New inhalation agents in paediatric anaesthesia.

A survey in August 1995 showed that, despite the introduction of topical analgesic creams, approximately 30% of anaesthetists responding used inhalation induction of anaesthesia more frequently than i.v. induction, especially in children less than 3–5 yr of age.9 In this age group, uptake of inhaled agents is particularly rapid. In children therefore, the induction characteristics of the ideal inhalation agent are particularly important although clearly the recovery profile, cardiovascular stability, minimal metabolism, stability in soda lime, lack of central nervous system excitation and antiemetic effect during recovery are as important as they are in adults (Table 1). Although cyclopropane provided rapid smooth induction, the risk of explosions led to its withdrawal from anaesthetic practice. In recent years, halothane has been accepted widely as the least pungent of the inhalation agents available, giving the smoothest induction with minimal risk of laryngospasm and hypoxaemia. Its disadvantages are well known and include myocardial irritability, especially in the presence of epinephrine, depression of myocardial and respiratory function, cerebral vasodilatation, biotransformation and rarely hepatotoxicity. Lack of familiarity with its use in adult practice by younger anaesthetists must now be added to this list of disadvantages. Two new inhalation agents have recently become available in this country: sevoflurane and desflurane. Both are fluorinated ethers, and as fluorine has 0.001% of the ozonedepleting activity of chlorine, both of these new drugs should be more environmentally friendly than halothane. Sevoflurane is relatively non-pungent, so that the vaporizer may be set to its maximum setting from the start of induction.77 Desflurane, however, is extremely pungent and causes severe irritation of the upper respiratory tract if used for induction of anaesthesia. Although desflurane is therefore not recommended for inhalation induction, there has been some recent interest in its use as a maintenance agent in infants, because of its shorter recovery time.65