title: Use of a pH-stat strategy during retrograde cerebral perfusion improves cerebral perfusion and tissue oxygenation.
abstract: BACKGROUND
  Although it is well documented that the use of a pH-stat strategy during hypothermic cardiopulmonary bypass improves cerebral blood flow, an alpha-stat strategy has been almost exclusively used during retrograde cerebral perfusion. We investigated the effects of pH-stat and alpha-stat management on brain tissue blood flow and oxygenation during retrograde cerebral perfusion in a porcine model to determine if the use of a pH-stat strategy during retrograde cerebral perfusion improves brain tissue perfusion.
  
  
  METHODS
  Fourteen pigs were managed by an alpha-stat strategy (alpha-stat group, n = 7) or by a pH-stat strategy (pH-stat group, n = 7) during 120 minutes of hypothermic retrograde cerebral perfusion. Retrograde cerebral perfusion was established through the superior vena cava. Brain tissue blood flow and oxygenation were measured continuously with a laser flowmeter and near infrared spectroscopy, respectively. Brain tissue water content was determined at the end of the experiments.
  
  
  RESULTS
  During cooling, brain tissue blood flow was significantly higher with use of the pH-stat strategy than with the alpha-stat strategy (86% +/- 10% versus 40% +/- 3% of baseline). During retrograde cerebral perfusion, brain tissue blood flow was also significantly higher (about three times higher) in the pH-stat group than in the alpha-stat group (15% +/- 4% versus 5% +/- 1% of baseline at 60 minutes of retrograde cerebral perfusion). Tissue oxygen saturation appeared to be higher during retrograde cerebral perfusion in the pH-stat group than in the alpha-stat group. Brain tissue blood flow during rewarming remained significantly higher with the use of pH-stat than with the use of alpha-stat. Brain tissue water contents were similar in both groups.
  
  
  CONCLUSIONS
  In our pig model, the use of a pH-stat strategy during retrograde cerebral perfusion significantly improves brain tissue perfusion. Therefore, to improve retrograde cerebral blood flow during retrograde cerebral perfusion, it may be preferable to use a pH-stat strategy, rather than an alpha-stat strategy.
authors.affiliation: Department of Surgery, University of Manitoba, Winnipeg, Canada. jian.ye@nrc-cnrc.gc.ca
authors.forename: Jian
authors.initials: J
authors.lastname: Ye
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Li
authors.forename: Yanmin
authors.initials: Y
authors.lastname: Yang
authors.forename: Luojia
authors.initials: L
authors.lastname: Yang
authors.forename: Allan
authors.initials: A
authors.lastname: Turner
authors.forename: Michael
authors.initials: M
authors.lastname: Jackson
authors.forename: Roxanne
authors.initials: R
authors.lastname: Deslauriers
mesh_terms: D000136:Acid-Base Equilibrium; D000818:Animals; D001921:Brain / Q000098:blood supply; D002315:Cardiopulmonary Bypass / Q000379:methods*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006454:Hemoglobins / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D017078:Laser-Doppler Flowmetry; D008833:Microcirculation / Q000502:physiology; D023421:Models, Animal; D010108:Oxyhemoglobins / Q000032:analysis; D011897:Random Allocation; D017694:Rewarming; D019265:Spectroscopy, Near-Infrared; D013552:Swine
chemical_list: D006454:Hemoglobins; D010108:Oxyhemoglobins; C100003:deoxyhemoglobin