Inhalation induction may be less traumatic than venous cannulation in:

• Children
• Needle phobic adults
• Adults with learning disabilities

Inhalation induction is valuable where venous access is difficult. After induction, peripheral venous vasodilation will facilitate cannulation. This needs to be balanced against the risk of inducing anaesthesia without IV access.

With inhalation induction spontaneous ventilation is maintained. This is valuable where a difficult airway is being managed, or where positive pressure ventilation is to be avoided.

Caution with deep levels of inhalation anaesthesia where apnoea can still occur.

Airway tone is better maintained than with IV induction.

Useful with difficult airway management.

Caution once deep volatile anaesthesia is achieved, as airway tone may be reduced.

It is possible to alter depth of anaesthesia during the course of induction. This compares with IV induction, where the dose cannot be changed once administered.

Acute anaphylaxis does not seem to occur with inhaled volatile agents. This may confer an advantage in patients with a history of anaphylaxis where the precipitating agent(s) has not been identified.

The bronchodilator effect of volatile agents may confer an advantage in brittle asthmatics. It appears to be mediated by lowering calcium concentrations in smooth muscle.

Caution with desflurane and isoflurane where the pungent smell may neurally mediate bronchoconstriction.

For brief outpatient anaesthesia, e.g. dental extractions in children, rapid elimination of volatile agents via the lungs may provide more rapid recovery than elimination of IV drugs. (This idea is now being challenged by short acting IV agents, e.g. propofol and remifentanil.)