Validation of cardiac output measurement by ultrasound dilution technique with pulmonary artery thermodilution in a pediatric animal model

Abstract

Novel COstatus system (Transonic Systems, Inc., NY), based on ultrasound dilution (UD), works off in situ arterial and central venous catheters in pediatric patients to measure cardiac output (CO). The purpose of the present study was to validate CO measurement by UD (COUD) with pulmonary artery (PA) thermodilution (COTD) in a prospective animal study. Ten anesthetized pigs (16-45 kg) were instrumented with pediatric PA, central venous, and peripheral artery catheters. For COUD measurements, normothermic saline (0.5-1.0 ml/kg body weight, up to a maximum of 30 ml) was injected into the venous limb of an arteriovenous loop that was connected between in situ catheters. For COTD measurements, 5-10 ml cold saline was injected into the PA catheter. Sixty-four averaged sets were obtained for comparison. COTD mean was 2.98 ± 1.21 l/min (range 1.33-6.29), and COUD mean was 2.68 ± 1.16 l/min (range 1.33-5.85). This study yielded a correlation r = 0.96, COUD = 0.91*(COTD) - 0.04 l/min; bias was 0.3 l/min with limits of agreement as -0.39 to 0.99 l/min; and the percentage error was 23.73% between the methods. CO measurements by UD agreed well with thermodilution measurements in the pediatric swine model.

Fig. 1

Schematic of the COstatus AV loop connected to the standard arterial and central venous catheters and the location of UD sensors. Using the roller pump, blood is circulated through the sterile AV loop from the artery to the vein without any blood loss for the duration (5–8 min) of measurements. During this time isotonic saline is injected into the venous end of the AV loop using the injection syringe. The venous sensor measures the injection volume, and the arterial sensor measures the dilution curve, from which the CO is calculated by Stewart-Hamilton equation. At the end of the session, the AV loop is flushed with heparinized saline from the flush syringe, and the blood from the AV loop is returned back to the venous side of the patient

Fig. 2

Correlation plot of COTD versus COUD in ten pigs (pediatric animal model)

Fig. 3

Bland–Altman plot of COTD and COUD