title: Nitrous oxide decreases solubility of isoflurane and halothane in blood.
abstract: This study investigated the effects of carrier gases on the solubility of isoflurane or halothane in blood. The blood/gas partition coefficients (lambda blood/gas) of 1 minimum alveolar anesthetic concentration of isoflurane or halothane in 100% oxygen, 30% oxygen with 70% nitrous oxide, 100% nitrous oxide or air were measured at 37 degrees C, with blood from four donors. The values of isoflurane or halothane in 100% nitrous oxide (1.42 +/- 0.03; 2.59 +/- 0.05) were lower (P < 0.05) than those obtained when using 100% oxygen (1.53 +/- 0.02; 2.71 +/- 0.05) or air (1.54 +/- 0.03; 2.74 +/- 0.05). To determine the effect of absence of oxygen in the blood containing nitrous oxide on solubility, lambda blood/gas of 1 minimum alveolar anesthetic concentration of isoflurane or halothane in 100% oxygen, a gas mixture (30% oxygen and 70% nitrous oxide) or 100% nitrous oxide were measured under the same conditions. The values of isoflurane or halothane in 100% nitrous oxide (1.29 +/- 0.03; 2.25 +/- 0.08) and in a gas mixture of 30% oxygen and 70% nitrous oxide (1.33 +/- 0.04; 2.29 +/- 0.05) were lower (P < 0.05) than those obtained with 100% oxygen (1.40 +/- 0.03; 2.37 +/- 0.04). We conclude that nitrous oxide decreases the lambda blood/gas of isoflurane or halothane, and that this change of solubility, although small, increases the uptake rate of halothane or isoflurane.
authors.affiliation: Institute for Anesthesiology and Intensive Care, University Hospital, Bern, Switzerland.
authors.forename: G M
authors.initials: GM
authors.lastname: Xie
authors.forename: R
authors.initials: R
authors.lastname: Lauber
authors.forename: A M
authors.initials: AM
authors.lastname: Zbinden
mesh_terms: D000328:Adult; D000368:Aged; D003864:Depression, Chemical; D006221:Halothane / Q000097:blood*; D006801:Humans; D007530:Isoflurane / Q000097:blood*; D008875:Middle Aged; D009609:Nitrous Oxide / Q000494:pharmacology*; D012995:Solubility / Q000187:drug effects
chemical_list: D007530:Isoflurane; D009609:Nitrous Oxide; D006221:Halothane