Complications with Local Anæsthetics
Injection of Local Anæsthetic within the Parotid Gland can lead to a temporary facial palsy (that is, a temporary paralysis of the muscles of facial expression). Although alarming, no permanent damage occurs and the patient should make a full recovery. An eye patch may be required until normal eyelid closure returns as the eye can be prone be being irritated by dust particles.
Chewing Muscle Injury (Trismus)
This may result in painful muscle spasm leading to limitation in mouth opening (trismus). This usually resolves spontaneously.
Local Anæsthetic should not be injected into inflamed or infected tissues. The locally inflamed +/- infected circulation may lead to rapid absorption of the Local Anæsthetic. In addition, the acid environment associated with infection reduces the effectiveness of the Local Anæsthetic.
These can sometimes occur with some Local Anæsthetics but they are extremely rare (often the preservatives and not the anaesthetic itself).
Adjacent Vascular Structures
These may be injured, resulting in a local blood clot. This may be seen following injections to ‘numb up’ lower jaw teeth as the Inferior Dental Nerve has in close proximity to it, the corresponding artery. Bleeding results in limitation of mouth opening (trismus).
Local Anæsthetic may be injected directly into the circulation. This may lead to rapid onset of toxic symptoms which can result in collapse and cardio-respiratory arrest. You may experience a mild form of this as a racing heart, tremor and a sense of impending doom. Rapid injection into the tissues by itself may also lead to toxicity.
Needle Track Infection
This is where infection ascends the path of the injection. This can lead to a limitation in mouth opening (trismus). It is very rare.
The patient must be aware to avoid smoking, drinking hot liquids or biting the lip, cheek or tongue until sensation has fully returned.
Useful Articles & Websites
J Can Dent Assn 2002. An Update on Local Anesthetics in Dentistry
JADA 2003. Avoiding complications in local anesthesia induction. Anatomical considerations
BDJ 2009. Numbness of the Ear following Inferior Alveolar Nerve Block – the Forgotten Complication
Balkan J Stomatol 2012. Case Report. An Unusual Laryngeal Complication following Inferior Alveolar Nerve Block
J Dent Anesth Pain Med 2015. Diplopia after Inferior Alveolar Nerve Block – Case Report & Related Physiology
S Afr Dent J 2015. Ocular complications with dental local anaesthesia – a systematic review of literature & case report
BDJ 2018. Severe Headache following Local Anaesthesia in a Patient with a History of Traumatic Brain Injury – A Case Report
J Dent Anesth Pain Med 2018. Delayed Paresthesia of Inferior Alveolar Nerve after Dental Surgery – Case Report & Related Pathophysiology