What is DO₂i (Oxygen Delivery Index) and what target range is used during CPB?

DO₂i (Oxygen Delivery Index) measures how much oxygen the heart delivers to body tissues per minute per square meter of body surface area, expressed in mL O₂/min/m². During normothermic cardiopulmonary bypass, target DO₂i is typically ≥280–300 mL/min/m² to prevent tissue hypoxia and anaerobic metabolism. Infants and neonates often require higher targets (≥350–380 mL/min/m²) due to elevated metabolic rates.

Does this perfusion calculator store or send patient data?

No. This is a static HTML-based calculator that runs entirely within your browser—all calculations are performed locally. No patient health information (PHI), clinical inputs, or personal data are saved to a database, sent to external servers, or transmitted over the internet. Your privacy and data security are completely protected.

Is this a medical device or replacement for clinical judgment?

This perfusion calculator is an educational tool for healthcare professionals and is not a medical device. It does not replace clinical judgment, institutional protocols, or direct patient monitoring. Results are for reference only. Always verify calculations manually and follow your facility's perfusion management guidelines and physician orders when managing oxygen delivery during cardiopulmonary bypass.

Perfusion Tools – CPB & ECMO Perfusion Calculators

Perfusion Tools provides evidence-based calculators for BSA, cardiac index (CI), DO2i, pump flow, and heparin dosing to support goal-directed perfusion during CPB and ECMO.

Goal-Directed Perfusion (GDP) Calculator

Set a DO₂i target and evaluate whether current pump flow is adequate.

Target DO₂i

Select a preset goal or enter a custom value.

Custom

Height (cm)

Weight (kg)

BSA (m²) * auto-calc

Formula

Hemoglobin (g/dL) *

Temperature (°C)

PaO₂ (mmHg) *

SaO₂ (%) *

Current pump flow (L/min)

Calculated CaO₂ (mL/dL)

* Required for DO₂i and target flow calculation. Temperature and current flow are optional.

Required pump flow

—

Current DO₂i

—

Status

Awaiting data

Provide required inputs to evaluate target vs. current flow.

Enter current flow to visualize DO₂i vs. target

This GDP calculator uses standard DO₂i formula: DO₂i = (Flow ÷ BSA) × CaO₂ × 10. Required flow is DO₂i × BSA ÷ (CaO₂ × 10).

Clinical decisions must follow institutional protocols and consider lactate, SvO₂/ScvO₂, urine output, and perfusion pressures.

▶ Methodology

Arterial oxygen content (CaO₂)

CaO₂ (mL/dL) = 1.34 × Hb (g/dL) × (SaO₂ / 100) + 0.0031 × PaO₂ (mmHg). We assume a Hüfner constant of 1.34 mL O₂ per gram of Hb and a dissolved O₂ coefficient of 0.0031 mL·dL⁻¹·mmHg⁻¹. The contribution of dissolved O₂ is usually small at normal PaO₂.
Indexed oxygen delivery (DO₂i)

DO₂i (mL/min/m²) = (Pump flow ÷ BSA) × CaO₂ × 10. Pump flow is entered in L/min and BSA in m². Multiplying by 10 converts CaO₂ from mL/dL to mL/L so that the final unit is mL O₂ per minute per m².
Temperature-adjusted metabolic demand

Patient temperature strongly affects whole-body oxygen consumption (VO₂). As a simplifying assumption, this calculator applies a Q₁₀-type relationship where VO₂ falls as temperature decreases from 37 °C, but a “dampened” curve is used so that targets do not drop as steeply as metabolic rate. This reflects common clinical practice: hypothermia reduces demand, but we still maintain a safety margin for organs such as the kidney and brain.
Target DO₂i bands (Goal-Directed Perfusion)

At normothermia (≈37 °C) many adult CPB programs aim to maintain DO₂i ≥ 280–300 mL/min/m² to reduce the risk of anaerobic metabolism and postoperative acute kidney injury. At lower temperatures the calculator reduces the recommended target range, but never below a conservative lower floor (e.g. around 220 mL/min/m²), even when theoretical VO₂ would allow lower values. Targets are displayed as “Low / Borderline / Target / High” bands on the gauge for quick bedside interpretation.
Required pump flow for a chosen DO₂i goal

