Oxygen metabolism under various bypass flow conditions during cardiopulmonary support in awake goats

Despite its wide clinical application, patient recovery from cardiopulmonar y support (CPS) is not necessarily satisfactory. To clarify what influence CPS has on organ perfusion, we investigated the oxygen metabolism under var ious bypass flow (BF) conditions in a series of chronic animal CPS experime nts. The CPS system, which consists of a pulsatile ventricular assist device and a compact artificial lung was installed without anesthesia in 6 adult goat s weighing 49-51 kg. BF was adjusted stepwise from 0% to 50%, 75%, 90%, and 100% of total systemic blood flow (TSF) by balancing the pulmonary arteria l flow. The animals' TSF and oxygen delivery (DO2) were sufficiently mainta ined throughout the experiments. The oxygen consumption (VO2) and the oxygen extraction rate (ExO(2)) increa sed from 178 +/- 14 to 342 +/- 19 ml/min, and from 28 +/- 2% to 64 +/- 1%, respectively in proportion to the increase of CPBF dependency from 0% to 10 0%. The blood lactate level did not change appreciably even at 90% BF from 5.7 +/- 0.3 to 11.2 +/- 1.2 mg/dl, but drastically elevated to 23.5 +/- 4.6 mg/dl at the total bypass. This indicates that CPS leads to a relative lack of oxygen and can induce o rgan dysfunction due to increasing VO2 and ExO(2) in proportion to the incr ease of BF dependence even if TSF and DO2 are sufficiently maintained.