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General anaesthetics are often defined as compounds that induce a loss of consciousness in humans or loss of righting reflex in animals. Clinical definitions are also extended to include an induced coma that causes lack of awareness to painful stimuli, sufficient to facilitate surgical applications in clinical and veterinary practice. General anaesthetics do not act as analgesics and should also not be confused with sedatives. General anaesthetics are a structurally diverse group of compounds whose mechanisms encompasses multiple biological targets involved in the control of neuronal pathways. The precise workings are the subject of some debate and ongoing research.
Inhalants are a broad range of household and industrial chemicals whose volatile vapors or pressurized gases can be concentrated and breathed in via the nose or mouth to produce intoxication, in a manner not intended by the manufacturer. They are inhaled at room temperature through volatilization or from a pressurized container, and do not include drugs that are sniffed after burning or heating. For example, amyl nitrite (poppers), nitrous oxide and toluene – a solvent widely used in contact cement, permanent markers, and certain types of glue – are considered inhalants, but smoking tobacco, cannabis, and crack are not, even though these drugs are inhaled as smoke.
Nitrous oxide, commonly known as laughing gas or nitrous, is a chemical compound, an oxide of nitrogen with the formula N
2O. At room temperature, it is a colourless non-flammable gas, with a slight metallic scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen. It is soluble in water.
Anesthesia or anaesthesia is a state of controlled, temporary loss of sensation or awareness that is induced for medical purposes. It may include some or all of analgesia, paralysis, amnesia, and unconsciousness. A patient under the effects of anesthetic drugs is referred to as being anesthetized.
Sedation is the reduction of irritability or agitation by administration of sedative drugs, generally to facilitate a medical procedure or diagnostic procedure. Examples of drugs which can be used for sedation include isoflurane, diethyl ether, propofol, etomidate, ketamine, pentobarbital, lorazepam and midazolam.
Dissociatives are a class of hallucinogen which distort perception of sight and sound and produce feelings of detachment – dissociation – from the environment and/or self. Although many kinds of drugs are capable of such action, dissociatives are unique in that they do so in such a way that they produce hallucinogenic effects, which may include sensory deprivation, dissociation, hallucinations, and dream-like states or trances. Some, which are nonselective in action and affect the dopamine and/or opioid systems, may be capable of inducing euphoria. Many dissociatives have general depressant effects and can produce sedation, respiratory depression, analgesia, anesthesia, and ataxia, as well as cognitive and memory impairment and amnesia.
A whipped cream charger is a steel cylinder or cartridge filled with nitrous oxide (N2O) that is used as a whipping agent in a whipped cream dispenser. The narrow end of a charger has a foil covering which is broken to release the gas. This is usually done by a sharp pin inside the whipped cream dispenser. The nitrous oxide in chargers is also used as an oxidizer in hybrid model rocket engines.
An anaesthetic machine or anesthesia machine is a medical device used to generate and mix a fresh gas flow of medical gases and inhalational anaesthetic agents for the purpose of inducing and maintaining anaesthesia.
An anesthetic or anaesthetic is a drug used to induce anesthesia — in other words, to result in a temporary loss of sensation or awareness. They may be divided into two broad classes: general anesthetics, which result in a reversible loss of consciousness, and local anesthetics, which cause a reversible loss of sensation for a limited region of the body without necessarily affecting consciousness.
Awareness under anesthesia, also referred to as intraoperative awareness or accidental awareness during general anesthesia (AAGA), is a rare complication of general anesthesia where patients regain varying levels of consciousness during their surgical procedures. While anesthesia awareness is possible any long-term memory of it, the more clinically significant complication is awareness with explicit recall, where patients can remember the events related to their surgery.
Desflurane is a highly fluorinated methyl ethyl ether used for maintenance of general anesthesia. Like halothane, enflurane, and isoflurane, it is a racemic mixture of (R) and (S) optical isomers (enantiomers). Together with sevoflurane, it is gradually replacing isoflurane for human use, except in economically undeveloped areas, where its high cost precludes its use. It has the most rapid onset and offset of the volatile anesthetic drugs used for general anesthesia due to its low solubility in blood.
Nitrous oxide, sold under the brand name Entonox among others, is an inhaled gas used as a pain medication and together with other medications for anesthesia. Common uses include during childbirth, following trauma, and as part of end-of-life care. Onset of effect is typically within half a minute and lasts for about a minute.
An inhalational anesthetic is a chemical compound possessing general anesthetic properties that can be delivered via inhalation. They are administered through a face mask, laryngeal mask airway or tracheal tube connected to an anaesthetic vaporiser and an anaesthetic delivery system. Agents of significant contemporary clinical interest include volatile anaesthetic agents such as isoflurane, sevoflurane and desflurane, as well as certain anaesthetic gases such as nitrous oxide and xenon.
Methoxyflurane, marketed as Penthrox among others, is an inhaled medication primarily used to reduce pain following trauma. It may also be used for short episodes of pain as a result of medical procedures. Onset of pain relief is rapid and of a short duration. Use is only recommended with direct medical supervision.
Gardner Quincy Colton was an American showman, medicine man, lecturer, and former medical student who pioneered the use of nitrous oxide, or laughing gas, in dentistry.
Twilight anesthesia is an anesthetic technique where a mild dose of sedation is applied to induce anxiolysis, hypnosis, and anterograde amnesia. The patient is not unconscious, but sedated. During surgery or other medical procedures, the patient is under what is known as a "twilight state", where the patient is relaxed and "sleepy", able to follow simple directions by the doctor, and is responsive. Generally, twilight anesthesia causes the patient to forget the surgery and the time right after. It is used for a variety of surgical procedures and for various reasons. Just like regular anesthesia, twilight anesthesia is designed to help a patient feel more comfortable and to minimize pain associated with the procedure being performed and to allow the medical practitioner to practice without interruptions.
In the study of inhaled anesthetics, the concentration effect is the increase in the rate that the Fa /Fi ratio rises as the alveolar concentration of that gas is increased. In simple terms, the higher the concentration of gas administered, the faster the alveolar concentration of that gas approaches the inspired concentration. In modern practice is only relevant for nitrous oxide since other inhaled anesthetics are delivered at much lower concentrations due to their higher potency.
The following outline is provided as an overview of and topical guide to anesthesia:
Nitrous oxide gas produces euphoriant effects when inhaled. First recorded in the 18th century at upper-class "laughing gas parties", the experience was largely constrained to medical students until the late 20th century when laws limiting access to the gas were loosened to supply dentists and hospitals. By the 2010s, nitrous oxide had become a moderately popular recreational drug in some countries. Possession of nitrous oxide is legal in many countries, although some have criminalised supplying it for recreational purposes.
Inhalation sedation is a form of conscious sedation where an inhaled drug should:
- Depress the central nervous system (CNS) to an extent that surgeons can operate with minimal physiological and psychological stress to the patient
- Modify the patient's state of mind such that communication is maintained and the patient can respond to verbal command
- Carry a margin of safety wide enough to render the unintended loss of consciousness and loss of protective reflexes unlikely.
References
- ↑ Dental Fear Central (2004). "Inhalation sedation (aka Laughing Gas)" . Retrieved 2010-04-18.
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