Platelet Transfusions in Children

1. Introduction and Pathophysiology

Platelets play a crucial role in primary hemostasis, forming the initial plug at sites of vascular injury. In children, thrombocytopenia or platelet dysfunction can result from various conditions:

Decreased production: leukemia, aplastic anemia, myelodysplastic syndromes
Increased destruction: immune thrombocytopenia (ITP), thrombotic thrombocytopenic purpura (TTP), hemolytic uremic syndrome (HUS)
Increased consumption: disseminated intravascular coagulation (DIC), massive transfusion
Sequestration: hypersplenism
Hereditary disorders: Wiskott-Aldrich syndrome, Bernard-Soulier syndrome

Understanding the underlying cause is crucial for appropriate management and transfusion decisions.

2. Indications for Platelet Transfusion

2.1 Prophylactic Transfusions

Aimed at preventing spontaneous bleeding in severely thrombocytopenic patients. Thresholds vary based on clinical context:

≤10,000/μL: Generally accepted threshold for stable patients
≤20,000/μL: Consider for patients with additional risk factors (fever, sepsis, coagulopathy)
≤30,000-50,000/μL: Patients undergoing invasive procedures or with active mucositis
≤100,000/μL: Neurosurgery or severe bleeding risk

2.2 Therapeutic Transfusions

Used to control active bleeding. Thresholds are generally higher:

≤50,000/μL: For most bleeding episodes
≤100,000/μL: For central nervous system bleeding or severe active hemorrhage

2.3 Perioperative Support

Platelet count goals vary by procedure type:

≥50,000/μL: Most minor surgeries
≥80,000-100,000/μL: Major surgery
≥100,000/μL: Neurosurgery or ophthalmic procedures

3. Platelet Products and Dosing

3.1 Types of Platelet Products

Random donor platelets: Pooled from multiple donors
Single donor apheresis platelets: Collected from a single donor
Volume-reduced platelets: For patients requiring fluid restriction
Pathogen-reduced platelets: Treated to reduce risk of transfusion-transmitted infections

3.2 Dosing Guidelines

Standard dosing:

10-15 mL/kg of platelet concentrate for children <20 kg
1 unit (typically ~200-300 mL) for children ≥20 kg
Expected increment: 50,000-60,000/μL per dose in absence of consumption or destruction

Calculation: Dose (units) = [(Desired platelet count - Current platelet count) × Body surface area (m²)] ÷ 20,000

4. Administration and Monitoring

4.1 Administration Guidelines

Use dedicated IV line or freshly flushed line
Infuse over 15-30 minutes (up to 4 hours maximum)
Do not infuse with other blood products simultaneously
Use standard blood administration set (170-260 micron filter)

4.2 Monitoring

Assess vital signs before, during, and after transfusion
Perform post-transfusion platelet count 10-60 minutes after completion
Calculate corrected count increment (CCI) to assess transfusion efficacy:
CCI = (Post-count - Pre-count) × Body surface area (m²) ÷ Number of platelets transfused (×10¹¹)
CCI ≥7,500 at 1 hour or ≥4,500 at 24 hours indicates adequate response

5. Special Considerations

5.1 ABO Compatibility

ABO-identical platelets are preferred but not mandatory. In order of preference:

ABO-identical
ABO-compatible plasma
Incompatible plasma (with caution, especially for repeated transfusions)

5.2 Rh Compatibility

Rh-negative girls and women of childbearing potential should receive Rh-negative platelets when possible
If Rh-positive platelets are used, consider Rh immunoglobulin prophylaxis

5.3 Additional Processing

Leukoreduction: Standard practice in many centers to reduce febrile reactions and alloimmunization
Irradiation: Recommended for:
- Patients with congenital immunodeficiencies
- Recipients of allogeneic hematopoietic stem cell transplants
- Patients receiving fludarabine or other potent T-cell suppressants
- Patients with hematologic malignancies undergoing intensive chemotherapy
CMV-seronegative: Consider for CMV-seronegative recipients, especially if immunocompromised

6. Complications and Management

6.1 Acute Complications

Febrile non-hemolytic transfusion reactions (FNHTR): Treat with antipyretics; consider pre-medication for future transfusions
Allergic reactions: Range from mild urticaria to anaphylaxis. Treat with antihistamines; severe cases may require epinephrine
Transfusion-related acute lung injury (TRALI): Supportive care, oxygen therapy; may require mechanical ventilation
Bacterial contamination: Stop transfusion immediately, initiate broad-spectrum antibiotics, supportive care

