Orthostatic Hypotension

Sep 16, 2019 admin THẦN KINH, TIM MẠCH 0

Orthostatic Hypotension

Aka: Orthostatic Hypotension, Postural Hypotension, Orthostatic Blood Pressure, Orthostasis, Orthostatic Syncope, Postural Blood Pressure, Postural Pulse

II. Definition: Orthostasis

  1. Measurement
    1. Occurs within 3 minutes of standing
  2. Orthostatic Blood Pressure
    1. Blood Pressure drop on standing of >20 mmHg systolic or 10 mHg diastolic
  3. Orthostatic Heart Rate
    1. Heart Rate increase on standing of 30 beats per minute

III. Efficacy

  1. Orthostatic Vital Signs have low utility and other measures should be used to assess volume status
    1. Swaminathan In Herbert (2013) EM: Rap 13(11): 6-7
  2. Orthostatic Blood Pressure and pulse are poor indicators of hypovolemia in Hemorrhage and dehydration
    1. McGee (1999) JAMA 281(11): 1022-9 [PubMed]
    2. Johnson (1995) Acad Emerg Med 2(8):692-7 [PubMed]
  3. Orthostasis is present in as many as 20-50% of those over age 65 years (and typically asymptomatic)
    1. Rutan (1992) Hypertension 19(6 pt 1): 508-19 [PubMed]
    2. Ooi (1997) jAMA 277(16):1299-304 [PubMed]

IV. Physiology

  1. Event: Rising from lying to standing position
    1. 300 to 800 ml of blood pools in legs
  2. Physiologic response
    1. Lower extremity Muscle contraction compresses veins
    2. Autonomic response
      1. Baroreceptors in aorta and carotids sense BP change
      2. Sympathetic Nervous System response
        1. Increases vascular tone
        2. Increases Heart Rate and cardiac contractility

V. Symptoms

  1. Dizziness or light headedness on standing

VI. Causes

  1. Medications
    1. See Medication Causes of Orthostatic Hypotension
  2. Cardiogenic
    1. Myocardial Infarction
    2. Arrhythmia
    3. Aortic Stenosis
    4. Myocarditis
    5. Pericarditis
    6. Bradycardia
  3. Hypovolemia (Tachycardia present, most common)
    1. Dehydration
    2. Hemorrhage
    3. Anemia
    4. Burn Injury
    5. Adrenal Insufficiency
    6. Diabetes Insipidus
    7. Straining
      1. Heavy lifting
      2. Urinating (Micturition Syncope)
  4. Neurogenic Causes
    1. Diabetic Neuropathy
    2. Spinal cord injury
    3. Guillain-Barre Syndrome
    4. Parkinsonism
    5. Tabes Dorsalis
    6. Amyloidosis
    7. Alcohol Abuse
    8. Vitamin B12 Deficiency (Pernicious Anemia)
    9. Syringomyelia
    10. Post-sympathectomy
    11. Human Immunodeficiency Virus (HIV)
    12. Idiopathic Orthostatic Hypotension
    13. Shy-Drager Syndrome
    14. Carotid Sinus Hypersensitivity
      1. Cardioinhibitory Syncope
      2. Vasodepressor Syncope
  5. Venous pooling
    1. Postprandial Hypotension (occurs within 75 minutes of a meal)
    2. Large leg Varices
    3. Prolonged bed rest
    4. Strenuous Exercise
    5. Fever
    6. Sepsis
    7. Heat exposure
    8. Alcohol
  6. Miscellaneous causes
    1. Aging (may be normal over age 70 years)
    2. Hypokalemia

VII. Labs

  1. Basic chemistry panel (electrolytes, Renal Function tests, Serum Glucose)
  2. Complete Blood Count
  3. Serum Vitamin B12
  4. Electrocardiogram
  5. Consider morning cortisol level
  6. Consider Holter Monitor

