Local complications

Local neurological complications include paraesthesia, dysaesthesia, temporary facial nerve paralysis (eg paralysis of the periocular muscles) and prolonged anaesthesia. Most cases of prolonged anaesthesia resolve spontaneously; permanent anaesthesia is rare. Nerve injuries are rare and can be caused by direct nerve trauma, indirect nerve trauma (from bleeding within the nerve sheath), or localised neurotoxicity. The risk of nerve damage is increased with repeat injections into a partially anaesthetised site or administration of higher concentration local anaesthetic solutions.

Trauma to the tissues (eg haematoma) can occur during injection of local anaesthetic. Accidental intramuscular injection of local anaesthetic can cause trismus, either as a direct effect of the drug or due to bleeding within the muscle. If trismus occurs, promptly seek specialist advice or refer to an oral medicine or oral surgical specialist, because early management can improve outcomes.

Rarely, local complications can arise from equipment failure (eg cartridge explosion).