bleeding-time testA virtually extinct test for evaluating haemostatic factors (platelets and vascular endothelium) by a skin incision—e.g., Duke and Ivy bleeding time tests.
• A blood pressure cuff is wrapped around the upper arm and inflated to 40 mm Hg;
• An area of the forearm free of superficial veins is cleaned and dried;
• A template is applied to the forearm and a spring-loaded blade is used to make 2 incisions, 1-mm deep and 5-mm long.
• A stopwatch is started.
• Taking care not to touch the cuts, drops of blood are gently blotted every 30 seconds until the bleeding of both cuts stops.
The BTT depends on the number and functional capacity of the platelets, as well as the elasticity of blood-vessel walls, and is a crude measure of the effectiveness of a person’s responses to vascular injury.
Range 2–8 minutes; the BT is the average of the 2. The BT test was once part of routine peoperative evaluation and performed on patients with a history of bleeding disorders, but with the advent of specific coagulation tests and accurate platelet measurements, has fallen into disuse. It is difficult to standardise and has a low reproducibility; it is not recommended for patients with low platelet counts; a large number of agents—e.g., aspirin, NSAIDs, antibiotics, anticonvulsants, cardiovascular drugs, and ethanol—interfere with the BT, as can the patient’s age, sex, and blood groups; screening of the preoperative BT is a poor indicator of clinically significant perioperative bleeding, and is regarded as a ineffective.