Clinical potency of nitrous oxide--is MAC the gold standard?

Nitrous oxide is delivered during most cases of general anaesthesia. Though it has a history of approx. 150 years there is no univocal understanding about its clinical potency. Research studies during the last 10 years support, however, the view that 1. the potency of nitrous oxide in the clinical settings is only 1/3 of the potency as estimated from the MAC value; 2. the potency of combinations of nitrous oxide and volatile anaesthetics is represented more appropriately by quantities which are derived from the EEG than by the addition of MAC fractions. The findings of the last 10 years do not support the hypothesis, that the addition of nitrous oxide to the breathing gas is more beneficial than waiving the use of nitrous oxide.