A patient becomes disoriented and lightheaded after standing up from the dental chair. What should you do first?

The presentation describes orthostatic (postural) hypotension, which occurs when blood pools in the lower extremities upon standing, reducing cerebral perfusion. The immediate management is to place the patient supine (lying flat), which allows gravity to redistribute blood to the head and restore cerebral blood flow. Trendelenburg (legs elevated) may also be used. Glucagon is indicated for hypoglycemia, not orthostatic hypotension. EMS is not needed unless the patient does not rapidly recover. Prevention includes raising the chair slowly and having the patient sit upright for a moment before standing.