What is the appropriate volume and platelet content of one unit of platelet concentrate for a 20‑kg child with aplastic anemia?

Platelet Transfusion Dosing for Pediatric Aplastic Anemia

For a 20-kg child with aplastic anemia, one unit of platelet transfusion should contain approximately 1.5–2.0 × 10¹¹ platelets in a volume of 50–100 mL, which can be achieved by volume-reducing a standard apheresis unit or pooling 2–3 whole blood-derived platelet concentrates. 1, 2

Standard Pediatric Dosing Calculation

The therapeutic dose of platelets for children is calculated as one platelet concentrate (60–80 × 10⁹ platelets) per 10 kg body weight. 1

For a 20-kg child, this translates to:

• Target platelet content: 1.2–1.6 × 10¹¹ platelets (approximately 1.5 × 10¹¹) 1
• Expected increment: approximately 3,500/m² per unit, or roughly 30,000–50,000/μL for a standard dose 1

Product Options for Pediatric Patients

Volume-Reduced Apheresis Unit (Preferred)

A standard apheresis unit contains 3–4 × 10¹¹ platelets in 150–450 mL of plasma, which is excessive volume for a 20-kg child. 1 Volume reduction is indicated to deliver an appropriate platelet dose without fluid overload. 1

• Method: Centrifuge a standard apheresis unit and remove excess plasma to achieve 50–100 mL final volume 1
• Platelet loss: 15–55% of platelets are lost during volume reduction 1
• Final product: Approximately 1.5–2.5 × 10¹¹ platelets in 50–100 mL 1, 3
• Clinical efficacy: Despite in vitro evidence of mild platelet activation, volume-reduced products show acceptable hemostatic function and posttransfusion increments 3, 4

Pooled Whole Blood-Derived Platelets (Alternative)

• Dose: Pool 2–3 single platelet concentrates 1
• Each unit contains: Approximately 7.5 × 10¹⁰ platelets in 50–60 mL 5
• Total: 1.5–2.25 × 10¹¹ platelets in 100–180 mL 5

Transfusion Thresholds for Aplastic Anemia

Prophylactic platelet transfusion should be administered when the platelet count falls below 10,000/μL in stable patients with aplastic anemia. 1

• Stable, non-bleeding patients: Transfuse at platelet count ≤10,000/μL 1
• Active bleeding or fever/infection: Consider transfusion at ≤20,000/μL 1
• Pre-procedure (bone marrow biopsy, central line): Target ≥50,000/μL 1, 6

Critical Considerations for Pediatric Aplastic Anemia

Volume Restriction Indications

Volume reduction should be limited to patients who require severe volume restriction, as 15–55% of platelets are lost during the additional centrifugation step. 1 For a 20-kg child, the circulating blood volume is approximately 1,600 mL (80 mL/kg), making standard apheresis volumes (200–400 mL) potentially problematic.

ABO Compatibility

The platelet concentrate must be ABO-identical or at least ABO-compatible to provide optimal platelet count increments. 1, 2 ABO-incompatible platelets result in reduced posttransfusion recovery and should be avoided unless no alternative exists. 1

Leukoreduction

All platelet products for pediatric aplastic anemia patients should be leukoreduced to minimize:

• Alloimmunization risk (critical for potential bone marrow transplant candidates) 1
• Febrile non-hemolytic transfusion reactions 2
• CMV transmission 2

Expected Response and Monitoring

Monitor the platelet count approximately 1 hour (or 10 minutes) post-transfusion to assess adequacy of response. 1

Expected Increment for 20-kg Child

• Corrected count increment (CCI): Should be ≥5,000 1
• Absolute increment: Approximately 3,500/m² per unit, or roughly 30,000–40,000/μL for 1.5 × 10¹¹ platelets 1
• Calculation: For a child with body surface area of ~0.8 m², transfusing 1.5 × 10¹¹ platelets should yield an increment of approximately 35,000/μL 1

Refractoriness

Platelet refractoriness should only be diagnosed after at least two ABO-compatible transfusions stored <72 hours result in poor increments (CCI <5,000). 1 In aplastic anemia patients being considered for bone marrow transplantation, early identification of alloimmunization is critical. 1

Common Pitfalls

• Oversizing the dose: Using a full apheresis unit (3–4 × 10¹¹ platelets) provides excessive platelets and volume for a 20-kg child, increasing donor exposure without additional benefit 1, 5
• Ignoring volume overload risk: Standard apheresis volumes (200–400 mL) represent 12–25% of circulating blood volume in a 20-kg child 1
• Delaying volume reduction: If volume reduction is needed, it should be performed in a closed system to maintain 5-day storage; open systems require use within 6 hours 1
• Using ABO-incompatible products: This significantly reduces platelet recovery and therapeutic efficacy 1