Red blood cell (RBC) exchange transfusion is a life-saving intervention for sickle cell disease (SCD) patients. This calculator uses hematocrit and HbS% targets to determine:
- Exchange volume to replace sickled cells
- Packed RBC units required
- Post-exchange HbS% prediction
Formulas & Calculation:
1. Total Blood Volume (TBV) =
Weight (kg) × Factor
2. Plasma Volume (PV) =
TBV × (1 – Hct)
3. Red Cell Volume (RCV) =
TBV × Hct
4. Exchange Volume (EV) =
RCV × (Initial HbS% – Target HbS%)
Donor HbS% – Target HbS%
5. RBCs Required =
Exchange Volume × Donor Hematocrit
6. Units Required =
RBCs Required (mL)
Volume per Unit (mL)
Key Parameters:
• Weight Factors:
– Male: 70 mL/kg
– Female: 65 mL/kg
– Children: 80 mL/kg
• Hematocrit (Hct): Fraction (e.g., 30% = 0.30)
• Donor HbS%: Typically 0% (S-negative blood)
• Donor Hct: 0.55-0.70 for packed RBCs
– Male: 70 mL/kg
– Female: 65 mL/kg
– Children: 80 mL/kg
• Hematocrit (Hct): Fraction (e.g., 30% = 0.30)
• Donor HbS%: Typically 0% (S-negative blood)
• Donor Hct: 0.55-0.70 for packed RBCs
Clinical Targets:
• Acute indications:
– Stroke prevention: HbS <30%
– Acute chest syndrome
– Priapism
– Pre-surgical prophylaxis
• Chronic management:
– HbS <50% for recurrent VOC
– Transfusion iron overload monitoring
– Stroke prevention: HbS <30%
– Acute chest syndrome
– Priapism
– Pre-surgical prophylaxis
• Chronic management:
– HbS <50% for recurrent VOC
– Transfusion iron overload monitoring
Calculation Example:
35kg child, Hct 0.25, Initial HbS 85%, Target HbS 30%
TBV = 35 × 80 = 2800 mL
RCV = 2800 × 0.25 = 700 mL
EV = 700 × (85 – 30) ÷ (0 – 30) = 700 × (55) ÷ (-30) = -1283 mL
(Absolute value: 1283 mL)
RBCs Required = 1283 × 0.60 = 770 mL
Units = 770 ÷ 300 ≈ 2.57 → 3 units
TBV = 35 × 80 = 2800 mL
RCV = 2800 × 0.25 = 700 mL
EV = 700 × (85 – 30) ÷ (0 – 30) = 700 × (55) ÷ (-30) = -1283 mL
(Absolute value: 1283 mL)
RBCs Required = 1283 × 0.60 = 770 mL
Units = 770 ÷ 300 ≈ 2.57 → 3 units
Physiological Principles:
• Exchange transfusion replaces sickle cells with normal RBCs
• Maintains hematocrit while reducing HbS percentage
• More efficient than simple transfusion
• Prevents complications of iron overload
• Formula based on isovolemic exchange principles
• Negative exchange volume indicates removal required
• Maintains hematocrit while reducing HbS percentage
• More efficient than simple transfusion
• Prevents complications of iron overload
• Formula based on isovolemic exchange principles
• Negative exchange volume indicates removal required
Special Considerations:
• Use leukoreduced, sickle-negative blood
• Match for Rh and Kell antigens
• Pre-medicate for allergic reactions
• Monitor for transfusion reactions
• Calculate iron load for chronic management
• Consider erythrocytapheresis for chronic exchanges
• Match for Rh and Kell antigens
• Pre-medicate for allergic reactions
• Monitor for transfusion reactions
• Calculate iron load for chronic management
• Consider erythrocytapheresis for chronic exchanges
Protocol Notes:
• Perform pre-exchange Hb electrophoresis
• Target hematocrit: 30-35% post-exchange
• Avoid hyperviscosity (Hct >36%)
• Exchange volume typically 1-2 blood volumes
• Automated exchange more efficient than manual
• Post-exchange HbS <30% reduces stroke risk by 90%
• Target hematocrit: 30-35% post-exchange
• Avoid hyperviscosity (Hct >36%)
• Exchange volume typically 1-2 blood volumes
• Automated exchange more efficient than manual
• Post-exchange HbS <30% reduces stroke risk by 90%
