Determination of cardiac output by an angle and diameter independent dual beam Doppler technique in critically ill infants

Abstract

Objective - To compare cardiac output measurements in critically ill infants by the dual beam Doppler and thermodilution techniques. Design - Prospective direct comparison of the two techniques. For statistical evaluation one randomly assigned paired measurement of every patient was used. Setting - Paediatric intensive care unit in a university hospital. Patients - 18 infants after open heart surgery aged 4-25 months (weight 4-10 kg). Interventions - Cardiac output measurements by dual beam Doppler and thermodilution techniques were performed within 10 minutes of each other and without knowledge of the results of the other methods. Multiple measurements were performed on some patients with a pharmacological or electrophysiological intervention or with a minimum of six hours between each pair of measurements. Measurements and main results - Three patients were excluded because of an inadequate Doppler signal or a significant residual shunt. Cardiac output measurements ranged from 0.4 to 2.2 l/min for the thermodilution technique and from 0.5 to 2.1 l/min for the dual beam Doppler technique. Agreement between both methods was acceptable. The mean difference between the two methods was 0.026 l/min with two standard deviations ranging from -0.20 to 0.26 l/min. Conclusion - The dual beam Doppler technique was shown to have promise for the non-invasive determination of cardiac output in critically ill infants.