Answer:USMLE step 2 Mcq 38:A 30yr old man was taken to surgery for suspected acute appendicitis

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Correct Answer: E
Explanation:
When Malignant Hyperthermia is diagnosed early and treated promptly, the mortality rate should be near zero. Whenever anesthesia is administrated, dantrolene should be readily available as well as a protocol for management of MH. Dantrolene is, at the moment, the only known drug that treats MH. It impairs calcium-dependent muscle contraction and controls hypermetabolism manifestations
Inheritance of MH is autossomal dominant with variable penetrance, such that 50% of children of MH susceptible parents are potentially at risk.
A mutation in the ryanodine receptor(a calcium release channel) has been shown to cause MH in about 20% of affected human families.
Malignant hyperthermia is an inherited abnormality of skeletal-muscle sarcoplasmic reticulum that causes a rapid increase in intracellular calcium levels in response to halothane and other inhalational anesthetics or to succinylcholine. Elevated temperature, increased muscle metabolism, rigidity and cardiovascular instability develop rapidly. Cessation of anesthesia and administration of dantrolene are the immediately indicated therapies.Intravenous dantrolene is indicated to reverse the symptoms of the malignant hyperthermic crisis syndrome occurring during or following surgery or anesthesia. By interfering with the release of calcium ion from the sarcoplasmic reticulum, dantrolene prevents or reduces the increase in myoplasmic calcium ion concentration that activates the acute catabolic processes associated with the malignant hyperthermic crisis syndrome. <br>Sodium nitroprusside is an anti-hypertensive drug used in hypertensive emergencies. It is not the correct answer because in this case it might lower the blood pressure but it will not reverse the other symptoms and also will not counter act the underlying mechanism for the hypertension.
Quinidine is an anti-arrhythmic drug. It will only control the tachycardia but will not reverse the other life threatening symptoms.Acetaminophen a very potent anti-pyrexia drug is of no use in malignant hyperthermia. It does no lower the body temperature nor does it reverse the other symptoms.
Baclofen is an active spasmolytic drug used to relieve the signs and symptoms of spasticity caused by multiple sclerosis, spinal cord diseases, or spinal cord injury. It is not used in malignant hyperthermia.


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