pH-stat versus alpha-stat acid-base management strategy during hypothermic circulatory arrest combined with embolic brain injury.
BACKGROUND
There is some evidence of beneficial metabolic effects associated with the pH-stat than with alpha-stat perfusion strategy, but this is tempered by a likely increased risk of embolism to the brain, especially in adult patients. We investigated this possible adverse effect in an experimental model that combined hypothermic circulatory arrest (HCA) and embolic brain injury.


METHODS
Twenty-four female juvenile pigs undergoing 25 minutes of HCA at a brain temperature of 18 degrees C were assigned to either alpha-stat (n = 12) or pH-stat (n = 12) strategy during cardiopulmonary bypass. Before the initiation of HCA, the descending aorta was clamped and 200 mg of albumin-coated polystyrene microspheres (250 to 750 microm in diameter) were injected into the isolated aortic arch in both groups.


RESULTS
The 7-day survival rate was 75% in the pH-stat group and 50% in the alpha-stat group (p = 0.40). The pH-stat group had significantly better behavioral scores on postoperative days 5 (p = 0.03) and 6 (p = 0.04). The pH-stat strategy was associated with better postoperative intracranial pressures and histopathologic scores, but such differences did not reach statistical significance. The alpha-stat group had lower brain glucose concentrations postoperatively as well as higher brain lactate/glucose and lactate/pyruvate ratios


CONCLUSIONS
These results suggest that pH-stat strategy does not cause any worse brain injury than the alpha-stat strategy. Indeed, the pH-stat strategy is associated with a slightly better outcome compared with the alpha-stat strategy, even in the setting of cerebral embolization. This observation suggests that the pH-stat strategy could also be used in adults during deep hypothermic cardiopulmonary bypass despite the increased risk of intraoperative cerebral embolization.
Dahlbacka
Sebastian
S
Department of Surgery, Oulu University Hospital, University of Oulu, Oulu, Finland.
Heikkinen
Janne
J
Kaakinen
Timo
T
Laurila
Päivi
P
Vainionpää
Vilho
V
Kiviluoma
Kai
K
Salomäki
Timo
T
Tuominen
Hannu
H
Ohtonen
Pasi
P
Biancari
Fausto
F
Lepola
Pasi
P
Juvonen
Tatu
T
D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology; D002545:Brain Ischemia / Q000517:prevention & control; D002245:Carbon Dioxide / Q000097:blood; D002315:Cardiopulmonary Bypass; D004569:Electroencephalography; D005947:Glucose / Q000378:metabolism; D006324:Heart Arrest, Induced / Q000009:adverse effects*; D006863:Hydrogen-Ion Concentration; D020766:Intracranial Embolism / Q000209:etiology*; D019344:Lactic Acid / Q000378:metabolism; D010101:Oxygen Consumption; D013552:Swine
D002245:Carbon Dioxide; D019344:Lactic Acid; D005947:Glucose