Plasma Volume Calculator - Nadler and Simple Methods

A plasma volume calculator is a clinical tool that turns sex, body weight, optional height, and hematocrit into the plasma volume in milliliters, the total blood volume that produced it, and the cellular volume that completes the same picture. The calculator supports the simple weight method (70 mL per kg for males and 65 mL per kg for females) and the more accurate Nadler 1962 sex specific height and weight equation.

• • Plasma donation planning: enter sex, weight, optional height, and a recent hematocrit to see the plasma volume available to donate during a plasmapheresis visit.
• • Bypass prime math: use the published Nadler 1962 total blood volume to size the crystalloid prime and to predict the dilutional hematocrit at the start of bypass.
• • Clinical fluid assessment: compare the calculated plasma volume against a measured plasma volume from a tracer dilution study to flag large volume shifts in trauma, sepsis, or critical care.
• • Worked example walk-through: recheck the calculation with male 70 kg, 175 cm, and hematocrit 45 percent to see how the Nadler 1962 sex specific equation sums to a plasma volume of 2653 mL.

The calculator is most useful when the weight, optional height, and hematocrit come from the same clinical encounter. Mixing a weight from a recent office visit with a hematocrit from a previous admission is a common source of error in plasma volume workups.

A second total blood volume tool that pairs with the adult plasma volume workflow is the Pediatric Blood Volume Calculator, which applies the same Nadler concept with pediatric coefficients to estimate blood volume in children.

The plasma volume calculator first estimates the total blood volume in liters from the Nadler 1962 sex specific height and weight equation (when height is provided) or from the 70 mL per kg and 65 mL per kg simple factors (when height is left at zero), then multiplies the total blood volume in milliliters by (1 minus hematocrit divided by 100) to produce the plasma volume in milliliters.

• sex: patient sex selector. Drives the published 70 or 65 mL per kg simple factor and the Nadler 1962 coefficients.
• weight: body weight in kilograms, used by every total blood volume equation.
• height: optional body height in centimeters. When above zero, the calculator uses the Nadler 1962 equation. When zero, the simple weight method.
• hematocrit: hematocrit from a complete blood count as a percent, used as the fraction in the formula.
• totalBloodVolume: total blood volume in milliliters. Equals 0.3669 times height in meters cubed plus 0.03219 times weight in kilograms plus 0.6041 liters for males, or 0.3561 times height in meters cubed plus 0.03308 times weight in kilograms plus 0.1833 liters for females (Nadler 1962). When height is zero, equals 70 mL per kg for males or 65 mL per kg for females.
• plasmaVolume: plasma volume in milliliters, the primary output of the calculator.

The simple weight method is the published clinical approximation used in most rapid transfusion and bypass estimates, and the Nadler 1962 equation is the published sex specific height and weight equation used when the height is known.

According to PubMed Nadler 1962 Blood Volume Prediction, total blood volume in liters is 0.3669 times height in meters cubed plus 0.03219 times weight in kilograms plus 0.6041 for adult males, and 0.3561 times height in meters cubed plus 0.03308 times weight in kilograms plus 0.1833 for adult females.

A second clinical tool that consumes the plasma volume number on the transfusion side is the Fresh Frozen Plasma Dose Calculator, which uses the same plasma volume to size a fresh frozen plasma dose for a target bump in coagulation factors.

Four concepts drive the result.

A second plasma chemistry tool that pairs with the calculated plasma volume during the same hematology and critical care workup is the Plasma Osmolality Calculator, which turns a basic metabolic panel into the calculated plasma osmolality and the osmolal gap.

The form works from a small set of demographics and lab values.

1. 1 Select the sex: use the sex selector to pick male or female. Both the Nadler 1962 equation and the simple weight method depend on this choice.
2. 2 Enter the body weight: type the patient's body weight in kilograms. The simple weight method scales linearly with weight, and the Nadler 1962 equation uses weight as one of the two input variables.
3. 3 Enter the body height or set to zero: type the patient's body height in centimeters to use the Nadler 1962 equation. Set height to 0 to use the 70 mL per kg or 65 mL per kg simple factor.
4. 4 Enter the hematocrit: type the patient's most recent hematocrit as a percent. A typical adult reference range is 38 to 52 percent for males and 36 to 48 percent for females.
5. 5 Read the plasma volume in milliliters: the result panel shows the plasma volume in mL, the total blood volume and blood cell volume in mL, the per kg in mL per kg with the 30 to 43 band, the method label, and a one line clinical interpretation.

A 70 kg male with a height of 175 cm and a hematocrit of 45 percent enters those three values plus the sex selector and gets a plasma volume of 2653 mL, a total blood volume of 4824 mL, a blood cell volume of 2171 mL, a per kg of 37.9 mL per kg, and a method label of Nadler 1962. The result supports a plasmapheresis donation plan or a bypass prime estimate.

A second clinical scheduling tool that pairs with the plasma donation workflow is the Blood Donation Due Date Calculator, which turns the most recent whole blood donation date and the interdonation interval into the next eligible donation date.

Using a plasma volume calculator offers several practical advantages over looking up a published table.

• • Standardized mL output: the calculator returns the plasma volume in milliliters, the unit used in every published plasmapheresis, bypass, and clinical fluid assessment workflow.
• • Two published methods in one form: the same form supports the simple 70 mL per kg and 65 mL per kg weight based estimate and the more accurate Nadler 1962 sex specific equation.
• • Transparent calculation: the total blood volume equation is shown in plain English so the user can see whether the calculator used the height based Nadler method or the simple weight method.
• • Built-in per kg band: the result is paired with the published 30 to 43 mL per kg adult reference band, the same range used in most adult hematology textbooks.
• • Companion blood cell volume output: the result panel also reports the blood cell volume in mL, which is the cellular side of the same total blood volume calculation.
• • Method label for cross-checking: the method label names Nadler 1962 or the simple weight factor so the user can recheck the calculation against the same method on a second tool or a published table.

A second clinical tool that uses a related blood volume concept on the pediatric side of the same workup is the Pediatric Transfusion Calculator, which sizes a packed red cell or platelet transfusion by weight and target hemoglobin change.

The output depends on the demographics and lab values entered and on the body habitus sitting in front of the calculator.

• • The plasma volume calculator is a clinical estimate, not a measured plasma volume. A tracer dilution study or a radioisotope labeled albumin study is still required when the user needs a measured plasma volume.
• • The Nadler 1962 equation was derived from non-obese adults and can overestimate the total blood volume in severely obese body habitus. The published Lemmens-Bernstein-Brodsky 2006 BMI adjusted equation is the recommended cross-check in that group.

According to PubMed Lemmens Bernstein Brodsky 2006, total blood volume in milliliters is weight in kilograms times 70 for males or 65 for females divided by the square root of (BMI divided by 22), which adjusts the simple weight factor for obese and non-obese body habitus.