Bleeding Time: Duke's Method

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Questions and Answers

What is bleeding time, and what does it measure?

Bleeding time is the time taken to stop bleeding, and it measures the primary phase of hemostasis, which is the interaction of platelets with the hemostatic plug.

What is the normal value range for bleeding time?

1-3 minutes

How is the bleeding time calculated in minutes?

By counting the number of spots and dividing it by 4.

What is the purpose of using a filter paper in the bleeding time test?

To wipe away the blood drop at 15-second intervals without touching the finger, thus preventing the plug from forming. Signup and view all the answers

What is clotting time, and what is its normal range?

Clotting time is the time required for clot formation, and its normal range is 5-8 minutes. Signup and view all the answers

How is the blood sample collected for the clotting time test?

By puncturing the finger with a lancet and drawing a large drop of blood into a non-heparinized capillary tube. Signup and view all the answers

What indicates the formation of a clot in the clotting time test?

The appearance of a fine fibrin thread between the two pieces of tubing. Signup and view all the answers

How is the clotting time calculated in minutes?

By dividing the number of pieces of tube by 2. Signup and view all the answers

What is the significance of measuring bleeding time and clotting time in assessing hemostasis?

They measure the primary phase of hemostasis and clot formation, respectively, and help diagnose platelet, vascular, and bleeding disorders. Signup and view all the answers

What is the primary reason for determining a person's blood group?

To ensure safe blood transfusion, resolve paternity disputes, address medicolegal problems, and facilitate organ transplantation. Signup and view all the answers

What triggers an immune response when incompatible blood is transfused?

The presence of foreign antigens on the plasma membrane of infused erythrocytes. Signup and view all the answers

What is the role of antibodies in a transfusion reaction?

Antibodies produced by plasma cells attach to the antigens on the infused erythrocytes, causing them to agglutinate and eventually leading to hemolysis. Signup and view all the answers

What is the significance of the ABO blood group system?

It is the most important blood group system, as it determines the compatibility of blood transfusions and prevents severe reactions. Signup and view all the answers

What is the result of hemolysis in a transfusion reaction?

The release of hemoglobin into the bloodstream. Signup and view all the answers

How many antigens have been identified on erythrocyte membranes?

More than 50. Signup and view all the answers

What is the primary function of plasma cells in a transfusion reaction?

To produce antibodies that attach to the antigens on infused erythrocytes. Signup and view all the answers

Study Notes

Bleeding Time (Duke's Method)

Measures the primary phase of hemostasis, focusing on platelet interaction with the hemostatic plug
Normal value: 1-3 minutes
Used to detect platelet and vascular abnormalities
Procedure:
- Clean and dry the finger tip with alcohol and cotton
- Puncture the finger with a lancet and record the time
- At 15-second intervals, wipe blood drops away with filter paper without touching the finger
- Continue until no more blood stains appear on the filter paper
- Count the number of spots and divide by 4 to obtain bleeding time in minutes

Clotting Time

Measures the time required for clot formation
Normal range: 5-8 minutes
Procedure:
- Clean and dry the finger tip with alcohol and cotton
- Puncture the finger with a lancet and obtain a large drop of blood
- Note the time when the drop appears
- Rapidly draw blood into a non-heparinized capillary tube
- Break off a small piece of the capillary tube (0.5cm) every 30 seconds
- Repeat until a fine fibrin thread is visible between the two pieces of tubing, indicating clotting
- Note the time when clotting appears
- Divide the number of pieces by 2 to obtain the clotting time in minutes

Blood Group Importance

Knowing a person's blood group is crucial in situations involving blood transfusion, paternity disputes, medicolegal problems, and organ transplantation.

Blood Typing and Transfusion

Blood groups are determined by the presence or absence of specific marker antigen molecules on the plasma membranes of erythrocytes.
Antigens are substances that trigger a defensive response from the immune system as they are not recognized as belonging to the self.
Antigens are typically large proteins.
Incompatible blood transfusions trigger an immune response, producing proteins called Antibodies (immunoglobulins).
Antibodies, produced by plasma cells, attach to antigens on the infused erythrocytes, causing them to agglutinate.
As erythrocyte clumps form, their Hemoglobin is released into the blood stream through hemolysis.
Over 50 antigens have been identified on erythrocyte membranes, with two groups being the most significant.