Cardiac output (C.O.)
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Instructions for use – Infinity Acute Care System – Monitoring Applications VG6.n
Overview of cardiac output monitoring
The M540 uses the thermodilution method to
compute cardiac output (C.O.) for adult and
pediatric patients. Cardiac output monitoring is not
intended for neonatal patients.
The MPod – QuadHemo, Hemo4, and Hemo2 pods
connect to the M540 and acquire the blood and
injectate temperatures which are used to compute
the cardiac output value.
Although the M540 processes the cardiac output
algorithms, you can only view the data and execute
cardiac output functions on the Cockpit.
Cardiac output measurement method
A solution of known temperature and volume is
injected into the blood stream in the right atrium. A
thermistor in the catheter tip continuously
measures the temperature of the blood as it leaves
the heart. The injectate mixes with and cools the
surrounding blood. The blood reaches its minimum
temperature relatively quickly and then warms up
slowly until it returns to the baseline blood
temperature. The total drop in blood temperature is
inversely related to the cardiac output of the patient.
The lower the cardiac output value, the more the
injectate cools the blood.
When computing cardiac output, the M540 takes
the following factors into account:
– Injectate volume, temperature, density, and
specific heat of the fluid that is being injected
– Baseline blood temperature, density, and
specific heat of the blood
– Temperature changes of the blood injectate
mixture
– Area under the temperature waveform
The M540 supports the automatic and manual
measuring modes.
The cardiac output monitoring functions are
configurable in the parameter-specific setup page
and the
Procedures
>
C.O.
page (see page 333).
Before performing any monitoring functions, refer
to the section "For your safety and that of your
patients" on page 13. Parameter-specific error
messages are listed on page 539.
Supported parameters
– C.O. – Cardiac output
– Tblood – blood temperature
– Tinj – injectate temperature
C.O. precautions
WARNING
An incorrect computation constant may yield
incorrect cardiac output measurements and
put the patient at risk. Confirm that the
manually entered computation constant is
correct for the catheter you are using.
WARNING
Verify that you enter the patient’s current
weight (not his or her ‘admit’ weight). Failure
to enter an accurate weight value can result in
inaccurate calculations and put the patient at
risk.
