Question
A patient presented with rigidity, tremors, and trismus after being administered an anesthetic agent. Which anesthetic agent is most likely to have been administered?
| A. |
Halothane
|
| B. |
Nitrous Oxide (NO₂)
|
| C. |
Thiopentone sodium
|
| D. |
Etomidate
|
Show Answer
|
Correct Answer » A:D
Explanation
|
|
- Halothane is a volatile inhalational anesthetic that is a well-known trigger of malignant hyperthermia in genetically susceptible individuals.
- Malignant hyperthermia results from mutations in the RYR1 (ryanodine receptor) gene, causing uncontrolled calcium release from the sarcoplasmic reticulum.
- This leads to sustained muscle contraction and a hypermetabolic state.
Clinical Features of Malignant Hyperthermia
- Masseter muscle spasm (trismus)
- Generalized muscle rigidity
- Rapid rise in end-tidal CO₂ (earliest sign)
- Hyperthermia (late sign)
- Tachycardia
- Metabolic and respiratory acidosis
- Hyperkalemia
- Myoglobinuria
- Rhabdomyolysis
Management
- Immediately discontinue the triggering anesthetic.
- Administer 100% oxygen.
- Give intravenous dantrolene (drug of choice).
- Active cooling.
- Correct acidosis and hyperkalemia.
- Treat arrhythmias (avoid calcium channel blockers with dantrolene).
Why Other Options are Incorrect
B. Nitrous oxide (N₂O)
- Nitrous oxide is not a trigger for malignant hyperthermia.
- It is considered safe in susceptible patients.
C. Thiopentone sodium (Thiopental sodium)
- Thiopentone is an intravenous induction agent.
- It does not trigger malignant hyperthermia.
D. Etomidate
- Etomidate is an intravenous anesthetic.
- It is not associated with malignant hyperthermia and is considered safe in susceptible individuals.
