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Thermodilution cardiac output measurement with a large left-to-right shunt
1Department of Anesthesia, Stanford University School of Medicine, CA 94305-5117.
Insights
The thermodilution method may inaccurately measure cardiac output in patients with left-to-right shunts. Slow injectate injection can lead to measuring systemic instead of pulmonary blood flow.
Area of Science:
- Cardiology
- Medical Devices
- Physiology
Background:
- Cardiac catheterization is a diagnostic procedure.
- Thermodilution is a common method for measuring cardiac output.
- Left-to-right shunts can complicate cardiac output measurements.
Observation:
- Thermodilution cardiac output measurement was performed in a patient with a left-to-right shunt.
- The measured flow appeared to represent systemic rather than pulmonary blood flow.
Findings:
- Slow injection of the thermodilution injectate in the presence of a large left-to-right shunt caused the discrepancy.
- Theoretical curves illustrate how injection duration and shunt size affect thermodilution measurements.
Implications:
- Clinicians should be aware of potential inaccuracies when using thermodilution in patients with significant left-to-right shunts.
- Further research may be needed to refine thermodilution techniques for complex cardiac conditions.
- Accurate cardiac output assessment is critical for patient management and treatment decisions.
Abstract:
Cardiac output was measured by the thermodilution method in a patient with a left-to-right shunt undergoing cardiac catheterization. It appeared that the thermodilution method measured systemic rather than pulmonary blood flow. This occurred because of the slow injection of injectate in the presence of a large left-to-right shunt. Theoretical thermodilution cardiac output curves are provided to illustrate the interaction of these two factors when three different durations of injection and four different shunt sizes are used.