A patient becomes short of breath shortly after local anaesthesia while you begin work on tooth #2. There is no rash, no swelling, no wheeze, and vital signs are stable apart from a raised pulse. What is the MOST likely cause?

Correct answer: C. Hyperventilation secondary to anxiety

• A. Anaphylaxis would produce urticaria, angioedema, bronchospasm and hypotension. True allergy to amide local anaesthetics is exceedingly rare.
• B. Emphysema causes chronic exertional breathlessness, not an abrupt onset triggered by the start of a procedure.
• C. Correct. ANXIETY-DRIVEN HYPERVENTILATION is by far the most common cause of acute dyspnoea in the dental chair. The patient over-breathes, blows off CO2, and develops respiratory alkalosis producing light-headedness, peri-oral and digital tingling, and carpopedal spasm. Management is reassurance, stopping treatment, and slowing the respiratory rate — never supplemental oxygen, which worsens the alkalosis.
• D. An epinephrine reaction produces palpitations, tremor and anxiety with a marked blood pressure rise, and settles within minutes.