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Partial Exchange Transfusion Calculator

Polycythemia — PET Calculator

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1 What is the Partial Exchange Transfusion Calculator?

The Partial Exchange Transfusion (PET) Calculator computes the volume of blood to withdraw and replace with warmed 0.9% Normal Saline to treat neonatal polycythemia. Given birth weight, gestation (term or preterm), observed hematocrit, and a desired hematocrit (default 55%), it calculates an exchange volume range using an estimated neonatal blood volume. The app cites AIIMS Protocols in Neonatology as the source for this approach.

2 When to use it

  • Calculating the exchange volume for a neonate with polycythemia (elevated hematocrit) who requires partial exchange transfusion
  • Estimating exchange volume differently for term versus preterm infants, since estimated blood volume per kg differs
  • Targeting a specific desired post-exchange hematocrit — the tool defaults to 55%, within a stated 50-55% target range
  • Guiding the procedure itself, since the calculated volume is replaced with warmed normal saline, withdrawn slowly in small aliquots
  • Supporting post-procedure monitoring, such as when to recheck hematocrit

3 Formula & method

Volume = Blood Volume x (Observed Hct - Desired Hct) / Observed Hct, as stated directly in the app. Blood volume is estimated from birth weight using 80-90 mL/kg for term infants or 90-100 mL/kg for preterm infants, which produces a low-high exchange volume range rather than a single number. The app requires observed hematocrit to be at least 65% (its stated polycythemia threshold) and a desired hematocrit typically in the 45-65% entry range, with 50-55% noted as the usual target.
  • AIIMS Protocols in Neonatology

4 Frequently asked questions

What fluid is used for the exchange?

Warmed 0.9% Normal Saline, replacing withdrawn blood in equal volumes.

Why does the calculator give a range instead of one number?

Because it applies a blood-volume-per-kg range — 80-90 mL/kg term, 90-100 mL/kg preterm — rather than a single fixed value, the output is a low-high exchange volume range.

What hematocrit threshold does the tool use to flag polycythemia?

The observed hematocrit field requires a value of at least 65%, which the app treats as the polycythemia threshold for this calculation.

How should the exchange be performed once the volume is calculated?

Per the app's guidance, the calculated volume of warmed normal saline should be exchanged for an equal volume of blood, withdrawn slowly over 30-60 minutes in small aliquots of 5-10 mL, via the umbilical vein or a peripheral vein.

What should be monitored during and after the procedure?

The app's clinical notes say to continuously monitor vital signs, glucose, and calcium during the procedure and to recheck hematocrit 4-6 hours afterward. It also notes that plasma, albumin, or blood should NOT be used for PET in polycythemia — saline only.

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ESPGHAN 2022
For qualified clinicians. This page and the PediAid app are a clinical aid only. Calculations and reference data must be verified against the patient's clinical context, the source guideline and your local protocols before any treatment decision is made.