Chapter 31-13: Orthostatic Hypotension

TEXTBOOK PRESENTATION

Orthostatic hypotension usually becomes symptomatic when patients stand. Patients typically note that they passed out almost immediately after standing from a chair or arising from bed. Other symptoms include near syncope, weakness, visual blurring, weakness, or leg buckling.

DISEASE HIGHLIGHTS

1. Orthostatic hypotension occurs in 20% of patients over age 75 and accounts for 12–30% of patients with syncope.

2. Classic orthostatic hypotension occurs within 3 minutes of standing. Orthostatic hypotension may also be delayed for > 3–10 minutes or develop rapidly, be transient, and difficult to detect with standard sphygmomanometry.

   1. Transient orthostatic hypotension is defined as a drop in systolic BP > 40 mm Hg or diastolic BP > 20 mm Hg within 15 seconds of standing.

   2. Due to its rapid improvement, this cannot be detected without beat-to-beat BP measurements, but patients may be symptomatic nonetheless.

   3. One study documented that 27% of patients with orthostatic dizziness but without demonstrable orthostatic hypotension had a history of syncope, suggesting that many of these patients had transient or intermittent orthostatic hypotension that was undetected. Another study documented that this accounted for 8% of syncope cases among young adults.

3. Etiology

   1. Hypovolemia

      1. Dehydration

         1. Decreased oral intake

         2. GI losses (vomiting, diarrhea)

         3. Urinary losses

            1. Uncontrolled diabetes mellitus

            2. Salt-losing nephropathy

            3. Adrenal insufficiency

      2. Hemorrhage

         1. GI

         2. Ruptured abdominal aortic aneurysm

         3. Ruptured spleen

         4. Ruptured ectopic pregnancy

      Intra-abdominal and retroperitoneal bleeding are uncommon causes of orthostatic syncope but can be life-threatening and occult! They should be considered in patients with marked orthostatic hypotension of unclear cause particularly if there is abdominal or back pain.

      3. Overdialysis

      4. Postprandial hypotension, particularly common in the elderly and worse with large carbohydrate meals or alcohol ingestion. Splanchnic pooling decreases venous return.

      5. Hot environments (hot tubs, baths, saunas)

   2. Medications

      1. Alpha- and beta-blockers

      2. Diuretics

      3. Vasodilators (ie, nitrates, calcium channel blockers, hydralazine)

      4. ACE inhibitors and angiotensin receptor blockers

      5. Tricyclic antidepressants

      6. Antipsychotic and anti-parkinsonism drugs

      7. Sildenafil and other phosphodiesterase inhibitors particularly when combined with nitrates

      8. Alcohol, sedative hypnotics, and opioids

   3. Autonomic insufficiency: Many (but not all) such patients demonstrate a fall in BP upon standing without a concomitant increase in pulse.

      1. Central neurologic disorders (eg, Parkinson disease, multisystem atrophy, pure autonomic failure, multiple sclerosis, and numerous others)

      2. Peripheral neurologic disorders: Diabetes mellitus, vitamin B₁₂ deficiency, uremia, Lyme disease, syphilis, HIV and other causes of autonomic neuropathies

      3. Prolonged bed rest

EVIDENCE-BASED DIAGNOSIS

1. Definition of orthostatic hypotension

   1. ≥ 20 mm Hg decrease in systolic BP within 3 minutes of standing; a decrease in systolic BP of ≥ 30 mm Hg may be a more appropriate criterion in patients with hypertension

   2. ≥ 10 mm Hg decrease in diastolic BP within 3 minutes of standing

   3. Or > 30 bpm increase in pulse within 3 minutes of standing

   4. The European Society of Cardiology also includes a fall in systolic BP to < 90 mm Hg.

2. 20% of the elderly have postural hypotension. Therefore, the presence of orthostatic hypotension alone does not confirm that syncope ...