title: Cerebral Critical Closing Pressure: Is the Multiparameter Model Better Suited to Estimate Physiology of Cerebral Hemodynamics?
abstract: Cerebral critical closing pressure (CrCP) is the level of arterial blood pressure (ABP) at which small brain vessels close and blood flow stops. This value is always greater than intracranial pressure (ICP). The difference between CrCP and ICP is explained by the tone of the small cerebral vessels (wall tension). CrCP value is used in several dynamic cerebral autoregulation models. However, the different methods for calculation of CrCP show frequent negative values. These findings are viewed as a methodological limitation. We intended to evaluate CrCP in patients with severe traumatic brain injury (TBI) with a new multiparameter impedance-based model and compare it with results found earlier using a transcranial Doppler (TCD)-ABP pulse waveform-based method.
  
  
  
  Twelve severe TBI patients hospitalized during September 2005-May 2007. Ten men, mean age 32 years (16-61). Four had decompressive craniectomies (DC); three presented anisocoria. Patients were monitored with TCD cerebral blood flow velocity (FV), invasive ABP, and ICP. Data were acquired at 50 Hz with an in-house developed data acquisition system. We compared the earlier studied "first harmonic" method (M1) results with results from a new recently developed (M2) "multiparameter method."
  
  
  
  M1: In seven patients CrCP values were negative, reaching -150 mmHg. M2: All positive values; only one lower than ICP (ICP 60 mmHg/ CrCP 57 mmHg). There was a significant difference between M1 and M2 values (M1 < M2) and between ICP and M2 (M2 > ICP).
  
  
  
  M2 results in positive values of CrCP, higher than ICP, and are physiologically interpretable.
authors.affiliation: Emergency Department and Intensive Care Unit, Hospital de Clínicas, Universidad de la República School of Medicine, Montevideo, Uruguay. coripuppo@gmail.com.
authors.forename: C
authors.identifier: 0000-0002-5808-795X
authors.initials: C
authors.lastname: Puppo
authors.affiliation: Group of Ultrasound Systems and Technologies (USTG), Spanish National Research Council (CSIC), Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Camacho
authors.affiliation: Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: G V
authors.initials: GV
authors.lastname: Varsos
authors.affiliation: Emergency Department and Intensive Care Unit, Hospital de Clínicas, Universidad de la República School of Medicine, Montevideo, Uruguay.
authors.forename: B
authors.initials: B
authors.lastname: Yelicich
authors.affiliation: Emergency Department and Intensive Care Unit, Hospital de Clínicas, Universidad de la República School of Medicine, Montevideo, Uruguay.
authors.forename: H
authors.initials: H
authors.lastname: Gómez
authors.affiliation: Emergency Department and Intensive Care Unit, Hospital de Clínicas, Universidad de la República School of Medicine, Montevideo, Uruguay.
authors.forename: L
authors.initials: L
authors.lastname: Moraes
authors.affiliation: Emergency Department and Intensive Care Unit, Hospital de Clínicas, Universidad de la República School of Medicine, Montevideo, Uruguay.
authors.forename: A
authors.initials: A
authors.lastname: Biestro
authors.affiliation: Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: M
authors.initials: M
authors.lastname: Czosnyka
mesh_terms: D000293:Adolescent; D000328:Adult; D062186:Arterial Pressure / Q000502:physiology*; D000070642:Brain Injuries, Traumatic / Q000503:physiopathology* / Q000601:surgery; D002560:Cerebrovascular Circulation / Q000502:physiology*; D056424:Decompressive Craniectomy; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D064926:Neurophysiological Monitoring / Q000379:methods*; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods*; D055815:Young Adult
keywords: Cerebral arterial time constant; Cerebral critical closing pressure; Intracranial pressure; Neuromonitoring; Transcranial doppler; Traumatic brain injury