Postural hypotension

Question 1

Postural hypotension is the most important cause for falls and faints in the elderly.

What is postural hypotension?

Answer 1

A drop in BP (>20mmHg systolic or >10mmHg diastolic) when standing for 3 minutes after lying down.

Question 2

What causes postural hypotension?

Answer 2

Decreased circulating volume (hypovolaemia) => earliest sign of hypovolaemia 
Autonomic neuropathy/failure
1. Ageing
2. Diabetes 
3. Parkinson's disease
4. Systemic amyloidosis

Interference with autonomic function by drugs
1. Tricyclic antidepressants

Interference with peripheral vasoconstriction by drugs

1. Nitrates
2. Calcium channel blocker
3. Alpha adrenoceptor-blocking drugs

Addison’s disease (adrenal failure - not enough aldosterone/cortisol produced)

Hypopituitarism (low ACTH)

After a marathon run (peripheral resistance is low for a few hours)

Idiopathic

Question 3

What is the clinical presentation of postural hypotension?

Answer 3

Typically asymptomatic

But can cause postural instability, dizziness and falls

Question 4

Which is the true BP measurement for postural hypotension - sitting or standing for guiding treatment?

Answer 4

Standing BP is the true BP value

Question 5

What is the management for postural hypotension (non-medicinal)?

Answer 5

1. Lie down if feeling faint
2. Stand slowly
3. Referral to ‘fall clinic’
4. Manage autonomic neuropathy
5. Physical measures i.e. leg crossing, squatting, elastic compression stockings
6. If post prandial dizziness, eat little and often - reduce carbs and alcohol intake
7. Head up tilt off the bed at night to increase renin release, so increase fluid and therefore increase standing BP

Question 6

What medications may be given for postural hypotension?

Answer 6

1st line drug: Fludrocortisone (retains fluid) 50mcg/d
*Caution if renal impairment, or decreased albumin as fludrocortisone can worsen oedema

2nd line drug: Sympathomimetics i.e. midodrine or ephedrine

Question 7

What is the pathophysiology underlying postural hypotension?

Answer 7

Physiology: Normally, BP rises if we stand up as a result of increased venous return due to venoconstriction, which maintains cerebral perfusion.

Pathology: Loss of extracellular fluid prevents this and causes a fall in blood pressure. This is ones of the earliest and most reliable signs of volume depletion (excluding other causes of postural hypotension)