TITLE

Measurement of systemic carbon dioxide production during cardiopulmonary bypass: a comparison of Fick's principle with oxygentor exhaust output

AUTHOR(S)
Alston, R. Peter; Glassford, Neil J.; Torrie, Amanda
PUB. DATE
November 2003
SOURCE
Perfusion;Nov2003, Vol. 18 Issue 6, p339
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
Theoretically, systemic carbon dioxide (VCO[sub 2]) production should be an alternative means to systemic oxygen uptake (VO[sub 2]) for estimating the global efficacy of cardiopulmonary bypass (CPB). This study compared two methods of estimating VCO : Fick's principle and oxygenator exhaust carbon dioxide (CO[sup 2]) output. Both of these estimates were then compared with VO[sup 2]. Fifty-one patients (39 male and 12 female) undergoing elective cardiac surgery requiring CPB were studied. Blood sampling was performed and measurements recorded during active cooling, environmental cooling/stable hypothermia and during rewarming. Blood samples were measured for CO[sup 2] tension from which content was estimated. VCO[sub 2] was calculated as the product of the arteriovenous difference in CO[sub 2] content and pump flow rate (Fick's principle), or the fresh gas flow rate and concentration of the oxygenator exhaust CO[sub 2] (output technique). Over all measurements, method comparison analysis revealed - alarge mean bias of 41 (95% confidence intervals (CI) 32 50) mL/min with very wide limits of agreement ( - 23, 105 mL/min). Regression analysis found that the bias was also proportional to the size of measurement (β= 0.75 (95% CI 0.55, 0.95)). Although both methods of VCO[sub 2] correlated significantly with VO[sub 2] (p < 0.01), regression analysis found that the coefficients (β) of both techniques had wide CI (Fick's principle: β= 1.37 (95% CI 1.20, 1.54); output technique: β= 0.58 (95%CI 0.44, 0.71)). In conclusion, both techniques of VCO[sub 2] cannot be used interchangeably, and both are imprecisely related to VO[sub 2] as estimated by Fick's principle.
ACCESSION #
12087818

 

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