Anesthetic potency of nitrous oxide in young swine (Sus scrofa)

Abstract

SUMMARY Determination of nitrous oxide (N 2 O) potency was accomplished by extrapolation using the concepts of minimum alveolar concentration ( mac ) and additivity among inhalation anesthetics. Halothane and isoflurane anesthetic requirement (alveolar concentration) necessary to achieve mac in 9 pigs decreased with each successive increase in the percentage of inspired N 2 O (25%, 50%, 75%). Halothane and isoflurane mac was determined to be 0.94 ± 0.03 and 1.75 ± 0.01 volumes percent, respectively. Halothane and isoflurane requirements decreased to 0.74 ± 0.02, 0.66 ± 0.02, and 0.58 ± 0.02; and to 1.56 ± 0.02, 1.38 ± 0.02, and 1.08 ± 0.03 volumes percent with 25%, 50%, and 75% N 2 O, respectively. The line of best fit derived from regression analysis of the combined data (isoflurane and halothane mac values) had a correlation coefficient of 0.987 and an X intercept equivalent to 195% N 2 O. The potency of N 2 O in pigs was similar to that of other domesticated mammals and reduced halothane and isoflurane anesthetic requirements by approximately 50% of the reduction observed in human beings.