bleeding time

Bleeding Time 

Definition

Bleeding time is a crude test of hemostasis (the arrest or stopping of bleeding). It indicates how well platelets interact with blood vessel walls to form blood clots.

Purpose

Bleeding time is used most often to detect qualitative defects of platelets, such as Von Willebrand's disease. The test helps identify people who have defects in their platelet function. This is the ability of blood to clot following a wound or trauma. Normally, platelets interact with the walls of blood vessels to cause a blood clot. There are many factors in the clotting mechanism, and they are initiated by platelets. The bleeding time test is usually used on patients who have a history of prolonged bleeding after cuts, or who have a family history of bleeding disorders. Also, the bleeding time test is sometimes performed as a preoperative test to determine a patient's likely bleeding response during and after surgery. However, in patients with no history of bleeding problems, or who are not taking anti-inflammatory drugs, the bleeding time test is not usually necessary.

Precautions

Before administering the test, patients should be questioned about what medications they may be taking. Some medications will adversely affect the results of the bleeding time test. These medications include anticoagulants, diuretics, anticancer drugs, sulfonamides, thiazide, aspirin and aspirin-containing preparations, and nonsteroidal anti-inflammatory drugs. The test may also be affected by anemia (a deficiency in red blood cells). Since the taking of aspirin or related drugs are the most common cause of prolonged bleeding time, no aspirin should be taken two weeks prior to the test.

Description

There are four methods to perform the bleeding test. The Ivy method is the traditional format for this test. In the Ivy method, a blood pressure cuff is placed on the upper arm and inflated to 40 mM Hg. A lancet or scalpel blade is used to make a stab wound on the underside of the forearm. An automatic, spring-loaded blade device is most commonly used to make a standard-sized cut. The area stabbed is selected so that no superficial or visible veins are cut. These veins, because of their size, may have longer bleeding times, especially in people with bleeding defects. The time from when the stab wound 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 completely.

The three other methods of performing the bleeding test are the template, modified template, and Duke methods. The template and modified template methods are variations of the Ivy method. A blood pressure cuff is used and the skin on the forearm prepared as in the Ivy method. A template is placed over the area to be stabbed and two incisions are made in the forearm using the template as a location guide. The main difference between the template and the modified method is the length of the cut made.

For the Duke method, a nick is made in an ear lobe or a fingertip is pricked to cause bleeding. As in the Ivy method, the test is timed from the start of bleeding until bleeding is completely stopped. The disadvantage to the Duke method is that the pressure on the blood veins in the stab area is not constant and the results achieved are less reliable. The advantage to the Duke method is that no scar remains after the test. The other methods may result in a tiny, hairline scar where the wound was made. However, this is largely a cosmetic concern.

Preparation

There is no special preparation required of the patient for this test. The area to be stabbed should be wiped clean with an alcohol pad. The alcohol should be left on the skin long enough for it to kill bacteria at the wound site. The alcohol must be removed before stabbing the arm because alcohol will adversely affect the tests results by inhibiting clotting.

Aftercare

If a prolonged bleeding time is caused by unknown factors or diseases, further testing is required to identify the exact cause of the bleeding problem.

Normal results

A normal bleeding time for the Ivy method is less than five minutes from the time of the stab until all bleeding from the wound stops. Some texts extend the normal range to eight minutes. Normal values for the template method range up to eight minutes, while for the modified template methods, up to 10 minutes is considered normal. Normal for the Duke method is three minutes.

Abnormal results

A bleeding time that is longer than normal is an abnormal result. The test should be stopped if the patient hasn't stopped bleeding by 20-30 minutes. Bleeding time is longer when the normal function of platelets is impaired, or there are a lower-than-normal number of platelets in the blood.

A longer-than-normal bleeding time can indicate that one of several defects in hemostasis is present, including severe thrombocytopenia, platelet dysfunction, vascular defects, Von Willebrand's disease, or other abnormalities.

Resources

Books

Henry, J. B. Clinical Diagnosis and Management by Laboratory Methods. Philadelphia: W. B. Saunders Co., 1996.

Key terms

Hemostasis — The stopping of bleeding or blood flow through a blood vessel or organ.

---

time (tīm) a measure of duration. Symbol t.

---

activated partial thromboplastin time  (APTT) (aPTT) (PTT) the period required for clot formation in recalcified blood plasma after contact activation and the addition of platelet substitutes; used to address the intrinsic and common pathways of coagulation.

bleeding time  the duration of bleeding after controlled, standardized puncture of the earlobe or forearm; a relatively inconsistent measure of capillary and platelet function.

circulation time  the time required for blood to flow between two given points.

clotting time , coagulation time the time required for blood to clot in a glass tube.

inertia time  the time required to overcome the inertia of a muscle after reception of a stimulus from a nerve.

one-stage prothrombin time  prothrombin t.

prothrombin time  (PT) the rate at which prothrombin is converted to thrombin in citrated blood with added calcium; used to assess the extrinsic coagulation system of the blood.

reaction time  the time elapsing between the application of a stimulus and the resulting reaction.

stimulus-response time  reaction t.

thrombin time  (TT) the time required for plasma fibrinogen to form thrombin, measured as the time for clot formation after exogenous thrombin is added to citrated plasma.