For a selected DO₂i target, the corresponding pump flow is: Required flow (L/min) = (Target DO₂i × BSA) ÷ (CaO₂ × 10). This is a theoretical value based on current Hb, SaO₂, PaO₂ and BSA. In practice, flow should also respect institutional minimum/maximum flow policies and patient-specific constraints (e.g. cannula size, arterial pressure, ventricular distension).
Clinical use and limitations

The calculator is intended to support goal-directed perfusion, not to replace local protocols or clinical judgment. Final flow and DO₂i settings should always be interpreted together with:
- Mixed or central venous saturation (SvO₂/ScvO₂)
- Lactate trends
- Urine output and other organ-perfusion markers
- Hemodynamics and surgical field conditions
All formulas assume complete mixing in the CPB circuit and do not account for ongoing blood loss, retransfusion, or major changes in oxygen extraction. Values are approximate and for educational use by trained clinicians only.

Body Surface Area

BSA Calculator

Enter height and weight to calculate BSA and perfusion flow guidance.

BSA (m²)

0.00

Updates in real time

Height (cm)

Weight (kg)

Formula

Mosteller is the clinical default; switch formulas as needed.

BSA Output

—

Calculated from height and weight only.

Formula

Mosteller

Blood Flow Rate by Cardiac Index

Scaled from the BSA result below.

CI 1.0–3.0

▶ Methodology

What is BSA and why does it matter?

Body surface area (BSA) is an estimate of a patient’s external body size. In perfusion it is used to index pump flow, DO₂i, drug dosing and heat-exchange settings. All formulas below use Height in cm and Weight in kg and are empiric fits to population data – they are not exact, but close enough for clinical use when applied consistently.

Mosteller formula

Mosteller:

BSA = √((Height(cm) × Weight(kg)) / 3600)

Very simple and fast to calculate (only one square-root).
For most adults with BMI 18–35, it gives values very close to more complex formulas.
Because of its simplicity, it has become a de-facto clinical default in many CPB and ECMO centers.

DuBois & DuBois formula

DuBois:

BSA = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425

Historical “reference standard” derived from direct body-surface measurements on a small adult cohort.
Slightly lower BSA than Mosteller in very light or very heavy patients, but differences are usually <3–5%.
Still used in some pharmacology and physiology papers, so it is useful when you want to reproduce values from the literature.

Haycock formula

Haycock:

BSA = 0.024265 × Height(cm)^0.3964 × Weight(kg)^0.5378

Developed from a large pediatric dataset.
Generally considered to have better accuracy in infants and children, especially in low-weight ranges.
Many pediatric cardiac programs prefer Haycock when indexing flow or valve/vascular dimensions.

Gehan–George / Boyd or other “obesity-friendly” formulas

These formulas adjust the exponents or constants to behave more realistically in patients with very high body weight or BMI.
They tend to give slightly lower BSA than Mosteller in severe obesity, avoiding extreme indexed values that clearly do not match the patient’s physiologic reserve.
Useful when you want to perform sensitivity analysis in obese patients (e.g. compare “standard BSA” vs “obesity-adjusted BSA”).

Practical tips for perfusionists

For general adult CPB/ECMO, using Mosteller as the default is reasonable and widely accepted.
For pediatric cases, consider Haycock (or your institutional standard) and keep the same formula throughout the case and across all flow/DO₂i calculations.
In obese patients (BMI ≥30), you may compare Mosteller vs an obesity-adjusted formula (e.g. Gehan–George / Boyd) to understand how much BSA – and therefore CI/DO₂i – changes.
More important than the “perfect” formula is internal consistency: once your program chooses a BSA formula, use it across perfusion flows, DO₂i targets, drug dosing and documentation.
Remember that BSA is only a surrogate for metabolic demand. Always interpret indexed values together with clinical context (temperature, SvO₂/ScvO₂, lactate, urine output, organ function).

