A Cutoff in Potency Exists in the Perfluoroalkanes

Abstract

Anesthetic potencies (minimum alveolar anesthetic concentration [MAC]) of perfluoroalkanes from perfluoromethane to perfluorooctane were assessed in male rats to determine whether a cutoff in anesthetic effect (i.e., an absence of any anesthetic effect) exists for the larger compounds in this series. Although hyperbaric measurements suggested a MAC of 38.9 +/- 6 atm (mean +/- SD) for CF4, this pressure was nearly identical to the lethal pressure of 41.1 +/- 5.8 atm. Hyperbaric studies of C2F6 caused death without causing anesthesia, the lethal pressure being 23.8 +/- 2.6 atm. Results from studies of additivity with desflurane suggested that the MAC of CF4 was 66.5 +/- 13.4 atm at an average CF4 test partial pressure of 17.7 +/- 4.0 atm (i.e., 17.7 atm of CF4 decreased the MAC of desflurane by 26.6%). Studies of additivity with desflurane, isoflurane, or halothane did not reveal an anesthetic effect of C2F6 at a pressure of 7.2 +/- 0.4 atm, or of larger perfluoroalkanes near to or at their saturated vapor pressures. We conclude that a cutoff in anesthetic potency for perfluoroalkanes exists between perfluoromethane and perfluoroethane.