Anesthesia

The chemical structure of diethyl ether, the first general anesthetic agent.

Anesthesia is the medical induction of insensibility. This is accomplished through the use of agents called anesthetics. There are two major forms of anesthesia used medically, general and local. General anesthetics work systematically, inducing complete insensibility which appears like a deep sleep. Local anesthetics work locally, inducing a local inability to feel pain, but allowing the patient to remain fully conscious and unsedated. The first safe general anesthetic was diethyl ether and the first local anesthetic was cocaine.

While Ethanol is often thought of as an anesthetic, and while it can technically induce anesthesia by its GABAergic action, it has the major problem that the difference between an effective and lethal dose is hard to determine and its dosage cannot be rapidly changed. Whereas, diethyl ether, being volatile enough to be inhaled, allows rapid reduction or augmentation of the received dose.

General Anesthetics

A WWI portable anesthetic kit, showing the cotton mask upon which chloroform would have been dropped.

The most easily produced general anesthetic agents to produce are diethyl ether and chloroform. However, of the two, diethyl ether is by far the safer. Chloroform is likely cancerous and has been known to cause sudden cardiac arrest. This is why its use was supplanted by that of ether in hospital settings by the late 19th century. However, chloroform does have one major advantage over diethyl ether which meant it was still used by military surgeons and other surgeons who had to preform surgery in makeshift environments, it is almost entirely nonflammable. Diethyl ether is incredibly flammable, to the extent where there are stories of open bottles of it being lit from candles set on other sides of desks. This, combined with the fact that only hospitals could afford expensive ventilation equipment, meant that it was regarded as a worthwhile tradeoff to allow for a slight chance of cardiac arrest in exchange for the flammability risk to be eliminated.

Local Anesthetics

The first local anesthetic to be discovered and used clinically was cocaine. In fact, it is still in use today in delicate surgeries involving the nose, as it has the highly desirable quality of acting as both a local anesthetic and a vasoconstrictor (a drug which causes the blood vessels to narrow). This is desirable as it provides a much longer duration of action for the local anesthesia than would otherwise be possible.

However, because cocaine requires the leaves of the tropical coca plant, it is likely to be impractical to use cocaine as a local anesthetic. The second local anesthetic to be discovered, benzocaine, is a convenient substitute as it can be relatively easily produced from aniline, an aromatic feedstock chemical which is one of the backbones of pharmaceutical chemistry.