VIII. Imaging

  1. Head CT or Head MRI
  2. Echocardiogram

IX. Diagnosis

  1. See Head-Up Tilt Table Test
  2. Orthostatic Blood Pressure and Pulse
    1. Supine Blood Pressure, pulse after 3 minutes
    2. Standing Blood Pressure, pulse after 3 minutes
    3. Abnormal if Blood Pressure drops >20 systolic or 10 diastolic
  3. Response to 15 second Valsalva Maneuver
    1. Normally pressure falls, then rises over baseline
    2. Abnormal if pressure does not overshoot baseline
  4. Pulse variation on deep breathing (sinus arrhythmia)
    1. Normal response
      1. Tachycardia on inspiration
      2. Bradycardia on expiration
    2. Abnormal if <9 beat/min difference during cycle

X. Evaluation

  1. See Head-Up Tilt Table Test
  2. Consider intravascular volume replacement (IV Fluids)
  3. Consider causes above (including medications)

XI. Complications

  1. Orthostatic Syncope

XII. Management

  1. Avoid medications related to Orthostasis
    1. See Medication Causes of Orthostatic Hypotension
    2. Decrease dose or change medication to one less likey to cause Orthostatic Hypotension
      1. Consider stopping Tricyclic Antidepressants, Antipsychotics
  2. Modify diet
    1. Increase salt
      1. Indicated for 24 hour urinary Sodium <170 mmol Sodium in 24 hours
      2. Supplement up to 1-2 grams extra-per day (avoid in CHF, edematous states)
    2. Increase water intake (>64 ounces daily)
    3. Avoid Alcohol
    4. Eat smaller, more frequent meals (avoid large carbohydrate rich meals)
  3. Modify activity
    1. Avoid heat exposure or strenuous Exercise
    2. Sleep with head of bed slightly elevated
    3. Rise from bed slowly allowing for equilibration
    4. Avoid standing for long periods of time
    5. Isometric Exercises to work arms, legs and abdominal muscles (e.g. toe raises, thigh contractions, forward flexion at waist)
    6. While standing, move frequently and stand with crossed legs (consider leaning forward)
    7. Avoid work with arms above Shoulder height
    8. Dorsiflex feet several times before standing
    9. Consider Compression stockings
  4. Consider medication therapy (esp. for neurologic causes)
    1. Review precautions before using
    2. Fludrocortisone (Florinef)
      1. Increases Sodium and water retention
      2. Precaution: Monitor for Hypokalemia
      3. Start at 0.1 mg daily, titrate weekly by 0.1 mg to maximum of 1mg daily
      4. Target
        1. Improved symptoms
        2. Significant Edema
        3. Weight gain > 3.6 kg
    3. Midodrine (ProAmitine)
      1. Limit to specialist use (FDA recommends removing from market due to lack efficacy)
      2. Risk of supine Hypertension (mediction should be taken before 6 pm)
      3. Increases Blood Pressure for 2-3 hours
      4. Contraindicated in Coronary Artery Disease, Hyperthyroidism, Acute Renal Failure
      5. Start at 2.5 three times daily, titrate weekly by 2.5 mg to maximum dose of 10 mg three times daily
    4. Pyridostigmine (Mestinon)
      1. Start at 30 mg bid to tid and titrate to symptom control or 60 mg three times daily
    5. Erythropoietin has been used if comorbid Anemia
    6. Northera (droxidopa)
      1. Very expensive ($7800/month) compared to other agents listed above (e.g. Fludrocortisone is $35/month)

XIII. References

  1. (2017) Presc Lett 24(2): 10
  2. Engstrom (1997) Am Fam Physician 56(5):1378-84 [PubMed]
  3. Lanier (2011) Am Fam Physician 84(5): 527-36 [PubMed]
  4. Low (2015) J Clin Neurol 11(3):220-6 +PMID:26174784 [PubMed]
  5. Mathias (1995) Neurology 45:S6-11 [PubMed]

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