Question 1

An obese 64 year-old man who has just completed an all-night train ride is brought to the emergency department with chest pain, shortness of breath, profuse sweating, and swelling of his right calf with a bluish discoloration. What is the most likely diagnosis?

Accepted Answer

The symptoms of chest pain, shortness of breath, profuse sweating, and swelling of one calf with bluish discoloration are indicative of a deep vein thrombosis (DVT) and pulmonary embolus (PE). This patient's obesity and sedentary lifestyle make him more susceptible to developing a DVT, and the prolonged train ride could have contributed to its development. The symptoms of chest pain and shortness of breath are also suggestive of a PE, which occurs when a blood clot from a DVT travels to the lungs. The other answer choices do not fit with the patient's presentation.

Question 2

A patient presents with a platelet count of 212 × 10³/µL and a bleeding time of 12 minutes. These results suggest which of the following?

Accepted Answer

The platelet count is within the normal range, indicating normal platelet production and no destruction. However, the prolonged bleeding time suggests defective platelet function, which means the platelets are not functioning properly and are not able to form a clot efficiently.

Question 3

Which one of the following substances cannot prevent coagulation when added to a blood sample (i.e., in the test tube)?

Accepted Answer

Coumarin works by inhibiting the synthesis of vitamin K-dependent clotting factors in the liver, which is a process that cannot occur in a test tube. The other substances directly interfere with the coagulation process in the blood sample itself.

Question 4

What is the purpose of the prothrombin test in monitoring hemostasis?

Accepted Answer

The prothrombin test measures the activity of factors in the extrinsic pathway of the coagulation cascade. This test is useful in monitoring hemostasis because it assesses the ability of the body to form a blood clot in response to injury. Platelet dysfunction and the presence of aspirin would not be detected by this test, and monitoring heparin function would require a different type of test such as the activated partial thromboplastin time (APTT).

Question 5

A 72-year-old woman is being treated with warfarin for chronic atrial fibrillation. She presents to the emergency department with an active nosebleed that is not readily controlled and a markedly prolonged prothrombin time. What is the most appropriate therapy?

Accepted Answer

The patient is likely experiencing an episode of over-anticoagulation from the warfarin, leading to a bleeding complication. Fresh frozen plasma contains clotting factors that can help reverse the effects of warfarin and should be given along with vitamin K to replenish the patient's clotting factors. Intravenous heparin would only further exacerbate the bleeding and tissue plasminogen activator is not indicated for this type of bleeding. Aspirin and cold compresses would not be effective in reversing the anticoagulation. DDAVP is used to increase production of von Willebrand factor, which is not the issue in this case.

Question 6

What condition leads to a deficiency in Factor IX that can be corrected by an intravenous injection of vitamin K?

Accepted Answer

Bile duct obstruction can lead to a deficiency in Factor IX because vitamin K, which is necessary for the synthesis of Factor IX, is a fat-soluble vitamin. Its absorption depends on bile acids. If the bile duct is obstructed, vitamin K absorption is impaired, leading to a deficiency in Factor IX that can be corrected by an intravenous injection of vitamin K.

Question 7

The excessive bleeding of a hemophiliac A (classical hemophilia) is usually caused by which of the following?

Accepted Answer

Hemophilia A is caused by a genetic lack of Factor VIII, which is a crucial clotting factor in the coagulation cascade. Without Factor VIII, the body is unable to properly form blood clots, leading to excessive bleeding. Choices A, C, and D are not associated with hemophilia A.

Question 8

Which of the following will not result in an increased bleeding tendency?

Accepted Answer

Vitamin A deficiency does not contribute to an increased bleeding tendency. In fact, it may even cause a decrease in bleeding tendency as it plays a role in the development and maintenance of epithelial tissues, which includes the lining of blood vessels. The other options listed can all lead to an increased bleeding tendency.

Question 9

A 2-year-old boy bruises easily and has a history of nosebleeds. He has also had bleeding into his knee joints after minimal trauma. You would suspect that this patient has a deficiency of which coagulation factor?

