WBR1010

Author	[[PageAuthor::Mohamed Moubarak, M.D. [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Emergency Room
Sub Category	SubCategory::Cardiovascular
Prompt	[[Prompt::A 56 year-old female presents to ED complaining of sudden onset of dizziness, palpitation, and light headedness. These symptoms have been occurring frequently for the past week, it lasts for few minutes, and resolve spontaneously. She has a history of hypertension, and ischemic heart disease. Her current medications are daily aspirin, Metoprolol, and hydrochlorothiazide. On examination, her heart rate is 110 b/pm and shows irregular irregularity, blood pressure is 130/80 mmHg, temperature is 37 C (98.6 F), and respiratory rate is 18/min. Her EKG shows atrial fibrillation. After controlling the ventricular rate with IV diltiazem drip, she is prescribed amiodarone for the maintenance of sinus rhythm, and warfarin as an anticoagulant. After 7 weeks of follow up, the patient presents to ED complaining of red urine, which turns to be hematuria after urine analysis. Which of the following could prevent this from happening?]]
Answer A	AnswerA::Stop Aspirin
Answer A Explanation	AnswerAExp::Aspirin is not the cause of the increased bleeding time
Answer B	AnswerB::Stop hydrochlorothiazide
Answer B Explanation	[[AnswerBExp::Incorrect Hydrochlorothiazide is not the cause of bleeding in this case]]
Answer C	AnswerC::Reduce warfarin dose
Answer C Explanation	[[AnswerCExp::Correct A mean reduction of 35% in the dose of warfarin, and frequent follow up of INR and prothrombin time is needed when amiodarone used with warfarin is suggested to prevent such s complication.]]
Answer D	AnswerD::Reduce amiodarone dose
Answer D Explanation	[[AnswerDExp::Incorrect Amiodarone cause cytochrome P450 inhibition, and warfarin is the drug to be monitored and reduced.]]
Answer E	AnswerE::Stop Metoprolol
Answer E Explanation	[[AnswerEExp::Incorrect Metoprolol is not the cause of this complication.]]
Right Answer	RightAnswer::C
Explanation	[[Explanation::Amiodarone augment the anticoagulant effect caused by warfarin, and results in an increase in international normalized ratio (INR) and increased risk of bleeding. The enhanced anticoagulant effect that happens when amiodarone and warfarin are prescribed is due to amiodarone induced cytochrome P450 inhibition. Coagulopathy might manifest as epistaxis, gingival bleeding, hematemesis, hematuria, hematochezia, menometrorrhagia, ecchymosis, petechial hemorrhages, intracranial hemorrhages, or bleeding that is disproportionate to the level of the injury The effects of interaction with amiodarone do not peak until seven weeks after the initiation of concomitant therapy. A mean reduction of 35% in the dose of warfarin, and frequent follow up of INR and prothrombin time is needed when amiodarone used with warfarin. Reference: "The incidence, magnitude, and time course of the amiodarone-warfarin interaction.",journal = Arch Intern Med, volume = 148, issue = 8, month = Aug, year = 1988, PMID = 3401099. Educational Objective: References: ]]
Approved	Approved::No
Keyword	[[WBRKeyword::Amiodarone]], [[WBRKeyword::Atrial fibrillation]]
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