Related Subjects:
|Red blood cells
|White blood cells
|Lymphocytes
|Platelets
|Cryoprecipitate
|Fresh Frozen Plasma
|Blood Cell Maturation
๐ฉธ About Platelets
- Platelets (thrombocytes) are small, disc-shaped cell fragments essential for clotting and wound healing.
- Produced in the bone marrow from megakaryocytes.
- Circulate for 7โ10 days before being cleared by spleen/liver.
- Main role: maintain hemostasis by forming platelet plugs at vessel injury sites.
๐ฌ Structure of Platelets
- Size: 2โ3 ฮผm, anucleate but highly specialized.
- Peripheral Zone: Phospholipid membrane with glycoprotein receptors (GPIb, GPIIb/IIIa) โ bind vWF & fibrinogen for adhesion/aggregation.
- Sol-Gel Zone: Actin + myosin cytoskeleton โ shape change from smooth discs โ spiky activated platelets.
- Organelle Zone: Alpha granules (growth factors, fibrinogen), Dense granules (ADP, serotonin, Caยฒโบ), Lysosomes (enzymes).
โ๏ธ Function in Hemostasis
- Adhesion: Bind to exposed collagen via vWF + GPIb receptors.
- Activation: Shape change + granule release (ADP, thromboxane Aโ) โ recruits more platelets.
- Aggregation: GPIIb/IIIa binds fibrinogen โ platelets cross-linked โ temporary plug formed.
- Also release growth factors (PDGF, TGF-ฮฒ) aiding tissue repair.
๐ Platelet Transfusion
- Pooled Platelets: From 4โ6 whole blood donations; ~240,000 platelets/unit.
- Single Donor (Apheresis): From one donor; ~550,000 platelets/unit โ โ risk of alloimmunisation.
- Storage: 20โ24 ยฐC, constant agitation; must be transfused within 4 hours of issue.
- Platelets ideally ABO- and Rh-compatible, but group-compatible units may be used if necessary.
๐จ Indications
- Active bleeding: if platelets <50,000/mmยณ; <100,000/mmยณ for CNS/eye surgery.
- Prophylaxis in thrombocytopenia:
- <10,000/mmยณ (no risk factors).
- <20,000/mmยณ (with risk factors e.g. fever, infection).
- Massive transfusion protocols or post-cardiopulmonary bypass.
๐ Clinical Guidelines
- Transfuse ~4 pooled units (โ250 mL each) over 30โ60 min.
- Check platelet count 1 hour post-transfusion to assess increment.
- Use Rh-negative platelets in Rh-negative patients (especially females of childbearing potential).
โ
Conclusion
- Platelets are central to clotting & healing ๐ฉน.
- Platelet transfusion is life-saving in bleeding, thrombocytopenia, and peri-operative care.
- Best practice: correct indication, correct storage, and compatibility matching for safety.
๐ References
