Orthostatic Intolerance

Orthostatic intolerance is a clinical syndrome in which symptoms of impaired cerebral perfusion, such as light headedness, visual disturbance and weakness, develop in the upright posture and are relieved by lying down. It is an umbrella term that includes orthostatic hypotension, postural orthostatic tachycardia syndrome, vasovagal syncope and delayed orthostatic hypotension, and the first task is to establish which haemodynamic pattern is present.

• Patterns on standing: (1) fall in blood pressure with inadequate heart rate rise (neurogenic orthostatic hypotension); (2) fall in blood pressure with brisk rise in heart rate (volume depletion, drugs); (3) excessive heart rate rise with preserved blood pressure (postural tachycardia syndrome); (4) sudden hypotension and bradycardia after a period of standing (vasovagal); (5) normal haemodynamics with symptoms (hyperventilation, anxiety, deconditioning).
• Common precipitants: dehydration, deconditioning after illness or bed rest, drugs, anaemia, pregnancy, heat, autonomic neuropathy, post-viral states, endocrine disease.
• Prevalence is high in adolescents and older adults.

• Light headedness, dizziness, fatigue, weakness, blurred or tunnel vision, palpitations, nausea, sweating, cognitive slowing, headache, tremor on standing.
• Chest discomfort, dyspnoea, neck pain (coat hanger distribution), leg heaviness.
• Presyncope, syncope, falls.
• Improves on sitting or lying down; worse with heat, meals, alcohol, hot showers, standing still, and after exertion.
• Examination: lying and standing blood pressure and heart rate, hydration, thyroid, cardiac examination, neurological examination including tremor, rigidity, neuropathy, joint hypermobility.
• Red flags: syncope with injury, chest pain, abnormal ECG, focal deficits, weight loss, gastrointestinal bleeding, features of adrenal insufficiency (pigmentation, hyponatraemia), sudden onset after head injury.

• Active stand test: supine for 5 minutes, then standing with measurements at 1, 3, 5 and 10 minutes.
• Interpretation: fall of 20/10 mmHg or more in blood pressure indicates orthostatic hypotension; sustained heart rate rise of 30 beats per minute or more (40 or more in adolescents) without hypotension indicates postural tachycardia syndrome; abrupt bradycardia and hypotension suggests a reflex process.
• Medication review; check for diuretics, antihypertensives, nitrates, antidepressants, antipsychotics, dopaminergic drugs, alpha blockers, phosphodiesterase inhibitors.
• Bloods: full blood count, ferritin, urea and electrolytes, glucose, HbA1c, thyroid function, morning cortisol, B12, folate, calcium.
• ECG in all; ambulatory ECG, echocardiography if palpitations, syncope or structural disease suspected.
• Autonomic function testing and tilt test through specialist if unclear.
• Differentials: arrhythmia, aortic stenosis, adrenal insufficiency, anaemia, hypoglycaemia, vestibular disease, anxiety, deconditioning, medication effect.

Common measures for every pattern

• Fluids 2 to 3 litres daily, with a water bolus of 500 mL before rising or prolonged standing.
• Salt 6 to 10 g daily unless hypertension, heart failure or renal disease.
• Slow positional changes; sit on the bed edge before standing.
• Physical counter manoeuvres: leg crossing, squatting, muscle tensing, calf pumping.
• Compression stockings or abdominal binder (20 to 40 mmHg).
• Avoid heat, large meals, alcohol, and prolonged standing.
• Graded recumbent then upright exercise over 3 months to rebuild venous return.
• Raise head of bed by 10 degrees where supine hypertension is not a problem.
• Correct anaemia, iron deficiency (ferrous sulphate 200 mg orally once daily or on alternate days) and vitamin B12 deficiency.

Pattern targeted therapy (specialist input for persistent symptoms)

• Hypotension with inadequate heart rate rise: fludrocortisone 0.05 to 0.1 mg orally in the morning (maximum 0.3 mg), or midodrine 2.5 to 10 mg orally three times daily (daytime only), with monitoring for supine hypertension, potassium and oedema.
• Postural tachycardia: propranolol 10 to 20 mg orally up to four times daily, or ivabradine 2.5 to 7.5 mg twice daily; avoid in pregnancy.
• Reflex (vasovagal) pattern: fluids, salt, counter pressure manoeuvres; midodrine or fludrocortisone only if recurrent and disabling.
• Drug induced: stop, reduce or reschedule the offending drug (for example give alpha blockers at night).

Special groups

• Adolescents: school adjustments, fluids, salt, graded exercise; exclude POTS and eating disorder.
• Pregnancy: left lateral position, fluids and compression; avoid fludrocortisone and midodrine unless specialist led.
• Older adults: falls assessment, bone health, vitamin D, careful review of antihypertensive and psychotropic burden.

Follow up and referral

• Review in 4 to 6 weeks and after each treatment change.
• Refer for syncope with injury, suspected autonomic failure, cardiac cause, or inadequate response.