Hypercapnic alteration of visual evoked responses in acute cerebral infarction

To determine the effect of inhaled carbon dioxide on acute ischemic cerebral injury, we have compared occipital visual evoked responses (VER) at baseline and during hypercapnia in 20 patients with acute unilateral cerebral infarction (ten with and ten without homonymous hemianopsia) and in ten normal controls. Visual evoked responses were judged on the basis of interhemispheral symmetry. In eight of ten controls and six of 20 patients, baseline VERs were symmetrical and remained unchanged during hypercapnia. In 14 patients with asymmetrical baseline VERs, hypercapnia caused improvement of symmetry in five, worsening in three, and no change in six. Hypercapnic vasodilation may be either beneficial or deleterious to cerebral function in patients with acute cerebral infarction.