Blood velocity waveforms in peripheral arteries vary such that decreasing vascular resistance results in a relative increase in diastolic velocity a t steady state.
We measured blood velocity in renal arteries of 20 children (age: 119 months * 37 months; weight: 38 kg 2 15 kg) to establish normal values, and to explore the relationship between these waveforms and central hemodynamics. Using image-directed pulsed Doppler echocardiography, M-mode measurements and cardiac index were recorded. Renal hila were visualized via the flank for Doppler sampling. Peak systolic velocity (A) and minimal diastolic velocity 03) were determined. The results (mean 2 SD) were as follows: Renal artery AIB = 2.9 2 0.74 (range 1.9 to 5.1). Characteristic waveforms were identical bilaterally and had continuous diastolic foward flow: AIB was independent of central hemodynamics within the resting normal range, varying inversely with age and size. Indexing Words: Doppler waveforms -Renal artery -Pediatrics
The kidney plays a central role in maintaining homeostasis, responding through its autoregulatory mechanisms to abnormalities in cardiovascular function such as congestive heart failure and hypertension. Adaptive mechanisms altering renal vascular resistance frequently involve complex factors at the ultrastructural level, and although great interest exists in investigating changes in renal hemodynamics relative to central cardiovascular status,' such alterations are difficult to assess directly in the pediatric population. Previously, the measurement of renal vascular resistance was possible only through the use of techniques involving intravascular catheters and infused indicators.
Recent technologic advances enable the investigator to obtain serially repeatable, noninvasive, and reliable quantitation of both central and renal hemodynamic status instantaneously by use of Doppler ultrasonography. Cardiac output has been reliably measured in a d ~l t s ~, ~ and the technique has been convincingly shown to From the