CEREBRAL BLOOD-FLOW MEASURED WITH INTRACEREBRAL LASER-DOPPLERFLOW PROBES AND RADIOACTIVE MICROSPHERES

We have measured cerebral blood flow with intracerebral laser-Doppler microprobes in pentobarbital-anesthetized pigs. We compared the result s with measurements from laser-Doppler probes placed on the surface of the brain and with blood flow estimation by the radioactive microsphe re method. The cerebral blood flow was varied by alterations in inspir ed carbon dioxide, hemorrhagic hypotension, and high cerebrospinal flu id pressure. The intracerebral probes and the surface probes showed pa rallel responses to variations in cerebral blood flow. The correlation was closest between surface probes and the intracerebral probes measu ring from the cerebral cortex (r = 0.46; P < 0.005). The r value betwe en laser-Doppler flowmetry and radioactive microspheres was 0.41 (P < 0.0005) for all measurements. The correlation to microspheres was best for the probes located 3 or 10 mm into the brain and poorest for the surface probe. In conclusion, intracerebral laser-Doppler flow measure ments reflect changes in blood flow, and the technique appears useful for continuous estimates of cerebral blood flow.