sickle_cell_rbc_exchange: Sickle Cell RBC Exchange Volume Calculator

In cliot: Clinical Indices and Outcomes Tools

Sickle Cell RBC Exchange Volume Calculator

Description

Calculates the volume of replacement packed Red Blood Cells (pRBCs) required for an automated red cell exchange procedure (erythrocytapheresis) in patients with Sickle Cell Disease. The calculation estimates Total Blood Volume (TBV) using Nadler's formula and uses a logarithmic depletion model to determine the volume needed to reduce Hemoglobin S (HbS) to a specific target percentage.

Usage

sickle_cell_rbc_exchange(sex, height_cm, weight_kg, initial_hct_percent,
                         target_hct_percent, replacement_hct_percent,
                         initial_hbs_percent, target_hbs_percent)

Arguments

sex	String. Patient sex ("Male" or "Female"). Used for Nadler's TBV formula.
height_cm	Numeric. Patient height in centimeters.
weight_kg	Numeric. Patient weight in kilograms.
initial_hct_percent	Numeric. Patient's initial hematocrit (%).
target_hct_percent	Numeric. Patient's desired target hematocrit at the end of the procedure (%).
replacement_hct_percent	Numeric. Hematocrit of the replacement pRBC units (%). Typically ranges from 60-80% depending on the additive solution (e.g., Adsol vs. CPDA-1).
initial_hbs_percent	Numeric. Initial percentage of Hemoglobin S (HbS).
target_hbs_percent	Numeric. Desired target percentage of Hemoglobin S (HbS) (e.g., 30%).

Details

The Total Blood Volume (TBV) is calculated using Nadler's formula. The exchange volume is derived using the formula for continuous flow exchange:

V_{replace} = \frac{TBV \times Hct_{avg}}{Hct_{replace}} \times \ln\left(\frac{HbS_{initial}}{HbS_{target}}\right)

Where Hct_{avg} is the average of the initial and target hematocrit.

Value

A list containing:

Replacement_Volume_mL	The estimated volume of donor RBCs required.
Total_Blood_Volume_mL	The estimated total blood volume of the patient.

References

Nadler SB, Hidalgo JH, Bloch T. Prediction of blood volume in normal human adults. Surgery. 1962;51(2):224-232. Padmanabhan A, et al. Guidelines on the Use of Therapeutic Apheresis in Clinical Practice. J Clin Apher. 2019.

Examples

# Example 1: Adult Male, reducing HbS from 80% to 30%
# Height 180cm, Weight 80kg, Hct 30% -> 30%, Donor Hct 60%
sickle_cell_rbc_exchange("male", 180, 80, 30, 30, 60, 80, 30)

# Example 2: Female, target Hct higher than initial
# Height 165cm, Weight 60kg, Hct 25% -> 30%, Donor Hct 70%, HbS 90% -> 30%
sickle_cell_rbc_exchange("female", 165, 60, 25, 30, 70, 90, 30)

cliot documentation built on Dec. 1, 2025, 1:06 a.m.