Chapter 1

Historical Development of Conscious Sedation

Aim

The aim of this chapter is to describe the historical development of conscious sedation techniques for dentistry.

Outcome

After reading this chapter you should have an understanding of the way conscious sedation techniques have evolved. You will also understand the close historical links between conscious sedation and general anaesthesia.

Introduction

The ability of twenty-first century dentists to provide comfortable treatment for their patients has its origin in the discovery and development of general anaesthetic drugs in the nineteenth century. Before the advent of these drugs, the dental patient was expected to endure considerable pain and distress. The most commonly performed surgical procedure was the extraction of teeth. Grim stoicism and occasional self-medication with alcohol were the only ways of coping.

Dentists contributed in no small measure to the early development of general anaesthesia and, later, to the introduction of local anaesthesia and conscious sedation techniques. In the USA, Horace Wells used nitrous oxide for the first time in 1844 and William Morton administered ether for dental extractions in October 1846. Both these men were dental surgeons. In England, another dentist, James Robinson, was the first to administer ether to a patient in London only two months after Morton.

Carl Koller pioneered the use of topical and injected cocaine for local anaesthesia in ophthalmology in 1884. Twenty years later, procaine was available for use in dental patients. This was superseded by lidocaine (lignocaine) in the late 1940s. Reports of dentists using nitrous oxide to provide inhalational conscious sedation, rather than general anaesthesia, started to appear in the early 1900s. By the 1930s, an intravenous barbiturate, hexobarbitone, was in use in UK dental practices for sedation.

Over the course of the second half of the twentieth century, there were further developments in the drugs and techniques used for dental conscious sedation. These are shown in Table 1-1.

Relative Analgesia

Joseph Priestley discovered oxygen in 1771 and nitrous oxide in 1772. The analgesic properties of nitrous oxide were discovered by Humphry Davy in 1798. It appears that Davy inhaled nitrous oxide in order to determine its effects, whilst suffering pain from a partially erupted wisdom tooth. He noticed that his painful pericoronitis was relieved. In 1800, Davy published a treatise on nitrous oxide in which he suggested that the gas “may probably be used with advantage during surgical operations”.

No further progress was made until 1844, when Horace Wells had one of his own teeth extracted under nitrous oxide anaesthesia. Edmund Andrews, a Chicago surgeon, reasoned that the asphyxia often seen during nitrous oxide anaesthesia was due to the oxygen in nitrous oxide not being available to oxygenate the blood. In 1868 he demonstrated that a mixture of 20% oxygen and 80% nitrous oxide was satisfactory for safe and effective anaesthesia. In 1881 nitrous oxide was first used as an analgesic during childbirth in St Petersburg. In 1889 nitrous oxide was used to provide analgesia for a dental procedure in Liverpool. By current standards, the machines used to deliver nitrous oxide and oxygen were crude and the gases far from pure. Many dentists manufactured their own nitrous oxide!

During the first half of the twentieth century interest in nitrous oxide sedation came and went. Success was variable, partly as a consequence of the use of inappropriate equipment, but also because of a misunderstanding about the properties of the gas and the best way to use it. Hitherto, the main emphasis had been placed on the analgesic properties of nitrous oxide, but attempts to achieve total analgesia in every patient often led to failure. Many patients experienced nausea, vomiting and excitement-stage symptoms. Appreciation of the excellent sedative properties of nitrous oxide came later following the work of Harry Langa (USA), Ulla Hoist (Denmark) and Paul Vonow (Switzerland) during the 1940s and 1950s. The change in use of nitrous oxide from analgesia to sedation led to alterations in technique, dosage and in the approach to the patient.

Langa used the term “Relative Analgesia” to describe his sedation technique. The tec/>

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