title: Continuous optical monitoring of cerebral hemodynamics during head-of-bed manipulation in brain-injured adults.
abstract: BACKGROUND
  Head-of-bed manipulation is commonly performed in the neurocritical care unit to optimize cerebral blood flow (CBF), but its effects on CBF are rarely measured. This pilot study employs a novel, non-invasive instrument combining two techniques, diffuse correlation spectroscopy (DCS) for measurement of CBF and near-infrared spectroscopy (NIRS) for measurement of cerebral oxy- and deoxy-hemoglobin concentrations, to monitor patients during head-of-bed lowering.
  
  
  METHODS
  Ten brain-injured patients and ten control subjects were monitored continuously with DCS and NIRS while the head-of-bed was positioned first at 30° and then at 0°. Relative CBF (rCBF) and concurrent changes in oxy- (ΔHbO2), deoxy- (ΔHb), and total-hemoglobin concentrations (ΔTHC) from left/right frontal cortices were monitored for 5 min at each position. Patient and control response differences were assessed.
  
  
  RESULTS
  rCBF, ΔHbO2, and ΔTHC responses to head lowering differed significantly between brain-injured patients and healthy controls (P < 0.02). For patients, rCBF changes were heterogeneous, with no net change observed in the group average (0.3 ± 28.2 %, P = 0.938). rCBF increased in controls (18.6 ± 9.4 %, P < 0.001). ΔHbO2, ΔHb, and ΔTHC increased with head lowering in both groups, but to a larger degree in brain-injured patients. rCBF correlated moderately with changes in cerebral perfusion pressure (R = 0.40, P < 0.001), but not intracranial pressure.
  
  
  CONCLUSIONS
  DCS/NIRS detected differences in CBF and oxygenation responses of brain-injured patients versus controls during head-of-bed manipulation. This pilot study supports the feasibility of continuous bedside measurement of cerebrovascular hemodynamics with DCS/NIRS and provides the rationale for further investigation in larger cohorts.
authors: Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA, 19104, USA, meeri@alumni.upenn.edu.
authors: Meeri N
authors: MN
authors: Kim
authors: Brian L
authors: BL
authors: Edlow
authors: Turgut
authors: T
authors: Durduran
authors: Suzanne
authors: S
authors: Frangos
authors: Rickson C
authors: RC
authors: Mesquita
authors: Joshua M
authors: JM
authors: Levine
authors: Joel H
authors: JH
authors: Greenberg
authors: Arjun G
authors: AG
authors: Yodh
authors: John A
authors: JA
authors: Detre
mesh_terms: D000293:Adolescent; D000328:Adult; D001513:Beds; D001930:Brain Injuries / Q000175:diagnosis* / Q000503:physiopathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003422:Critical Care / Q000379:methods; D005260:Female; D005336:Fiber Optic Technology / Q000379:methods; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000175:diagnosis* / Q000503:physiopathology; D007427:Intracranial Pressure / Q000502:physiology; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D064847:Multimodal Imaging / Q000379:methods*; D010865:Pilot Projects; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D013345:Subarachnoid Hemorrhage / Q000175:diagnosis* / Q000503:physiopathology; D055815:Young Adult
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