Resistance Index of Cerebral Artery Blood Flow Impedance in Preterm Neonates.† 939

Abstract

Color flow and pulsed Doppler ultrasonography provides non-invasive estimates of blood flow impedance and has been applied to the evaluation of hemodynamics in newborns. Specctral doppler flow profiles of middle and anterior cerebral arteries of 151 preterm neonates <35 wks GA were obtained with an Acuson XP color and duplex Doppler unit, using a 5.0/7.0 MHZ sector probe. Resistance index (RI = Peak systolic flow velocity - end diastolic flow velocity/peak systolic flow velocity) was calculated by a software program during 5 - 6 consecutive hemogeneous cardiac cycles; normal = RI of 0.5 to 0.8. There were 609 Doppler flow studies performed. The mean number of studies per patient was four. 98 of these neonates (BW 1329 ± 645g SD; GA 29.2± 3.8 wks SD) had at least one study with elevated RI. 53 infants had all normal RI (BW 1582 ± 785g SD; GA 31 ± 4.3 wks SD), and 3 had low RI. Infants with elevated RI had significantly more sepsis (30% vs 0% P<.002), and Intraventricular Hemorrhage (IVH) (34.6% vs 9.1, P<.03) than those with normal RI. There was no difference between high and normal RI in Patent Ductus Arterious (PDA) (72% vs 59%), Periventricular Leucomalacia(PVL) (7.9% vs 4.5%), apnea (72.4% vs 59.2%) or the need for inotrope therapy. All three infants with low RI had IVH and/or PVL. 14/151 patients died; 10/98 infants with elevated RI, 2/3 infants with low RI, and 1/51 infants with normal RI. So far, 58 patients have completed neurodevelopmental screening; suspicious developmental screening was found in 46.3% of elevated RI and 1.7% of normal RI patients. Summary: Elevated RI appears to correlate with sepsis and IVH, and may be associated with increased risk of developmental delay. Low RI, a sign of loss of autoregulation, may correlate with an increased risk of IVH, PVL, and death.