Physiologic reactions of awake animals to an immediate switch from a pulsatile to nonpulsatile systemic circulation

The purpose of this study is to clarify physiologic reactions to an immediate switch of flow pattern from pulsatile to nonpulsatile. A pulsatile ventricular assist device (VAD) was implanted in four 40-64 kg goats. Blood was drawn from the left atrium and ventricle and expelled into the aorta. After 2 weeks the VAD was quickly replaced by a centrifugal pump, MD-10 (Iwaki Pump, Tokyo, Japan), 760 g in weight and phi 70 mm x 84 mm in size, set on the back, without anesthesia. A 100% nonpulsatile bypass flow was immediately obtained, and the pump was set to maintain the same mean aortic pressure as before the switch; central venous pressure, cardiac output, systemic vascular resistance, oxygen consumption, blood lactate, plasma adrenalin, noradrenalin, renin activity, angiotensin II, and aldosterone were measured. Behavior of the goats did not change, and fluid infusion and higher cardiac outputs were not required. Most of the parameters did not deviate from control levels after the switch. In conclusion, a mammal immediately accommodates well to nonpulsatile flow.