Cardiac Output by Thermodilution (Stewart-Hamilton)

Cardiac Output by Thermodilution (Stewart-Hamilton) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Health
Input types: number
Output type: json
Sample coverage: 4
API ready: Yes

Overview

The Cardiac Output by Thermodilution calculator computes pulmonary blood flow using the Stewart-Hamilton equation from pulmonary artery catheter (Swan-Ganz) measurements. By evaluating injectate volume, blood and injectate temperatures, and the integrated temperature-time curve area, it calculates absolute cardiac output (L/min) and optional body surface area-adjusted cardiac index (L/min/m²).

When to use

Evaluating hemodynamic blood flow parameters after pulmonary artery catheter placement in intensive care settings.
Validating manual or automated thermodilution measurements obtained with iced (0°C) or room-temperature (~21°C) injectates.
Normalizing cardiac output against patient body surface area (BSA) to evaluate cardiac index during shock management.

How it works

1Enter the injectate volume (mL), pulmonary artery blood temperature (°C), and injectate temperature (°C).
2Provide the area under the thermodilution temperature-time curve (°C·s) reported by the monitoring system.
3Optionally enter the density factor (default 1.08) and the patient's body surface area (m²).
4The tool applies the Stewart-Hamilton formula CO = V × (T_b − T_i) × 60 × 1.08 / A to yield cardiac output and cardiac index.

Use cases

Verifying monitor-generated hemodynamic parameters in cardiothoracic intensive care units.
Tracking cardiac index trends during inotrope or vasopressor titration for shock patients.
Providing quantitative examples for hemodynamic physiology teaching and clinical simulation training.

Examples

1. Iced Injectate Hemodynamic Assessment

Critical Care Physician

Background

A postoperative cardiac surgery patient is monitored with a Swan-Ganz catheter for hemodynamic stabilization.

Problem

Calculate cardiac output and index using a 10 mL iced injectate at 0°C with an integrated curve area of 4795.2 °C·s and BSA of 1.8 m².

How to use

Input 10 mL for injectate volume, 37°C for blood temp, 0°C for injectate temp, 4795.2 for curve area, and 1.8 m² for BSA.

Outcome

Returns a cardiac output of 5.00 L/min and a normal cardiac index of 2.78 L/min/m².

2. Room-Temperature Injectate Calculation

ICU Nurse

Background

A patient with septic shock undergoes routine bedside cardiac output measurement using room-temperature saline.

Problem

Determine cardiac output using 10 mL saline at 21°C, core blood temperature of 37°C, and a curve area of 2592 °C·s.

How to use

Set injectate volume to 10 mL, blood temp to 37°C, injectate temp to 21°C, and curve area to 2592.

Outcome

Computes a cardiac output of 4.00 L/min within normal physiological resting limits.

FAQ

What is the standard normal range for cardiac output and cardiac index?

Normal resting cardiac output is typically 4.0 to 8.0 L/min, and normal cardiac index is 2.5 to 4.0 L/min/m².

What does the 1.08 density factor represent?

It is a constant accounting for the specific heat and specific gravity ratio between the injectate solution and blood.

Can room-temperature saline be used instead of iced injectate?

Yes, room-temperature saline can be used because the equation automatically accounts for the smaller temperature gradient.

How does curve area relate to cardiac output?

Cardiac output is inversely proportional to curve area; a larger area corresponds to a lower cardiac output.

What conditions can distort thermodilution results?

Severe tricuspid regurgitation, intracardiac shunts, and uneven or slow injection rates can distort curve shape and accuracy.

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Key facts

Overview

When to use

How it works

Use cases

Examples

1. Iced Injectate Hemodynamic Assessment

2. Room-Temperature Injectate Calculation

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