title: The Upper Limit of Cerebral Blood Flow Autoregulation Is Decreased with Elevations in Intracranial Pressure.
abstract: The upper limit of cerebrovascular pressure autoregulation (ULA) is inadequately characterized. We sought to delineate the ULA in a neonatal swine model.
  
  
  
  Neonatal piglets with sham surgery (n = 9), interventricular fluid infusion (INF; n = 10), controlled cortical impact (CCI; n = 10), or impact + infusion (CCI + INF; n = 11) had intracranial pressure monitoring and bilateral cortical laser-Doppler flux recordings during arterial hypertension until lethality. An increase in red cell flux as a function of cerebral perfusion pressure was determined by piecewise linear regression and static rates of autoregulation (SRoRs) were determined above and below this inflection.
  
  
  
  When identified, the ULA (median [interquartile range]) was as follows: sham group: 102 mmHg (97-109), INF group: 75 mmHg (52-84), CCI group: 81 mmHg (69-101), and CCI + INF group: 61 mmHg (52-57; p = 0.01). Both groups with interventricular infusion had significantly lower ULA compared with the sham group.
  
  
  
  Neonatal piglets without intracranial pathological conditions tolerated acute hypertension, with minimal perturbation of cerebral blood flow. Piglets with acutely elevated intracranial pressure, with or without trauma, demonstrated loss of autoregulation when subjected to arterial hypertension.
authors.affiliation: Division of Pediatric Critical Care, Department of Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA. mkpesek@texaschildrens.org.
authors.forename: Matthew
authors.initials: M
authors.lastname: Pesek
authors.affiliation: Division of Pediatric Anesthesiology, Department of Anesthesiology, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Kibler
authors.affiliation: Division of Pediatric Critical Care, Department of Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.|Division of Pediatric Anesthesiology, Department of Anesthesiology, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.
authors.forename: R Blaine
authors.initials: RB
authors.lastname: Easley
authors.affiliation: Touro University, College of Osteopathic Medicine, Vallejo, CA, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mytar
authors.affiliation: Division of Neonatology, Department of Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Rhee
authors.affiliation: Division of Pediatric Anesthesiology, Department of Anesthesiology, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.
authors.forename: Dean
authors.initials: D
authors.lastname: Andropolous
authors.affiliation: Division of Pediatric Critical Care, Department of Pediatrics, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.|Division of Pediatric Anesthesiology, Department of Anesthesiology, Baylor College of Medicine, Texas Children's Hospital, Houston, TX, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Brady
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001783:Blood Flow Velocity; D000070642:Brain Injuries, Traumatic / Q000150:complications / Q000503:physiopathology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D006706:Homeostasis / Q000502:physiology*; D019586:Intracranial Hypertension / Q000209:etiology / Q000503:physiopathology*; D007427:Intracranial Pressure; D017078:Laser-Doppler Flowmetry; D016014:Linear Models; D013552:Swine
keywords: Cerebral perfusion pressure; Intracranial pressure; Upper limit of cerebrovascular pressure autoregulation