title: Static autoregulation is intact early after severe unilateral brain injury in a neonatal Swine model.
abstract: BACKGROUND
  Autoregulation is impaired by traumatic brain injury. Cerebral blood flow disturbances are spatially heterogeneous, but autoregulation is often reported as a global metric.
  
  
  OBJECTIVE
  We tested lateralization of autoregulatory responses in the neonatal piglet brain during hypotension early after unilateral injury.
  
  
  METHODS
  Neonatal piglets (5-7 days old) had controlled cortical impact (severe, n = 12; moderate, n = 13; sham, n = 13) and recovery for 6 hours. The lower limit of autoregulation (LLA) and static rate of autoregulation (SRoR) were determined for each subject and compared among groups and between the ipsilateral and contralateral hemispheres.
  
  
  RESULTS
  The LLA was not increased by injury (sham, 34 mm Hg [29-39 mm Hg]; moderate injury, 37 mm Hg [33-41 mm Hg]; severe injury, 35 mm Hg [32-38 mm Hg]; P = .93, mean [95% confidence interval]). SRoR, when measured ipsilateral to injury and above the LLA, showed intact autoregulation and was not lower than SRoR in uninjured subjects (sham, 0.82 [0.53-1.1]; moderate injury, 1.0 [0.60-1.5]; severe, 0.91 [0.33-1.5]; P = .44). The average hemispheric LLA difference was 2.7 mm Hg, (95% limits of agreement, -7.5 to 7.0; bias, -0.25; Spearman r = 0.73; P < .0001). Ipsilateral and contralateral SRoR measurements also showed correlation in the injured groups (Spearman r = 0.85, P < .0001).
  
  
  CONCLUSIONS
  LLA was not increased by controlled cortical impact, nor did SRoR measurements demonstrate ineffective autoregulation when cerebral perfusion pressure was greater than and within 10 mm Hg of the LLA. Cerebral perfusion pressure optimization, indicated by autoregulation measurements, was significantly similar in the 2 hemispheres despite severe unilateral injury.
authors.affiliation: College of Osteopathic Medicine, Touro University, Vallejo, CA, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mytar
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Kibler
authors.forename: R Blaine
authors.initials: RB
authors.lastname: Easley
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Dean B
authors.initials: DB
authors.lastname: Andropoulos
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D001783:Blood Flow Velocity; D001930:Brain Injuries / Q000150:complications* / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D007839:Functional Laterality / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D007022:Hypotension / Q000209:etiology*; D007427:Intracranial Pressure / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D012720:Severity of Illness Index; D013552:Swine; D013997:Time Factors