Influence of equianaesthetic concentrations of nitrous oxide and isoflurane on regional cerebral blood flow, regional cerebral blood volume, and regional mean transit time in human volunteers

Nitrous oxide and isoflurane have cerebral vasodilatory effects. The use of isoflurane in neuroanaesthesia is widely accepted, whereas the use of nitr ous oxide in neuroanaesthesia is still the subject of debate. In the presen t study, contrast-enhanced magnetic resonance (MR) perfusion measurement wa s used to compare the effects of 0.4 MAC nitrous oxide (n=9) and 0.4 MAC is oflurane (n=9) on regional cerebral blood flow (rCBF), regional cerebral bl ood volume (rCBV) and regional mean transit time (rMTT) in spontaneously br eathing human volunteers. Nitrous oxide increased rCBF and rCBV in supraten torial regions more than did isoflurane. Isoflurane, by contrast, increased rCBF and rCBV in basal ganglia more than did nitrous oxide. An increased r MTT was caused by a relatively greater increase in rCBV than in rCBF suprat entorially by isoflurane and infratentorially by nitrous oxide. In conclusi on, nitrous oxide increases rCBF and rCBV predominantly in supratentorial g rey matter, whereas isoflurane increases rCBF and rCBV predominantly in inf ratentorial grey matter.