Pure autonomic failure: low blood pressure on standing, causes and management

The autonomic nervous system controls things you do not consciously think about: blood pressure, heart rate, sweating, digestion and bladder function. When you stand, blood tends to pool in the legs, and autonomic nerves signal the blood vessels to tighten so that pressure to the brain is maintained. In pure autonomic failure this reflex is lost.

A case report from Nepal describes PAF as a neurodegenerative disorder of the autonomic nervous system which usually presents with orthostatic hypotension, and notes that orthostatic hypotension is far more often associated with ageing and with diseases such as diabetes, other neuropathies and multiple system atrophy, and only rarely due to PAF. The Clinical Autonomic Research discussion notes that the condition was formerly known as Bradbury-Eggleston syndrome and is characterised by sympathetic noradrenergic failure.

The leading symptom is lightheadedness or fainting shortly after standing, which eases on sitting or lying down. The case reports describe warning dizziness and visual disturbance before loss of consciousness, brief episodes of less than a minute with spontaneous recovery, and symptoms that improve on lying flat. The Clinical Autonomic Research discussion adds that nOH can present with non-specific symptoms such as generalised weakness, falls, leg buckling, fatigue and neck pain, which may be worse after eating.

Other autonomic features can accompany it. The case report from Nepal lists altered sweating, constipation, gastroparesis, impotence, syncope and bladder dysfunction as typical of autonomic disorders, and its patient also had frequent urination at night, constipation and erectile dysfunction.

• Dizziness, blurred vision or fainting on standing, in hot weather or after meals.

• Symptoms that ease when sitting or lying down.

• Reduced or absent sweating, bowel or bladder symptoms.

• High blood pressure when lying flat (supine hypertension).

The NHS describes low blood pressure with fainting and says to see a GP if you keep getting symptoms such as dizziness and fainting, and notes that symptoms on standing up may indicate postural hypotension. A faint with injury, chest pain, a fast or irregular heartbeat, or symptoms of stroke is an emergency: call 999. Anyone with PAF who faints and is injured, or who has new weakness, speech or vision change, should be assessed urgently.

Diagnosis starts with measuring blood pressure and heart rate lying and standing. The Clinical Autonomic Research case describes supine hypertension with orthostatic hypotension and no appropriate compensatory rise in heart rate. UCLH's referral guidance describes an active standing test, with baseline measurements sitting at rest followed by serial measurements while standing at 1, 3 and 5 minutes, and appropriate cardiology work-up such as ECG and Holter monitoring to rule out cardiac conditions.

Other causes of low pressure on standing need excluding: the report from Nepal describes full blood count, kidney, thyroid and other tests, and neurological examination to exclude secondary causes. The Clinical Autonomic Research discussion notes that measurement of supine and standing plasma norepinephrine is useful: levels are characteristically very low in PAF and do not rise on standing. UCLH describes six laboratories offering cardiovascular assessment, sudomotor (sweat) testing, pupillometry and a catecholamine laboratory, with results discussed in multidisciplinary meetings.

Because symptoms and blood pressure fluctuate through the day, the discussion recommends home blood pressure monitoring, seated or lying and after 3 minutes standing, and where available 24-hour ambulatory monitoring.

Orthostatic hypotension due to autonomic failure also occurs in Parkinson disease, multiple system atrophy (MSA) and dementia with Lewy bodies. The Clinical Autonomic Research discussion notes that patients first diagnosed with PAF may develop features of parkinsonism over time and be re-diagnosed, which is why periodic review by a neurologist is advised. Because the picture can change, ask your neurologist how often you should be reviewed.

UCLH's list of conditions managed by its national autonomic multidisciplinary meeting includes pure autonomic failure and autonomic disorders in neurodegenerative conditions such as Parkinson disease, MSA and dementia with Lewy bodies, as well as autoimmune autonomic disorders and autonomic neuropathies.

Management starts with measures that do not involve medicines. The Clinical Autonomic Research case used fluid and salt loading, an abdominal binder, and raising the head of the bed at night to ease supine hypertension and reduce night-time urine loss. UCLH's guidance for orthostatic intolerance suggests awareness of situations likely to cause symptoms such as standing in hot weather or exercising after a large meal, sitting, crouching or lying down at the onset of symptoms, drinking up to 500 ml of water immediately on getting out of bed, maintaining fluid intake and salt intake, calf pump exercises, and small meals with caution over alcohol.

Medicines are added when symptoms persist. The case from Nepal was treated successfully with midodrine, fludrocortisone and non-pharmacological measures, and the Clinical Autonomic Research discussion describes droxidopa, which it notes was in a supplement sponsored by its manufacturer, so it should be read with that in mind. Its expert commentary states the goal of therapy for neurogenic orthostatic hypotension is not to normalise standing blood pressure but to relieve symptoms and improve quality of life. Which medicines are available and licensed for you is a decision for your specialist.

Most people begin with a GP, who excludes common causes such as medicines and dehydration, and then a neurologist or cardiologist. The UCLH Autonomic Unit accepts GP referrals via NHS e-Referral and tertiary referrals from consultants across the UK, and says it cannot accommodate benign intermittent reflex disorders unless a thorough assessment in primary or secondary care has been done first.

Private autonomic testing and neurology consultations are available in some centres. As PAF is rare and may evolve, continuity of specialist follow-up matters more than which sector performs a single test.