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This process has three main steps 1-contraction of blood vessel: contraction of the smooth muscles in the wall of the blood vessel, this reduce the blood flow and loss from the defect in the vessel wall. 2-Aggregation of platelets: Activated platelets become sticky and adhere to the defect to form temporary platelet plug due to bind of platelets to collagen tissue. 3- Formation of blood clot. cRAim: = To determine the bleeding time of a patient to assess platelet function and the body’s ability for complete stopping of blood flow. CS cxPrinciple The test involves making a puncture wound in a superficial area of the skin and monitoring the time needed for bleeding to stop. The bleeding Time test is usually used on: CS 1, Patients who have a history of prolonged bleeding after cuts, 2. Patients who have a family history of bleeding disorders. 3. The test is sometimes performed as a preoperative test to determine a patient's likely bleeding response during and after surgery. 4. The test helps identify people who have defects in their platelet function. amg 7 Duke's Method CS ph Clean the lobe of the ear or tip of a finger with alcohol and let dry. 2 Pierce the lower portion of the ear lobe (or tip of a finger) with the lancet _.making the incision 3-4 mm deep start the stopwatch. » Wipes the blood every 30 seconds with a filter paper without squeezing. « At the time when blood fails to appear on the filter paper, stop the stop: watch. s Count the spot of blood on the filter paper. « Record the result and calculate the bleeding time. (each 2 spots = | min.) is the time interval from oozing of blood after a cut or injury till formation of clot. © Aim: To determine the clotting time of a subject. Principle: A measure of the time required for blood to solidify (coagulate) after it has been removed from the body. Material and instrument for clotting time test: CS 1.Fine capillary glass tubes of about 10 mm length 2.Lancet. 3.Stop watch. 4.Cotton and Alcohol 70%. Procedure: CS 1. Clean the finger with alcohol 70% and allow to dry. 2. Prick the finger by lancet. 3. Draw blood up in the capillary glass tube. | 4. Start the stop watch. | 5. After one minute start breaking small pieces of the capillary tube every 30 second until a fibrin thread is E seen between the two broken ends. | ES Ca* Thromboplastin —_— Add citrated plasma XI vil x Suna are Prothrombin The prothrombin test specifically evaluates the presence of factors VII, V, and X, prothrombin, and fibrinogen. A prothrombin time within the 11 -15 second range (depends on the source of thromboplastin used) indicates that the patient has normal amounts of the above clotting factors. Aprolonged prothrombin time indicates a deficiency in any of factors VII, X, V, prothrombin, or fibrinogen. It may mean that the patient has a vitamin K deficiency (vitamin K is a co-factor in the synthesis of functional factors II (prothrombin), VI, IX and X) or a liver disease (the liver is the site of synthesis of the plasma protein factors). The prothrombin time of patients receiving a vitamin K-competing coumarin drug such as warfarin (anticoagulation therapy used in deep venous thrombophlebitis) will also be prolonged, usually in the range of one and one half to two times the normal PT time. Activated Partial Thromboplastin Time test The activated partial thromboplastin time (aPTT) is a test performed to investigate bleeding disorders and to monitor patients taking an anticlotting drug such as heparin which inhibits factors X and thrombin, while activating anti-thrombin. The aPTT test uses blood which is decalcified to prevent clotting before the test begins. The plasma is separated by centrifugation. (lonized) Calcium and activating substances are added to the plasma to start the intrinsic pathway of the coagulation cascade. The substances are: kaolin (hydrated aluminum silicate) and cephalin. Kaolin serves to activate the contact-dependent Factor XII, and cephalin substitutes for platelet phospholipids. The partial thromboplastin time is the time it takes for a clot to form, measured in seconds. Normally, the sample will clot in 35 seconds. Cat Kaolin _~ ra Phospholipid ee 7 XIV Jaa i Prothrombin Y Fibrinogen’ Sribrin clot PTT measures the integrity of the intrinsic system (Factors XII, Xl, VIll, IX) and common clotting pathways. Increased levels in a person with a bleeding disorder indicate a clotting factor may be missing or defective. At this point, further investigation is needed and warrants the use of sensitive assays for specific coagulation factors. Liver disease decreases production of factors, increasing the PTT. 
