Effects of the Level of PaCO2 on Recovery of Energy Metabolism: Is Normocarbia or Hypocarbia Better for Ischemia-Reperfused Cat Brain?

Abstract

Background : The effect of arterial carbon dioxide tension(PaCO2) during ischemia and reperfusion has been a controversial issue. In this study, the effect of PaCO2 during ischemia and reperfusion was evaluated by 31P magnetic resonance spectroscopy(MRS). Methods : Incomplete global cerebral ischemia was induced by ligation of carotid artery under lowered mean blood pressure(mean blood pressure= 40 mmHg) for 30 minutes followed by 2 hours of reperfusion. Eighteen cats were divided into 3 groups: For group 1(n=6)(control group), animals were subjected to normocarbia(PaCO2=28∼33 mmHg) during ischemia and reperfusion, for group 2(n=6), animals were subjected to hypocarbia(PaCO2=18∼23 mmHg) during ischemia and reperfusion, and for group 3(n=6), animals were subjected to normocarbia during ischemia and hypocarbia during reperfusion. Results : For group 1, the energy metabolism measured by [PCr/Pi] was recovered about 74.7 6.4%. For group 2, the energy metabolism failed to be completely recovered by 120 minutes of reperfusion(69.3 7.3%), whereas for group 3, the energy matabolism was completely recovered by 120 minutes of reperfusion(97.6 2.4%). There were statistically significant differences between group 1 and group 3(p ＜0.05). The changes in pH were not significantly different among the groups Conclusion: In this study, a condition of hypocarbia during reperfusion seems better for the energy metabolism after incomplete global ischemia of cats. (Korean J Anesthesiol 1997; 33: 610∼616)