title: Cerebral Critical Closing Pressure During Infusion Tests.
abstract: We studied possible correlations between cerebral hemodynamic indices based on critical closing pressure (CrCP) and cerebrospinal fluid (CSF) compensatory dynamics, as assessed during lumbar infusion tests. Our data consisted of 34 patients with normal-pressure hydrocephalus who undertook an infusion test, in conjunction with simultaneous transcranial Doppler ultrasonography (TCD) monitoring of blood flow velocity (FV). CrCP was calculated from the monitored signals of ICP, arterial blood pressure (ABP), and FV, whereas vascular wall tension (WT) was estimated as CrCP - ICP. The closing margin (CM) expresses the difference between ABP and CrCP. ICP increased during infusion from 6.67 ± 4.61 to 24.98 ± 10.49 mmHg (mean ± SD; p < 0.001), resulting in CrCP rising by 22.93 % (p < 0.001), with WT decreasing by 11.33 % (p = 0.005) owing to vasodilatation. CM showed a tendency to decrease, albeit not significantly (p = 0.070), because of rising ABP (9.12 %; p = 0.005), and was significantly different from zero for the whole duration of the tests (52.78 ± 22.82 mmHg; p < 0.001). CM at baseline correlated inversely with brain elasticity (R = -0.358; p = 0.038). Neither CrCP nor WT correlated with CSF compensatory parameters. Overall, CrCP increases and WT decreases during infusion tests, whereas CM at baseline pressure may act as a characterizing indicator of the cerebrospinal compensatory reserve.
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK. georgios.varsos@cantab.net.
authors.forename: Georgios V
authors.initials: GV
authors.lastname: Varsos
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
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: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Garnett
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Liu
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.|Department of Neurosurgery, St Radboud University Medical Center, Nijmegen, The Netherlands.
authors.forename: Hadie
authors.initials: H
authors.lastname: Adams
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, UK.
authors.forename: Zofia
authors.initials: Z
authors.lastname: Czosnyka
mesh_terms: D000328:Adult; D000368:Aged; D062186:Arterial Pressure / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology*; D002555:Cerebrospinal Fluid; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000503:physiopathology*; D057446:Hydrodynamics; D007263:Infusions, Parenteral; D007427:Intracranial Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D017585:Ultrasonography, Doppler, Transcranial
keywords: Closing margin; Critical closing pressure; Hydrocephalus; Infusion tests; Ischemia