INFLUENCE OF NON PULSATILE SYSTEMIC CIRCULATION ON TISSUE BLOOD-FLOW AND OXYGEN-METABOLISM

Influence of non pulsatile systemic circulation on oxygen metabolism w as examined regarding tissue perfusion in 12 adult goats weighing from 46 to 55 kg. Under general anesthesia, a flow character, changeable t otal left heart bypass circuit consisting of pulsatile and non pulsati le pumps was installed through a left thoracotomy. Systemic flow was c onverted from pulsatile to non pulsatile in 7 of 12 animals, and in th e reverse order in the other 5, by changing the driving pump. Esophage al mucosal blood flow was determined by a colored microsphere method t hat estimated tissue blood flow at the pre capillary level. Esophageal intramucosal pH was evaluated with a silicone balloon tonometer cathe ter surgically placed in the submucosal space. Hemodynamic and arteria l blood gas parameters were unchanged at flow mode conversion. Althoug h oxygen delivery was comparable between pulsatile and non pulsatile c irculation, oxygen extraction ratio was lower and venous oxygen satura tion was higher in non pulsatile than pulsatile circulation. Although statistically not significant, serum lactate level tended to be higher with non pulsatile circulation. No difference was observed in esophag eal mucosal blood flow between pulsatile and non pulsatile circulation , whereas intramucosal pH, which strongly correlated with arterial pH regardless of the flow mode, was significantly lower under non pulsati le than pulsatile conditions. In conclusion, systemic oxygen uptake is less efficient in non pulsatile than pulsatile circulation in the set ting of an acute experiment using animals, which may be accounted for by the disparity between the pre capillary blood flow and actual tissu e oxygen metabolism.