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Monitoring of cardiac output by thermodilution after open-heart surgery
Insights
Thermodilution is a valid method for measuring cardiac output after open-heart surgery, showing superior reproducibility compared to dye-dilution. This technique is useful for assessing treatments and conditions in critically ill cardiac patients.
Area of Science:
- Cardiovascular Physiology
- Critical Care Medicine
- Medical Technology Assessment
Background:
- Accurate cardiac output monitoring is crucial in post-cardiac surgery patients.
- Existing methods like dye-dilution have limitations in reproducibility.
- Thermodilution offers a potential alternative for real-time assessment.
Purpose of the Study:
- To compare the accuracy and reproducibility of thermodilution and dye-dilution cardiac output measurements.
- To evaluate the clinical applicability of thermodilution in the immediate post-open-heart surgery period.
- To identify specific clinical scenarios where thermodilution may be particularly advantageous.
Main Methods:
- Simultaneous thermodilution and dye-dilution cardiac output measurements were performed.
- 125 determinations were made in 10 patients following open-heart surgery.
- Reproducibility was assessed using the coefficient of variation and linear regression analysis.
Main Results:
- Mean thermodilution cardiac output was slightly higher (1.6%) than dye-dilution.
- Thermodilution demonstrated superior reproducibility (CV 8.6%) versus dye-dilution (CV 12.3%).
- A strong correlation (r=0.9) was observed, with discrepancies noted at very low output states.
Conclusions:
- Thermodilution is a valid and reproducible method for cardiac output determination post-cardiac surgery.
- Its reliability supports use in dynamic clinical settings, including evaluating inotropic agents and intra-aortic balloon pump efficacy.
- Routine use in patients with moderate to severe heart disease (Class III/IV) is justified.
Abstract:
One hundred twenty-five separate cardiac output determinations were obtained after open-heart surgery in 10 patients by simultaneous use of thermodilution and dye-dilution techniques. Mean thermodilution cardiac output was 1.6 per cent greater than mean dye-dilution cardiac output (5.24 versus 5.16 L. per minute). Reproducibility of thermodilution cardiac output (coefficient of variation, 8.6 per cent) was superior to that of dye-dilution cardiac output (coefficient of variation, 12.3 per cent) for outputs ranging from 2.5 to 8.7 L. per minute (p less than 0.001). Linear regression analysis revealed a correlation showing that COtd = 0.86 COdye + 0.80 (r = 0.9, p less than 0.001) and indicating a similarity between thermodilution and dye-dilution output figures except in extremely low output states. In such cases, thermodilution cardiac output becomes progressively larger than dye-dilution cardiac output. The results indicate that thermodilution cardiac output is a valid method for determining cardiac output in the rapidly changing clinical setting following cardiopulmonary bypass. Clinical applications of this technique include evaluation of the efficacy of inotropic agents, effectiveness of intra-aortic balloon counterpulsation, and status of the low output syndrome postoperatively. Routine use in patients with Class III or IV cardiac disease appears justified.
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