Isoflurane is always administered in conjunction with air and/or pure oxygen. Often nitrous oxide is also used. Although its physical properties imply that anaesthesia can be induced more rapidly than with halothane,[1] its pungency can irritate the respiratory system, negating this theoretical advantage conferred by its physical properties. It is usually used to maintain a state of general anesthesia that has been induced with another drug, such as thiopentone or propofol. It vaporizes readily, but is a liquid at room temperature. It is completely nonflammable.
Animal studies have been raised safety concerns of certain general anesthetics, in particular ketamine and isoflurane in young children. The risk of neurodegeneration was increased in combination of these agents with nitrous oxide and benzodiazepines such as midazolam.[3] Whether these concerns occur in humans is unclear.[3]
Elderly
Concerns exist with regard to the relationship between administration of isoflurane and postoperative cognitive dysfunction (POCD), for which the elderly are especially vulnerable.[4]
Biophysical studies using state-of-the-art NMR spectroscopy has provided molecular details of how inhaled anesthetics interact with three amino acid residues (G29, A30 and I31) of amyloid beta peptide and induce aggregation. This area is important as "some of the commonly used inhaled anesthetics may cause brain damage that accelerates the onset of Alzheimer’s disease".[5]
Similar to many general anesthetics, the exact mechanism of the action has not been clearly delineated.[7] Isoflurane reduces pain sensitivity (analgesia) and relaxes muscles. Isoflurane likely binds to GABA, glutamate and glycine receptors, but has different effects on each receptor. It potentiates glycine receptor activity, which decreases motor function. It inhibits receptor activity in the NMDA glutamate receptor subtypes. Isoflurane inhibits conduction in activated potassium channels. Isoflurane also affects intracellular molecules. It activates calcium ATPase by increasing membrane fluidity. It binds to the D subunit of ATP synthase and NADH dehydrogenase.
Environment
The average lifetime of isoflurane in the atmosphere is 3.2 years, its global warming potential is 510 and the yearly emissions add up to 880 tons.[8]
^M. C. Lewis; I. Nevoa; M. A. Paniaguaa; A. Ben-Aric; E. Prettoa; S. Eisdorfera; E. Davidsona; I. Matotc; C. Eisdorfer (2007). "Uncomplicated general anesthesia in the elderly results in cognitive decline: Does cognitive decline predict morbidity and mortality?". Medical Hypotheses. 68 (3): 484–492. doi:10.1016/j.mehy.2006.08.030. PMID17141964.
^Martin K. Vollmer; Tae Siek Rhee; Matt Rigby; Doris Hofstetter; Matthias Hill; Fabian Schoenenberger; Stefan Reimann (2015). "Modern inhalation anesthetics: Potent greenhouse gases in the global atmosphere". Geophysical Research Letters. 42 (5): 1606. doi:10.1002/2014GL062785.
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