Predicted Hct on CPB

Dilutional hematocrit calculator

Patient Type (EBV Coef)

EBV Coef (mL/kg)

Weight (kg)

Pre-CPB Hct (%)

Circuit Volumes

Prime Volume (mL)

Addl. Crystalloid (mL)

Ultrafiltration Removed (mL)

Blood Products

RBC Units

Vol/Unit (mL)

Unit Hct (%)

EBV

Total Vol

Result Hct

Clinical Context

• Target Hct: Often 21–25% on bypass. Lower Hct reduces viscosity but also oxygen carrying capacity.

• Adjustments: Reducing prime volume (RAP/VAP) or adding RBCs increases Hct. Adding crystalloid decreases Hct.

• Hemoconcentration: Use Ultrafiltration (UF) to remove plasma water and increase Hct.

For educational use only.

▶ Methodology

Estimated blood volume (EBV)

This calculator uses a simple weight-based model for circulating blood volume: EBV (mL) = Weight (kg) × EBV coefficient (mL/kg). Typical default coefficients are:
- Adult male: 70 mL/kg
- Adult female: 65 mL/kg
- Child: 75 mL/kg
- Infant: 80 mL/kg
- Neonate: 90 mL/kg
These values are derived from population averages and may be adjusted in this tool when clinical judgment suggests a higher or lower blood volume (e.g. severe obesity, cachexia, fluid overload or dehydration).
Pre-CPB red cell volume

Pre-bypass red cell volume is estimated from the patient’s hematocrit (Hct) and EBV: RBC_patient (mL) = EBV × (Pre-CPB Hct ÷ 100). This assumes the pre-CPB Hct is measured after induction and line placement, and that blood is evenly distributed in the circulation.
Circuit prime and crystalloid / ultrafiltration

The total intravascular volume at the time of sampling is modeled as:

V_total (mL) = EBV + Prime volume + Additional crystalloid / colloid + RBC product volume − Ultrafiltration removed.

“Prime volume” includes the cardiopulmonary bypass circuit prime and any pre-bypass volume added directly to the patient through the circuit. “Additional crystalloid” represents fluids such as cardioplegia carrier solution, albumin, mannitol, or other volume expanders that effectively dilute the circulating red cell mass. “Ultrafiltration removed” accounts for hemoconcentration techniques (UF, MUF, Z-BUF) that remove plasma water and reduce total volume.
Packed red blood cell (RBC) products

Red cell volume contributed by transfused RBCs is modeled as:

RBC_products (mL) = (Number of units × Volume per unit) × (Unit Hct ÷ 100).

Default values often assume ~300 mL/unit with a unit Hct around 60%, but these may be adjusted to reflect local blood bank characteristics or specific product labels.
Predicted hematocrit on CPB

The predicted hematocrit after mixing patient blood, prime, additional fluids and RBC products is:

Predicted Hct (%) = (RBC_patient + RBC_products) ÷ V_total × 100.

This represents a simple mixing model at the time of interest (e.g. shortly after going on CPB or after a planned RBC addition). It assumes complete and rapid mixing in the circuit and does not automatically account for ongoing bleeding, cell saver reinfusion, or major changes in plasma volume after the calculation.
Clinical interpretation and typical targets

Many adult programs aim for an on-pump Hct around 21–30%, balancing lower viscosity and improved microcirculatory flow against adequate oxygen carrying capacity. Pediatric and neonatal patients often require higher Hct targets because of limited physiologic reserve and higher relative metabolic demand. Hct targets should be individualized according to patient age, comorbidities (e.g. cerebrovascular disease, coronary disease, pulmonary hypertension), procedural complexity, and institutional policy.

