A patient is considered to have orthostatic hypotension when the systolic blood pressure falls by more than 20 mm Hg,m or diastolic blood pressure drop by more than 10 mm Hg, or pulse rise of more than 20-30 beats per minute within 3-5 minutes of standing.
Don't be surprised if you hear different numbers from med students/nurses. There is a great deal of variation in how Orthostatics are checked and what numbers are used to call them significant.
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Symptoms of orthostatic hypotension are lightheadedness, dizziness, blurred vision, weakness, fatigue, nausea, palpitations, headache, and syncope.
When do we get Orthostatic Vitals?
Lying/Standing blood pressure or Orthostatic Vitals are generally done for patients with h/o volume loss (vomiting, dehydration, syncope, those who are on diuretics, alpha blockers) to make an assumption about their volume status. Majority of physicians treat orthostatic hypotension with Oral/IV fluids regardless of a patient's Orthostatic Symptoms.
I often get asked about this whenever I try and admit a high risk syncope under Internal Medicine. Emergency Physicians are aware of these pitfalls of Orthostatic Vitals, but we continue to play this game of numbers to sell admits to our colleagues who strongly believe in Orthostatics. Watch Anand Swaminathan diving into the literature behind these numbers.
How reliable are Orthostatic Vitals to predict mild dehydration?
Current literature states that orthostatic vital signs are highly unreliable to predict mild volume loss. Almost 50% can test positive for orthostatic vitals even when asymptomatic. In addition, elderly may have multiple other reasons such as autonomic neuropathy, medications that interfere with orthostatic vitals making them even more unreliable. Looking for orthostatic symptoms is more reliable than treating the numbers.
Problems with Orthostatic Vitals
- Poor Sensitivity and Specificity
- Poor reliability in elderly due to altered physiology, mediations, neuropathies
- Time Consuming (Nurses hate doing it!)
- Wide variation in how these numbers are interpreted
- Often not done in an ideal manner
- Treat the patient, not these numbers (Treat Orthostatic Symptoms)
- Orthostatic Vitals are not reliable to predict mild volume loss