WBR0393

Author	[[PageAuthor::Serge Korjian M.D. (Reviewed by Serge Korjian)]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Pharmacology
Sub Category	SubCategory::Neurology
Prompt	[[Prompt::During a minor abdominal surgery, a patient receives an injection of succinylcholine to facilitate access to the surgical site by paralyzing his abdominal muscles. Several minutes after the injection is administered, the patient's heart rate increases to 135/min and his blood pressure to 182/99 mmHg. The monitor shows an increase in minute ventilation and end-tidal carbon dioxide. His core temperature also begins to increase steadily, reaching 41.2 ᵒC (106.1 ᵒF). Alerted by the patient's status, the anesthesiologist administers an intravenous agent to counteract the effects of the muscle relaxant. The patient's vitals slowly begin to stabilize. Which of the following intravenous agents did the anesthesiologist most likely administer to the patient?]]
Answer A	AnswerA::Enflurane
Answer A Explanation	AnswerAExp::Enflurane is an inhaled anesthetic that can cause malignant hyperthermia. It has no role in the treatment of malignant hyperthermia.
Answer B	AnswerB::Dantrolene
Answer B Explanation	AnswerBExp::Dantrolene is the treatment of choice for malignant hyperthermia. It acts by inhibiting excitation-contraction coupling in skeletal muscle by binding to the ryanodine receptor.
Answer C	AnswerC::Etomidate
Answer C Explanation	AnswerCExp::Etomidate is anesthetic agent that can cause malignant hyperthermia. It has no role in the treatment of malignant hyperthermia.
Answer D	AnswerD::Physostigmine
Answer D Explanation	AnswerDExp::Physostigmine is a reversible cholinesterase inhibitor. It has no role in the treatment of malignant hyperthermia.
Answer E	AnswerE::Pralidoxime
Answer E Explanation	AnswerEExp::Pralidoxime is a sympathomimetic drug used in the treatment of organophosphate poisoning. It has no role in the treatment of malignant hyperthermia.
Right Answer	RightAnswer::B
Explanation	[[Explanation::Malignant hyperthermia is a condition characterized by a severe reaction to certain anesthetic drugs and muscle relaxants in patients with prior susceptibility to develop this condition. There are no clinical features specific for malignant hyperthermia. Typically, early signs include tachycardia and tachypnea, progressing to hyperthermia, generalized muscle rigidity, oliguria, arrhythmia and eventual death if treatment is not initiated. Recognition of early signs are important to warrant rapid intervention. Dantrolene is the medication of choice for the treatment of malignant hyperthermia. Dantrolene depresses excitation-contraction coupling in skeletal muscle by binding to the ryanodine receptor, and decreasing free intracellular calcium concentration. Educational Objective: Dantrolene is the treatment of choice in malignant hyperthermia. References: Hopkins PM. Malignant hyperthermia: advances in clinical management and diagnosis. Br J Anaesth. 2000;85(1):118-28. First Aid 2015 page 498]]
Approved	Approved::Yes
Keyword	WBRKeyword::Dantrolene, WBRKeyword::Succinylcholine, WBRKeyword::Malignant hyperthermia, WBRKeyword::Anesthesia, WBRKeyword::Anesthesiology, WBRKeyword::Antidote, WBRKeyword::Adverse effect
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