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(Stroke. 2001;32:1514.)
© 2001 American Heart Association, Inc.

Original Contributions

Effect of Apolipoprotein E Genotype on Cerebral Autoregulation During Cardiopulmonary Bypass

Lian K. Ti, MMed; Joseph P. Mathew, MD; G. Burkhard Mackensen, MD; Hilary P. Grocott, MD, FRCPC; William D. White, MPH; J. G. Reves, MD; Mark F. Newman, MD for the C.A.R.E. Investigators

From the Division of Cardiothoracic Anesthesiology and Critical Care, Department of Anesthesiology, Duke University Medical Center, Durham, NC.

Correspondence and reprint requests to Joseph P. Mathew, MD, Box 3094, Duke University Medical Center, Durham, NC 27710. E-mail mathe014{at}mc.duke.edu

Background and Purpose—The presence of the apolipoprotein E 4 (apoE4) allele has been associated with cognitive decline after cardiac surgery. We compared autoregulation of cerebral blood flow (CBF), cerebral metabolic rate for oxygen (CMRO₂), and arterial-venous oxygen content difference [C(A-V)O₂], 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 -stat management. CBF was measured by using ¹³³Xe washout methods. C(A-V)O₂, CMRO₂, 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 CMRO₂.

Results—In patients with (n=41) or without (n=113) the apoE4 allele, there were no differences in CBF, CMRO₂, C(A-V)O₂, 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.

Key Words: apolipoproteins • autoregulation • cerebral blood flow