(1989; 60 pages) [French]
Group: volatile inhalational anaesthetic agent
Ether (diethyl ether) is a colourless, highly volatile and flammable liquid that, in anaesthetic dosage, depresses cerebral activity.
Ether is a reliable and potent anaesthetic that is particularly useful when elaborate apparatus is not available and cost is an important consideration. It may be used safely in closed circuits containing soda lime. The vasomotor centre is resistant to the doses required for full surgical anaesthesia. Because it is highly soluble in body tissues induction is slow and follows the classical stages of general anaesthesia. Full muscle relaxation is achieved in deep anaesthesia. Although irritant to the upper airway, ether is a bronchodilator and it can be of value in treating bronchospasm resistant to other drugs. It does not potentiate the dysrhythmic effect of sympathomimetic agents as much as other potent inhalational anaesthetics.
Because ether is both flammable and explosive it can be used in hot dry climates only when special precautions are taken to prevent sparking and combustion; diathermy is contraindicated when ether is used with oxygen. Premedication with atropine is essential to avoid excessive bronchial and salivary secretion. Laryngeal spasm may occur during induction and intubation. Localized capillary bleeding can be troublesome. Postoperative nausea and vomiting are frequent and recovery time is slow, particularly after prolonged administration.
Induction and maintenance of anaesthesia during surgery.
Dosage and administration
Ether may be administered from many types of vaporizer. In emergency it may be dropped on to an open mask.
Premedication with atropine is necessary to reduce salivary and bronchial secretions.
When supplementary oxygen is used it can be fed under an open mask or into an open-ended T-piece connected to a draw-over vaporizer.
Administration from vaporizers
Concentrations of ether vapour in the inspired gases should not exceed 15% during induction and should subsequently be reduced during maintenance of anaesthesia. Light anaesthesia (with or without muscle relaxants) can be sustained using 3-5% in air. Deep anaesthesia requires concentrations of up to 10%.
“Open drop” technique
This technique should be used only when no other means of delivering a general anaesthetic is available.
Ether is applied from a drop bottle to an open mask covered with multilayered gauze. During induction 12 drops/minute are applied for 2 minutes, then 1 drop/second until the patient loses consciousness (usually within 5 minutes). The rate is subsequently adjusted to provide the required depth of anaesthesia. Deep levels of surgical anaesthesia cannot be achieved with this technique in less than 20-30 minutes.
• Severe liver disease.
• Raised cerebrospinal fluid pressure.
In febrile children exposure to ether increases the risk of potentially fatal convulsions. If convulsions occur, ether should immediately be withdrawn, and the child’s body temperature reduced by sponging with tepid water. Small doses of diazepam or thiopental should be administered intravenously until convulsions cease.
Diathermy must not be used when ether/oxygen mixtures are in use and the operating theatre and its equipment should be designed to minimize the risk of static discharge, particularly in hot, dry climates. Electrical sockets and switches situated within 1 metre of the floor should be spark-proof. No potential source of combustion or sparking should be allowed within 30 cm of an expiratory valve emitting ether vapour.
Use in pregnancy
Ether should be used during pregnancy only when the need outweighs any possible risk to the fetus.
Low concentrations (no more than 4%) should be employed in obstetric procedures to avoid loss of uterine tone, excessive postpartum haemorrhage and respiratory depression in the neonate.
Laryngeal spasm is common during induction.
Severe nausea, vomiting and bronchopneumonia are liable to occur postoperatively, particularly after prolonged, deep anaesthesia.
Transient postoperative effects include impairment of liver function and leukocytosis.
Dependence can occur in individuals who are repeatedly exposed to ether.
The action of non-depolarizing neuromuscular blocking agents is potentiated. In patients receiving β-adrenoceptor-blocking agents such as propranolol, ether may cause myocardial depression.
Overdosage leads to severe central depression, characterized first by respiratory failure and later by cardiac arrest.
Spontaneous respiration is usually restored if intermittent positive pressure ventilation with oxygen is instituted promptly.
Ether should be stored in sealed containers protected from light, below 25°C. Naphthols, polyphenols, aromatic amines and aminophenols may be added in trace amounts to commercial supplies as stabilizers.