Effect of apolipoprotein E genotype on cerebral autoregulation during cardiopulmonary bypass.
OBJECTIVE
The presence of the apolipoprotein E epsilon4 (apoE4) allele has been associated with cognitive decline after cardiac surgery. We compared autoregulation of cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO(2)), and arterial-venous oxygen content difference [C(A-V)O(2)], during cardiopulmonary bypass (CPB) in patients with and without the apoE4 allele to help define the mechanism of association with cognitive decline.


METHODS
One hundred fifty-four patients underwent coronary artery bypass grafting with CPB, nonpulsatile flow, and alpha-stat management. CBF was measured by using (133)Xe washout methods. C(A-V)O(2), CMRO(2), and oxygen delivery were calculated. Pressure-flow autoregulation was tested by using 2 CBF measurements at stable hypothermia: the first at stable mean arterial pressure (MAP) and the second 15 minutes later, when MAP had increased or decreased >/=20%. Metabolism-flow autoregulation was tested by varying the temperature and measuring the coupling of CBF and CMRO(2).


RESULTS
In patients with (n=41) or without (n=113) the apoE4 allele, there were no differences in CBF, CMRO(2), C(A-V)O(2), pressure-flow and metabolism-flow autoregulation corrected for age, gender, non-insulin-dependent diabetes, hemoglobin, CPB time, and temperature.


CONCLUSIONS
We conclude that apoE genotype does not affect global CBF and oxygen delivery/extraction during CPB, which suggests that other mechanisms are responsible for the apoE isoform-related neurocognitive dysfunction seen in patients undergoing CPB.
Ti
L K
LK
Division of Cardiothoracic Anesthesiology and Critical Care, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA.
Mathew
J P
JP
Mackensen
G B
GB
Grocott
H P
HP
White
W D
WD
Reves
J G
JG
Newman
M F
MF
D001057:Apolipoproteins E / Q000235:genetics*; D001794:Blood Pressure; D002315:Cardiopulmonary Bypass; D002540:Cerebral Cortex / Q000098:blood supply* / Q000378:metabolism; D002560:Cerebrovascular Circulation; D005260:Female; D005838:Genotype; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D017694:Rewarming
D001057:Apolipoproteins E; D010100:Oxygen