This calculator is intended to support planning of prime composition, ultrafiltration strategy and transfusion timing. Final decisions must be based on real-time laboratory measurements, hemodynamics, organ perfusion markers and local protocols.
Limitations

This is an approximate model for educational and decision-support use only. It does not replace actual Hct measurement from arterial or venous blood samples, nor does it account for:
- Acute intra-operative blood loss not yet replaced,
- Large volume cardiotomy suction return or cell-saver reinfusion,
- Rapid shifts between intravascular and extravascular compartments,
- Changes in temperature-dependent plasma volume or hemoconcentration beyond the entered UF value.
Always verify predicted values with real laboratory data and use clinical judgment when adjusting CPB flow, prime strategy or transfusion.

Lean Body Mass LBM

Fat-free body mass calculator

Height (cm)

Weight (kg)

Sex

Formula

BSA Formula

LBM Result

0 kg

BMI

—

BSA (Actual)

—

Mosteller formula

BSA (Lean)

—

Boer/Hume LBM — kg

Flow comparison table (CI 1.0 – 3.0)

BSA actual vs BSA lean flow comparison

CI	Flow (Actual BSA)	Flow (Lean BSA)

Clinical Notes

• LBM Definition: Total body weight minus adipose tissue mass (fat-free mass).

• Clinical Use: Drug dosing, nutritional assessment, and metabolic calculations.

• Formulas: Hume (1966) and Boer (1984) equations are commonly used in clinical practice.

For educational use only. Not medical advice.

▶ Methodology

1. Definition of Lean Body Mass (LBM)

Lean body mass represents total body weight minus adipose tissue mass (fat-free mass). In perfusion and anesthesia it is often used as a surrogate for metabolically active tissue, which better reflects drug distribution and oxygen demand than total body weight in obese patients.

2. LBM formulas used in this calculator

Two adult LBM equations are provided. Height is in centimeters and weight in kilograms.

Boer (1984) – commonly recommended for adults, including obesity

Male: LBM (kg) = 0.407 × Weight + 0.267 × Height − 19.2

Female: LBM (kg) = 0.252 × Weight + 0.473 × Height − 48.3

Hume (1966) – earlier reference formula

Male: LBM (kg) = 0.32810 × Weight + 0.33929 × Height − 29.5336

Female: LBM (kg) = 0.29569 × Weight + 0.41813 × Height − 43.2933

The calculator allows switching between Boer and Hume so clinicians can compare results when evaluating very obese or very underweight patients.

3. BMI and BSA (actual)

BMI (kg/m²) = Weight (kg) ÷ [Height (m)]². BMI is shown for context only (e.g., normal range 18.5–24.9, obesity ≥30).

Actual Body Surface Area – BSA (Mosteller)

BSA_actual (m²) = √{ [Height (cm) × Weight (kg)] ÷ 3600 }.

Mosteller is widely used in clinical practice because it is simple and performs well across a broad range of body sizes.

4. Lean BSA based on LBM

To approximate the body surface area of lean mass only, the calculator first computes LBM (Boer or Hume) and then applies the same Mosteller structure using lean weight:

BSA_lean (m²) = √{ [Height (cm) × LBM (kg)] ÷ 3600 }.

This “lean BSA” is not a directly measured parameter, but a derived index that helps visualize how much of the patient’s large BSA is due to fat mass versus lean tissue.

5. Flow comparison table (CI 1.0–3.0)

The flow table shows how perfusion flow requirements change when indexed to actual BSA and lean BSA.

Flow_actual (L/min) = CI × BSA_actual

Flow_lean (L/min) = CI × BSA_lean

This allows quick comparison such as “At CI 2.4 L/min/m², how much flow do I deliver if I index to full BSA?” and “If I index to lean BSA instead, how much lower would the flow be for the same CI?”

In markedly obese patients, BSA_actual may suggest very high flows that exceed what is needed for metabolically active tissue, while BSA_lean can illustrate a more physiologic lower bound. Final flow selection must still consider SvO₂, lactate, arterial pressure, and institutional protocols.

6. Intended use and limitations

These formulas are validated for adults; they are not intended for pediatric patients. LBM and lean BSA are estimates, not direct measurements. Fluid shifts, edema, sarcopenia and extreme body habitus can all reduce accuracy.

The flow comparison table is a decision-support aid, not a prescription. Perfusion strategy should always be guided by real-time clinical monitoring and local guidelines.

