Bleeding Time: The Test
Bleeding time is used to measure the duration of bleeding after a measured skin incision. Bleeding time may be measured by one of three methods: template, Ivy, or Duke. The template method is the most commonly used and the most accurate because the incision size is standardized. Bleeding time depends on the elasticity of the blood vessel wall and on the number and functional capacity of platelets.
Although this test is usually performed on patients with a personal or family history of bleeding disorders, it's also useful- along with a platelet count for preoperative screening.The test is usually not recommended for patients with a platelet count of less than 75,000/u1.
- To assess overall hemostatic function (platelet response to injury and functional capacity of vasoconstriction).
- To detect congenital and acquired platelet function disorders.
- Explain to the patient this test is used to measure the time required to form a clot and stop bleeding.
- Tell him who will perform the test and when it will take place.
- Inform him that he need not restrict food or fluids before the test.
- Reassure the patient that, although he may feel some discomfort from the incisions, the antiseptic, and the tightness of the blood pressure cuff, the test takes only 10 to 20 minutes to perform.
- Advise the patient that the incisions will leave two small, hairline scars that should be barely visible when healed.
- Check the patient's history for recent use of drugs that prolong bleeding time, including sulfonamides, thiazide diuretics, antineoplastics, anticoagulants, non steroidal anti-inflammatory drugs, aspirin and aspirin compounds, and some non narcotic analgesics. If the patient has taken such drugs, check with the laboratory for special instructions. If the test is being used to identify a suspected bleeding disorder, it should be postponed and the drugs discontinued. If the test is being used preoperatively to assess hemostatic function, it should proceed as scheduled.
Blood pressure cuff, disposable lancet, template with 9-mm slits (template method), 70% alcohol or povidone-iodine solution, filter paper, small pressure bandage, stopwatch.
Procedure and posttest care
- Template method: Wrap the pressure cuff around the upper arm and inflate the cuff to 40 mm Hg. Select an area on the forearm with no superficial veins, and clean it with antiseptic. Allow the skin to dry completely before making the incision. Apply the appropriate template lengthwise to the forearm. Use the lancet to make two incisions, I mm deep and 9 mm long. Start the stopwatch. Without touching the cuts, gently blot the drops of blood with filter paper every 30 seconds, until the bleeding stops in both cuts. Average the time of the two cuts, and record the result.
- Ivy method: After applying the pressure cuff and preparing the test site,
make three small punctures with a disposable lancet. Start the stopwatch immediately. Taking care not to touch the punctures, blot each site with filter paper every 30 seconds, until the bleeding stops. Average the bleeding time of the three punctures, and record the result.
- Duke method: Drape the patient's shoulder with a towel. Clean the earlobe, and let the skin air-dry. Then make a puncture wound 2 to 4 mm deep on the earlobe with a disposable lancet. Start the stopwatch. Being careful not to touch the ear, blot the site with filter paper every 30 seconds, until bleeding stops. Record bleeding time.
- In a patient with a bleeding tendency (hemophilia, for example), maintain a pressure bandage over the incision for 24 to 48 hours to prevent further bleeding; check the test area frequently; keep the edges of the cuts aligned to minimize scarring.
- In other patients, a piece of gauze held in place by an adhesive bandage is sufficient.
- Resume administration of medications discontinued before the test.
- Be sure to maintain a cuff pressure of 40 mm Hg throughout the test.
- If the bleeding does not diminish after 15 minutes, discontinue the test.
The normal range of bleeding time is from 3 to 6 minutes in the template method; from 3 to 6 minutes in the Ivy method; and from I to 3 minutes in the Duke method
Prolonged bleeding time may indicate the presence of disorders associated with thrombocytopenia, such as Hodgkin's disease, acute leukemia, disseminated intra vascular coagulation, hemolytic disease of the newborn, Schonlein-Henoch purpura, severe hepatic disease (cirrhosis, for example), or severe deficiency off actors I, II, V, VII, VIII, IX, and XI. Prolonged bleeding time in a person with a normal platelet count suggests a platelet function disorder (thrombasthenia, thrombocytopathia) and requires further investigation with clot retraction, prothrombin consumption, and platelet aggregation tests.
- Sulfonamides, thiazide diuretics, antineoplastics, anticoagulants, nonsteroidal anti-inflammatory drugs, aspirin and aspirin compounds, and some nonnarcotic analgesics (prolonged bleeding time).