Module 1 Calculator — Hb correction for plasma volume distortion

Estimate true Hemoglobin concentration when Plasma Volume distorted by Albumine level and Dehydration

Inputs

Sex (for Nadler & defaults)

Used for Nadler TBV and default baseline Hct suggestion (editable).

Units

Calculator converts internally to cm/kg.

Height

Weight

Hct (measured)

Decimal (e.g., 0.40 not 40).

Hb (measured)

g/dL

Albumin (measured)

g/dL

MCHC

g/dL RBC

Hct_baseline (euvolemic assumption)

Used to derive PV_e from TBV_e (Nadler). If unknown, keep conservative/typical.

DV_min (minimum intravascular plasma loss)

mL. Conservative lower-bound. This module then yields MINIMUM Hb correction.

Alb_ref (reference for deficit)

Using 3.5 reduces risk of over-attributing PV loss to hypoalbuminemia.

k midpoint (mL/g)

Range fixed at 15–25 for output; midpoint is for single-point view.

Outputs are ranges (k = 15–25) DV = minimum loss

What this module does (plain language)

Dehydration shrinks plasma volume, so Hb and albumin can look falsely high. We treat DV_min as a minimum plausible intravascular plasma loss. We then compute the smallest correction to Hb consistent with that minimum loss. Albumin is handled via mass conservation and an oncotic coupling coefficient k (15–25 mL per gram of circulating albumin deficit), reported as a range.

Outputs

Expected volumes (two methods)

BMI

—

BSA (Mosteller), m²

—

TBV_e (Nadler)

—

PV_e (from TBV_e & Hct_baseline)

—

TBV_e (BSA method)

—

PV_e (BSA method)

—

Show formulas used

Nadler TBV (L)

Male: TBV = 0.3669·h³ + 0.03219·w + 0.6041

Female: TBV = 0.3561·h³ + 0.03308·w + 0.1833

h in meters, w in kg

BSA (Mosteller)

BSA = √(height_cm · weight_kg / 3600)

BSA volumes (common transfusion-dilution method)

TBV = 2740 · BSA (mL)

PV = 1630 · BSA (mL)

Module 1 corrections (per method)

Each method (Nadler vs BSA) yields its own PV_e, TBV_e, then runs the same Module 1 logic. Outputs shown as ranges for k = 15–25 mL/g (and midpoint).

Nadler-based correction

Alb_true (measured)

—

Alb deficit mass (g)

—

PV_alb range (mL)

—

TBV_corr range (mL)

—

Hb_corr,A (with MCHC) range

—

Hb_corr,B (no MCHC) range

—

A vs B midpoint difference

—

A vs B midpoint % difference (Bland–Altman)

—

Internal Agreement (A vs B)

—

Note: “Good” or “Excellent” agreement increases confidence in the urgency of intervention.

BSA-based correction

Alb_true (measured)

—

Alb deficit mass (g)

—

PV_alb range (mL)

—

TBV_corr range (mL)

—

Hb_corr,A (with MCHC) range

—

Hb_corr,B (no MCHC) range

—

A vs B midpoint difference

—

A vs B midpoint % difference (Bland–Altman)

—

Internal Agreement (A vs B)

—

Percent difference definition (Bland–Altman style): %Δ = (A − B) / ((A + B)/2) × 100. This symmetric normalization avoids denominator bias (dividing by only A or only B).

iInternal Agreement (A vs B) compares two independent estimates of corrected Hemoglobin.

Method A uses red cell packing (MCHC) to estimate hemoglobin mass.
Method B uses hemoglobin mass from Hb × corrected TBV (no MCHC).

Positive values mean Method A estimates a higher corrected Hb than Method B.
Negative values mean Method B estimates a higher corrected Hb than Method A. Quality Checks/Warnings

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Important: This calculator does not provide medical advice. Its purpose is to support clinical reasoning by illustrating how measurement consistency, volume distortion, and physiologic constraints may influence Hemoglobin interpretation. Because TBV estimation formulas (e.g., Nadler vs BSA-based) are derived from stadying different populations and assumptions, the estimates are expected to be different, and are used in tandem to improve reliability of this hemoglobin correction approach. DV (Dehydration Volume) is treated as a minimum intravascular plasma loss in setting of dehydration; therefore Hb corrections are minimum corrections (true Hb may be lower).