Intracranial resistive index (RI) values in normal term infants during the first day of life

Abstract

Purpose. The purpose of this study was to determine normal resistive index (RI) values for term neonates during the first day of life as part of an ongoing prospective study of RI values in term infants with perinatal asphyxia.¶Materials and methods. Forty normal term neonates underwent cranial sonography and Doppler during the first 24 h after birth. Transfontanelle Doppler was performed of the internal carotid, anterior cerebral, and middle cerebral arteries bilaterally. In addition, transtemporal Doppler was performed of the middle cerebral arteries bilaterally. Mean and median RI values were calculated in all vessels interrogated. The transfontanelle and transtemporal middle cerebral artery measurements were compared using paired t-tests.¶Results. The overall mean RI of all interrogated vessels was 0.726 with a standard deviation of 0.057. The mean RI value in the middle cerebral arteries was not significantly different with the two different measurement techniques.¶Conclusion. Normal intracranial RI values for a term infant in the first day of life were calculated for comparison with RI values in term infants with perinatal asphyxia.