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

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 on going prospective study of RI values in term infants with perinatal asphyxi a. Materials and methods. Forty normal term neonates underwent cranial sonogra phy and Doppler during the first 24 h after birth. Transfontanelle Doppler was performed of the internal carotid,anterior cerebral, and middle cerebra l arteries bilaterally. In addition, transtemporal Doppler was performed of the middle cerebral arteries bilaterally. Mean and median RI values were c alculated in all vessels interrogated. The transfontanelle and transtempora l middle cerebral artery measurements were compared using paired t-tests. Results. The overall mean RI of all interrogated vessels was 0.726 with a s tandard deviation of 0.057. The mean RI value in the middle cerebral arteri es was not significantly different with the two different measurement techn iques. Conclusion. Normal intracranial RI values for a term infant in the first da y of life were calculated for comparison with RI values in term infants wit h perinatal asphyxia.