For educational use only. Not medical advice or a regulated medical device.

Time Calculator

Enter 24-hour start/end times to see elapsed minutes and an H:MM readout.

시계 아이콘을 누르면 현재 시간이 입력됩니다.

Start time

End time

Duration

Start time

End time

Duration

Start time

End time

Duration

Start time

End time

Duration

Start time

End time

Duration

▶ Methodology

1. Purpose

This time calculator is designed to quickly estimate elapsed time in minutes and H:MM format between two clock times. It is intended for tasks such as documenting CPB time, cross-clamp time, cardioplegia intervals, ECMO procedure time blocks, or other peri-operative events where only start and end times are known.

2. Input format

Times are entered in 24-hour format as HH:MM.

Valid range: 00:00–23:59.

Examples: 07:15, 13:40, 21:05.

The fields accept four digits; after four digits are typed (e.g., 1345), the value is auto-formatted to 13:45.

Each row is independent and can be labelled (e.g., “CPB on–off”, “Cross-clamp”, “Circulatory arrest”).

3. Core calculation

For each row:

Convert start and end times to total minutes from midnight:

totalMinutes = 60 × HH + MM

If the end time is later or equal to the start time (same day):

durationMinutes = endMinutes − startMinutes

If the end time is earlier than the start time, the tool assumes the interval crosses midnight and adds 24 hours:

durationMinutes = (endMinutes + 24 × 60) − startMinutes

The result is reported as:

Minutes (integer), and
H:MM format, obtained by: hours = floor(durationMinutes ÷ 60) and minutes = durationMinutes mod 60, displayed as H:MM with a leading zero for minutes (e.g., 3:05).

4. Validation and rounding

Inputs outside 00:00–23:59 are rejected.

Seconds are not supported; any sub-minute timing should be rounded to the nearest minute before entry.

All durations are exact in minutes; no additional rounding is applied.

5. Clinical use & limitations

Useful for: CPB pump time, cross-clamp time, circulatory arrest time; cardioplegia dosing intervals or ECMO procedure segments; operating room or ICU workflow time stamps.

The calculator does not store dates and cannot distinguish different calendar days; any interval longer than 24 hours must be split manually.

Results are for documentation and workflow support only and do not replace clinical records, perfusion charts, or institutional time-keeping systems. For educational use only. Not medical advice or a regulated medical device.

Heparin Management (CPB)

Calculate an initial loading dose for CPB and view an optional risk-adjusted range when heparin resistance factors are present.

1. Base dose (Standard)

Actual body weight Ideal body weight

Actual weight (kg)

Ideal weight (kg)

Height (cm) (IBW calculation, optional)

Sex

BSA (m²) copy from BSA tab

Target ACT (reference)

Heparin protocol

Heparin concentration (U/mL)

e.g. 1,000 U/mL or 5,000 U/mL

2. Risk-adjusted dose (Optional)

Check risk factors that increase heparin resistance. The calculator applies empirical multipliers to display a suggested range rather than a single number.

Sepsis / SIRS / CRP > 100 (×1.2–1.4) ATIII < 70% (×1.4–1.8) Pediatric < 15 kg (×1.3–1.5) Obesity (BMI > 35, IBW-based dosing) Recent LMWH use (×1.2–1.5)

Obesity factor will also encourage IBW dosing when height/sex are provided.

Perfusion Tools – CPB & ECMO Perfusion Calculators

Goal-Directed Perfusion (GDP) Calculator

BSA Calculator

Blood Flow Rate by Cardiac Index

What is BSA and why does it matter?

Mosteller formula

DuBois & DuBois formula

Haycock formula

Gehan–George / Boyd or other “obesity-friendly” formulas

Practical tips for perfusionists

Predicted Hct on CPB

Clinical Context

Lean Body Mass LBM

Flow comparison table (CI 1.0 – 3.0)

Clinical Notes

Time Calculator

Heparin Management (CPB)

1. Base dose (Standard)

2. Risk-adjusted dose (Optional)

Frequently Asked Questions

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