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A. Causes [1]navigator

  1. Shock
    1. Volume depletion - hemorrhage, severe dehydration
    2. Sepsis Syndrome
    3. Cardiogenic Shock
    4. Neurogenic Shock - usually due to spinal cord injury
  2. Orthostatic Changes
    1. Increasing incidence with age
    2. Symptoms and objective signs are most common in morning hours [2]
  3. Autonomic Instability [7]
    1. Age related; quite common in the elderly
    2. Neuropathy due to systemic disease (eg. Diabetes)
    3. Autonomic Insufficiency
    4. Parkinsonism (hypotension is exacerbated by many anti-Parkinsonian Drugs)
    5. Pure Autonomic Insufficiency
    6. Shy-Drager Syndrome (Multiple Systems Atrophy)
  4. Endocrine Failure
    1. Adrenal Insufficiency
    2. Hyperthyroidism
    3. Pituitary Failure / Pituitary Apoplexy [3]
  5. Drugs (usually have autonomic action)
    1. L-dopa
    2. Anti-depressants (anti-alpha adrenergic activity)
    3. Monoamine oxidase inhibitors
    4. Anti-hypertensives (such as ß-blockers and alpha-blockers)
    5. Cholinergics
    6. Phenothiazines (anti-alpha adrenergic activity)
    7. alpha-adrenergic blockers for benign prostatic hyperplasia (BPH)
  6. Normal blood pressure (BP) range for particular persons

B. Orthostatic Hypotension [1,7]navigator

  1. Orthostatic hypotension is a classic manifestation of sympathetic vasoconstrictor failure
  2. Definition
    1. On standing up from sitting or lying down:
    2. Systolic BP decrease of at least 20mm Hg OR
    3. Diastolic BP decrease of at least 10mm Hg
    4. Heart rate typically and normally increases >10bpm on standing
    5. In most cases of orthostatic hypotension, heart rate does not increase (<10bpm) on standing
  3. Physiology
    1. On rising to standing position, 500-1000 mL of blood pools in lower extremities
    2. BP and particularly cerebral and cardiac perfusion must be maintained
    3. Baroreceptors mainly in carotid and aortic vessels detect drop in pressure
    4. This normally stimulates sympathetic nervous system
    5. Both neurological and hormonal systems are rapidly activated
    6. Heart rate usually increases and vasoconstriction occurs
    7. Failure of any of these systems can lead to orthostatic changes
  4. Major Systems for Maintaining BP on Standing
    1. Muscle contraction in legs and abdomen compress veins, reduces blood pooling
    2. In euvolemia, extra blood is held normally in venous system, acting as a reservoir
    3. Sympathetic nervous system adjusts arterial, venous, and cardiac tone
    4. Increased cardiac inotropy and chronotropy (contractility and rate) normally occur
    5. Renin-Angiotensin-Aldosterone system activated
    6. Vasopressin (antidiuretic hormone) levels increase
  5. Classification of Orthostatic Hypotension
    1. Neurogenic
    2. Non-Neurogenic: Cardiogenic and others
    3. Iatrogenic: usually due to medications, overall most common cause
  6. Differential Diagnosis
    1. Symptomatic or asymptomatic orthostatic hypotension
    2. Lightheadedness / Dizziness
    3. Pres-syncope or Syncope from other causes
    4. True Vertigo
  7. Neurogenic Causes
    1. Spinal cord problems: syrngomyelia, transverse myelitis, tumors, tabes dorsalis
    2. Peripheral Nervous System: HIV/AIDs, diabetes, alcoholism, amyloidosis, renal failure, paraneoplastic syndrome, Guillain-Barre syndrome, vitamin B12 or folate deficiency
    3. Autonomic Failure: Parkinson's disease, dysautonomias, multiple system atrophy, pure autonomic failure
    4. Central Nervous System: stroke, multiple sclerosis, brain tumors, brain-stem lesions
    5. Carotid sinus hypersensitivity
    6. Neurocardiogenic syncope
  8. Non-Neurogenic Causes
    1. Cardiac Pump Failure: congestive heart failure, cardiomyopathies, many other causes
    2. Reduced intravascular volume: dehydration, burns, diarrhea, hemorrhage, vomiting
    3. Salt-lsing nephropathies
    4. Cirrhosis with ascites
    5. Endocrinopathies: adrenal insufficiency, thyroid dysfunction
    6. Venous pooling: alcoholism, fever, heat stroke, sepsis, postprandial splanchnic dilation
    7. Vigorous exercise with dilation of skeletal vessel beds
  9. Drugs
    1. alpha and beta blockers
    2. Other antihypertensives
    3. Dopamine Agonists: bromocriptine, levodopa
    4. Diuretics
    5. Monoamine oxidase inhibitors
    6. Narcotics, sedatives, minor tranquilizers
    7. Nitrates
    8. Phenothiazines
    9. Phosphodiesterase 5 Inhibitors: sildenafil, vardenafil, others
    10. Sympatholytics
    11. Tricyclic antidepressants
    12. Vincristine > vinblastine

C. Treatment [1] navigator

  1. Correction of Underlying Problem
    1. Volume repletion - fluids, blood products
    2. Cardiac support
    3. Correct septic causes
    4. Stop or change medications
  2. Some patients with hypotension will require specific BP raising therapy
  3. Intravenous Sympathomimetics
    1. Dopamine
    2. Phenylephrine
    3. Norepinephrine
  4. Oral Sympathomimetics
    1. Midodrine
    2. Pseudoephedrine
    3. Clonidine (0.4mg po qd) - may be effective in some patients [4]
    4. Dihydroergotamine - generally not recommended for chronic use [4]
  5. Midodrine (ProAmatine®) [2,5]
    1. Improves vascular resistance by agonist action on alpha1-adrenergic receptors
    2. Shown to be effective in increasing BP ~22mm at 10mg po tid
    3. Side effects minimal, mainly supine hypertension
    4. Scalp pruritis may also occur due to drug, but no cardiotoxic effects seen
    5. Initiate therapy at 2.5-5mg po tid; last dose taken before 6:00 PM
  6. Fludrocortisone (Flurinef®)
    1. Used to increase vascular volume (fluid loading)
    2. Mineralocorticoid replacement; aldosterone analog
    3. Baseline and follow-up potassium, sodium, magnesium
    4. Begin 0.1mg qd-bid po, up to ~ 0.4mg qd-bid
  7. Orthostatic Hypotension with Anemia [6]
    1. Treatment with erythropoietin (Epogen®, Procrit®)
    2. SBP increased ~20 mmHg and DBP increased ~15 mmHg
    3. HCT increased from 34% to 45%
    4. Dizziness resolves in many of the patients
    5. Long term effects not known, but some patients develop mild supine hypertension

Resources navigator

calcMean Arterial Pressure (MAP)

References navigator

  1. Bradley JG and Davis KA. 2003. Am Fam Phys. 68(12):2393 abstract
  2. Low PA, et al. 1997. JAMA. 277:1046 abstract
  3. Kaiser UB and Hedley-Whyte ET. 2001. NEJM. 344(20):1536 (Case Record)
  4. Victor RG and Talman WT. 2002. Am J Med. 112(5):361 abstract
  5. Midodrine. 1997. Med Let. 39(1003):59 abstract
  6. Ward C and Kenny RA. 1996. Am J Med. 100(4):418 abstract
  7. Freeman R. 2008. NEJM. 358(6):615 abstract