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CARDIOVASCULAR
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Volume 5, 2000, No 3 |
Magnetic
Resonance Studies of the Effects of Cardiopulmonary Bypass and Selective Brain
Perfusion on Brain Metabolism and Function
J. Ye, R.
Deslauriers, L. N. Ryner
Neurological and neuropsychological impairment are important sequelae of cardiac surgery with cardiopulmonary bypass, particularly aortic arch surgery requiring circulatory arrest. Clinical studies have shown a fairly high incidence of neuropsychological dysfunction in patients who underwent cardiopulmonary bypass. The nature of the undelying brain injuries remains poorly understood. Hypothermic circulatory arrest is commonly used for brain protection during aortic arch surgery, but the safe duration of this technique is limited. Other techniques used for brain protection have been proposed and used clinically. However, none of the techniques is completely satisfactory. Precise, and preferably quantitative, definition of the localization and nature of the underlying injuries is a precondition for rigorous evaluation of the efficacy of prophylactic measures. Magnetic resonance (MR) spectroscopy and imaging have been demonstrated to be unique, non-invasive tools that are amenable to repetitive monitoring of the anatomical, biochemical and physiological status of the brain. The ability of magnetic resonance spectroscopy and imaging to detect physiological and pathological changes in the brain is described. Results of serial experiments studying the biochemical and physiological sequelae of cardiopulmonary bypass and various selective brain perfusion techniques in an in vivo pig model are presented. MR imaging can provide noninvasive information on physiological and pathological changes and MR spectroscopy can follow changes in metabolism and intracellular pH in the brain in various body perfusion situations. The combined information can help understand the nature of underling brain injuries and the evaluation/optimization of neuroprotective interventions used during cardiac surgery.
(CVE. 2000; 5 (3): 205-215)
Key words: magnetic resonance, imaging, spectroscopy, cardiopulmonary bypass, antegrade cerebral perfusion, retrograde cerebral perfusion, circulatory arrest, brain metabolism, hypothermia
Jian
Ye, M.D.
Institute for Biodiagnostics
National Research Council of Canada
435 Ellice Ave., Winnipeg
Manitoba R3B 1Y6
Canada
E-mail: jian.ye@nrc.ca
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