Hyperventilation reverses the nitrous oxide-induced increase in cerebral blood flow velocity in human volunteers
Hörmann, C.; Schmidauer, C.; Haring, H.P.; Schalow, S.; Seiwald, M.; Benzer, A.
British Journal of Anaesthesia 74(5): 616-618
1995
ISSN/ISBN: 0007-0912 PMID: 7772442 Document Number: 446091
Because hypocapnia is routine during general anaesthesia for intracranial procedures, we have compared, in 13 healthy volunteers, the effect of normocapnia (PE'CO-2 5.3 kPa) and hypocapnia (PE'CO-2 3.3 kPa) on mean blood flow velocity in the middle cerebral artery (Vmca) during normoventilation and hyperventilation with air and with 50% nitrous oxide in oxygen. After replacement of air with 50% nitrous oxide in oxygen, there was an increase in mean Vmca during normoventilation (air: mean 68.23 (SD 16.98) cm s-1 vs nitrous oxide in oxygen: 90.69 (20.41) cm s-1; P lt 0.01), whereas during hyperventilation mean Vmca values were similar regardless of the inhaled gas mixture (air: 43.46 (9.97) cm s-1 vs nitrous oxide in oxygen: 41.69 (8.08) cm s-1. Our data suggest that the nitrous oxide-induced increase in mean Vmca can be blocked by hyperventilation.