Complications with Local Anæsthetics

Incorrect Placement

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.

Infected Tissues

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.

Hypersensitivity-Type Reaction

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).

Toxic Symptoms

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.