TOC | Cardiology   

Hypotension                                  Neurogenic Orthostatic Hypotension  
[REF: POL Outlines in Clinical Medicine 1998]

A. Causes

Shock

• Volume depletion - hemorrhage, severe dehydration
• Sepsis Syndrome
• Cardiogenic Shock
• Neurogenic Shock - usually due to spinal cord injury

Orthostatic Changes

• Increasing incidence with age
• Symptoms and objective signs are most common in morning hours

Normal BP range for particular persons

• Autonomic Instability
• Age related; quite common in the elderly
• Neuropathy due to systemic disease (eg. Diabetes)
• Autonomic Insufficiency

Drugs (usually have autonomic action)

• L-dopa
• Anti-depressants (anti-alpha adrenergic activity)
• Monoamine oxidase inhibitors
• Anti-hypertensives (eg. ß-blockers)
• Cholinergics
• Phenothiazines (anti-alpha adrenergic activity)
• Alpha-adrenergic blockers for benign prostatic hyperplasia (BPH)

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B. Treatment

Correction of Underlying Problem

• Volume Repletion - fluids, blood products
• Cardiac support
• Correct septic causes
• Stop or change medications
• Some patients with hypotension will require specific BP raising therapy
• Sympathomimetics (eg. Ephedrine, Pseudoephedrine)
• Fludrocortisone (Florinef®) 0.1mg qd-bid, up to ~ 0.4mg qd-bid
  -Fluid load; mineralocorticoid replacement
  -Baseline and follow-up Na/K, Ca/Mg
  -Begin 0.1mg qd-bid, up to ~ 0.4mg qd-bid
• Midodrine (ProAmatine®) 2.5 - 5 mg tab 2 tab tid (shortly before or upon rising in the morning)
  -Improves vascular resistance by agonist action on alpha1 adrenergic receptors
  -Shown to be effective in increasing BP ~22mm at 10mg po tid
  -Side effects minimal, mainly supine hypertension (take drug >3-4 hours before bedtime)
  -Scalp pruritis may also occur due to drug, but no cardiotoxic effects seen
• Orthostatic Hypotension with Anemia
  -Treatment with erythropoietin (Epogen®, Procrit®)
  _SBP increased ~20 mmHg and DBP increased ~15 mmHg
  -HCT increased from 34% to 45%
  -Dizziness resolves in many of the patients
  -Long term effects not known, but some patients develop mild supine hypertension

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03172000

Orthostatic hypotension
is a common problem among elderly patients, associated with significant morbidity and mortality. While acute orthostatic hypotension is usually secondary to medication, fluid or blood loss, or adrenal insufficiency, chronic orthostatic hypotension is frequently due to altered blood pressure regulatory mechanisms and autonomic dysfunction. The diagnostic evaluation requires a comprehensive history including symptoms of autonomic nervous system dysfunction, careful blood pressure measurement at various times of the day and after meals or medications, and laboratory studies. Laboratory investigation and imaging studies should be based upon the initial findings with emphasis on excluding diagnoses of neurodegenerative diseases, amyloidosis, diabetes, anemia, and vitamin deficiency as the cause. Whereas asymptomatic patients usually need no treatment, those with symptoms often benefit from a stepped approach with initial nonpharmacological interventions, including avoidance of potentially hypotensive medications and use of physical counter maneuvers. If these measures prove inadequate and the patient remains persistently symptomatic, various pharmacotherapeutic agents can be added, including fludrocortisone, midodrine, and nonsteroidal anti-inflammatory drugs. The goals of treatment are to improve symptoms and to make the patient as ambulatory as possible rather then trying to achieve arbitrary blood pressure goals. With proper evaluation and management, the occurrence of adverse events, including falls, fracture, functional decline, and myocardial ischemia, can be significantly reduced.

American J of Med October 2007

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