The Journal of Thoracic and Cardiovascular Surgery, Vol 74, 577-585, Copyright © 1977 by The American Association for Thoracic Surgery and The Western Thoracic Surgical Association
Effects of methoxamine on the coronary circulation during cardiopulmonary bypass
JB Symmonds, LH Kleinman and AS Wechsler
Effects of perfusion pressure augmentation with methoxamine on transmural
distribution and adequacy of coronary blood flow during cardiopulmonary
bypass were investigated. Flow in normal, nonworking canine hearts was
measured with tracer microspheres and electromagnetic flow probes while
heart rate, myocardial oxygen consumption, left ventricular contractility
and epicardial ST-segment stability were monitored. Measurements during
normotensive cardiopulmonary bypass were compared with values during
intraoperative hypotension and subsequent normotension achieved following
methoxamine infusion. Total and regional coronary blood flow returned to
levels not different from normotensive controls after methoxamine infusion
with a redistribution of flow to the subendocardium. We conclude that
elevating perfusion pressure during cardiopulmonary bypass with methoxamine
infusion increases total coronary and subendocardial blood flow by means of
peripheral and selective subepicardial alpha adrenergic vasoconstriction.