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CASE 24.1

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A 59-year-old male presents for follow-up. He is well known to you, receiving chronic anticoagulation with warfarin for a mechanical aortic valve. His PT and INR have been in the therapeutic range for years. When asked, he denies taking any other medications. He has had no new medical problems and is feeling well. Today his INR is 6.2 (therapeutic range 2.5–3.5). You inquire about dietary changes, focusing on foods rich in vitamin K.

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Question 24.1.1 Which of the following is true regarding vitamin K?

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A) Vitamin K is a water-soluble vitamin

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B) Broccoli and olive oil are good sources of vitamin K

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C) Vitamin K deficiency results in a hypercoagulable state

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D) Warfarin reduces the absorption of vitamin K

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E) Vegetarians are at risk for developing vitamin K deficiency

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Answer 24.1.1 The correct answer is "B." Vitamin K is a fat-soluble vitamin present in leafy green vegetables such as spinach and cabbage and in other foods such as milk, butter, bacon, and vegetable oils. Olive oil and broccoli are particularly rich in vitamin K. Therefore, vegetarians who consume these regularly are not at high risk for developing vitamin K deficiency. Vitamin K deficiency causes a hypocoagulable state resulting in a reduction in clotting factors and elevated prothrombin time and INR, leading to poor clotting ability and hemorrhage. Warfarin does act on vitamin K, but by reducing conversion of vitamin K to its active form rather than reducing absorption.

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Question 24.1.2 You would be more likely to suspect vitamin K deficiency in this patient if he also suffered from which of the following conditions?

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A) Crohn disease

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B) Irritable bowel syndrome

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C) Well compensated hepatitis C with mild fibrosis

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D) Coronary artery disease (CAD)

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E) All of the above

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Answer 24.1.2 The correct answer is "A." Vitamin K deficiency can occur with chronic small bowel disease, after small bowel resection, and with use of broad-spectrum antibiotics. Microorganisms in the bowel synthesize vitamin K, and use of broad-spectrum antibiotics reduces the numbers of these organisms. The majority of vitamin K is absorbed in the distal small bowel, and any disease affecting this area—including Crohn disease and celiac disease—can reduce the absorption of the vitamin. Irritable bowel syndrome is a functional disease not associated with impaired absorption. "C" is of special note. Patients with cirrhosis and decompensated liver disease are often vitamin K deficient. However, the mere presence of ...

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