Articles on Medical Diseases and Conditions

Entries Tagged ‘Blood Coagulation’

Investigation of Bleeding Disorders

There is no standardized protocol for workup of bleeding problems. Also, one should differentiate between workup of a patient who is actively bleeding and the use of screening tests in persons who are not bleeding. Any algorithm presented could be criticized by someone who prefers a different approach or different test procedures. Nevertheless, I will […]

Bleeding Problems in Surgery

Bleeding constitutes a major concern to surgeons. Problems may arise during operation or postoperatively, and bleeding may be concealed or grossly obvious. The major causes are the following: 1. Physical defect in hemostasis—improper vessel ligation, overlooking a small transected vessel or other failure to achieve adequate hemostasis, or postoperative tissue devitalization and release of a […]

Platelet Defects

According to one report, platelet counts on capillary (fingerstick) blood average ±3% lower than on venous blood samples and about 25% of the capillary samples were 25% or more below venous results. Platelet-associated abnormality is most commonly produced by decreased number (thrombocytopenia) or defective function (thrombocytopathia). A bleeding tendency may also appear with a greatly […]

Anticoagulant Systems

Coumarin anticoagulants Liver cells produce certain coagulation factors that require vitamin K for synthesis into a form that can be activated. Drugs of the coumarin family inhibit vitamin K utilization by liver cells. The vitamin K–dependent factors, listed in order of decreasing sensitivity to coumarin, are factor VII, factor IX, factor X, and prothrombin. Factor […]

Coagulation Tests in Newborns

The APTT is elevated in the newborn compared to the adult reference range. At least in part this is due to reduction of 30%-50% in activity of factors XI, XII, HMWK, and Fleher Factor. Activity is even lower in premature infants. Adult values are reached in 3-6 months. Vitamin K–dependent factors are reduced to 20%-60% […]

Coagulation Pathway Factors

In this section the various coagulation pathway factors are discussed individually, with emphasis on abnormalities for which laboratory tests are useful. Factor I (fibrinogen) Fibrinogen is a glycoprotein that is synthesized in the liver, the liver being a major source of many coagulation factors. Conversion of fibrinogen to fibrin under the influence of thrombin is […]

Basic Tests in Hemorrhagic Disorders

History. A history of easy bleeding or easy bruising should lead to further investigation. Platelet count. Platelet disorders will be discussed later. Using the direct count (reference values 150,000-400,000/mm3; 150-400 x 109/L), a platelet count less than 100,000/mm3 indicates moderate thrombocytopenia, and one less than 50,000/mm3 indicates severe thrombocytopenia. Platelet number can be estimated with […]

Blood Coagulation Theory

According to current theories of blood coagulation, the clotting mechanism is activated in two ways. The first activation pathway begins either when the endothelial lining of a blood vessel is damaged or when blood comes into contact with certain types of foreign surfaces. This activating sequence is begun by substances normally present within blood and […]

Blood Coagulation

Normally, blood remains fluid within a closed vascular system. Abnormalitiesof blood coagulation take two main forms: failure to clot normally (and thus toprevent abnormal degrees of leakage from the vascular system) and failure to prevent excessive clotting (and thus to maintain the patency of the blood vessels). Most emphasis in clinical medicine has been on […]