2. Objectives
• Understand basics related to the
autonomic nervous system
• Describe normal orthostatic response in
transitioning from supine to upright
position
• Identify symptoms associated with POTS
• Name the most common form of
orthostatic intolerance
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8. Normal Orthostatic Response
• Standing transfers more than 17 ounces of
blood into the abdomen and legs
• Initial period of instability (initial orthostatic
hypotension) ensues and blood pressure
may decrease by 30% for 10 to 20
seconds after standing
• Reflex tachycardia happens
• Blood pressure restored within 30 to 60
seconds
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9. Normal Orthostatic Response
• Mechanisms to restore hemodynamics
– Arterial vasoconstriction
– Elastic recoil of venous blood in dependent
veins
– Active venoconstriction in splanchnic veins
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17. Orthostatic Hypotension
• Non-neurogenic orthostatic hypotension
– Common in young
– Cause – drugs, dehydration, hemorrhage
– Mechanism- incomplete autonomic nervous
system compensation for stressors
– Treatment- stop medication, prevent
dehydration
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18. Orthostatic Hypotension
• Neurogenic orthostatic hypotension
– Rare in young people, no increase in heart
rate
– Associated with diabetes, amyloidosis,
Parkinson’s disease
– Cause- autonomic vasoconstrictor failure
– Treatment- physical counter-maneuvers,
• Medications- IV saline, corticosteroids, midodrine,
droxidopa
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21. Postural Orthostatic Tachycardia
Syndrome
• Definition: chronic day-to-day symptoms of
orthostatic intolerance plus excessive
increase in heart rate when upright
– HR>30 from baseline
or >120 after 10 minutes during tilt test in adults
– HR>40 from baseline in children and teens
– Blood pressure usually not low
• Cause: alterations in autonomic nervous
system
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24. Epidemiology
• Females > Males 3:1 to 5:1; > 500,000 in 1999
• Triggers: Onset often follows flulike illness, selflimited autoimmune disease, surgery or injury,
pregnancy, rapid growth spurt
• May be associated with joint hypermobility
syndromes
• Young women may be underweight; need to
differentiate from eating disorders
• Hot weather or hot showers worsens symptoms
• Cognitive function may be affected
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26. POTS
• Neuropathic POTS
– Cause- loss of regional vasoconstrictive ability
– Blood pooling in lower extremities
– Heart rate increases to compensate for
decreased circulating blood volume now
pooling in lower extremities
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27. Treatment
• Neuropathic POTS- defect is loss of
regional vasoconstrictive ability
– Physical counter-manuevers
– Salt and water loading
– Midodrine
– Mestinon
– Exercise
– Rapid water ingestion
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28. POTS
• Hyperadrenergic POTS
– Increased circulating norepinephrine
– May have increased orthostatic blood
pressure
– Less common than neuropathic form
– Symptoms attributed- anxiety, tremor, cold
sweaty extremities
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30. OUTCOME for patients with
POTS
• Adolescent-onset: 80% recover by mid
20’s
• Adult-onset: large percentage recover
within 2-5 years
• Some patients will suffer from long term
disability associated with POTS
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32. Postural Vasovagal Syncope
• Most common form of orthostatic
intolerance
• Onset age 15, 2/3 are female
• 40% of the population has had at least one
episode in their lifetime
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33. Treatment
• Postural vasovagal syncope- defect ?
Loss of regional vasoconstrictive ability,
acute reversible baroreflex dysfunction
– Physical counter manuevers
– Salt and water
– Acute water ingestion
– Midodrine
– Rapid water ingestion
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34. Summary
• Orthostatic Intolerance defined by
symptoms when upright that are relieved
by lying down
• Orthostatic hypotension is a form of
orthostatic intolerance
• Initial orthostatic hypotension is a common
form of orthostatic intolerance in the young
• Postural vasovagal syncope is the most
common form of orthostatic intolerance
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35. Summary
• POTS is a form of chronic orthostatic
intolerance results
• (1) from a circulatory system not
responding to autonomic inputs properly
• (2) hyperadrenergic state
• (3) chronic bed rest
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