title: pH-stat versus alpha-stat perfusion strategy during experimental hypothermic circulatory arrest: a microdialysis study.
abstract: BACKGROUND
  The superiority of the pH-stat to the alpha-stat acid-base strategy during cardiopulmonary bypass as a neuroprotective method during hypothermic circulatory arrest is still controversial. In the present study, brain metabolism and outcome have been evaluated in a surviving model of experimental hypothermic circulatory arrest.
  
  
  METHODS
  Twenty pigs undergoing 75-minutes of hypothermic circulatory arrest at a brain temperature of 18 degrees C were randomly assigned to the alpha-stat (n = 10) or pH-stat (n = 10) strategy during cardiopulmonary bypass.
  
  
  RESULTS
  The 7-day survival rate was 90% (9 of 10) in the pH-stat group and 10% (1 of 10) in the alpha-stat group. At the end of cooling, pH-stat strategy was associated with significantly lower brain lactate and pyruvate concentrations and brain lactate-glucose ratio. After reperfusion, brain concentrations of glycerol, lactate, pyruvate, and lactate-glucose ratio were significantly lower in the pH-stat group. This strategy was associated with a faster rise of brain tissue temperature and reoxygenation on reperfusion, which is likely secondary to improved cerebral perfusion.
  
  
  CONCLUSIONS
  During cardiopulmonary bypass before and after a period of hypothermic circulatory arrest, acid-base management according to the pH-stat principles seemed to be associated with less derangements in cerebral metabolism, lower intracranial pressures, and excellent behavioral recovery and survival outcome. Because there is strong evidence of the beneficial metabolic effects related to this method, further studies using an experimental model of combined HCA and embolic brain injury are required to exclude a possible increased risk of cerebral embolism associated with the pH-stat strategy.
authors.affiliation: Department of Surgery, University of Oulu, Oulu University Hospital, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Pokela
authors.forename: Sebastian
authors.initials: S
authors.lastname: Dahlbacka
authors.forename: Fausto
authors.initials: F
authors.lastname: Biancari
authors.forename: Vilho
authors.initials: V
authors.lastname: Vainionpää
authors.forename: Timo
authors.initials: T
authors.lastname: Salomäki
authors.forename: Kai
authors.initials: K
authors.lastname: Kiviluoma
authors.forename: Erkka
authors.initials: E
authors.lastname: Rönkä
authors.forename: Timo
authors.initials: T
authors.lastname: Kaakinen
authors.forename: Janne
authors.initials: J
authors.lastname: Heikkinen
authors.forename: Jorma
authors.initials: J
authors.lastname: Hirvonen
authors.forename: Pekka
authors.initials: P
authors.lastname: Romsi
authors.forename: Vesa
authors.initials: V
authors.lastname: Anttila
authors.forename: Tatu
authors.initials: T
authors.lastname: Juvonen
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism*; D002315:Cardiopulmonary Bypass; D005260:Female; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D006324:Heart Arrest, Induced / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D007036:Hypothermia, Induced; D020766:Intracranial Embolism / Q000517:prevention & control; D007773:Lactates / Q000378:metabolism; D017551:Microdialysis; D011773:Pyruvates / Q000378:metabolism; D011897:Random Allocation; D013552:Swine; D016896:Treatment Outcome
chemical_list: D007773:Lactates; D011773:Pyruvates; D005947:Glucose; D005990:Glycerol