Blood Physiology: Bleeding Time (BT) & Clotting Time (CT)

Blood Physiology Bleeding Time (BT) & Clotting Time (CT) Hematocrit Measurement Bleeding time The time interval between the skin puncture and spontaneous (without pressure) stopping of bleeding. (the time taken for the cessation of bleeding from capillaries) most basic assessment of platelet count and function Normal value : 2- 3 minutes Materials :  for sterile finger-prick (disposable needle or a special lancet )  Clean filter papers  Stopwatch Bleeding time procedure 1. Clean the finger with alcohol 2. Get a deep finger-prick under aseptic conditions to get free-flowing blood (in 3-4 mm depth) 3. Start the stop watch when blood first appears on the skin . 4. After every half a minute, absorb/remove the blood drops by touching the skin with the edge of the filter paper (30 sec interval ), without pressing or squeezing. 5. Note the time when bleeding stops, This is the end point. Or Count the number of blood spots and divide by 2. Abnormal Bleeding Time  Prolonged bleeding time may indicate: • A vascular (blood vessel) defect • Low platelets count :(thrompocytopenia) • A platelet function defect • Drugs include indomethacin, salicylates (including aspirin) • Anemia pernicious and Leukemia Clotting time (CT) The time taken for the formation of blood clot( fibrin threads) Procedure: Clotting time: Capillary tube method 1. Sterilize the finger using cotton & alcohol. 2. Puncture the finger using sterile lancet. 3. Fill the non-heparinized capillary tube (capillary action) 4. After 2 minutes break a piece of the capillary tube 5. continue breaking every 30 seconds until a fibrin thread is formed. Normal range: 3-7 min Non-heparinized Capillary Tubes : blue stain Heparinized capillary tube: Red stain Clotting Time : Slide Method  The surface of the glass tube or slide initiates the clotting process. 1. Obtain the blood from the finger by puncture with a sterilized lancet. 2. put the drop of blood onto a slide and placed in a moist chamber (Petridish) and start the timer. 3. Draw a needle through the drop in every 30 seconds. 4. Stop the timer when the first fibrin fiber appears. • The expected range : 4-10 min. Hematocrit  = packed cell volume (PCV) The percentage of RBCs volume in whole blood. If a portion of blood is centrifuged or allowed to stand for a long time in a tube with anticoagulant: 1. 2. The blood cells will settle towards the bottom of the tube. while the plasma remains on top. Hematocrit (Hct) : PCV volume percentage of RBCs volume of the RBCs in 100mL (dl) of blood. normally about: 40-48% for men 36-42% for women Hematocrit Measurements 1-Microhaematocrit tube (A glass capillary with a red stain) 2- dough (sealant) 3-Microhaematocrit centrifuge 4-Microhaematocrit reader Protocol for Hct measuring 1. Fill the heparinized capillary tube with blood (filled by capillary action). 2. The other end (dry end) of the glass capillary is sealed with a dough. 3. The capillary is placed with its sealed end outwards into a centrifuge 4. centrifuged for 5 min (1000 RPM). 5. Place the centrifuged tube vertically on the Microhaematocrit reader 6. Slide the tube along the chart until the plasma level intersects the 100% line. 7. The hematocrit value can be directly read by means of a calibrated scale