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 Explanation |
 |
The patient develops:
- Generalized muscle rigidity
- Tremors
- Trismus (masseter muscle spasm)
- Features suggestive of malignant hyperthermia (MH) following anesthesia.
Malignant hyperthermia is a pharmacogenetic disorder of skeletal muscle caused by abnormal calcium release from the sarcoplasmic reticulum due to mutations in the RYR1 (ryanodine receptor) gene.
The condition is classically triggered by:
- Volatile inhalational anesthetics (especially halothane, sevoflurane, isoflurane, desflurane)
- Succinylcholine (most common triggering muscle relaxant)
A. Halothane
- Correct.
- Halothane is a potent trigger of malignant hyperthermia.
- Clinical features include:
- Masseter muscle rigidity (trismus)
- Generalized muscle rigidity
- Hypercapnia (earliest sign)
- Tachycardia
- Hyperthermia (late sign)
- Metabolic acidosis
- Hyperkalemia
- Myoglobinuria
Treatment:
- Immediately discontinue triggering agents.
- Administer intravenous dantrolene (drug of choice).
- Active cooling.
- Correct acidosis and hyperkalemia.
- Supportive intensive care.
Why the Other Options are Incorrect
B. Nitrous oxide (N₂O)
- Does not trigger malignant hyperthermia.
- Considered safe in susceptible patients.
C. Thiopentone sodium (Thiopental sodium)
- Intravenous induction agent.
- Does not trigger malignant hyperthermia.
D. Etomidate
- Intravenous induction agent.
- Does not trigger malignant hyperthermia.
- Safe for patients susceptible to malignant hyperthermia.