volatile liquids, heated to gases

main target is brain

lung = superb organ for drug uptake due to surface area

anesthetic potency measure by MAC (minimum alveolar concentration) = concentration of anesthetic that prevents movement in 50% of subjects in response to pain

• Meyer Overton rule: correlation between lipid solubility of substance and MAC
• anesthesia = when sufficient # of inhaled molecules dissolve in cell membrane
• higher solubility = lower MAC = more potent
• Mullins: Critical Volume Hypothesis, absorption of molecules expands volume of hydrophobic region within membrane and distort ion channels
• increase GABA (all -anes) and/or decrease NMDA

least to greatest

nitrous oxide <<< desflurane < sevoflurane < isoflurane = enflurane < halothane

1st successful volatile anesthetic

nonflammable, halogenated alkane

pleasant on inspiration

ADR: may trigger malignant hyperthermia, 20% metabolized, which leads to halothane hepatitis, tachyarrhythmia due to histamine release

not used in adults

nonflammable fluorinated ethyl methyl ether

can cause changes in EEG (seizure activity)

only 2% metabolized

halogenated methyl ethyl ether

0.2% metabolized

too much fluoride

fluorinated isopropyl ether

4% metabolized

reacts with CO2 to form haloalkene Compound A (kidney damage)

least fat soluble = rapid elimination and awakening

eg halothane fat soluble, goes to tissues, desflurane does not

0.04% metabolized

fluorinated methyl ethyl ether

inorganic nonflammable gas

NMDA antagonist, no GABA agonism

sympathomimetic (like ketamine)

inhibits vitamin B12 and B12 dependent enzymes (myelin and RBC production)