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For health professionals

The Blood Pressure Clinic of the Austin Hospital is happy to receive referrals from anywhere in Australia if they are referred by a medical practitioner. Our particular area of expertise is postural hypotension or autonomic nervous system dysfunction.

Referrals can be made by contacting clinpharm@austin.org.au and information can be obtained from Dr Chris O'Callaghan (christopher.o'callaghan@austin.org.au)

Approach to postural hypotension

Postural hypotension or Autonomic Nervous System dysfunction is often difficult to diagnose. It classically manifests as fainting, but can also present as drop attacks, dyspnoea, fatigue or nocturia. More rarely it presents with symptoms that suggest a hyper-adrenergic state.

Our approach to postural hypotension combines frequent 24 hour ambulatory blood pressure monitoring with judicious manipulation of antihypertensive therapy and occasional use of pressor treatments.

It is important to note that:

  • Autonomic failure is the most common cause of fainting in the elderly, and is much more common than is recognised.
  • In autonomic failure, failure of vasoconstriction leaves volume control as the main regulator of BP.
  • Autonomic frequently causes over-production of urine at night - resulting in nocturia (up to 5/night), morning hypovolaemia and therefore, morning hypotension.
  • Postural hypotension can be dramatically improved by using ambulatory BP to manipulate anti-hypertensive therapy.
  • Midodrine is a medication available under the TGA's Special Access Scheme and is the most potent and effective vasoconstricting agent.

 

What is postural hypotension?

-20 mm Hg systolic (at least) after 3 minutes standing from the supine position.

Common causes of postural hypotension (or, common causes of autonomic failure)

Elderly:

  • Drugs (but usually only if the autonomics are deranged)
  • Idiopathic/age-related autonomic nervous system failure
  • Diabetes mellitus
  • Parkinson's disease/Multiple system atrophy
  • Rheumatoid arthritis & other auto-immune/collagen diseases

Young:

  • Postural orthostatic tachycardia syndrome/orthostatic intolerance

 

Why postural hypotension is difficult to diagnose

Patients, especially elderly, with significant postural hypotension may not complain of classic postural al symptoms. Also, falls in postural BP may be episodic and it is difficult to accurately measure postural BP changes over 3 minutes using manual measurements. Suspect autonomic failure in any patient with reversed diurnal variation of blood pressure.

Pathophysiology

Autonomic failure is frequently associated with day hypotension but night hypertension. The physiological renal response to hypotension is decreased urine production. Thus, patients with postural hypotension have day anuria, night polyuria and morning dehydration.

Management of postural hypotension

Behavioural techniques:
Pharmacological techniques:
  • Manipulate concomitant anti-hypertensive therapy:
    1. Avoid diuretics
    2. Administer antihypertensive medications at nigh
  • Pharmacologically Increase Daytime BP:
    1. Volume expansion eg, fludrocortisone, NSAIDS, DDAVP (Minirin)
    2. Vaso-constricting agents e.g. pseudoephedrine, ergotamine, caffeine derivatives and midodrine (authorisation via TGA