Surgical Stimulation Antagonizes the Respiratory Depression Produced by Forane

In 15 patients anesthetized with Forane and in an additional 15 patients anesthetized with Forane and nitrous oxide, the authors found that surgical stimulation induced increases in ventilation which significantly reduced PaCO2 The mean reductions in CO2 from control values prior to surgical stimulation ranged from 5 to 13 torr, the magnitudes being similar in the two groups and for all depths of anesthesia. The reductions were sufficient to cause all average CO2 values to be less than 50 torr even at deep levels of anesthesia. Prior to operation, the respiratory depression for a given anesthetic concentration appeared to be somewhat greater when Forane was given without nitrous oxide.