Studies have found a relationship between fluid responsiveness and respiratory variation in the arterial blood flow peak velocity in the ascending aorta.
This was a prospective observational study of 30 infants undergoing cardiac surgery. Before and after the administration of 10ml · kg–1 crystalloid, established measures – respiratory variation of the aorta blood flow peak velocity, pulse pressure variation, and central venous pressure were obtained. The respiratory variation of the internal carotid artery blood flow peak velocity was measured using transfontanelle ultrasound.
In this study the respiratory variation of the internal carotid artery blood flow peak velocity as measured using transfontanelle ultrasound predicts an increase in stroke volume in response to an intravenous fluid bolus.
Cutoffs for respiratory variation were different than aortic velocity and further larger studies are needed in diverse populations before this potentially useful non-invasive fluid responsiveness assessment modality can be more widely recommended in infants.