title: Continuous measurement of autoregulation by spontaneous fluctuations in cerebral perfusion pressure: comparison of 3 methods.
abstract: OBJECTIVE
  Clinical application of continuous autoregulation monitoring would benefit from a comparison of curves generated by online monitoring with standard autoregulation curves in animal models. We characterized the accuracy of 3 continuous monitors of autoregulation in a piglet model of hypotension.
  
  
  METHODS
  Piglets 5 to10 days old with intracranial pressure (ICP) at naïve or elevated (20 mm Hg) levels had gradual arterial hypotension induced by a balloon catheter in the inferior vena cava. Elevated ICP was maintained by a continuous infusion of artificial cerebrospinal fluid. Three indices of autoregulation were simultaneously and continuously calculated. A moving, linear Pearson's coefficient between spontaneous slow waves of cerebral perfusion pressure and slow waves of laser-Doppler flux or cortical oxygenation rendered the laser-Doppler index and cerebral-oximetry index, respectively. Similar correlation between slow waves of arterial blood pressure and ICP rendered the pressure-reactivity index. The lower limit of autoregulation was determined directly for each animal by plotting laser-Doppler cortical red blood cell flux as a function of cerebral perfusion pressure. Receiver-operator characteristics were determined for the 3 indices.
  
  
  RESULTS
  The areas under the receiver-operator characteristics curves for discriminating the individual lower limit of autoregulation at low and high ICP were 0.89 and 0.85 for the laser-Doppler index, 0.89 and 0.84 for the cerebral-oximetry index, and 0.79 and 0.79 for the pressure-reactivity index. The pressure-reactivity index performed equally well at low and high ICPs.
  
  
  CONCLUSIONS
  Continuous monitoring of autoregulation by spontaneous slow waves of cerebral perfusion pressure can accurately detect loss of autoregulation due to hypotension in piglets by all 3 modalities.
authors.affiliation: Department of Anesthesiology, Division of Pediatric Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, 600 N Wolfe St, Blalock 904, Baltimore MD 21287, USA. kbrady5@jhmi.edu
authors.forename: Ken M
authors.initials: KM
authors.lastname: Brady
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Lee
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Kibler
authors.forename: R Blaine
authors.initials: RB
authors.lastname: Easley
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Koehler
authors.forename: Donald H
authors.initials: DH
authors.lastname: Shaffner
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001794:Blood Pressure / Q000502:physiology*; D001921:Brain / Q000098:blood supply / Q000502:physiology; D002536:Cerebral Arteries / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004195:Disease Models, Animal; D006706:Homeostasis / Q000502:physiology*; D019586:Intracranial Hypertension / Q000503:physiopathology; D019585:Intracranial Hypotension / Q000175:diagnosis / Q000503:physiopathology*; D017078:Laser-Doppler Flowmetry / Q000379:methods*; D010092:Oximetry / Q000379:methods*; D010101:Oxygen Consumption / Q000502:physiology; D010827:Physiology / Q000379:methods; D034421:Sus scrofa