Impairment of cerebral blood flow autoregulation after hypertonic urea administration.

The effect of unilateral intracarotid administration of 3 M urea on resting cerebral blood flow, arterial blood pressure, perfusion pressure-cerebral blood flow relation, ECoG and Evans blue permeability was tested in dogs. The injection of urea was without effect on ECoG and enhanced the arterial blood pressure temporarily. Cerebral blood flow measured 10 min after the urea injection was not affected. Extravasation of Evans blue was observed in the urea-perfused hemisphere for about 40 min following the urea administration. Cerebral perfusion pressure-blood flow relation for the urea affected hemisphere studied at the time when blood-brain barrier to protein was restored revealed loss of the normal autoregulatory response, despite that it was preserved in the control hemisphere.