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A practical method of measuring oxygen consumption in children with complex mixing circulations by the use of
Daryl I Schantz1, Robert P Chen
1Department of Pediatric Cardiology, Dalhousie University, Halifax, Nova Scotia, Canada.
Insights
Predicting oxygen consumption (VO2) using standard formulas is unreliable in patients with bidirectional cavopulmonary anastomosis (BDCPA). Measured VO2 is essential for accurate pulmonary vascular resistive index (PVRI) assessment in this complex circulation group.
Area of Science:
- Cardiology
- Pediatric Cardiology
- Cardiovascular Physiology
Background:
- Complex congenital heart disease often involves altered hemodynamics.
- Patients with bidirectional cavopulmonary anastomosis (BDCPA) present unique circulatory challenges.
- Accurate assessment of oxygen consumption (VO2) is crucial for managing these patients.
Purpose of the Study:
- To describe a method for measuring VO2 and pulmonary vascular resistive index (PVRI) using thermodilution cardiac output.
- To evaluate the reliability of predicted VO2 formulas in patients with BDCPA.
- To determine the correlation between measured VO2 and other hemodynamic parameters.
Main Methods:
- Cardiac catheterization data from 25 patients with BDCPA were reviewed.
- Thermodilution cardiac output was used to calculate VO2 and PVRI.
- Correlations between predicted and measured VO2, and other hemodynamic parameters, were analyzed.
Main Results:
- No significant correlation was found between predicted and measured VO2 (r = -0.258, P = 0.21).
- A strong correlation was observed between the difference and the measured VO2 (r = 0.963, P < .0001), indicating formula unreliability.
- Body surface area and mixed venous oxygen content showed no significant or weak correlation with measured VO2, respectively.
Conclusions:
- Predicted VO2 formulas are unreliable for assessing PVRI in BDCPA patients.
- No single hemodynamic parameter reliably correlates with VO2 in this population.
- Direct measurement of VO2 is necessary for accurate PVRI determination in patients with BDCPA.
Objective:
We describe a method to measure oxygen consumption (VO2) and pulmonary vascular resistive index (PVRI) based on thermodilution cardiac output in patients with complex mixing circulations. We apply this method to patients with a bidirectional cavopulmonary anastomosis (BDCPA). We compare our measured VO2 with a predicted VO2 based on a formula using height and weight.
Methods:
We reviewed data based on cardiac catheterization and thermodilution cardiac output in a series of 25 catheterizations in patients with BDCPA. We used this data to measure VO2 and PVRI, and looked for a correlation between the predicted and measured VO2. We also assessed whether any other hemodynamic parameter correlated with measured VO2.
Results:
There was no significant correlation between the predicted and the measured VO2 (correlation coefficient = -0.258, P = .21). We did find a significant correlation in the difference between the measured and predicted VO2 against the measured VO2 such that at a lower measured VO2 the predictive formula tended to overestimate VO2 and at a higher VO2 the formula underestimated VO2 (correlation coefficient = 0.963, P < .0001). Body surface area did not correlate with measured VO2 (correlation coefficient = 0.28, P < .16). Mixed venous oxygen content showed a weak negative correlation with VO2 (correlation coefficient = -0.54, P = .005).
Conclusions:
An assessment of PVRI that is based on a predicted VO2 is unreliable in this patient population. No hemodynamic parameter correlated well with VO2. The use of a measured VO2 is necessary in determining PVRI in these patients.
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