Orthostatic Hypotension

Synonyms:

a.k.a. postural hypotension

Diagnosis:

Definition:

  • Drop in BP >30 mmHg systolic or >10 mmHg diastolic when changing from lying to standing (not sitting), after 2-5 minutes of standing
  • Or ≥20 mm Hg (or ≥20%) drop in systolic pressure, either immediately or after 2 min of standing.
  • If negative but symptomatic, do orthostatic stress test:
    • BP lying & then standing after 12 squats

The normal pulse BP response:

  • BP: systolic falls by 5-10 mmHg, diastolic increases by 5-10 mmHg
  • Pulse: increases by 10-25 beats/min.
  • Pulse:
    • If increases >15 beats/min, nonneurogenic causes are suggested.
    • If doesn’t increase by >15 beats/min, autonomic dysfunction is suggested
  • The reason for the wait 2-5 minute is that the baroreceptor response may be sluggish in the elderly, hence sustained drop in BP on standing is what is looked for in orthostatic hypotension

Postural blood pressure & pulse:

  • After ≥5 min in a supine position
  • Immediately after standing
  • 2 min after standing
  • Supine hypertension also suggests autonomic dysfunction

Tilt table testing or formal autonomic nervous system testing can diagnose the condition

Investigations to consider:

Postural BP & pulse
FBC (hematocrit, anemia)
Stool occult blood
U&E
Blood glucose
Syphilis serology (tabes dorsalis)
Physiological & pharmacological autonomic tests
Nerve conduction studies
Tilt table
Autonomic nervous system testing

Treatment:

General measures:
Standing up gradually. Especially in the morning.
Elevate the head of the bed on blocks, 10-20 degrees
Avoid:

  • Hot environment
  • Valsalva manoeuvre
  • High fibre diet +/-Laxatives

If presyncope occurs:

  • Squat, lean forward with head between knees
  • Leg crossing
  • 500-1000ml water ingestion

Diet:

  • High salt,
  • Small meals, lots of fluids, avoid alcohol.

Shave while sitting
Waist high elasticized support hosiery
Stop offending drugs
Treat underlying cause
Medication:

  • Goal is symptom control, not BP control. The risk of complications often out-weighs benefits
  • Fludrocortisone P.O. for idiopathic & diabetic cases. Monitor supine BP, K+, heart failure
  • Midodrine P.O. Monitor supine BP
  • Salt tablets
  • Desmopressin intranasally. Monitor Na+ closely.
  • Erythropoietin subQ Monitor HCT, Hb, iron stores
  • Pyridostigmine P.O.

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