Cerebrovascular permeability to protein in the rat during nitrous oxide anaesthesia at various blood pressure levels.

Rats anaesthetized with 70% nitrous oxide in oxygen have a high mean arterial pressure (MAP), usually in the range of 130–155 mmHg. It occasionally reaches higher levels, aiid when MAP exceeds 160 mmHg the cerebrovascular permcability may increase. In the prescnt study all rats with MAP>170 mmHg showed areas of protcin leakage in ihc brain. When dcaling with substancm that normally do not pass the blood-brain barrier (BBB), this permeability increase may have important consequences. It is suggcsted that rats under nitrous oxide anaesthesia with MAP> 160 mmHg should not be included in studies in which an intact BBB is essential.