MOLECULAR-PROPERTIES OF THE IDEAL INHALED ANESTHETIC - STUDIES OF FLUORINATED METHANES, ETHANES, PROPANES, AND BUTANES

We examined 35 unfluorinated, partially fluorinated, and perfluorinate d methanes, ethanes, propanes, and butanes to define those molecular p roperties that best correlated with optimum solubility (low) and poten cy (high). Limited additional data were obtained on longer-chained alk anes. Using standard techniques, we assessed anesthetic potency (minim um alveolar anesthetic concentration [MAC] in rats); vapor pressure; s tability in soda lime; and solubility in saline, human blood, and oil. If nonflammability, stability, low solubility in blood, clinically us eful vapor pressures, and potency permitting delivery of high concentr ations of oxygen are essential components of an anesthetic that might supplant those presently available, our data indicate that such a drug would have three or four carbon atoms with single or dual hydrogenati on of two carbons, especially terminal carbons. We conclude that: 1) s maller and larger molecules and lesser hydrogenation provide insuffici ent potency; 2) high vapor pressures of smaller molecules do not permi t the use of variable bypass vaporizers; 3) greater hydrogenation enha nces flammability, and complete hydrogenation decreases potency; 4) in ternal hydrogenation decreases stability; and 5) greater hydrogenation increases blood solubility.