Low perfusion pressure during CPB may induce cerebral metabolic and ultrastructural changes.
BACKGROUND
Recently we reported on cerebral metabolic changes suggesting ischemia in piglets during nitroprusside-induced low-pressure CPB. We here investigated whether a mean arterial pressure (MAP) of 40-45 mmHg could provoke similar changes by a NO-independent intervention.


METHODS
Piglets underwent 60 minutes normothermic followed by 90 minutes hypothermic CPB. The LP-group (n=8) had MAP of 40-45 mmHg by phentolamine while the HP-group (n=8) had MAP of 60-80 mmHg by norepinephrine. Cerebral glucose, lactate, pyruvate and glycerol were determined. In the last two animals of each group, cerebral tissue was examined by electron microscopy.


RESULTS
Cerebral lactate was higher in the LP-group than the HP-group during normothermic CPB. Compared with baseline, cerebral glucose of the LP-group decreased whereas lactate/pyruvate-ratio, lactate and glycerol-concentrations increased during normothermic CPB. In the HP-group these parameters remained unchanged. Electron microscopy showed 31.2% and 8.3% altered mitochondria in the cortical micrographs taken from the LP- and the HP-group, respectively (p<0.001).


CONCLUSIONS
MAP below 45 mmHg during CPB was associated with cerebral biochemical and morphological changes consistent with anaerobic metabolism and subcellular injury.
Haugen
Oddbjørn
O
Department of Anesthesia and Intensive Care, Haukeland University Hospital, Bergen, Norway.
Farstad
Marit
M
Myklebust
Reidar
R
Kvalheim
Venny
V
Hammersborg
Stig
S
Husby
Paul
P
D000818:Animals; D015415:Biomarkers; D002545:Brain Ischemia / Q000209:etiology*; D002315:Cardiopulmonary Bypass / Q000009:adverse effects* / Q000379:methods; D002540:Cerebral Cortex / Q000187:drug effects* / Q000648:ultrastructure; D006439:Hemodynamics; D007022:Hypotension / Q000209:etiology*; D015425:Myocardial Reperfusion; D010477:Perfusion; D012307:Risk Factors; D013552:Swine
D015415:Biomarkers