Agreement of cardiac index measurements between ultrasonic cardiac output monitor and transthoracic echocardiography in neonates.

Objectives: To evaluate the agreement of cardiac index (CI) calculated by Ultrasonic sonic cardiac output monitor (USCOM) and transthoracic thoracic echocardiography (TTE) in order to know if we can recommend USCOM in our pediatric intensive care unit (PICU).

Design: Prospective observational evaluative study carried out over a period of 3 months Setting: PICU at children's hospital in Tunis Participants: All newborns without tracheostomy or a known congenital heart disease, admitted to the PICU during the study period were enrolled.

Interventions: Paired and consecutive measurements of CI were obtained in all patients with both technologies. All measurements by TTE and USCOM were performed by two distinct operators. It is the average of three successive measures of the CI, in the same patient, with each technology, which was considered. Agreement of CI between the 2 techniques was assessed by Bland-Altman analysis and percentage error.

Measurements and main results: Forty-two infants were analyzed with the mean (standard deviation) gestation 36 weeks ( 5 days), age 1 days (1.09) , and weight 2.9 kg (0.87). Respiratory failure was the main cause of admission 75%. At the time of the study, 33 (75.%) patients were ventilated artificially. Bias (mean difference) of the CI between the two methods was 1.2 l/min/m2 and precision (± 2 SD of differences) was 1.08 l/min/m2. The MPE of CI measurement for USCOM vs TTE was 54.9%.

Conclusions: The USCOM showed a poor agreement to TTE measures of CI. The two methods cannot be considered interchangeable.