EFFECTS OF NITROUS-OXIDE ON PSYCHOLOGICAL PERFORMANCE - A DOSE-RESPONSE STUDY USING INHALATION OF CONCENTRATIONS UP TO 15-PERCENT

In this six-period randomised double-blind study, 12 healthy volunteer s inhaled mixtures of nitrous oxide at concentrations of 0% (placebo); 3%, 5%, 7%, 10%, and 15% in oxygen. Each concentration was inhaled fo r 55 min, each period being on a separate day. The order of treatments was randomised using a Latin-Square design. The effects of nitrous ox ide were assessed using a battery of performance tests which included measures of attention, psychomotor function, memory and cognition. Moo d was assessed using visual analogue scales. Measures of attention and psychomotor performance showed impairment at 15% nitrous oxide, and s ubjective measures showed sedation at this dose. The Buschke Selective Reminding Task showed impairment to long-term recall at all doses of nitrous oxide compared to placebo, while short-term recall was impaire d only at 15%. These results suggest that consolidation of memory may be particularly sensitive to disruption as a result of CNS depression.