Monitoring Parameters:
• Vital signs during exchange
• Calcium levels (citrate toxicity)
• Post-exchange HbS percentage
• Hematocrit and hemoglobin
• Transfusion reactions monitoring
• Iron studies for chronic management
• Calcium levels (citrate toxicity)
• Post-exchange HbS percentage
• Hematocrit and hemoglobin
• Transfusion reactions monitoring
• Iron studies for chronic management
Clinical Pearls:
• One blood volume exchange reduces HbS by ~65%
• 1.5 blood volumes reduces HbS by ~85%
• 1 unit PRBCs ≈ 3-4% HbS reduction in adults
• Maintain HbA >70% for acute stroke prevention
• Automated RBC exchange preferred for rapid reduction
• Chronic exchange every 3-6 weeks prevents complications
• 1.5 blood volumes reduces HbS by ~85%
• 1 unit PRBCs ≈ 3-4% HbS reduction in adults
• Maintain HbA >70% for acute stroke prevention
• Automated RBC exchange preferred for rapid reduction
• Chronic exchange every 3-6 weeks prevents complications
Key Formulas Reference:
• TBV (mL) = Weight (kg) × Factor [M:70, F:65, C:80]
• PV (mL) = TBV × (1 – Hct)
• RCV (mL) = TBV × Hct
• Exchange Volume (mL) = RCV × (Initial HbS% – Target HbS%) ÷ (Donor HbS% – Target HbS%)
• RBCs Required (mL) = Exchange Volume × Donor Hematocrit (0.60-0.70)
• Units Required = RBCs Required (mL) ÷ Unit Volume (mL) [≈300 mL]
• Adjusted Body Weight (kg) = IBW + 0.25×(Actual – IBW) [For obese patients]
• TBV (mL) = Weight (kg) × Factor [M:70, F:65, C:80]
• PV (mL) = TBV × (1 – Hct)
• RCV (mL) = TBV × Hct
• Exchange Volume (mL) = RCV × (Initial HbS% – Target HbS%) ÷ (Donor HbS% – Target HbS%)
• RBCs Required (mL) = Exchange Volume × Donor Hematocrit (0.60-0.70)
• Units Required = RBCs Required (mL) ÷ Unit Volume (mL) [≈300 mL]
• Adjusted Body Weight (kg) = IBW + 0.25×(Actual – IBW) [For obese patients]
🩸 Sickle Cell RBC Exchange Volume Calculator
🔍 Overview:
This calculator estimates the RBC exchange volume and donor blood units needed for patients with sickle cell disease. It uses patient weight, hematocrit, and HbS% levels to guide transfusion strategies.
📐 Formulas Used:
- Total Blood Volume (TBV): Weight × Factor (M: 70, F: 65, Child: 80)
- Plasma Volume (PV): TBV × (1 - Hct)
- Red Cell Volume (RCV): TBV × Hct
- Exchange Volume: RCV × ((Initial HbS% - Target HbS%) / (Target HbS% - Donor HbS%))
- RBCs Required: Exchange Volume × Donor Hematocrit
- Units Required: RBCs Required ÷ Volume per unit (≈300 mL)
🖊️ Enter Patient Details:
Clinical Application Example:
Patient: 12-year-old child (40 kg), Hct 28%, HbS 85% → Target 30%.
- TBV =
40 × 80 = 3,200 mL - PV =
3,200 × (1 - 0.28) = 2,304 mL - RCV =
3,200 × 0.28 = 896 mL - EV =
896 × [(85 - 30) / (0 - 30)] = 896 × (55 / -30) = -1,643 mL→ 1,643 mL - Packed RBC Volume =
1,643 × 0.60 = 986 mL - Units =
986 ÷ 300 = 3.3 → **4 units**
Clinical Protocol:
| Parameter | Standard | Critical Notes |
|---|---|---|
| Target HbS% | ||
| – Acute Chest | ≤30% | Exchange within 4 hours |
| – Stroke Prevention | <30% long-term | Monthly exchanges |
| Donor Blood | HbS-negative, C-E-K- | Leukoreduced, antigen-matched |
| Exchange Method | Automated (vs. manual) | Automated reduces complications |
Key Safety Considerations:
⚠️ Avoid If:
- Hyperviscosity risk (post-exchange Hct >30%)
- Iron overload (use erythrocytapheresis)
- Alloimmunization history (require full phenotype match)
✅ Essential Monitoring:
- Post-exchange HbS% (within 1 hour)
- Hematocrit (keep ≤30%)
- Electrolytes (Ca²⁺, K⁺) during exchange
