Baroreflex dysfunction and autonomic dysreflexia in hypertensive emergency

Large fluctuations in BP may indicate autonomic dysreflexia or baroreceptor failure.

Autonomic dysreflexia most often occurs in patients who have spinal injuries. An uncontrolled response to a (usually noxious) stimulus leads to an excessive rise in BP. Complications and symptoms that might occur in a hypertensive urgency or emergency may occur at lower BP levels in a patient with a spinal injury. First-line management is to seek and treat the stimulus, which usually results in resolution of elevated BP without the need for specific BP-lowering drugs. Common causes include urinary retention, catheter blockage, constipation, urinary tract infection and pressure sore complication. Seek specialist advice if BP remains excessively elevated despite management of the causeMiddleton, 2014.

Baroreceptor dysfunction can present as acute severe hypertension (usually above 250 mmHg systolic), chronic volatile hypertension (hypertension with short periods of hypotension) and/or tachycardia (sometimes orthostatic)Ketch, 2002. Differentiation from other causes is difficult and a recent history of carotid artery surgery, neck trauma or neck irradiation is a key diagnostic feature. Acute presentations are easily mistaken for phaeochromocytoma. Seek specialist advice to manage these patients.