Accepted Answer

The symptoms described suggest a deficiency in Factor VIII, which is essential for blood clotting. Nosebleeds and easy bruising indicate a tendency to bleed, and bleeding into joints after minimal trauma suggests a problem with clotting factors. Deficiency of Factor VIII is known as hemophilia A, a genetic disorder primarily affecting males.

Question 10

A 60-year-old man who is receiving warfarin for recurrent deep vein thrombosis and has had stable, therapeutically appropriate anticoagulation for several months is treated by his physician for a urinary tract infection. Twelve days later he presents to the emergency department with lower gastrointestinal bleeding and is found to have a markedly prolonged prothrombin time. What is the most likely cause?

Accepted Answer

The most likely cause of the prolonged prothrombin time is reduced production of vitamin K by gut flora due to the antibiotic treatment. Antibiotics can disrupt the gut microbiome, leading to decreased synthesis of vitamin K, which is essential for the synthesis of clotting factors. This effect is particularly significant in patients on warfarin, as warfarin works by inhibiting vitamin K-dependent clotting factors.

Question 11

Which of the following is a function of thrombin?

Accepted Answer

Thrombin's main function is to convert fibrinogen to fibrin, which is the final step in blood clot formation. It also activates Factor XIII to stabilize fibrinolysis, but this is a secondary function. Thrombin does not convert Factor VII to VIIa, and while it does enhance some coagulation factors' activity, it primarily cleaves fibrinogen.

Quiz 37: Hemostasis and Blood Coagulation

An obese 64 year-old man who has just completed an all-night train ride is brought to the emergency department with chest pain, shortness of breath, profuse sweating, and swelling of his right calf with a bluish discoloration. What is the most likely diagnosis?

A patient presents with a platelet count of 212 × 10³/µL and a bleeding time of 12 minutes. These results suggest which of the following?

Which one of the following substances cannot prevent coagulation when added to a blood sample (i.e., in the test tube) ?

What is the purpose of the prothrombin test in monitoring hemostasis?

A 72-year-old woman is being treated with warfarin for chronic atrial fibrillation. She presents to the emergency department with an active nosebleed that is not readily controlled and a markedly prolonged prothrombin time. What is the most appropriate therapy?

What condition leads to a deficiency in Factor IX that can be corrected by an intravenous injection of vitamin K?

The excessive bleeding of a hemophiliac A (classical hemophilia) is usually caused by which of the following?

Which of the following will not result in an increased bleeding tendency?

A 2-year-old boy bruises easily and has a history of nosebleeds. He has also had bleeding into his knee joints after minimal trauma. You would suspect that this patient has a deficiency of which coagulation factor?

Which of the following is a function of thrombin?

Quiz 37: Hemostasis and Blood Coagulation

An obese 64 year-old man who has just completed an all-night train ride is brought to the emergency department with chest pain, shortness of breath, profuse sweating, and swelling of his right calf with a bluish discoloration. What is the most likely diagnosis?

A patient presents with a platelet count of 212 × 103/µL and a bleeding time of 12 minutes. These results suggest which of the following?

Which one of the following substances cannot prevent coagulation when added to a blood sample (i.e., in the test tube) ?

What is the purpose of the prothrombin test in monitoring hemostasis?

A 72-year-old woman is being treated with warfarin for chronic atrial fibrillation. She presents to the emergency department with an active nosebleed that is not readily controlled and a markedly prolonged prothrombin time. What is the most appropriate therapy?

What condition leads to a deficiency in Factor IX that can be corrected by an intravenous injection of vitamin K?

The excessive bleeding of a hemophiliac A (classical hemophilia) is usually caused by which of the following?

Which of the following will not result in an increased bleeding tendency?

A 2-year-old boy bruises easily and has a history of nosebleeds. He has also had bleeding into his knee joints after minimal trauma. You would suspect that this patient has a deficiency of which coagulation factor?

Which of the following is a function of thrombin?

A patient presents with a platelet count of 212 × 10³/µL and a bleeding time of 12 minutes. These results suggest which of the following?