Nitrous Oxide: the first anaesthetic: from hero to villain

Nitrous oxide was manufactured by Joseph Priestley in 1772 but it was not till 1844 when it was used as the first anaesthetic

Humphry Davy studied the effects of nitrous oxide on the body the gas in the early eighteen hundreds but its first use was in entertainment.  In Boston entertainers would hire a hall. Volunteers from the audience would be called on stage and invited to inhale the gas. The entertainment was watching the antics of those volunteers under the influence. Nitrous oxide was soon referred to as laughing gas.

In 1844 a young dentist, Horace Wells, attended. There was no anaesthesia for surgeons or dentists. Extraction of teeth for dental abscesses (the only treatment) was extremely painful. Wells watched while one of volunteers fell and was injured and did not appear to experience any pain. Wells obtained some nitrous oxide. At that stage it was stored in a large leather bag so not available in commercial quantities. Wells gave the nitrous oxide by to some of his patients requiring tooth extraction by getting them to inhale from the bag. The results were miraculous.

Wells organised a demonstration of a dental extraction in the operating theatre at the Massachusetts general Hospital in Boston. The demonstration was not a success. Nitrous oxide provides excellent pain relief and for many years was used for pain relief in labour. It does not provide general anaesthesia on its own. To the dentist’s embarrassment, the patient screamed and leapt of the operating table. A young doctor went after the patient and learned that the patient had no memory of the extraction. That doctor went on to successfully use ether for surgery but that is another story.

Nitrous oxide until recently has been an important supplement to general anaesthesia. As a gas its utilisation required storage and then delivery to the patient via the lungs. Manufacturers provided the gas in cylinders, compressed to liquid. Enterprising doctors and engineers developed anaesthesia delivery machines incorporating valves and rotameters to accurately deliver the gas to an anaesthesia breathing circuit. Nitrous oxide was always combined with oxygen and in a 50/50 mix was known as Entonox and used in ambulances and given to women in labour for pain relief. Midwife’s were experienced in teaching mothers how to use the breathing devices provided. In anaesthesia nitrous oxide was combined with a strong anaesthesia drug. First ether then trichlorethylene and later halothane, isoflurane, and more modern anaesthesia drugs as they were discovered.

Early anaesthesia made the patient deeply unconscious. Ether was the first strong anaesthetic and was easy to learn to use when introduced in 1846. A poor understanding of human physiology meant that unless patients did not have lung or heart disease death rates were high and doctors did not understand why. Adding nitrous oxide reduced the amount of strong anaesthetic required.

A radical improvement in death rates came with the concept of paralysis of the patients muscles.

Only enough anaesthesia to provide unconsciousness was required as paralysis stopped reflex movement of the patient. The patients’ lungs were ventilated. Nitrous oxide provided 70% of the anaesthetic in conjunction with only a small amount of the powerful anaesthetic drugs. The safety of anaesthesia was dramatically increased with this technique.

Nitrous oxide now a villain

Nitrous oxide is however a greenhouse gas. In recent years with the advent of powerful intravenous anaesthetic drugs, inhalation anaesthesia has become less necessary and nitrous oxide is not necessary in the majority of anaesthetics.