6.2 Delayed Complications

Alloimmunization: May lead to refractoriness; manage with HLA-matched or crossmatched platelets
Transfusion-associated graft-versus-host disease: Rare but often fatal; prevention with irradiation is crucial
Post-transfusion purpura: Rare in children; treat with IVIG and corticosteroids

7. Platelet Refractoriness

Defined as inadequate post-transfusion platelet increment on two consecutive occasions. Causes include:

Non-immune: sepsis, DIC, splenomegaly (more common)
Immune: HLA alloimmunization, ABO incompatibility

Management:

Identify and treat underlying causes
For immune causes, consider HLA-matched or crossmatched platelets
Increased dosing or frequency of transfusions may be necessary

8. Emerging Therapies and Future Directions

Thrombopoietin receptor agonists (e.g., eltrombopag, romiplostim) in certain conditions
Ex vivo generated platelets from stem cells
Platelet-derived microparticles
Artificial platelet substitutes

Platelet Transfusions in Children

What is the primary indication for platelet transfusion in children?
Answer: Prevention or treatment of bleeding due to thrombocytopenia or platelet dysfunction
What is the typical threshold for prophylactic platelet transfusion in stable patients?
Answer: 10,000/µL (10 x 10^9/L)
How many units are in a standard adult dose of platelets?
Answer: 4-6 units (one apheresis unit)
What is the recommended dose of platelets for children?
Answer: 10-15 mL/kg or 1 unit per 10 kg body weight
Which of the following is not a common cause of thrombocytopenia in children?
Answer: Polycythemia vera
What is the expected increment in platelet count after a standard dose transfusion?
Answer: 30,000-50,000/µL
How long do transfused platelets typically survive in circulation?
Answer: 3-5 days
What is the maximum storage time for platelets at room temperature?
Answer: 5-7 days
Which of the following is a sign of platelet refractoriness?
Answer: Failure to achieve expected increment after two consecutive transfusions
What is the most common cause of immune-mediated platelet refractoriness?
Answer: HLA alloimmunization
Which blood group antigen is expressed on platelets?
Answer: ABO antigens
What is the recommended platelet count threshold for major surgery or invasive procedures?
Answer: 50,000/µL
Which of the following conditions typically requires a higher platelet transfusion threshold?
Answer: Intracranial hemorrhage
What is the primary difference between random donor platelets and apheresis platelets?
Answer: Apheresis platelets are collected from a single donor, while random donor platelets are pooled from multiple donors
Which of the following is not a typical indication for platelet transfusion?
Answer: Immune thrombocytopenia (ITP) without active bleeding
What is the recommended method for ABO compatibility in platelet transfusions?
Answer: ABO-identical or ABO-compatible
Which of the following is a potential complication specific to platelet transfusions?
Answer: Bacterial contamination
What is the recommended storage temperature for platelets?
Answer: 20-24°C with continuous gentle agitation
Which test is commonly used to assess the effectiveness of platelet transfusions?
Answer: Corrected count increment (CCI)
What is the typical volume of an apheresis platelet unit?
Answer: 200-300 mL
Which of the following is not a typical cause of non-immune platelet refractoriness?
Answer: ABO incompatibility
What is the recommended platelet count threshold for lumbar puncture in children?
Answer: 50,000/µL
Which of the following medications can affect platelet function and should be considered before transfusion?
Answer: Aspirin
What is the primary advantage of using platelet additive solutions?
Answer: Reduced plasma volume and decreased risk of allergic reactions
Which of the following is not a typical sign of a successful platelet transfusion?
Answer: Immediate cessation of all bleeding
What is the recommended maximum time for administering a unit of platelets?
Answer: 4 hours
Which of the following conditions may require HLA-matched platelet transfusions?
Answer: Platelet refractoriness due to HLA alloimmunization
What is the primary reason for using leukoreduced platelet products?
Answer: To reduce the risk of febrile non-hemolytic transfusion reactions and HLA alloimmunization
Which of the following is not a typical indication for therapeutic platelet transfusion?
Answer: Stable patient with platelet count of 15,000/µL
What is the recommended approach for platelet transfusion in neonates with alloimmune thrombocytopenia?
Answer: Use of antigen-negative or washed maternal platelets

Platelet Transfusions in Children