Assessment of orthostatic hypotension
If a diagnosis of orthostatic hypotension is made, a thorough history is vital to investigate the cause and guide management.
Factors that precipitate or exacerbate orthostatic hypotension include warm environments, prolonged sitting or standing and inadequate fluid intake.
A postural drop in blood pressure (BP) may be secondary to one or more acute pathologies (such as those related to peripheral vasodilatation [eg sepsis] or reduced circulating volume [eg haemorrhagic shock, dehydration]); these must be excluded before orthostatic hypotension is diagnosed. If a serious underlying cause is suspected, prompt assessment and referral to hospital for further investigations may be required.
Conduct a thorough review of the patient’s drug therapy. Drugs that exacerbate orthostatic hypotension include alpha blockers, diuretics, nitrates, antidepressants (particularly tricyclics [eg amitriptyline] and selective serotonin reuptake inhibitors [eg paroxetine]) and antipsychotics. Poorly treated hypertension, as well as withdrawal of antihypertensives, can exacerbate orthostatic hypotension; see Drug management of orthostatic hypotension for more information.
Investigate for and document cardiovascular comorbidities, including hypertension and heart failure. Also investigate for conditions associated with autonomic failure such as diabetes and neurodegenerative disorders (eg Parkinson disease, multiple system atrophy, dementia with Lewy bodies); orthostatic hypotension may be an early presentation of these conditions. In patients with autonomic failure, orthostatic hypotension is commonly worse in the morning and after prolonged supine bedrest with resultant diuresis.
Symptoms occurring after meals (especially meals with high glycaemic index) may indicate postprandial hypotension, which occurs in the 2 hours following a meal due to accumulation of blood in the splanchnic veins. Postprandial hypotension may be seen in isolation or may coexist with orthostatic hypotension. Alcohol consumption compounds hypotension due to its vasodilator effect.
In patients with an eating disorder such as anorexia nervosa, postural hypotension may be related to dehydration and low blood volume, but autonomic dysfunction of unclear aetiology may also play a role.
Large fluctuations in BP may indicate baroreceptor dysfunction or autonomic dysreflexia.