A P-31-MAGNETIC RESONANCE STUDY OF ANTEGRADE AND RETROGRADE CEREBRAL PERFUSION DURING AORTIC-ARCH SURGERY IN PIGS

To evaluate the effect of hypothermic circulatory arrest on brain meta bolism, we used P-31-magnetic resonance spectroscopy to monitor brain metabolites in pigs during 2 hours of ischemia and 1 hour of reperfusi on. Twenty-eight pigs were divided into five groups, Anesthesia (n = 5 ) and hypothermic cardiopulmonary bypass groups (n = 5) served as cont rols, In the circulatory arrest (n = 6), antegrade perfusion (n = 6), and retrograde (n = 6) brain perfusion groups, the bypass flow rate wa s 60 to 100 ml . kg(-1). min(-1). In the antegrade group, the brain wa s perfused via the carotid arteries at a blood flow rate of 180 to 200 ml . min(-1) during circulatory arrest at 15 degrees C. In the retrog rade group, the brain was perfused through the superior vena cava at a flow rate of 300 to 500 ml . min(-1) during circulatory arrest at 15 degrees C. The intracellular pH was 7.1 +/- 0.1 and 7.3 +/- 0.1 in the anesthesia and hypothermic cardiopulmonary bypass groups, respectivel y, In the circulatory arrest group, the intracellular pH decreased to 6.2 +/- 0.1 and did not recover to its initial value (7.0 +/- 0.1) dur ing reperfusion (p < 0.05 compared with the value obtained from the co ntrol groups at the corresponding time), Inorganic phosphate did not r eturn to its initial level during reperfusion, In three animals in thi s group, levels of high-energy phosphates, adenosine triphosphate and phosphocreatine, recovered partially but did not reach the levels obse rved before arrest. In the group receiving antegrade perfusion, cerebr al metabolites and intracellular pH were unchanged throughout the prot ocol, During circulatory arrest in the retrograde perfusion group the intracellular pH decreased to 6.4 +/- 0.1 and recovered fully during r eperfusion (7.1 +/- 0.1), High-energy phosphates also returned to thei r initial levels during reperfusion, These studies show that deep hypo thermic circulatory arrest with antegrade brain perfusion provides the best brain protection of the options investigated.