Variability of resistive indices in the anterior cerebral artery during fontanel compression in preterm and term neonates measured by transcranial duplex sonography.

OBJECTIVE: To determine the normal range of resistive index (RI) variability in clinically/neurologically unremarkable preterm and term infants and to compare the hemodynamic response to transient elevation of intracranial pressure. STUDY DESIGN: We measured RIs at baseline and following brief fontanel compression, assessing for differences in mean baseline and compression values and percent change. RESULT: One hundred and twenty-nine subjects were included in the study. Mean baseline RI and normal range were 0.7 in preterm (0.54 to 0.86) and 0.66 in term infants (0.52 to 0.8; P=0.001). Mean RI during compression was 0.71 in preterm and 0.68 in term infants (P=0.015). Mean percent change between baseline and compression was 5.86% in preterm and 7.45% in term infants (P=0.092). CONCLUSION: No difference in the hemodynamic response to transient elevation of intracranial pressure between different gestational groups, suggesting no significant differences in autoregulatory response.