25

25 CASE 25


A 58-year-old man comes to the emergency department complaining of bleeding in his mouth.


The bleeding began 24 hours ago and has been continuous in spite of compression. The patient suffered a myocardial infarction 18 months earlier and since that time has stopped smoking, has begun a moderate exercise program, and is on a low dose of warfarin (Coumadin) as a blood thinner. One month ago he began taking herbal supplements containing garlic and ginkgo biloba extract.



PHYSICAL EXAMINATION



VS: T 36.8°C, P 85/min, R 18/min, BP 95/65 mm Hg, BMI 29

PE: Patient has multiple small bleeding sites on the mucous membranes of the mouth and nose.


LABORATORY STUDIES



Hematocrit: 35% (normal: males 42%)

Stool sample test: Positive for blood

Prothrombin time (PT): 35 seconds (normal: 11-15 seconds)

Partial thromboplastin time (PTT): 48 seconds (normal: 26-35 seconds)


DIAGNOSIS


Coumadin-type herbal supplement toxicity



PATHOPHYSIOLOGY OF KEY SYMPTOMS


Blood lost from damaged blood vessels is limited by the process of hemostasis. Hemostasis has two major components: the formation of the platelet plug and the activation of the clotting cascade. The elevation of the clotting times, particularly the prothrombin time, indicates an impairment of the clotting cascade.


Hemostasis helps repair the vascular damage that accompanies daily living. For this patient, vascular damage is not being repaired, resulting in visible bleeding in the mucous membranes and likely more significant bleeding, particularly in the gastrointestinal tract and other internal organs. Cardiovascular signs consistent with a moderate hemorrhage include mild hypotension and a baroreceptor-mediated activation of the sympathetic nervous system resulting in an elevation of heart rate and respiratory rate.


The platelets, or thrombocytes, are fragments of megakaryocytes. Circulating platelets have a lifespan of approximately 10 days, and platelet formation is regulated by the hepatic hormone thrombopoietin. Platelets have three different types of granules. Dense granules contain adenosine triphosphate (ATP), adenosine diphosphate (ADP), and serotonin. Alpha granules contain proteins that enhance coagulation and platelet adhesion, such as fibrinogen, fibronectin, vitronectin, and von Willebrand factor. Platelets also contain lysosomal granules.


Exposure to a damaged section of the endothelial cell causes the platelets to adhere and to undergo a release reaction, secreting ADP, serotonin, and thromboxane A. ADP attracts additional platelets to aggregate and to seal the damaged area.


More extensive vascular damage is sealed by the formation of a blood clot. A series of plasma proteins called clotting factors result in the formation of fibrin. Fibrin is polymerized to form a mesh that traps red blood cells and platelets to help form a clot and seal the opening (Fig. 25-1).


image

FIGURE 25–1 Effective circulation requires a balance between the ability to form clots to repair vascular injury and the need to maintain blood flow through vessels. The clotting cascade results in the formation of a fibrin mesh, which traps platelets and red blood cells to form a clot. Formation of the fibrin mesh is blocked by anticoagulants. Fibrinolytic agents, but not anticoagulants, can dissolve a clot after it is formed.

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Jul 4, 2016 | Posted by in PHYSIOLOGY | Comments Off on 25

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