title: Detection of delayed cerebral ischemia (DCI) in subarachnoid haemorrhage applying near-infrared spectroscopy: elimination of the extracerebral signal by transcutaneous and intraparenchymatous measurements in parallel.
abstract: BACKGROUND
  Detection of delayed cerebral ischemia (DCI) in high-grade subarachnoid haemorrhage (SAH) is an unsolved issue. Conventional near-infrared spectroscopy (NIRS) with optodes applied over the skin is controversial because the NIRS signal is contaminated by extracerebral tissue. The objective is to quantify and subtract the contribution from extracerebral tissue from the signal by using measurements in parallel with a NIRS brain tissue probe and conventional NIRS.
  
  
  METHODS
  In a patient with high-grade SAH, two approaches for NIRS were applied. First, a conventional brain tissue probe for intracranial pressure (ICP) monitoring, supplied by optical fibres, was placed into the brain tissue 2 cm deep from the dura. Second, for conventional NIRS, a plaster-based patch carrying optodes (one emitter, two detectors) was attached to the skin. Central venous injections of 0.3 mg/kg body weight (bw) indocyanine green (ICG) were performed. ICG dye dilution curves obtained with the probe and patch were collected simultaneously and analysed for blood flow values.
  
  
  RESULTS
  Twelve measurements in parallel with the probe and patch were performed. Mean cerebral blood flow (CBF) for the probe was higher (24.8 ± 9.1 ml/100 g/min) compared with the values obtained with the patch (for detector 1, extra-cerebral blood flow [ECBF] mean 5.1 ± 1.8 ml/100 g/min; p = 0.002; for detector 2, 6.6 ± 2.1 ml/100 g/min; p = 0.002). CBF values obtained with the probe correlated with blood flow values obtained with the patch (for CBF vs. ECBF detector 1, r = 0.72 [p = 0.008]; ECBF detector 2, r = 0.79 [p = 0.002]).
  
  
  CONCLUSIONS
  Blood flow values obtained with conventional NIRS correlated significantly with absolute CBF values obtained directly within the brain tissue. Simultaneous measurements with the NeMo Probe and NeMo Patch allow quantification and subtraction of the contribution from extracerebral tissues from the signal obtained with conventional NIRS.
authors.affiliation: Neurocritical Care Unit, Department of Neurosurgery, University Hospital Zurich, Frauenklinikstrasse 10, Zuerich, CH-8091, Switzerland, emanuela.keller@usz.ch.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Keller
authors.forename: J
authors.initials: J
authors.lastname: Froehlich
authors.forename: D
authors.initials: D
authors.lastname: Baumann
authors.forename: C
authors.initials: C
authors.lastname: Böcklin
authors.forename: C
authors.initials: C
authors.lastname: Sikorski
authors.forename: M
authors.initials: M
authors.lastname: Oberle
authors.forename: M
authors.initials: M
authors.lastname: Muser
mesh_terms: D000465:Algorithms; D001776:Blood Circulation Time / Q000295:instrumentation / Q000379:methods; D002545:Brain Ischemia / Q000175:diagnosis* / Q000209:etiology / Q000378:metabolism; D002560:Cerebrovascular Circulation; D004396:Coloring Agents; D003198:Computer Simulation; D006801:Humans; D007208:Indocyanine Green; D007427:Intracranial Pressure; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods*; D009010:Monte Carlo Method; D012815:Signal Processing, Computer-Assisted; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation / Q000379:methods*; D013345:Subarachnoid Hemorrhage / Q000150:complications*; D013997:Time Factors
chemical_list: D004396:Coloring Agents; D007208:Indocyanine Green