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Bleeding and Coagulation Time 13

الكلية كلية طب الاسنان     القسم  العلوم الاساسية     المرحلة 2
أستاذ المادة وسن نجم عبد السادة الربيعي       23/02/2019 00:02:48


Bleeding And Coagulation Time

Bleeding means loss of blood from damaged or injured small vessels. The bleeding time is the time taken from the onset of wound until bleeding cease. The nutural process or mechanism of prevention of blood loss through the injured vessel is called Hemostasis .This process has three main events (Fig.1) these are :
1.Contraction of blood vessel :Contraction of the smooth muscles in the wall of the blood vessel. This reduces the flow of blood and loss from the defect in the vessel wall. The term for this reduction in the diameter of a vessel is vasoconstriction; they occur due to serotonin and other vasoconstriction liberated from the platelets.
2.Aggregation of platelets :Activated platelets become sticky and adhere to the defect to form a temporary platelet plug; due to bind of platelets to collagen tissue.
3.Formation of a blood clot .

The clotting or coagulation process is a well-controlled series of separate events involving 12 different factors .The final step in these reactions is the conversion of soluble plasma protein called fibrinogen into insoluble solid threads of fibrin, which form the clot or thrombus (Fig.2,3).
Coagulation time: Is the time required for blood to clot under certain conditions.

The Principle


Purpose
1.To find time that occur between the puncture of the skin and the stoppage of oozing .
2.To determine clotting time .


Figure (1): Hemostatic mechanism

Figure (3): Final steps in the formation of a blood clot.

(A) Bleeding Time (Duke Method)

Apparatus and Reagents
1.Alcohol .
2.Sterile disposable lancet .
3.Stopwach .
4.Filter paper .
5.Glass slide .

Procedure
1.Clean the lobe of the ear or tip of a finger with alcohol and let dry .
2.Punture of ear lobe or finger using sterile blood lancet ,for ear; glass slide is placed behind the ear lobe .
3.Start the stopwatch at the moment of the puncture .
4.Blot the blood with the filter paper every 30 second ;avoid touching the skin ,move the filter paper so that each drop of blood touches a clean area (Fig.4). .
5.When the filter paper no longer shows signs of blood ,stop the stopwatch and record the time .
Normal value is 1-5 minutes .

Figure (4):Normal blots on filter paper.

Clinical Applications
Bleeding Time prolonged in :
1.Hemophilia :Which is a rare hereditary bleeding disorder. Characterized by a deficiency of a specific clotting factor, so that any cut or bruise may cause serious abnormal bleeding .
2.Thrombocytopenia :Is a deficient number of circulating platelets (below 60,000 platelet / mm3) , may be occur due to decreased production or to increased destruction of platelets .
3.Platelets functional disorder .
4.Aspirin prolonged the bleeding time by 2-3 times in normal persons, so patients should be instructed not to take it one week before the test is performed.
5.Pateints on long-term oral anticoagulant therapy usually have a moderately prolonged bleeding time.



(B) Clotting Time (Capillary Tube Method)

Apparatus and Reagents
1.Capillary tube (without heparin) .
2.Lancet .
3.Stopwach .
4.Alcohol .
5.Waterbath 37 C° .
6.Plasticine clay .

Procedure
1.Clean your finger with spirit and allow the spirit to dry .
2.Pricked the finger by lancet ;and record the time immediately .
3.Squeeze the finger to obtain a large drop of blood and fill the capillary tube with blood .
4.The capillary tubes are sealed plasticine and immersed in water bath at 37C° .
5.After one minute start breaking small pieces of the capillary tube every 30 second slowly and gently ;until a fibrin thread is seen between the two broken end .
Normal value of coagulation time by this method is 5-10 minutes at 37 C° .

Clinical Applications
Clotting Time prolonged in :
1.Hemophilia
2.Disseminated intravascular coagulation (DIC):Which involves the production of small clots (microthrombosis) and the lysis of these clots throughout the body. This massive clotting consumes the platelets and coagulation factors so that they are not available when normal coagulation is needed.
3.In hypofibrinogenemia.


المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .