Clinical validation of cardiac output measurements using femoral artery thermodilution with direct Fick in ventilated children and infants.

OBJECTIVE

To validate clinically cardiac output (CO) measurements using femoral artery thermodilution in ventilated children and infants by comparison with CO estimated from the Fick equation via a metabolic monitor.

DESIGN

Prospective, comparison study.

SETTING

Paediatric intensive care unit of a university hospital.

PATIENTS

24 ventilated infants and children, aged 0.3 to 175 months (median age 19 months).

INTERVENTIONS

Oxygen consumption measurements were made and averaged over a 5-min period, at the end of which arterial and mixed venous blood samples were taken and oxygen saturations measured by co-oximetry, with CO being calculated using the Fick equation. Over this 5-min period, five sets of femoral arterial thermodilution (FATD) measurements were made and averaged. One comparison of CO values was made per patient.

RESULTS

Mean Fick CO was 2.55 l/min (range 0.24 to 8.71 l/min) and mean FATD CO was 2.51 l/min (range 0.28-7.96 l/min). The mean bias was 0.03 l/min (95% confidence interval -0.07 to 0.14 l/min), with limits of agreement of -0.45 to 0.52 l/min. When indexed to body surface area, the mean Fick cardiac index became 3.51 l/min per m2 (1.52-6.98 l/min per m2) and mean FATD 3.49 l/min per m2 (1.74-6.84 l/min per m2). The mean bias was 0.02 l/min per m2 (95% confidence interval -0.11 to 0.15 l/min per m2) with limits of agreement of-0.57 to 0.61 l/min per m2. The mean FATD coefficient of variation was 5.8% (SEM 0.5%).

CONCLUSIONS

FATD compares favourably with Fick derived CO estimates in infants and children and may represent an advance in haemodynamic monitoring of critically ill children.