Failure to replicate negative effects of trace anaesthetics on mental performance

Twenty-four male subjects individually undertook a selection of cognitive tasks during each of two different 2-h sessions in a climatic chamber. Twelve subjects breathed a mixture of air, nitrous oxide 1600 p.p.m. (v/v) and halothane 16 p.p.m. (v/v) during the first session, and air alone during the second session 1 week later. For the other 12 subjects the order was reversed. The tests comprised learning a list of word-number pairs, solving a set of anagram problems, recognizing words and numbers, recalling word-number pairs and performing a four-choice audiovisual reaction time task. Testing was commenced after 45 min of exposure to the atmospheric conditions. A strong learning effect both within and between sessions was observed on the audiovisual task. None of the tasks, however, reflected any adverse effect of the trace anaesthetics.