title: Noninvasive monitoring of cerebrovascular reactivity with near infrared spectroscopy in head-injured patients.
abstract: Monitoring of cerebrovascular pressure reactivity (PRx) has diagnostic and prognostic value in head-injured patients, but requires invasive monitoring of intracranial pressure (ICP). Near infrared spectroscopy (NIRS) is a noninvasive method that is suitable for continuous detection of cerebral blood volume changes. We compared a NIRS-based index of cerebrovascular reactivity, called total hemoglobin reactivity (THx), against standard measurements of PRx in a prospective observational study. Forty patients with closed-head injury were monitored daily with arterial blood pressure (ABP), ICP, and a NIRS-based total hemoglobin index. PRx and THx were calculated as the moving correlation coefficients using 5-min time windows between 10-sec averaged values of ICP and ABP, and total hemoglobin index and ABP, respectively. A total of 120 recordings were performed between the median first (IQR 0.75-2) and fourth (IQR 2-6) day after head injury, giving a total duration of 1760 hours. PRx and THx demonstrated a significant association across averaged individual recordings (r = 0.49, p < 0.0001), and across patients (r = 0.56, p = 0.0002). Assessment of optimal cerebral perfusion pressure (CPP) and ABP using THx was possible in about 50% of recordings, and showed a significant agreement with the optimal CPP and ABP assessed with PRx. THx may be of diagnostic value to optimize therapy oriented toward restoration and continuity of cerebrovascular reactivity, especially in patients for whom direct ICP monitoring is not feasible.
authors.affiliation: Academic Neurosurgical Unit, University of Cambridge Clinical School, Cambridge, United Kingdom. zweifelch@gmx.ch
authors.forename: Christian
authors.initials: C
authors.lastname: Zweifel
authors.forename: Gianluca
authors.initials: G
authors.lastname: Castellani
authors.forename: Marek
authors.initials: M
authors.lastname: Czosnyka
authors.forename: Adel
authors.initials: A
authors.lastname: Helmy
authors.forename: Anne
authors.initials: A
authors.lastname: Manktelow
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Carrera
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Brady
authors.forename: Peter J A
authors.initials: PJ
authors.lastname: Hutchinson
authors.forename: David K
authors.initials: DK
authors.lastname: Menon
authors.forename: John D
authors.initials: JD
authors.lastname: Pickard
authors.forename: Peter
authors.initials: P
authors.lastname: Smielewski
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D001930:Brain Injuries / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003422:Critical Care; D003627:Data Interpretation, Statistical; D004569:Electroencephalography; D005260:Female; D015600:Glasgow Coma Scale; D023261:Glasgow Outcome Scale; D016489:Head Injuries, Closed / Q000503:physiopathology*; D006454:Hemoglobins / Q000378:metabolism; D006706:Homeostasis / Q000502:physiology; D017052:Hospital Mortality; D006801:Humans; D007427:Intracranial Pressure / Q000502:physiology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D012372:ROC Curve; D015398:Signal Transduction; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D055815:Young Adult
chemical_list: D006454:Hemoglobins