Effect of hypertonic mannitol and isoproterenol on regional coronary flow following right ventriculotomy

The authors studied the changes which occurred in regional coronary blood flow after right ventriculotomy and the subsequent effects of hypertonic mannitol or isoproterenol infusion. Regional coronary flows were measured with radioactive microspheres (9 micron) in open chest anesthetized dogs. Either hypertonic mannitol (25%) was infused at 3.2 ml/min for 30 minutes, or normal saline at 7.6 ml/min for 30 minutes followed by isoproterenol at 0.05 to 0.10 μg/kg/min. In the mannitol treated animals right ventricular, left atrial and aortic pressures, heart rate, and cardiac output did not change significantly following vertical ventriculotomy, whereas in the saline isoproterenol treated animals aortic pressures fell significantly. Coronary flow to the peri incisional area fell from 41 to 24 ml/min.100 g (P < 0.05) following ventriculotomy, increased by 34% (P < 0.05) when osmolality rose after mannitol by 37 mOsm, but was unchanged with isoproterenol. The data indicate that a vertical ventriculotomy reduces flow to adjacent myocardium and that subsequent infusion of hypertonic mannitol at moderate rates significantly increases coronary flow to this region.