REGIONAL PERFUSION ABNORMALITIES WITH PHENYLEPHRINE DURING NORMOTHERMIC BYPASS

Background. Hypotension and vasopressors during cardiopulmonary bypass may contribute to splanchnic ischemia. The effect of restoring aortic pressure on visceral organ, brain, and femoral muscle perfusion durin g cardiopulmonary bypass by increasing pump flow or infusing phenyleph rine was examined. Methods. Twelve anesthetized swine were stabilized on normothermic cardiopulmonary bypass. After baseline measurements, i ncluding regional blood flow (radioactive microspheres), aortic pressu re was reduced to 40 mm Hg by decreasing the pump now. Next, aortic pr essure was restored to 65 mm Hg either by increasing the pump flow or by titrating phenylephrine. The animals had both interventions in rand om order. Results. At 40 mm Hg aortic pressure, perfusion to all visce ral organs and femoral muscle, but not to the brain, was significantly reduced. Increasing pump flow improved perfusion to the pancreas, col on, and kidneys. In contrast, infusing phenylephrine (2.4 +/- 0.6 mu g . kg(-1). min(-1)) increased aortic pressure but failed to improve sp lanchnic perfusion, so that significant perfusion differences existed between the pump flow and phenylephrine intervals. Conclusions. Increa sing systemic pressure during cardiopulmonary bypass with phenylephrin e causes significantly lower values of splanchnic blood flow than does increasing the pump flow. Administering vasoconstrictors during normo thermic cardiopulmonary bypass may mask substantial hypoperfusion of s planchnic organs despite restoration of perfusion pressure. (C) 1997 b y The Society of Thoracic Surgeons.