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, and when MAP exceeds 160 mmHg the cerebrovascular permeability may increase. In the present study all rats with MAP greater than 170 mmHg showed areas of protein leakage in the brain. When dealing with substances that normally do not pass the blood-brain barrier (BBB), this permeability increase may have important consequences. It is suggested that rats under nitrous oxide anaesthesia with MAP greater than 160 mmHg should not be included in studies in which an intact BBB is essential.