WBR0958

Author	[[PageAuthor::Mugilan Poongkunran M.B.B.S [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Emergency Room
Sub Category	SubCategory::Hematology
Prompt	[[Prompt::A 50 year old woman comes to the emergency department with complaints of shortness of breath and chest pain. She has these symptoms for the past one day. On further review of history she reveals a recent history of travel outside the United States 3 days back. Her past history is otherwise insignificant and her family history is unremarkable. She has smoked one pack of cigarette for the past 10 years. She attained menopause at the age of 48 and not on any medications. Her vitals are temperature: 36.7 C, blood pressure: 140/80 mmHg, pulse: 80/min and respiration: 15/min. The patients pulse oximetry shows 95 % on 4-litres of oxygen. All system examinations are normal. V/Q scan shows high probability for pulmonary embolism. Her laboratory values comes as : Hb : 13 g/dl Hct : 38% RBC’s : 2.5 million/cmm WBC’s : 6000/cmm Platelet’s : 300,000/cmm PT : 13 sec (N 11-15 sec) INR : 1.03 You start the patient on unfractionated heparin and warfarin. Her symptoms resolve the next day and a repeat CBC on the second day reveals Hb : 12 g/dl Hct : 37.5% RBC’s : 2.8 million/cmm WBC’s : 8000/cmm Platelet’s : 190,000/cmm PT : 19 sec (N 11-15 sec) APTT : 60 sec (N 25-40 sec) BT : 11 min (N 2-7 min) INR : 2 What is the best next step in the management of this patient ?]]
Answer A	AnswerA::Serotonin release assay for diagnosis of HIT
Answer A Explanation	[[AnswerAExp:: Incorrect  : The 14C-serotonin release assay remains the gold standard among the diagnostic tests for HIT, where platelets from normal donors are radiolabeled with 14C-serotonin are added to patient’s serum along with either high or low heparin concentrations. A positive test is the release of 14C-serotonin when therapeutic (0.1 U/mL) concentrations of heparin are used, rather than high (100 U/mL) concentrations. This assay is not generally available and due to its high cost it is not done routinely.]]
Answer B	AnswerB::Add corticosteroids
Answer B Explanation	[[AnswerBExp:: Incorrect  : There is no role for steroids in HIT. They are used in the treatment of ITP.]]
Answer C	AnswerC::Stop all heparin and initiate argatroban
Answer C Explanation	AnswerCExp::''' Incorrect ''' : The first intervention in a patient with suspected HIT type 2 should be immediate cessation of all exposure to heparin and replacement with a suitable alternative anticoagulant as they are still at the risk of thrombosis.
Answer D	AnswerD::Stop heparin, observe and then restart after 2 days
Answer D Explanation	[[AnswerDExp:: Incorrect  : The type I heparin-induced thrombocytopenia is typically characterized by a slight fall in platelet count that occurs within the first two days after heparin initiation and often returns to normal with continued heparin administration.]]
Answer E	AnswerE::Continue the usual heparin regimen
Answer E Explanation	AnswerEExp::''' Correct ''' : This patient has type I HIT patients and can recover even if heparin is continued to be administered.
Right Answer	RightAnswer::E
Explanation	[[Explanation::There are two types of heparin induced thrombocytopenia, type I and type II. Type I HIT patients characteristically have a transient decrease in platelet count (rarely <100,000) without any further symptoms and can recover even if heparin is continued to be administered. It occurs in 10-20% of all patients on heparin and is not due to an immune reaction and antibodies are not found upon investigation. HIT-1 is due to heparin-induced platelet clumping; it is innocuous. Type II is due to an autoimmune reaction with antibodies formed against platelet factor 4 (PF4), neutrophil-activating peptide 2 (NAP-2) and interleukin 8 (IL8) which form complexes with heparin. Educational Objective: References: ]]
Approved	Approved::Yes
Keyword	WBRKeyword::Heparin induced thrombocytopenia, WBRKeyword::HIT
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