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

Abstract

Objective: To show the equivalence of the transpulmonary thermodilution method to the direct Fick principle in children. Design: Prospective single-centre study. Setting: A 16-bed paediatric cardiac ICU and a cardiac catheterisation laboratory at an university affiliated centre for paediatric cardiology and congenital heart disease. Patients: We consecutively investigated 18 patients (mean age 12.1±6.4 years) during cardiac catheterisation and after corrective cardiac operation. Methods and results: We prospectively defined limits of equivalence for cardiac index (CI) for both methods of +/-0.25 l/min·m2. 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 CIFick was 2.88±1.07 l/min·m2 (range 1.10-4.62 l/min·m2) and CITPID was 2.85±1.03 l/min·m2 (range 1.02-4.49 l/min·m2). The mean difference between CIFick and CITPID was 0.030±0.168 l/min·m2 and limits of agreement -0.306 to 0.366 l/min·m2 (90% confidence interval -0.040 to 0.099 l/min·m2). The regression equation was: CIFick=1.0244×CITPID-0.040, r2=0.976, P <0.0001. The intraclass coefficient of reliability for three repeated measurements of CITPID was 0.97, the corresponding lower limit of the 95% confidence interval was 0.94. Conclusion: 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.