Regional cerebral blood flow and carbon dioxide reactivity after noncerebral injury in the rat.

A loss of cerebral autoregulation and vascular reactivity to CO2 has been reported after a direct head injury; however, little has been published concerning the effect of CO2 after peripheral injury. In the present study, the effects of extracranial injury (bilateral hindlimb ischaemia followed by reperfusion) were studied on regional cerebral blood flow in the hypothalamus and cortex and on the changes in these blood flows induced by altering PaCO2 in the conscious rat. After release of the tourniquets, when fluid was being lost from the circulation into the postischaemic hindlimbs, there was a decrease in regional cerebral blood flow (rCBF). Administration of CO2 at this time markedly increased rCBF. There was no evidence that cerebrovascular responsiveness to hypercapnia was impaired after peripheral injury in the rat.