In 1917, diethyl ether was the safest available anaesthetic agent. Common practice was to rely on ether, used as a single agent, to depress all four aspects of the nervous system in a dose-dependent manner.
Diethyl ether has several features that makes it a good agent for trauma anaesthesia:
- Excellent analgesic at clinical doses
- Tends to stimulate respiration and maintain blood pressure
- Causes a reliable ‘cascade’ of muscle relaxation as the inhaled dose increases, beginning with the abdomen before affecting the intercostal respiratory muscles and finally the diaphragm
However, ether has several undesirable features:
- Pungent and irritant smell and causes coughing, retching and breath-holding during induction and emergence
- Causes postoperative nausea and vomiting
- High blood to gas solubility (12:1) which prolongs induction and emergence
- Flammable in air and explosive in oxygen
Fig 1 A typical ether container
The four aspects of the nervous system are:
- Loss of recall (amnesia)
- Sensory loss (analgesia)
- Depression of motor tone (relaxation)
- Reflex depression (HR, BP and movement in response to surgery)