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
⚠️ Disclaimer:
The content on LabTestsGuide.com is for informational and educational purposes only. We do not guarantee the accuracy, completeness, or timeliness of the information provided. Always consult qualified healthcare professionals for medical advice, diagnosis, or treatment. LabTestsGuide.com is not liable for any decisions made based on the information on this site.
