What is the clinical presentation of patients with a vasovagal response to local anesthesia? How is this presentation best treated?

Psychological factors, including needle phobia and altered pain perception, may induce a vasovagal response, the clinical features of which include pallor, diaphoresis, hyperventilation, nausea, vomiting, hypotension, and syncope. Usually, placing the patient in the Trendelenburg position (i.e., supine, with the head lower than the legs) and the application of moist towels to the patient’s face is sufficient to reverse the condition. Aromatic spirits of ammonia may also be of benefit. For prolonged hypotension, an intravenous line must be established and vasopressors given, as needed. ACLS protocols should be followed.