Inhalational Anaesthetic Agents

Comprehensive vocabulary flashcards covering the classification, history, properties, and clinical specifics of inhalational anaesthetic agents as per the lecture transcript.

Inhalational Anaesthetic Agents

Drugs or agents administered by being inhaled or passed through the nose or respiratory tract.

Classification of Vapours

A category including Ethers (Diethyl ether, Desflurane, Sevoflurane, Isoflurane, Enflurane), Halogenated Hydrocarbons (Halothane, Trichloroethylene, Chloroform), and Hydrocarbons (Cyclopropane, ethylene).

Classification of Gases

A category including Nitrous oxide ($N_2O$), Oxygen, Xenon, Entonox, and Medical air.

Diethyl ether

Originally produced in 1540 by Valerius Cordus and first used as an anaesthetic agent in 1842 by Crawford W. Long and William E. Clark.

Chloroform

Introduced into clinical practice by Sir James Simpson for pain relief in labour but abandoned due to cardiac arrhythmias, respiratory depression, and hepatotoxicity.

Trichloroethylene

A non-explosive agent that decomposes to dechloroacetylene, a toxic nerve poison, when used with sodalime.

Methoxyflurane

Developed in 1958 and released in 1960; no longer in use because it causes vasopressin resistance high output renal failure.

Ideal Blood/Gas Solubility

A property where a low blood/gas solubility leads to rapid induction of anaesthesia.

Halothane

Synthesized in 1951 and introduced in 1956; it is stored in brown bottles with $0.01\%$ thymol to prevent decomposition by light and it corrodes metals in breathing systems.

Isoflurane

A stable agent synthesized in 1965 with a pungent odour and irritant effect on the airway, making it not ideal for inhalational induction.

Desflurane

An agent first used in humans in 1988 with a boiling point of $23.5^\circ C$, meaning it cannot be used in standard vapourizers.

Enflurane

An inhalational agent first synthesized in 1963 that is epileptogenic and should be avoided in patients with epilepsy.

Sevoflurane

A non-pungent agent with low blood/gas solubility that allows for rapid emergence, which can be associated with delirium in paediatric patients treated with fentanyl $1-2\,mg/kg$.

Nitrous Oxide ($N_2O$)

A weak anaesthetic gas manufactured by heating ammonium nitrate to $245-270^\circ C$ and stored in French blue cylinders at $44\,bar$ ($4400\,kPa$).

Entonox

A $50:50$ mixture of $N_2O$ and $O_2$ stored at $137\,bar$ in cylinders with a blue body and white/blue quartered shoulder.

Xenon

An inert gas with anaesthetic properties first reported in 1951, though not routinely used because it is expensive.

Medical Air

Purified air with a purity of $99.9\%$ stored in cylinders at $137\,bar$; in the U.K., the cylinder has a grey body and black and white quartered shoulder.

Blood/gas partition coefficient

A measure of the solubility of an inhaled anaesthetic agent in blood; low solubility leads to faster alveolar partial pressure build-up and faster uptake.

Second gas effect

The acceleration of the uptake of a volatile agent when administered in association with a rapidly absorbed second gas, such as nitrous oxide.

Minimum Alveolar Concentration (MAC)

The concentration of an anaesthetic at $1\,atmosphere$ that prevents movement in $50\%$ of patients in response to a standard stimulus.

Oil/gas solubility

The measure of lipid solubility of an agent; it is inversely related to the Minimum Alveolar Concentration (MAC).

Halothane Hepatitis

A rare but severe hepatic dysfunction characterized by fulminating dysfunction and a mortality rate of $30-70\%$, increasing with repeated exposure.

Cylinder Colour for Nitrous Oxide

French blue.

Boiling Point of Desflurane

$23.5^\circ C$.

MAC of Halothane

$0.75$.

MAC of Nitrous Oxide

$104$.