Did you get the orthostatics yet?

A 70 y/o male presents from a nursing facility with symptoms of weakness after 2 days of diarrhea.  He states it has been watery and occurring 4-5 times per day.  His heart rate is 80 bpm and regular, BP 130/70, respirations of 16, skin warm and dry. He appears well but shows a little general weakness overall.  He knows he takes medications for his blood pressure; however, he is not sure of the name.

Q: Would you get orthostatic vital signs on this patient to assess for volume loss?

Orthostatic vital signs have been used to assess for volume loss by measuring the body’s response to positional change.  Upon standing from a supine position, vasoconstriction and changes in heart rate help to maintain perfusion.  It is thought that when a person is hypovolemic this system fails and blood pools in the lower extremities causing a drop in blood pressure and/or an increase in heart rate.   Symptoms of orthostatic hypotension are lightheadedness, dizziness, blurred vision, weakness, fatigue, cognitive impairment, nausea, palpitations, tremulousness, headache, and syncope.  Orthostatic vital signs are considered positive when there is a drop in systolic blood pressure of ≥ 20 mmHg, drop in diastolic blood pressure of ≥ 10 mmHg, or heart rate increase of ≥ 30 beats per minute within 3 minutes of standing from a supine position.¹

The utility of orthostatic vital signs came into question over 20 years ago.  A study in 1990 looked at orthostatic vitals in 132 self-proclaimed euvolemic patients aged 18-80 years old (mean 34.1 +/- 13.6 years).  Of these patients 43% tested positive.  The study concluded that normal patients may present with orthostatic vitals given the current criteria.²

In 1997, a study examined orthostatics in 911 non-acutely ill patients aged greater than 60 from 45 different nursing homes.  To be included in the study, patients had to be able to stand for at least one minute.  The study found that over 50% of patients had orthostatic changes at baseline and it was most prevalent in the morning when patients first rise.³

Besides the elderly, orthostatic vitals were examined in adolescents as well.  307 healthy high school students aged 15-17 were checked for orthostatic vitals.  The study found pulse changes within the population to be 61% sensitive and 56% specific.  They also found orthostatic blood pressure changes to be within the adult range for 98% of adolescents, and a third of participants experienced orthostatic symptoms.  The study concluded the orthostatic heart rate criterion to be likely inappropriate for adolescents.⁴  Another study examining blood pressure changes in 23 healthy adolescents concluded transient orthostatic hypotension is common in their population.⁵

In addition to examining orthostatics in the non-acutely ill and adolescents, they were also studied in patients with known blood volume loss.  A study in 1992 examined 100 blood donors aged 19-83 years old and 100 senior center volunteers aged 55-94. The blood donors all gave 450 mL of blood.  Orthostatics had no clinical difference between ages.  Furthermore, a pulse rise >20 bpm or a diastolic BP drop > 10 mmHg had a specificity of 17%, sensitivity of 98%.  Systolic changes yielded no better.⁶ A similar study from 1994 looked at orthostatics in blood donation of 450 mL between two age groups, patients <65 and patients 65 or older.  These were healthy volunteers at baseline prior to blood donation.   A pulse change >20 bpm was found to have a sensitivity of 43% and a specificity of 94% in patients less than 65 years old.  In the age 65 and older group, pulse change was found to have a sensitivity of 25% and a sensitivity of 100%.  When they looked at blood pressure, they found it was worse than the flip of a coin.⁷

Besides blood volume loss, fluid volume loss and orthostatics were also studied. A study of 23 pregnant women with hyperemesis gravidarum studied the sensitivity of orthostatics in pre and post rehydration of 6 liters of lactated Ringer’s solution.  The study found that orthostatic changes lack sufficient sensitivity to be effectively used as quantitative screening tests for dehydration.⁸

In summary, the review above shows that using orthostatic vital signs alone to determine volume loss is highly unreliable.  Many patients can test positive for orthostatic signs even when asymptomatic.  We would never want to utilize a test that is so sensitive yet essentially with minimal specificity.  This would then cause the healthcare provider to act on all of the “positive” results by assuming the patient is hypovolemic. To make matters worse, the proportion of patients on beta blockers causing a blunting of the testing would make this even more unreliable than it already is.  When patients were known to have volume loss, orthostatic vitals still lacked a sufficient sensitivity to be deemed an effective test.  Looking for orthostatic clinical signs, not the numbers, is a far more reliable means to assess volume loss.  If the patient stands up and feels either lightheaded or passes out, this is sufficient enough to determine significant hypovolemia.  

References

1.         Naccarato M, Leviner S, Proehl J, et al. Emergency Nursing Resource: orthostatic vital signs. Journal of emergency nursing: JEN : official publication of the Emergency Department Nurses Association. Sep 2012;38(5):447-453.

2.         Koziol-McLain J, Lowenstein SR, Fuller B. Orthostatic vital signs in emergency department patients. Annals of emergency medicine. Jun 1991;20(6):606-610.

3.         Ooi WL, Barrett S, Hossain M, Kelley-Gagnon M, Lipsitz LA. Patterns of orthostatic blood pressure change and their clinical correlates in a frail, elderly population. Jama. Apr 23-30 1997;277(16):1299-1304.

4.         Skinner JE, Driscoll SW, Porter CB, et al. Orthostatic heart rate and blood pressure in adolescents: reference ranges. Journal of child neurology. Oct 2010;25(10):1210-1215.

5.         Stewart JM. Transient orthostatic hypotension is common in adolescents. The Journal of pediatrics. Apr 2002;140(4):418-424.

6.         Baraff LJ, Schriger DL. Orthostatic vital signs: variation with age, specificity, and sensitivity in detecting a 450-mL blood loss. The American journal of emergency medicine. Mar 1992;10(2):99-103.

7.         Witting MD, Wears RL, Li S. Defining the positive tilt test: a study of healthy adults with moderate acute blood loss. Annals of emergency medicine. Jun 1994;23(6):1320-1323.

8.         Johnson DR, Douglas D, Hauswald M, Tandberg D. Dehydration and orthostatic vital signs in women with hyperemesis gravidarum. Academic emergency medicine : official journal of the Society for Academic Emergency Medicine. Aug 1995;2(8):692-697.