# Cardiac Output by Thermodilution (Stewart-Hamilton)

Compute CO = V × (T_b − T_i) × 60 × 1.08 / A from a thermodilution curve, with optional cardiac index from BSA (normal 2.5–4.0 L/min/m²). Not medical advice.

> Canonical page: https://elysiatools.com/en/tools/cardiac-output-thermodilution

- **Category:** Health

- **Keywords:** cardiac output, thermodilution, stewart hamilton, swan ganz, pulmonary artery catheter, cardiac index, critical care, hemodynamics, icu, indicator dilution

## 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).

## Inputs

- **Injectate Volume (mL)** (number): Injectate volume in mL (usually 10 mL of iced or room-temperature saline/dextrose).
- **Blood Temperature (°C)** (number): Blood (pulmonary artery) temperature in °C.
- **Injectate Temperature (°C)** (number): Injectate temperature in °C: 0 for iced saline, ~21 for room temperature.
- **Thermodilution Curve Area (°C·s)** (number): Area under the thermodilution temperature-time curve (°C·s), as reported by the monitoring system.
- **Density Factor (optional)** (number): Injectate density factor (specific heat × specific gravity vs blood). Default 1.08.
- **Body Surface Area (m², optional)** (number): Body surface area in m²; if provided, the cardiac index CI = CO/BSA is computed.
- **Decimal Places** (number)

## 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

- Enter the injectate volume (mL), pulmonary artery blood temperature (°C), and injectate temperature (°C).
- Provide the area under the thermodilution temperature-time curve (°C·s) reported by the monitoring system.
- Optionally enter the density factor (default 1.08) and the patient's body surface area (m²).
- The 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.

## Frequently asked questions

### 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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