A review of mechanisms of inhalational anesthetic agents

Abstract

Long before the discovery of intravenous techniques, man has inhaled vapors to mitigate pain. Smoking cannabis and opium to achieve both pleasurable sensations and decreased consciousness has been described for over 3,000 years. Theodoric, a thirteenth-century monk and surgeon, devised a balanced anesthetic of opium, mulberry, hyoscyamine, hemlock, mandragora, woody ivy, dock, and water hemlock. These ingredients were to be boiled on a sponge, with or without the addition of alcohol, until dried out. The sponge could be rehydrated and inhaled until the patient became unconscious and surgery could commence. Reversal from the hypnotic state was by inhalation from a sponge soaked in vinegar. And while use of the spongia somnifera was largely abandoned by the end of the Middle Ages, ether and chloroform were to become the children of alcohol. Paracelsus discovered the hypnotic effect of ether around 1540, and the first surgical use was credited to Crawford Long in 1842. The first public demonstration of ether was on October 16, 1846, in Boston in what is now known as the “Ether Dome“. As cautery became integral to surgical technique during the twentieth century, anesthetic agents that did not explode had to be found. The halogenated anesthetics were born. Nitrous oxide, a weak agent, was discovered by Joseph Priestly in 1772. It was widely used as a recreational drug for over 40 years but later found places both in dentistry and as an analgesic or anesthetic-sparing component of balanced techniques.