title: Neurophysiologic monitoring to assure delivery of retrograde cerebral perfusion.
abstract: BACKGROUND
  Patients undergoing complex aortic procedures performed with deep hypothermia and circulatory arrest have a significant risk of an adverse neurologic event when the arrest period is prolonged. Retrograde cerebral perfusion appears to improve cerebral protection, although collapsed cortical veins or functional jugular venous valves may restrict flow at the frequently recommended maximum pressure of 25 mm Hg. Therefore, the purpose of this study was to demonstrate the benefit of multimodality neurophysiologic monitoring in assuring delivery of retrograde cerebral perfusion.
  
  
  METHODS
  Electroencephalography, cerebral blood flow velocity, and regional cerebral venous oxygen saturation were used to quantify the intraoperative neurophysiologic changes accompanying retrograde cerebral perfusion. The magnitude of changes was compared with those previously observed during arrest without retrograde cerebral perfusion.
  
  
  RESULTS
  Thirty patients underwent complex aortic procedures necessitating circulatory arrest, 22 with retrograde cerebral perfusion. The mean retrograde perfusion pressure of 40 mm Hg (30 to 49 mm Hg, 95% confidence interval) and flow rate of 1.2 L/min (0.9 to 1.6 L/min) necessary to achieve documented retrograde cerebral perfusion was much higher than previously recommended. During both retrograde cerebral perfusion and rewarming, cerebral oximetric monitoring guided adjustments in perfusion parameters to limit the rate of desaturation to 0.4% per minute (0.3% to 0.6%). With retrograde cerebral perfusion there was a rapid (1) recovery of electroencephalographic activity during rewarming (21 minutes [range 16 to 26 minutes]) and (2) return of consciousness after the operation (81% [58% to 95%, 95% confidence interval] awake by 12 hours). There was no transcranial Doppler evidence of cerebral edema with retrograde cerebral perfusion. Two neurologic complications occurred in the 22 patients managed with retrograde cerebral perfusion and one in the eight patients managed with arrest only.
  
  
  CONCLUSIONS
  Multimodality neurologic monitoring assured optimal brain cooling and bihemispheric delivery of retrograde cerebral perfusion. Necessary retrograde pressure and flow were often higher than values previously reported. Avoidance of profound cerebral venous oxygen desaturation during retrograde cerebral perfusion and rewarming was associated with rapid recovery of neurologic function.
authors.affiliation: Division of Thoracic and Cardiovascular Surgery, University of Louisville School of Medicine, Ky. 40292, USA.
authors.forename: B L
authors.initials: BL
authors.lastname: Ganzel
authors.forename: H L
authors.initials: HL
authors.lastname: Edmonds
authors.forename: J R
authors.initials: JR
authors.lastname: Pank
authors.forename: L J
authors.initials: LJ
authors.lastname: Goldsmith
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001018:Aortic Diseases / Q000601:surgery*; D002545:Brain Ischemia / Q000175:diagnosis / Q000209:etiology / Q000517:prevention & control*; D004569:Electroencephalography; D005260:Female; D006324:Heart Arrest, Induced / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods*; D010092:Oximetry; D010477:Perfusion / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D019265:Spectroscopy, Near-Infrared; D017585:Ultrasonography, Doppler, Transcranial