in malignant hyperpyrexia cases.
**Clinical Pearl / High-Yield Fact**
It is essential to identify patients at risk of malignant hyperpyrexia before administering volatile anesthetics or succinylcholine, as early recognition and treatment can be lifesaving.
**Correct Answer: A. Succinylcholine is not typically listed as a cause of malignant hyperpyrexia in the current literature.