Anaesthesia, (literally: without sensations) is the drug-induced mental state created to make any kind of painful or distressful therapeutic or diagnostic procedure possible. General anaesthesia today, including intravenous induction, Total Intravenous Anaesthesia (TIVA) and inhalational or intravenous maintenance, is truly ‘state of the art’.
During anaesthesia, highly-trained and dedicated anaesthesia personnel monitor the drug delivery, basic vital signs and the surgical intervention throughout the procedure.
The combination of safe and efficacious drugs, good monitoring equipment and drug delivery devices and, not least, highly-trained and dedicated personnel, has made general anaesthesia overwhelmingly safe.
Nitrous oxide in anaesthesia
Nitrous oxide is a safe, cost-effective and predictable anaesthetic agent that is predominately used as a background anaesthetic. This is usually supplemented with either a potent, volatile or intravenous anaesthetic. When used in this way, it can cut the dosage of the other agents used. The use of nitrous oxide allows for faster induction times when used with a volatile agent, due to its low blood/gas solubility.
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History of anaesthesia
Nitrous oxide or laughing gas as it is commonly known, was first synthesised by Joseph Priestley in 1772. It was first used as an analgesic in dentistry forty years after this. One may argue whether the first use of ether in 1846 or the first use of nitrous oxide in 1844 marks the birth of modern anaesthesia. General anaesthesia today is a basic and natural part of the general management of surgical patients.
The barbiturates introduced during the first half of the last century represent an important step in the evolution of general anaesthesia. By injecting these intravenously a rapid induction of anaesthesia was achieved. The next major milestone in modern anaesthesia was the introduction of ‘Halothane’ the first halogenated inhaled anaesthetic. Halothane replaced ether as a non-explosive highly potent vapour. In concentrations of about 1 %volume, the majority of patients experienced an acceptable level of anaesthesia in general surgery.
Halothane was followed by a series of other halogenated inhaled anaesthetics; penthrane, enflurane, isoflurane and, during the last decade, desflurane and sevoflurane. All these vapours are highly efficacious and safe.
During the second half of the last century a number of potent and safe analgesics were also introduced. One of the first was fentanyl, a highly potent opioid to be used intravenously during anaesthesia. A family of other semi-synthetic and synthetic opioids for intra operative and postoperative use also followed.
Along with these drugs came an increasing knowledge of basic physiology and the pathophysiology associated with trauma/stress. These all mark important milestones in the fast evolution of modern, safe and effective anaesthesia.