title: Cerebral oxygenation using near-infrared spectroscopy in the beach-chair position during shoulder arthroscopy under general anesthesia.
abstract: OBJECTIVE
  To examine the risks of shoulder arthroscopy in the beach-chair position (BCP) as opposed to the lateral decubitus position. The challenge during general anesthesia, particularly with the patient in the BCP, has been to ascertain the lower limit of blood pressure autoregulation, correctly measure mean arterial pressure, and adequately adjust parameters to maintain cerebral perfusion. There is increasing concern about the BCP and its association with intraoperative cerebral desaturation events (CDEs). Assessment of CDEs intraoperatively remains difficult; the emerging technology near-infrared spectroscopy (NIRS) may provide noninvasive, inexpensive, and continuous assessment of cerebral perfusion, offering an "early warning" system before irreversible cerebral ischemia occurs.
  
  
  METHODS
  A systematic review was undertaken to determine the incidence of intraoperative CDEs as measured by NIRS and whether it is possible to risk stratify patients for intraoperative CDEs, specifically the degree of elevation in the BCP.
  
  
  RESULTS
  Searching Medline, Embase, and the Cochrane Central Register of Controlled Trials from inception until December 30, 2013, we found 9 studies (N = 339) that met our search criteria. The Level of Evidence was III or IV.
  
  
  CONCLUSIONS
  There remains a paucity of high-level data. The mean incidence of CDEs was 28.8%. We found a strong positive correlation between CDEs and degree of elevation in the BCP (P = .056). Emerging evidence (Level IV) suggests that we may be able to stratify patients on the basis of age, history of hypertension and stroke, body mass index, diabetes mellitus, obstructive sleep apnea, and height. The challenge remains, however, in defining the degree and duration of cerebral desaturation, as measured by NIRS, required to produce measureable neurocognitive decline postoperatively.
  
  
  METHODS
  Level IV, systematic review of Level III and IV studies.
authors.affiliation: Department of Orthopaedic Surgery, Sydney Adventist Hospital and University of Sydney, New South Wales, Australia. Electronic address: sushpant@gmail.com.
authors.forename: Sushil
authors.initials: S
authors.lastname: Pant
authors.affiliation: Department of Orthopaedic Surgery, Macquarie University, New South Wales, Australia.
authors.forename: Desmond J
authors.initials: DJ
authors.lastname: Bokor
authors.affiliation: Department of Orthopaedic Surgery, Sydney Adventist Hospital and University of Sydney, New South Wales, Australia; Department of Orthopaedic Surgery, Macquarie University, New South Wales, Australia.
authors.forename: Adrian K
authors.initials: AK
authors.lastname: Low
mesh_terms: D000328:Adult; D000368:Aged; D000768:Anesthesia, General / Q000009:adverse effects*; D001182:Arthroscopy; D001921:Brain / Q000378:metabolism; D002545:Brain Ischemia / Q000453:epidemiology / Q000209:etiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006801:Humans; D007022:Hypotension; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption / Q000502:physiology; D056888:Patient Positioning / Q000009:adverse effects* / Q000379:methods; D012785:Shoulder Joint / Q000601:surgery*; D019265:Spectroscopy, Near-Infrared