Cardiac output determination in children: equivalence of the transpulmonary thermodilution method to the direct Fick principle.

Abstract

To show the equivalence of the transpulmonary thermodilution method to the direct Fick principle in children. Prospective single-centre study. A 16-bed paediatric cardiac ICU and a cardiac catheterisation laboratory at an university affiliated centre for paediatric cardiology and congenital heart disease. We consecutively investigated 18 patients (mean age 12.1 +/- 6.4 years) during cardiac catheterisation and after corrective cardiac operation. We prospectively defined limits of equivalence for cardiac index (CI) for both methods of +/- 0.25 l/min x m(2). We measured oxygen consumption for determination of CI by Fick as the clinical "gold standard" and performed a set of three transpulmonary thermodilution measurements. The mean CI(Fick) was 2.88 +/- 1.07 l/min x m(2) (range 1.10-4.62 l/min x m(2)) and CI(TPID)was 2.85 +/- 1.03 l/min x m(2)(range 1.02-4.49 l/min x m(2)). The mean difference between CI(Fick) and CI(TPID)was 0.030 +/- 0.168 l/min x m(2), and limits of agreement -0.306 to 0.366 l/min x m(2)(90% confidence interval -0.040 to 0.099 l/min x m(2)). The regression equation was : CI(Fick)=1.0244 x CI(TPID)-0.040, r(2) = 0.976, P < 0.0001. The intraclass coefficient of reliability for three repeated measurements of CI(TPID) was 0.97, the corresponding lower limit of the 95% confidence interval was 0.94. We demonstrated the equivalence of CI measurement by transpulmonary thermodilution and the Fick principle in children. This new method may improve hemodynamic monitoring and management in seriously ill children.