A 6-year-old boy is brought to the emergency department due to bleeding after a dental extraction earlier this morning. The patient's past medical history is significant for painful swelling of his knee joints after minor trauma. Aspiration of the joints during several occasions yielded frank blood, and he was diagnosed with hemarthrosis. He has no known allergies. Currently, hemostasis in this patient most likely can be achieved by the administration of which of the following?

Question

A 6-year-old boy is brought to the emergency department due to bleeding after a dental extraction earlier this morning.  The patient's past medical history is significant for painful swelling of his knee joints after minor trauma.  Aspiration of the joints during several occasions yielded frank blood, and he was diagnosed with hemarthrosis.  He has no known allergies.  Currently, hemostasis in this patient most likely can be achieved by the administration of which of the following?

Quizplus · Accepted Answer

11ec160b_397d_31ad_9249_79cc40452b07_MD0001_00 A history of prolonged bleeding following procedures (eg, dental extractions, surgeries) and spontaneous hemorrhages into the joints (hemarthrosis) is typical for hemophilia, an X-linked recessive bleeding disorder due to decreased levels of factor VIII (hemophilia A) or factor IX (hemophilia B). Factors VIII and IX are components of the intrinsic coagulation pathway and activate factor X; activated factor X (Xa) then catalyzes the conversion of prothrombin (factor II) into thrombin as part of the final common pathway. In the absence of factors VIII or IX, activation of factor X and subsequent conversion of prothrombin into thrombin do not occur. Administration of thrombin, however, will make up for the deficiency and lead to blood clotting. In practice, prothrombin complex concentrates (containing factors II, VII, IX, and X, which lead to thrombin formation) were used for management of hemophilia B, although thrombogenic risks have limited their application. In both types of hemophilia, the bleeding time and platelet count are normal. The prothrombin time (PT) is also normal as it tests the extrinsic clotting pathway and reflects the function of factors II, V, VII, and X (mnemonic: PeT). However, the activated partial thromboplastin time (PTT) is prolonged as it assesses the activity of factors II, V, VIII, IX, X, XI and XII, the intrinsic clotting pathway (mnemonic: PiTT). Diagnoses of hemophilia A and B are made by measuring plasma levels of factors VIII and IX, respectively. (Choice A) Factor XII (Hageman) is synthesized by the liver and is activated by endothelial injury. It triggers the intrinsic coagulation pathway by activating factor XI. The addition of factor XII does not clot the blood of patients with hemophilia because the downstream clotting factors VIII or IX are deficient. (Choice B) Fibrinogen is a protein synthesized by the liver. Thrombin mediates cleavage of fibrinogen to form fibrin, the main component of thrombi; therefore, without thrombin, fibrinogen administration alone would not be helpful. (Choice C) Protein C is a vitamin K-dependent factor synthesized in the liver. It is a physiologic anticoagulant that degrades factors Va and VIIIa. (Choice E) Urokinase is a thrombolytic agent used for treatment of myocardial infarction and pulmonary embolism. It acts by converting plasminogen to plasmin, which then breaks down fibrinogen and fibrin into their respective degradation products. The addition of urokinase would prevent thrombosis. Educational objective: Bleeding after a tooth extraction and history of hemarthrosis are suggestive of hemophilia. Decreased levels of factor VIII or IX lead to failure to convert prothrombin into thrombin and deficient thrombus formation. The addition of thrombin to the blood of a patient with hemophilia results in clotting. __________ References: Prothrombin complex concentrates in emergency bleeding disorders. (http://www.ncbi.nlm.nih.gov/pubmed/22648513)

A 6-Year-Old Boy Is Brought to the Emergency Department Due