title: The Ontogeny of Cerebrovascular Pressure Autoregulation in Premature Infants.
abstract: Our objective was to quantify cerebrovascular autoregulation as a function of gestational age (GA) and across the phases of the cardiac cycle. One hundred eighty-six premature infants, with a GA range of 23-33 weeks, were monitored using umbilical artery catheters and transcranial Doppler insonation of middle cerebral artery flow velocity (FV) for 1-h sessions over the first week of life. Autoregulation was quantified as a moving correlation coefficient between systolic arterial blood pressure (ABP) and systolic FV (Sx); mean ABP and mean FV (Mx); diastolic ABP and diastolic FV (Dx). Autoregulation was compared across GAs for each aspect of the cardiac cycle. Systolic FV was pressure-passive in infants with the lowest GA, and Sx decreased with increased GA (r = -0.3; p < 0.001). By contrast, Dx was elevated in all subjects, and showed minimal change with increased GA (r = -0.06; p = 0.05). Multivariate analysis confirmed that GA (p < 0.001) and the "closing margin" (p < 0.01) were associated with Sx. Premature infants have low and almost always pressure-passive diastolic cerebral blood FV. Conversely, the regulation of systolic cerebral blood FV by autoregulation was manifested in this cohort at a GA of between 23 and 33 weeks.
authors.affiliation: Section of Neonatology, Department of Pediatrics, Texas Children's Hospital, Baylor College of Medicine, 6621 Fannin Street, W6-104, Houston, TX, USA. cjrhee@texaschildrens.org.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rhee
authors.affiliation: University of Texas at Houston School of Medicine, Houston, TX, USA.
authors.forename: Charles D
authors.initials: CD
authors.lastname: Fraser
authors.affiliation: Departments of Pediatrics and Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Kibler
authors.affiliation: Departments of Pediatrics and Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Ronald B
authors.initials: RB
authors.lastname: Easley
authors.affiliation: Departments of Pediatrics and Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Dean B
authors.initials: DB
authors.lastname: Andropoulos
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.affiliation: Division of Neurosurgery, Addenbrooke's Hospital, Cambridge University, Cambridge, UK.
authors.forename: Georgios V
authors.initials: GV
authors.lastname: Varsos
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
authors.affiliation: Department of Cardiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Craig G
authors.initials: CG
authors.lastname: Rusin
authors.affiliation: Departments of Pediatrics and Anesthesiology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
authors.affiliation: Section of Neonatology, Departments of Pediatrics and Obstetrics and Gynecology, Texas Children's Hospital, Baylor College of Medicine, Houston, TX, USA.
authors.forename: Jeffrey R
authors.initials: JR
authors.lastname: Kaiser
mesh_terms: D062186:Arterial Pressure / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003971:Diastole; D005260:Female; D005865:Gestational Age; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D062071:Infant, Extremely Premature; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging*; D008991:Monitoring, Physiologic; D013599:Systole; D017585:Ultrasonography, Doppler, Transcranial; D014469:Umbilical Arteries
keywords: Arterial blood pressure; Cerebrovascular pressure autoregulation; Closing margin; Prematurity