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

Kim, Jong Uk; Park, Pyung Hwan; Song, Myung Hee; Shin, Ji Yeon; Lim, Kun Ho; Lee, Jung Hee

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.