The authors measured the rate of carbon dioxide elimination (V̇CO2) in 25 pediatric patients (age 2 days to 9 yr) during total cardiopulmonary bypass at average venous blood temperatures ranging from 19.5 to 35.9°C. A multiplexed mass spectrometer was connected to the gas inlet and exhaust ports of the bubble oxygenator, and the gas-phase Fick principle was used to determine V̇CO2. A curvilinear relationship was found between log V̇CO2 and venous blood temperature, and a quadratic regression equation (r2 = 0.74) was fit to the data. Q10 (the ratio of V̇CO2 before and after a 10°C temperature change) was estimated to be 2.7 or 3.0, depending on the analytic method used. Venous blood temperature as a predictor variable explained a greater proportion of the variability of log V̇CO2 than did nasopharyngeal or rectal temperatures. Analysis of covariance revealed that total circulatory arrest during bypass (utilized in 10 patients for 34 ± 4 min, mean ± SEM) affected the relationship of venous blood temperature with log V̇CO2, by increasing the y-intercept (P = .008) but not the slope. These data, with associated 95% prediction intervals, define the expected CO2 elimination rates at various temperatures during standard bypass conditions in our patients. Real-time measurement of V̇CO2 using mass spectrometry can be a useful routine monitor during CPB that may help to assess patient metabolic function, adequacy of perfusion, and oxygenator performance.
All Science Journal Classification (ASJC) codes
- Anesthesiology and Pain Medicine