WHO Model Prescribing Information: Drugs Used in Anaesthesia
(1989; 60 pages) [French] View the PDF document
Table of Contents
View the documentPreface
View the documentIntroduction
Open this folder and view contentsPremedication
Close this folderGeneral anaesthetics and oxygen
View the documentKetamine
View the documentThiopental
View the documentEther
View the documentHalothane
View the documentTrichloroethylene
View the documentNitrous oxide
View the documentOxygen
Open this folder and view contentsLocal anaesthetics
Open this folder and view contentsNon-opioid analgesics
Open this folder and view contentsOpioid analgesics and antagonists
Open this folder and view contentsMuscle relaxants and cholinesterase inhibitors
Open this folder and view contentsBlood substitutes
Open this folder and view contentsSolutions for correcting water and electrolyte imbalance
Open this folder and view contentsAntacid for use in obstetric practice
View the documentAnaesthesia at the District Hospital
View the documentSelected WHO publications of related interest
View the documentBack cover


Group: inhalational gas

General information

Pressurized oxygen cylinders for industrial use that contain gas at about 13 000 kPa are acceptable for use in anaesthesia. Cylinders intended for anaesthetic use are supplied with pin-index valves. They contain more than 99% oxygen by volume with small residues of nitrogen or argon. Cylinders should always be connected to anaesthetic apparatus by a suitable pressure-reducing valve and they should be replaced as soon as the cylinder pressure falls below 800 kPa.

Oxygen concentrators have recently been developed that offer a more economical source of oxygen and avert the need for frequent delivery and storage of cylinders.

Clinical information


To maintain an adequate oxygen tension in inhalational anaesthesia.

Dosage and administration

The concentration of oxygen in inspired anaesthetic gases should never be less than 21%.

It may be administered with the anaesthetic gases, or from a face mask or via a nasal catheter.


Combustion or sparking creates a danger of fire or explosion at high oxygen tensions. Use of cautery is contraindicated whenever oxygen is used in combination with ether. Reducing valves should not be greased, since this creates a danger of explosion.

Oxygen should not be used for longer or at a greater concentration than is necessary to prevent hypoxaemia.

Adverse effects

After prolonged administration, concentrations greater than 80% at atmospheric pressure have a toxic effect on the lungs, which presents initially as a mild substernal irritation progressing to pulmonary congestion, exudation and atelectasis.

Use of unnecessarily high concentrations of oxygen in incubators has led to the development of retrolental fibroplasia and permanent blindness in premature infants.


Oxygen is supplied under pressure in cylinders, which must be kept below 25°C.

Cylinders containing premixed oxygen 50% and nitrous oxide 50% are available for analgesia in some countries. However, the constituents separate out at -6°C, in which case adequate mixing must be assured before use. When the two components are supplied from separate cylinders a safety device must be installed that cuts off the flow of nitrous oxide should the oxygen pressure fall.

Identification of cylinders

An ISO standard1 requires that cylinders containing oxygen intended for medical use should bear the name of the contents in legible and permanent characters and, preferably, also the chemical symbol O2. The neck, from the valve to the shoulder, should be coloured white. Cylinders containing nitrous oxide and oxygen mixtures should be similarly labelled, and the neck coloured white and blue.

1International Standard 32. Gas cylinders for medical use - marking for identification of content. Switzerland, International Organization for Standardization, 1977.

to previous section
to next section
The WHO Essential Medicines and Health Products Information Portal was designed and is maintained by Human Info NGO. Last updated: October 29, 2018