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Cardiac output
Problem Solution
￭
Allow the baseline to stabilize between
injections. If automatic program is not being
used, allow one minute between injections. If
automatic program is being used, follow the
monitor prompts to inject.
￭
It is also recommended that you inject at the
patient’s end expiration. This helps reduce any
respiratory noise and therefore lessens error.
￭
A minimum difference of 10° C (18° F)
between the patient blood temperature
and solution/injectate temperature is
recommended.
●
Respiration. The patient’s inspiratory/expiratory
cycle and placement of the catheter affects the
cardiac output value. Whenever the patient
inhales and exhales, the temperature in the lung
changes. During inspiration, the patient’s blood
temperature decreases and during expiration it
increases. Therefore, placement of the catheter
in relation to proximity of the lung fields affects
the baseline. If there is a significant amount of
respiratory noise on the patient’s baseline, cardiac
output may be calculated even if no injection was
performed. There is no differentiation between
temperature change caused by breaths versus
injections. It simply looks for a change in baseline
temperature.
●
Baseline blood temperature. As little as a half
a degree Celsius change in blood temperature
due to respiratory noise may cause a C.O. value
to be displayed when an injection has not been
performed. Using auto mode looks for a stable
baseline before allowing an injection.
●
Pulmonary artery catheter. The catheter itself may
be damaged (e.g., defective thermistor or defective
tubing).
●
Hemodynamics. The patient’s rhythm can affect
the cardiac output value. If cardiac output trials
are being done at a time when the patient has
arrhythmias, you may notice a discrepancy in the
cardiac output values.
●
Rapid IV solutions. Any rapid IV solution that is
infusing at the time when the solution is injected
can alter the cardiac output value. Maintain a
constant rate, or if possible, stop the solution 30
seconds before the C.O. injection and then restart
the infusion after the cardiac output is calculated.
272 CARESCAPE Modular Monitors 2062971-001