Hyperventilation restores autoregulation of cerebral blood flow in postictal piglets.

Autoregulation of cerebral blood flow is impaired in the postictal state. This loss of autoregulation may in part be mediated by a rise in perivascular hydrogen ion and carbon dioxide concentration. We hypothesized that hypocarbia with a concomitant reduction in perivascular hydrogen ion and carbon dioxide concentration would restore autoregulation during the postictal state. We studied autoregulation of cerebral blood flow in 13 ventilated, awake 3- to 4-d-old piglets during the postictal state under normocarbic and hypocarbic conditions. During the postictal state, cerebral blood flow was pressure-passive in normocarbic piglets, whereas the relationship between cerebral blood flow and cerebral perfusion pressure was described by a polynomial curve in hypocarbic piglets. Because hypocarbia restores cerebral blood flow autoregulation in postictal newborn piglets, we speculate that the perivascular hydrogen ion and carbon dioxide concentration contribute significantly to the state of cerebral autoregulation in the postictal subject.