Complications: Local & Systemic

Local complications

Complication	Usual cause	Management
Needle breakage	Bending the needle, 30-gauge needles, inserting to the hub, sudden patient movement	Keep the patient still; retrieve if visible; refer if buried. Prevent: 25- or 27-gauge for blocks, never insert to the hub
Persistent anesthesia or paresthesia	Trauma to the nerve (lingual most often), hemorrhage, possibly solution neurotoxicity (4% solutions reported more often)	Document, reassure, follow up regularly; refer if not improving
Transient facial nerve palsy	IANB solution deposited into the parotid gland (needle too posterior)	Reassure; protect the eye (close the lid manually, eye patch, lubricant) until it resolves in a few hours
Trismus	Trauma or bleeding in the medial pterygoid; contaminated needle; multiple injections	Heat, analgesics, gentle opening exercises; antibiotics if infection
Hematoma	PSA (pterygoid plexus) or IANB (inferior alveolar vessels)	Direct pressure, ice for the first day, then heat; analgesics
Soft tissue self-injury	Child or disabled patient chewing a numb lip or tongue	Warn caregivers; cotton roll; phentolamine mesylate can shorten soft tissue anesthesia
Post-injection lesions	Recurrent aphthous ulcers or herpes after trauma	Symptomatic care
Tissue sloughing	Excess vasoconstrictor or volume in palatal tissue; prolonged topical	Self-limiting; analgesics

Reaction	Signs	Response
Local anesthetic overdose (toxicity)	Early: circumoral numbness, tinnitus, light-headedness, slurred speech, tremor. Later: seizures, then CNS and respiratory depression, bradycardia, hypotension	Stop, position, basic life support, oxygen; benzodiazepine for prolonged seizures if trained; EMS; lipid emulsion in hospital
Epinephrine reaction	Anxiety, palpitations, tachycardia, raised blood pressure, headache	Upright position, reassure, monitor; usually resolves in minutes
Vasovagal syncope	Pallor, sweating, nausea, bradycardia, loss of consciousness	Supine with legs raised, airway, oxygen; the most common emergency
Allergy	Rash, urticaria; rarely bronchospasm or anaphylaxis	Antihistamine for mild; epinephrine 0.3 mg IM (adult) for anaphylaxis. True amide allergy is very rare; consider sulfite
Methemoglobinemia	Gray-blue cyanosis that does not improve with oxygen, hours after prilocaine, articaine or benzocaine	Oxygen and IV methylene blue in hospital

Cardiovascular disease: limit epinephrine (commonly 0.04 mg); avoid in unstable angina, recent MI or stroke, uncontrolled hypertension or arrhythmia.
Nonselective β-blockers (propranolol): epinephrine can cause hypertension with reflex bradycardia. Recent cocaine use: no epinephrine (commonly taught: wait 24 hours).
Atypical plasma cholinesterase: avoid ester anesthetics. Liver disease: reduce amide doses. Malignant hyperthermia: amide anesthetics are considered safe.
Pregnancy: lidocaine is the usual first choice; elective care is easiest in the second trimester.

Treating cyanosis that does not respond to oxygen as a simple airway problem: think methemoglobinemia.
Mistaking an epinephrine reaction (anxious, tachycardic) for anaphylaxis.
Inserting a needle to the hub.
Applying heat on day one for a hematoma: ice first, heat later.

Pick an answer to see right away whether it is correct and why.

Right after an IANB, the patient cannot close the eye on that side and the corner of the mouth droops. The most likely cause is:
Which nerve is most often affected by persistent paresthesia after an IANB?
Earliest signs of local anesthetic overdose are usually:
A patient becomes cyanotic 3 hours after receiving a large dose of prilocaine, and oxygen does not help. Treatment is:
Which local complication is most associated with the PSA block?

0 of 5 answered

Answer key: 1 A · 2 B · 3 C · 4 A · 5 B

Dental School Map · Original study material, written and checked by our team; always confirm clinical decisions against current guidelines.