Bleeding time
| Bleeding time | |
|---|---|
| Intervention | |
| MeSH | D001760 |
Bleeding time is a medical test done on someone to assess their platelets function. It involves making a patient bleed then timing how long it takes for them to stop bleeding.
The term template bleeding time is used when the test is performed to standardized parameters.
The bleeding time test is a rather old method and indicated when other more reliable and less invasive tests for determining coagulation are not available. However, it is still to this date the most reliable way of assessing clinical bleeding in patients with uremia. Historically it was indicated whenever the physician needed information about platelet activation.
It involves cutting the underside of the subject's forearm, in an area where there is no hair or visible veins. The cut is of a standardized width and depth, and is done quickly by an automatic device.
A blood pressure cuff is used above the wound, to maintain venous pressure at a specified value. The time it takes for the bleeding to stop (i.e. the time it takes for a platelet plug to form) is measured. Cessation of bleeding can be determined by blotting away the blood every several seconds until the site looks "glassy".
The IVY method is the traditional format for this test. While both the IVY and the Duke method require the use of a sphygmomanometer, or blood pressure cuff, the IVY method is more invasive than the Duke method, utilizing an incision on the ventral side of the forearm, whereas the Duke method involves puncture with a lancet or special needle. In the IVY method, the blood pressure cuff is placed on the upper arm and inflated to 40 mmHg. A lancet or scalpel blade is used to make a shallow incision that is 1 millimeter deep on the underside of the forearm.
A standard-sized incision is made around 10 mm long and 1 mm deep. The time from when the incision is made until all bleeding has stopped is measured and is called the bleeding time. Every 30 seconds, filter paper or a paper towel is used to draw off the blood.
The test is finished when bleeding has stopped con 9 and a half minutes.
A prolonged bleeding time may be a result from decreased number of thrombocytes or impaired blood vessels. However, it should also be noted that the depth of the puncture or incision may be the source of error.
Normal values fall between 3 – 10 minutes depending on the method used.
With the Duke method, the patient is pricked with a special needle or lancet, preferably on the earlobe or fingertip, after having been swabbed with alcohol. The prick is about 3–4 mm deep. The patient then wipes the blood every 15 seconds with a filter paper. The test ceases when bleeding ceases. The usual time is about 2–5 minutes.
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