Aetiology

The causes of postural hypotension may be considered in terms of:

• venous pooling of blood:
  • severe varicose veins
  • prolonged standing
• impaired vasomotor tone:
  • diabetic autonomic neuropathy
  • Shy-Drager syndrome
  • Parkinson's disease
• reduced muscle tone:
  • prolonged bed rest
• hypovolaemia:
  • dehydration
  • exsanguination e.g. gastrointestinal bleed
• drugs:
  • hypotensive agents
  • tranquilisers
  • phenothiazines
  • levodopa
• Addisonian disease:
  • Addison's disease
  • hypopituitarism
  • abrupt cessation of steroid therapy
• idiopathic

Alternatively can be consider in terms of neurogenic and non-neurogenic causes:

Neurogenic causes

• neurodegenerative disease - e.g. as Parkinson's disease, Parkinson-plus syndromes
• peripheral neuropathy - e.g. diabetes, vitamin B12 deficiency, renal failure, amyloidosis, rheumatological, autoimmune, and paraneoplastic conditions

Non-neurogenic causes

• volume depletion - Anaemia, dehydration, haemorrhage, hyperglycaemia
• cardiovascular disease - Aortic stenosis, hypertension, heart failure, atherosclerosis or vascular stiffening, arrhythmias
• other - Adrenal insufficiency, physical deconditioning, ageing

Either mechanism

• medications - alpha blockers, antihypertensives, nitrates, diuretics, selective serotonin reuptake inhibitors, tricyclic antidepressants, antipsychotics, beta blockers
• alcohol consumption
  • short term: diuretic effect, impairment of vasoconstriction
  • long term or chronic: neurotoxic effects

Idiopathic

Reference:

1. Low VA, Tomalia TA. Orthostatic Hypotension: Mechanisms, Causes, Management.J Clin Neurol. 2015 Jul; 11(3): 220-226.
2. Gilani A et al. Postural Hypotension. BMJ 2021;373:n922 http://dx.doi.org/10.1136/bmj.n922