Effect of Nitrous Oxide and of Narcotic Premedication on the Alveolar Concentration of Halothane Required for Anesthesia

Abstract

Sixty-eight surgical patients were divided into 3 groups and anesthetized with either halothane and oxygen, halothane-oxygen following narcotic premedication, or halothane-oxygen and 70% nitrous oxide. The minimum alveolar concentration of halothane required to prevent movement in response to surgical incision was 0.74%. Addition of narcotic premedication decreased this value to 0.69% and addition of nitrous oxide (without narcotic premedication) allowed a reduction in the alveolar halothane concentration to 0.29%. Advantages of administering nitrous oxide with halothane are: decreased cost of anesthesia, increased speed of recovery, and possible decreased hepatotoxicity. We believe that these advantages outweigh the disadvantage of decreased percentage of oxygen administered. The narcotic premedication resulted in only a slight decrease in required alveolar halothane concentration. This decrease is insignificant relative to the possible cardiovascular depression that may accompany narcotic premedication.