pH-stat versus alpha-stat perfusion strategy during experimental hypothermic circulatory arrest: a microdialysis study.
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.
Pokela
Matti
M
Department of Surgery, University of Oulu, Oulu University Hospital, Finland.
Dahlbacka
Sebastian
S
Biancari
Fausto
F
Vainionpää
Vilho
V
Salomäki
Timo
T
Kiviluoma
Kai
K
Rönkä
Erkka
E
Kaakinen
Timo
T
Heikkinen
Janne
J
Hirvonen
Jorma
J
Romsi
Pekka
P
Anttila
Vesa
V
Juvonen
Tatu
T
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
D007773:Lactates; D011773:Pyruvates; D005947:Glucose; D005990:Glycerol