---

bleeding time,

the time required for blood to stop flowing from a tiny wound. A test of bleeding time is the Ivy method. See also hemostasis, simplate bleeding time.

---

bleeding [blēd´ing]

1. escape of blood from an injured vessel; see also hemorrhage.

2. phlebotomy.

dysfunctional uterine bleeding bleeding from the nonmenstruating uterus when no organic lesions are present.

implantation bleeding that occurring at the time of implantation of the zygote in the decidua.

occult bleeding escape of blood in such small quantity that it can be detected only by chemical tests or by microscopic or spectroscopic examination.

bleeding time the time required for a standardized wound to stop bleeding. The bleeding time test is used as a screening procedure to detect both congenital and acquired platelet disorders; it measures the ability of platelets to arrest bleeding and hence gives an estimate of platelet number and level of functioning. There are several methods of performing the bleeding time. In Ivy's test, incisions are made on the forearm, a sphygmomanometer is inflated to a standard of 40 mm around the upper arm, and the time until cessation of bleeding is recorded. The template method is a variation in which a template with a slit in it is laid on the forearm, and the slit and the knife making the skin incision are both standardized. The most widely used template is the Simplate. Normally bleeding will cease in 2 to 9 minutes. Qualitative platelet disorders, thrombocytopenia (platelet count of less than 100,000/mm³), and the use of aspirin will prolong the bleeding time.

---

time [tīm]

a measure of duration. See under adjectives for specific times, such as bleeding time.

activated partial thromboplastin time (APTT, aPTT) the period required for clot formation in recalcified blood plasma after contact activation and the addition of platelet substitutes such as brain cephalins or similar phospholipids; used to assess the coagulation pathways. A prolonged aPTT can indicate a deficiency of any of various coagulation factors, including factors XII, XI, IX, VIII, X, V, and II, and fibrinogen.

AEC minimal response time the shortest duration at which x-ray exposure can be terminated by automatic exposure control.

atrioventricular sequential time a fixed nonprogrammable interval that extends from the atrial stimulus to the ventricular stimulus.

bleeding time the time required for a standardized wound to stop bleeding; used as a test for platelet disorders; see also bleeding time.

circulation time the time required for blood to flow between two given points; see also circulation time.

clotting time (coagulation time) the time required for blood to clot in a glass tube; see also clotting.

cold ischemia time the time between the placement of a traumatically amputated body part in ice and the time of surgical replantation.

inertia time the time required to overcome the inertia of a muscle after reception of a stimulus.

ischemia time the total time between traumatic amputation of a limb or portion of a limb and its surgical reimplantation; it is the sum of warm and cold ischemia times.

minimal response time in radiology, the shortest possible exposure time for an x-ray film to be exposed automatically.

one-stage prothrombin time prothrombin time.

prothrombin time see prothrombin time.

real time a term used to describe a recording device that shows events simultaneously to their occurrence.

R peak time intrinsicoid deflection.

thrombin time the time required for plasma fibrinogen to form thrombin; see also thrombin time.

warm ischemia time the time interval between traumatic amputation of a limb or part and its placement on ice.

---

bleeding,

n the flowing of blood.

bleeding disorders,

n.pl hemorrhagic disorders including capillary abnormalities, platelet deficiencies, and blood clotting defects characterized by spontaneous and sometimes uncontrollable bleeding. Consideration before most invasive dental procedures.

bleeding, gingival,

n See gingival bleeding.

bleeding, occult

n a hemorrhage of such small proportions that the blood can be detected only by chemical test, microscope, or spectroscope.

bleeding points,

n.pl a series of puncture points made through the gingival tissue; used as a guide for making the gingivectomy incision.

bleeding time,

n the time required for blood to stop flowing from a tiny wound. Normal bleeding time is from 2 to 6 minutes. Bleeding time is increased in disorders of platelet count, uremia, and ingestion of aspirin and other antiinflammatory medications.

---

bleeding

1. the escape of blood, as from an injured vessel. See also hemorrhage.

2. the purposeful withdrawal of blood from a vessel of the body; venesection; phlebotomy. See also blood sampling.

---

bleeding disorders

see hemorrhagic disease, coagulopathy.

incomplete bleeding

the carcass of an animal slaughtered for meat which is incompletely bled out has a darker meat and more blood in vessels and the heart cavities than a properly slaughtered animal. This gives it an appearance resembling a fevered carcass.

occult bleeding

escape of blood in such small quantity that it can be detected only by chemical tests or by microscopic or spectroscopic examination.

bleeding time

the time required for a small pinpoint wound to cease bleeding. If done properly, the test can be helpful in determining the functional capacity of platelets and of vasoconstriction.