WBR0393
| Author | [[PageAuthor::Rim Halaby, M.D. [1], Alison Leibowitz [2] (Reviewed by Alison Leibowitz)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Pharmacology |
| Sub Category | SubCategory::Neurology |
| Prompt | [[Prompt::During a major abdominal surgery, a patient receives an injection of pancuronium, which paralyzes his abdominal muscles in order to facilitate access to the surgical site. Several minutes after the injection is administered, the patients experiences an increase in minute ventilation, carbon dioxide production, heart rate to 135 bpm, blood pressure to 182/99 mmHg, and core temperature to 41.2 °C. Troubled by the unstable vitals, the anesthesiologist administers a second intravenous agent to counteract the effects of the muscle relaxant. The patient's vitals stabilize soon after the second injection and he begins to defervesce. Which of the following intravenous agents did the anesthesiologist most likely administer to the patient?]] |
| Answer A | AnswerA::Succinylcholine |
| Answer A Explanation | [[AnswerAExp::Succinylcholine, a muscle relaxant, can result in 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, an anesthetic agent, can cause malignant hyperthermia.]] |
| Answer D | AnswerD::Physostigmine |
| Answer D Explanation | [[AnswerDExp::Physostigmine, a reversible cholinesterase inhibitor, has no role in the treatment of malignant hyperthermia.]] |
| Answer E | AnswerE::Pralidoxime |
| Answer E Explanation | [[AnswerEExp::Pralidoxime, a sympathomimetic drug used in the treatment of organophosphate poisoning, has no role in the treatment of malignant hyperthermia.]] |
| Right Answer | RightAnswer::B |
| Explanation | [[Explanation::Malignant hyperthermia, a condition characterized by a severe reaction frequently occurring under general anesthesia, manifests with the exposure to certain anesthetic drugs and muscle relaxants in patients with prior susceptibility. There are no clinical features specific to malignant hyperthermia, but early signs typically include tachycardia and tachypnea, progressing to hyperthermia, generalized muscle rigidity, oliguria, and arrhythmia. Without rapid intervention, malignant hyperthermia can lead to death. Dantrolene, frequently used in treatment of malignant hyperthermia, depresses excitation-contraction coupling in skeletal muscles by binding to the ryanodine receptor, and decreasing free intracellular calcium concentration. Educational Objective: 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. Without intervention, malignant hyperthermia is often fatal. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Dantrolene, WBRKeyword::Pancuronium, WBRKeyword::Malignant hyperthermia, WBRKeyword::anesthesia, WBRKeyword::adverse reaction, WBRKeyword::muscle relaxent, WBRKeyword::anestthetic agent |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |