Achievement of physiologic pulsatile flow on cardiopulmonary bypass with a 24 French cannula.

In 1990, the NIH formally recognized the need for investigation of the problem of damaging the effects of cardiopulmonary bypass, issuing RFA HL-90-12-H, which emphasized production of neurologic defects in the very young and the elderly. The authors were at that time involved in comparison of pulsatile flow to steady flow cardiopulmonary bypass in large ungulates. The world literature recognizes five damaging effects of steady flow cardiopulmonary bypass that can be mitigated by pulsatile flow: metabolic acidosis, interstitial fluid accumulation, elevated systemic vascular resistance, arteriovenous shunting, and impaired brain oxygenation. To maximize the beneficial effect of pulsatile flow, however, it is necessary that its morphology be physiologic. It has been stated in the past that this goal may not be possible using standard size aortic cannulas. The purpose of this publication is to describe a method by which this feat has been achieved in 150 pound ungulates undergoing prolonged cardiopulmonary bypass.