CEREBRAL METABOLISM AND EFFECTS OF PULSATILE FLOW DURING RETROGRADE CEREBRAL PERFUSION

We evaluated cerebral metabolism during retrograde cerebral perfusion (RCP) and circulatory arrest under profound hypothermia, and also inve stigated the effect of pulsatile flow on RCP. Eighteen adult mongrel d ogs were placed on cardiopulmonary bypass and were cooled to a nasopha ryngeal temperature of 20 degrees C. At this temperature, hypothermic circulatory arrest (HCA; n = 6), non-pulsatile RCP (NP-RCP; n = 6), an d pulsatile RCP (P-RCP; n = 6) were performed for 60 minutes; Retrogra de cerebral perfusion was performed via the bilateral internal maxilla ry veins, and retrograde flow rate was regulated to maintain a mean pe rfusion pressure of 20 mmHg in the external jugular vein. During RCP, the temperature was maintained in a narrow range, oxygen consumption a nd carbon dioxide excretion could be observed, the excess lactate was maintained at a negative value, and cerebral tissue ATP concentration was significantly higher than in the HCA group. The cerebral tissue wa ter content was significantly lower in the P-RCP group than in the NP- RCP group. These findings suggest that hypothermia of the central nerv ous system, the supply of oxygen, the excretion of metabolites, aerobi c metabolism and the cerebral ATP level were maintained by RCP. In con clusion, RCP may possibly provide: adequate metabolic support for the brain during total circulatory arrest, and pulsatile flow appears to r educe cerebral edema when compared with non-pulsatile flow in dogs.