The primary route of elimination for inhaled anesthetics is exhalation through the lungs. The anesthetic is removed from the body through the reverse process of absorption: the agent moves from the bloodstream to the alveoli and is exhaled with each breath. The speed of elimination depends largely on the blood-gas solubility of the anesthetic. Agents with low solubility, like desflurane, are eliminated more quickly than those with higher solubility, like isoflurane. This allows for faster recovery from anesthesia, particularly with agents like desflurane and sevoflurane, which is useful for outpatient or short-duration surgeries where rapid emergence is desirable.
Inhaled anesthetics are not significantly excreted through the kidneys or bile because of their limited metabolism. Only a small fraction of the inhaled dose is processed by the liver and excreted through the kidneys or bile. For example, while a portion of sevoflurane is metabolized into fluoride ions, the majority of the drug is exhaled unchanged. The same applies to isoflurane and desflurane, which undergo minimal metabolic transformation. Exhalation is the most efficient route of elimination for most inhaled anesthetics, accounting for more than 95% of the total dose.
