Systemic Complications of Local Anesthesia

Systemic Complications of Local Anesthesia

• Local anesthetics can cause systemic complications including syncope, toxicity (overdose), idiosyncrasy, and allergy.

Syncope

• Definition: Sudden transient loss of consciousness secondary to cerebral ischemia.
• Incidence: Most common complication in dental offices.
• Synonyms: Psychogenic syncope, vasodepressor attack, vasovagal syncope, fainting.
• Predisposing Factors (Psychogenic): Anxiety, severe pain, emotional stress, sight of blood/surgical instruments.
• Predisposing Factors (Physical): Prolonged standing, exhaustion/starvation, hot/crowded environments.
• Clinical Manifestations (Presyncope): Paleness, sweating, visual disturbances, restlessness, coldness in hands/feet, nausea, and dizziness.
• Clinical Manifestations (Syncope): Low blood pressure, bradycardia, thready pulse, pupillary dilation, irregular breathing, loss of consciousness.
• Clinical Manifestations (Postsyncope): Weakness, short-period mental confusion/disorientation, gradual reestablishment of vital signs.
• Management:
  • Terminate the procedure
  • Call medical assistance/activate emergency code
  • Place patient in Trendelenburg position (supine with head below legs)
  • Acquire vital signs (blood pressure, respiratory rate, pulse, temperature, blood glucose)
  • Monitor vital signs continuously
• Management of Vasodepressor Syncope: Inhalation of aromatic ammonia spirit, administration of 6L/min oxygen via mask/nasal hood.

Toxicity (Overdose)

• Definition: Clinical manifestations resulting from an overly high blood level of a drug in various target organs/tissues.
• Causes:
  • Intravascular Injection: Inadvertent injection leading to rapid, serious overdose reactions (prevented by aspiration test)
  • Rapid Absorption: Local anesthetics, used in dentistry often have vasodilating properties, leading to rapid absorption into the cardiovascular system, potentially leading to shorter procedure duration/increased blood levels and toxicity. The faster the injection, the quicker toxicity will occur.
  • Vasoconstrictor Presence: Reduces systemic absorption of the drug because of slowed absorption, therefore reducing potential toxicity
  • Too large dose: Using a larger dose than required.
  • Slow biotransformation: Slow biotransformation resulting from plasma pseudocholinesterase deficiency or hepatic disease.
  • Slow elimination: Slow elimination due to renal dysfunction.
• Most toxic local anesthetic: Bupivacaine (long-acting).
• Prevention: Aspiration test, use of vasoconstrictors, attention to recommended dosages, use small amount of topicals, preoperative evaluations.

Idiosyncrasy

• Definition: Any response to a local anesthetic that is different from expected and cannot be attributed to overdose or allergy.
• Cause: Genetic mechanism.

Allergy

• Definition: Exaggerated or inappropriate immune response to a substance normally harmless to most people.

• Allergens: Esters (related to para-amino-benzoic-acid metabolism products), sodium bisulfite/metabisulfite (anesthetics used as antioxidants for vasoconstrictors), methylparaben (no longer used in dental cartridges).

• Prevention: Adequate preanesthetic evaluation, avoid drugs reported in patient history as causing allergic reactions, refer for local anesthetic allergy testing.

• Signs:

  • Dermatological Reactions (Skin Signs): Urticaria (smooth, elevated skin patches with intense itching), Angioedema (sudden swelling under skin, around eyes/lips).
  • Respiratory Reactions: Bronchospasm (dyspnea, wheezing, cyanosis, sweating), Laryngeal Edema (larynx obstruction), Cardiovascular Symptoms (tachycardia, palpitations, hypotension, cardiac arrest), Neurologic Manifestations (lightheadedness, anxiety, impending doom), Gastrointestinal Manifestations (malaise, nausea, vomiting, abdominal cramps), Genitourinary Manifestations (urinary incontinence), Skin Reactions (urticaria).

• Management of Immediate-onset skin signs (erythema, urticaria, pruritus): Stop the current medication, get immediate medical assistance; administer an antihistamine (IM or IV); administer a corticosteroid; monitor vital signs; consult a physician; Observe for 1 hour

• Management of Anaphylaxis (With/Without skin signs): Immediately stop procedure, clear airway of materials, call for help, place patient supine (semi-reclined if lower respiratory involvement), administer epinephrine.