Grading of cerebral autoregulation in preterm and term neonates

The response of cerebral blood flow velocity to a single spontaneous transi ent rise in blood pressure was studied to grade the cerebral autoregulatory response of newborns. Blood pressure was measured continuously through an umbilical or peripheral arterial catheter; continuous flow velocity recordi ngs were taken from the middle cerebral artery using continuous wave Dopple r ultrasound. From a cohort of 62 healthy term and preterm neonates, 325 tr ansients in mean arterial blood pressure and mean cerebral blood flow veloc ity were identified for analysis using a foot-seeking algorithm. An initial classification of active or impaired autoregulation was given to each tran sient using a self-clustering technique. The grading of the transients was studied by examining the slope of the return of the cerebral blood flow vel ocity to baseline. Negative slopes indicate a normal autoregulation; slopes of 0 or greater indicate an absence of autoregulation. This classification was in agreement with the self-clustering method (Cohen's kappa = 0.94, P < 0.0001). The relationship between the autoregulatory response assessed by the grading method and gestational age, postnatal age, and Pco(2) was exam ined using linear regression analysis. A significant relationship with gest ational age (P = 0.002) but not Pco(2) (P = 0.06) or postnatal age (P = 0.1 4) was evident. (C) 2000 by Elsevier Science Inc. All rights reserved.