Adverse effects of local anaesthetics.

Complications of local anaesthesia in general have been considered in so far as they may be confused with adverse effects of local anaesthetic drugs. Local anaesthetics may give rise to adverse reactions by a number of mechanisms. They affect nerve conduction and vasculature at the site of injection: a local effect; but is it unlikely that they ever produce an irreversible noxious effect on nerve fibres. They produce regional effects resulting from nerve conduction blockade; hypotension and respiratory depression by this mechanism are frequently mistaken for pharmacological effects of the agent concerned. They produce focal effects, usually when carried in high concentration via the arterial supply to the brain. They produce systemic effects following absorption or intravenous administration, which are manifested principally in the central nervous system. Ignorance or carelessness are frequently causative factors in serious reactions. Adequate oxygenation is vital in prophylaxis and immediate treatment of systemic toxicity, while resuscitative skill and equipment must always be to hand. Idiosyncrasy or allergy can only rarely be an excuse for adverse reactions to local anaesthesia.