In the acute stage of selected cerebrovascular occlusive disease, it is essential to prevent irreversible neuronal changes caused by ischemic insult by restoring decreased cerebral blood flow through appropriate methods. As an active and non-surgical method for enhancement of perfusion flow, inhalation of carbon dioxide has been considered.
Previous experiments of the authors clarified that mild hypercapnia between 43 to 55 mmHg was effective in enhancing perfusion flow in the area of ischemia. However, an additional verification of effectiveness of mild hypercapnia was needed with respect to restoration of neuronal activity in ischemic brains.
Accordingly, somatosensory evoked potential (SEP) as well as regional cerebral blood flow (rCBF) were monitored under mild hypercapnia in ischemic brains of dogs produced by occlusion of a middle cerebral artery.
Under normocapnia, the primary component (V₁) of the evoked potential was depressed by 53.8% with a 31.3% decrease of rCBF 30 minutes following occlusion of a middle cerebral artery.
During mild hypercapnia, recovery of SEP by 63.4% was noted with an increase of rCBF by 23.4%.
The authors concluded that mild hypercapnia was beneficial not only in increasing rCBF but also in restoring neuronal activity in acute ischemic brains of a mild degree.