The effect of nicotinic acid on the cerebral circulation, with observations on extra-cerebral contamination of cerebral venous blood in the nitrous oxide procedure for cerebral blood flow.

Measurement of cerebral blood flow by the nitrous oxide method before and during intravenous administration of nicotinic acid indicates that cerebral vessels do not respond to this drug. Evidence that contamination of cerebral by extracerebral blood occurs in about 20 per cent of subjects is adduced from the effects of nicotinic acid on the measured cerebral blood flows; studies making use of the intravascular catheter technic to sample internal jugular blood tend to confirm this hypothesis.