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Bleeding Time Experiment in Humans

Abstract:-

Bleeding time is a medical test used to assess platelet function and the body's ability to form a clot. It measures the duration of bleeding following a standardized skin incision. This experiment aims to determine the bleeding time in healthy human subjects using the Ivy method and to understand the factors influencing hemostasis. The results can help identify potential bleeding disorders, such as thrombocytopenia. This report details the methodology, observations, results, and clinical significance of the bleeding time test.

Introduction:-

Hemostasis is the physiological process that stops bleeding at the site of vascular injury. It involves vasoconstriction, platelet plug formation, and blood coagulation. Bleeding time (BT) is a simple yet informative test that evaluates primary hemostasis, particularly platelet function and vascular integrity.

The two most common methods for measuring bleeding time are:

1.Ivy Method– 

A blood pressure cuff is inflated on the upper arm, and a standardized incision is made on the forearm.

2.Duke Method– 

A puncture is made on the earlobe or fingertip, and the time until bleeding stops is recorded.

This experiment focuses on the Ivy method due to its higher reproducibility and clinical relevance. Normal bleeding time ranges between 2 to 9 minutes, but prolonged values may indicate platelet dysfunction or vascular defects.

Objective:-

- To measure bleeding time in healthy human subjects using the Ivy method.

- To understand the role of platelets and vascular response in hemostasis.

- To correlate bleeding time with potential bleeding disorders.

Materials and Methods

Materials Required

1. Sterile lancet or surgical blade

2. Blood pressure cuff (sphygmomanometer)

3. Stopwatch

4. Filter paper or blotting paper

5. Alcohol swabs

6. Gloves

7. Ruler

8. Sterile gauze

9. Marker

Procedure (Ivy Method)

1.Preparation of the Subject:-  

   - Explain the procedure and obtain informed consent.

   - Ensure the subject has no history of bleeding disorders or recent aspirin/NSAID use (as these can prolong BT).

   - Have the subject sit comfortably with the forearm exposed.

2.Application of Blood Pressure Cuff:- 

   - Place the cuff on the upper arm and inflate to 40 mmHg to maintain consistent venous pressure.

   - This standardizes capillary pressure and ensures uniform conditions.

3.Cleaning and Marking the Site

   - Clean the volar surface of the forearm (avoiding visible veins) with an alcohol swab.

   - Allow the area to dry.

   - Mark two incision sites (5 cm apart) using a sterile marker.

4.Making the Incision  

   - Using a sterile lancet or surgical blade, make two 5 mm long and 1 mm deep incisions.

   - Start the stopwatch immediately after making the incision.

5.Measuring Bleeding Time 

   - Gently blot the blood with filter paper every 30 seconds without touching the wound.

   - Record the time when bleeding stops completely from both incisions.

   - The average of the two readings is taken as the bleeding time.

6.Post-Procedure Care 

   - Apply gentle pressure with sterile gauze if minor oozing persists.

   - Clean the area and apply an adhesive bandage if necessary.

Precautions:-

- Use sterile instruments to prevent infection.

- Avoid areas with visible veins or scars.

- Ensure the subject is not on anticoagulant therapy.

- Maintain a controlled environment to avoid vasoconstriction due to cold.

Results:-

-Normal Bleeding Time (2-9 minutes):Observed in Subjects 1 and 2.

- Borderline Prolonged (7-9 minutes):Subject 3 may require further evaluation.

-Prolonged Bleeding Time (>9 minutes):Subject 4 may have a platelet disorder disease.

Discussion

Factors Affecting Bleeding Time

1.Platelet Count & Function

   - Low platelet count (thrombocytopenia) or dysfunctional platelets (e.g., due to aspirin) prolong BT.

2.Vascular Integrity

   - Weak blood vessels increase BT.

3.Temperature & Stress 

   - Cold temperatures cause vasoconstriction, artificially shortening BT.

Clinical Significance

-Prolonged BT (>9 min)suggests platelet dysfunction (e.g., Glanzmann’s thrombasthenia) or vascular defects.

-Normal BT with bleeding symptoms may indicate coagulation factor deficiencies (e.g., hemophilia), which do not affect primary hemostasis.

Limitations of Bleeding Time Test

-Operator-dependent:

 Depth and length of incision must be precise.

-Variable results:

Affected by skin thickness, temperature, and patient anxiety.

-Not specific:

Does not differentiate between platelet disorders and vascular defects.

Conclusion

The bleeding time test is a valuable tool for assessing primary hemostasis. In this experiment, most subjects had normal BT, while one showed prolonged BT, indicating possible platelet dysfunction. Further diagnostic tests (e.g., platelet function assay, vWF testing) would be needed for confirmation. Despite its limitations, the Ivy method remains useful in screening for bleeding disorders.

 

Appendix

- Sample Consent Form  

- Diagram of Incision Technique

- Comparative Table: Duke vs. Ivy Method  

This report provides a comprehensive overview of the bleeding time experiment, its methodology, and clinical relevance in diagnosing bleeding disorders. Further studies could compare different methods or assess BT in patients with known platelet defects.