Bilateral brachial paralysis from watershed infarction after coronary artery bypass. A report of two cases and review of the predisposing anatomic and physiological mechanisms.

Bilateral brachial paralysis and bilateral visual field defects developed after coronary artery bypass in two patients. These deficits, caused by cerebral watershed infarctions, probably resulted from global cerebral hypoperfusion during cardiopulmonary bypass, although bypass had been maintained with high perfusion flows (2.0 to 3.0 L/min/m2) and perfusion pressures from 50 to 90 mm Hg. No systemic hypoperfusion or hypotension occurred before or after cardiopulmonary bypass. Cerebral watershed infarctions occur predominantly in the boundary zones between the anterior, middle, and posterior cerebral arteries. In previous reports, watershed infarctions most often occurred as preterminal events in patients after sustained episodes of obvious hypoperfusion. The occurrence of such major neurological deficits in two patients without systemic hypoperfusion suggests that traditionally accepted flows and perfusion pressures do not assure adequate cerebral blood flow during cardiopulmonary bypass.