MEASURING CARDIAC-OUTPUT DURING CARDIAC-C ATHETERIZATION - MARKED DIFFERENCES BETWEEN DIRECT FICK CARDIAC-OUTPUT AND THERMODILUTION

During cardiac catheterization (cath) there are often marked differenc es between cardiac output measured by thermodilution as compared to di rect Fick cardiac output. using assumed values of oxygen uptake (V-02) . In 50 patients cardiac output was determined during: cath by thermod ilution as well as by direkt Fick, using assumed values of oxygen upta ke, Thermodilution cardiac output was 5.9 +/- 1.8 l/min as compared to direct Fick cardiac output of 4.3 +/- 1.3 l/min (p < 0.0001). The mea n difference between the two methods in percent was -43%. There was a linear correlation between the two measurements with a Pearson correla tion of 0.69 (p < 0.0001). In 29 patients oxygen uptake was measured d irectly using breath-by-breath gas exchange measurements during cath i mmediately before the beginning of the investigation (Aktuell-1) and d uring the investigation (Aktuell-2). These values were compared to tho se of a nomogramm derived from basal metabolic rate studies on normal subjects. Mean oxygen uptake using the nomogramm was 220 +/- 33 ml/min . These values were not significantly different to Aktuell-1 values of 217 +/- 56 ml/min (p = 0.8110), but there was a significant differenc e between Aktuell-1 and Aktuell-2 values (217 +/- 56 ml/min versus 257 +/- 66 ml/min, p = 0.0228). Conclusion: The use of assumed values of oxygen uptake leads to a considerable underestimation of actual oxygen uptake during cardiac catheterization. Therefore to calculate direkt Pick cardiac output during cath oxygen uptake should be measured direc tly or thermodilution should be used.