LAB 1 & 2

• Capillary fragility can be described as either weak or strong, with thin capillaries being fragile and prone to rapture, while thick capillaries are strong and can withstand pressure.
• Capillaries are smaller than arteries or veins, but a little bit bigger than arteriole.
• Vascular fragility particularly affects the capillary as it belongs to the vascular system.
• The capillary fragility test measures the ability of small capillaries to retain blood when subjected to increased stress, such as hydrostatic pressure and anoxia.
• Increased stress in the capillary fragility test includes pressure of 100mmHg for 5 minutes.
• Applying in vitro pressure in the arm can constrict blood vessels, increasing intravascular pressure (blood pressure).
• The capillary fragility test is a non-specific evaluation to measure capillary weakness and deficiencies in platelet number and function.
• Decreased capillary resistance causes the capillaries to rupture, leading to bleeding and the formation of petechiae.
• If positive for petechiae in the capillary fragility test, it indicates capillary weakness, thrombocytopenia, or both.
• Repeated skin trauma can lead to increased vascular fragility.
• Vitamin C deficiency is important for the immune system and helps in the integrity of blood vessels, making the blood flow smooth.
• Purpuras and hemorrhage (bleeding) are signs of increased vascular fragility.
• Interpretation of the Rumpel-Leede tourniquet test involves examining the forearm, hands, and fingers for the presence of petechiae, and noting the number and location of petechiae.
• Platelets are thin disks, 2-4 µm in diameter and 5-7 fL in volume.
• Platelets are 1/10 of the size of the RBC.
• Normal platelet count is 150,000–450,000/uL.
• Platelets function primarily in hemostasis and in maintaining capillary integrity.
• Light Microscopy Method: Tocantin’s Method uses Rees-Ecker reagent, sodium citrate as anticoagulant, and Brilliant Cresyl Blue to stain the platelets.
• Abnormally low platelet count is less than 100,000/uL.
• The total volume of the entire grid of Hemocytometer is 0.9mm3.
• PLT⁄cumm is the formula for platelet count, calculated by the number of platelets counted in 4 squares times the dilution factor (DF) times the volume correction factor (VCF).
• VCF is calculated by dividing 1mm2 by the volume of one square used multiplied to the number of squares used.
• Purpose of platelet count: to confirm if the patient is really suffering from thrombocytopenia or thrombocytosis.
• Bleeding possible platelet count is 30,000–50,000/uL.
• Severe spontaneous bleeding platelet count is less than 5,000/uL.
• Criteria for a good diluent are that it should prevent platelet adherence to glass, should prevent platelet aggregation, should not promote premature platelet lysis, and should make platelets visible in microscope.
• DF is calculated by dividing the total volume by the volume of the sample used.
• Platelet numbers must be sufficient for them to play their supportive role in hemostasis.
• When evaluating a bleeding problem that may be traceable to platelets, the counting of platelets is an important and logical starting point.
• Spontaneous bleeding platelet count is less than 30,000/uL.
• Levy chamber with improved Neubauer ruling is a feature of Hemocytometer.
• Two factors that affect capillary fragility: genetics and platelet.
• Phase-Contrast Microscopy Method: Brecker-Cronkite Method uses 1% NH4 oxalate as diluent, EDTA as sample, and counts platelets in 5 R squares.
• HEMOCYTOMETER is an instrument used to count blood cells.