Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
SEVOrane (Abbott Australasia)
250 mL bottles
When given by vaporisation, sevoflurane liquid has anaesthetic effects. Its mechanism of action is probably similar to that of other inhaled anaesthetics such as halothane or isoflurane.
Sevoflurane is not pungent, so it can be used for inhalation induction e.g. in children. Anaesthesia can be achieved within two minutes. The minimum alveolar concentration (MAC) which results in 50% of patients not responding to a skin incision decreases with age. The MAC is also reduced by giving sevoflurane with nitrous oxide.
The drug is eliminated by exhalation. Adults usually emerge from anaesthesia in 8 minutes, slightly faster than with isoflurane.
Approximately 5% of the sevoflurane absorbed is metabolised. This results in the release of inorganic fluoride with concentrations usually peaking within two hours, but taking up to two days to return to baseline. This may potentially reduce the urine concentrating power of the kidneys. Metabolism does not produce trifluoracetic acid, which may be responsible for the adverse effects of halothane on the liver.
A degradation product (Compound A) results from sevoflurane coming into contact with CO2 absorbants in the anaesthetic circuit. Although Compound A may not reach concentrations that are deleterious to humans, it is nephrotoxic in rats. Sevoflurane is contraindicated in anaesthetic equipment employing rebreathing circuits which contain Baralyme.
Like other inhaled anaesthetics, sevoflurane causes cardio respiratory depression; hypotension and bradycardia occur commonly. Other frequent adverse effects include agitation, breath-holding and laryngospasm during induction, and coughing, nausea and vomiting during recovery. Malignant hyperthermia may be triggered in susceptible patients.
Sevoflurane reacts with other drugs used in anaesthesia e.g. neuromuscular blocking agents and opioids. Dose adjustments are required.
At present, it is not clear if sevoflurane is any better overall than similar anaesthetic drugs.