Extracorporeal Arteriovenous Ultrasound Measurement of Cardiac Output in Small Children

Theodor S. Sigurdsson, M.D.; Anders Aronsson, M.D.; Lars Lindberg, M.D., Ph.D.

Disclosures

Anesthesiology. 2019;130(5):712-718. 

In This Article

Abstract and Introduction

Abstract

Background: Technology for cardiac output (CO) and blood volume measurements has been developed based on blood dilution with a small bolus of physiologic body temperature saline, which, after transcardiopulmonary mixing, is detected with ultrasound sensors attached to an extracorporeal arteriovenous loop using existing central venous and peripheral arterial catheters. This study aims to compare the precision and agreement of this technology to measure cardiac output with a reference method, a perivascular flow probe placed around the aorta, in young children. The null hypothesis is that the methods are equivalent in precision, and there is no bias in the cardiac output measurements.

Methods: Forty-three children scheduled for cardiac surgery were included in this prospective single-center comparison study. After corrective cardiac surgery, five consecutive repeated cardiac output measurements were performed simultaneously by both methods.

Results: A total of 215 cardiac output measurements were compared in 43 children. The mean age of the children was 354 days (range, 30 to 1,303 days), and the mean weight was 7.1 kg (range, 2.7 to 13.6 kg). The precision assessed as two times the coefficient of error was 3.6% for the ultrasound method and 5.0% for the flow probe. Bias (mean COultrasound 1.28 l/min − mean COflow probe 1.20 l/min) was 0.08 l/min, limits of agreement was ±0.32 l/min, and the percentage error was 26.6%.

Conclusions: The technology to measure cardiac output with ultrasound detection of blood dilution after a bolus injection of saline yields comparable precision as cardiac output measurements by a periaortic flow probe. The difference in accuracy in the measured cardiac output between the methods can be explained by the coronary blood flow, which is excluded in the cardiac output measurements by the periaortic flow probe.

Introduction

The clinical examination of a severely hemodynamically unstable child has obvious limitations and may give unreliable estimates of the overall hemodynamic status. The cause of arterial desaturation, degree of hypovolemia, and systemic hypoperfusion are parameters that may be particular difficult to evaluate because of compensatory mechanisms.[1–5] Easily adapted and safe monitoring devices with good reliability and reproducibility are needed to address these parameters, especially in children.[6–8]

An available invasive cardiac output (CO) measuring method, such as thermodilution technique, although applicable for adults, has size restrictions for use in young children and may cause a substantial risk of complications (bleeding, thrombosis, embolism, and arrythmia). Noninvasive methods are less accurate and precise in measuring CO in small children (electrical bioimpedance, carbon dioxide rebreathing, and Doppler methods), require high level of training (echocardiography), or are clinically impractical and time consuming (magnetic resonance imaging).[9,10]

A technology that uses ultrasound detection of blood dilution by means of a saline bolus injection and an extracorporeal arteriovenous loop between existing central venous and peripheral arterial lines has been developed for hemodynamic assessment in young children and neonates.[11] It is minimally invasive, because it uses existing catheters and does not require additional invasive procedures. It measures total CO, including coronary blood flow.

The hypothesis of the study is that blood dilution detected by ultrasound is comparable with the reference method, perivascular flow probe around aorta to determine cardiac output. The aim of the study was to estimate the precision of this technology in young children compared with CO measured by a perivascular flow probe around the aorta (reference method) through five simultaneously replicated CO measurements and to assess the agreement by quantifying the difference (bias) between the two methods.

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