(Dis)utility of Orthostatics in Volume Depletion

05 Mar
March 5, 2018

Definition: Orthostatic hypotension (OH) is a form of low blood pressure that occurs with positional change (i.e. sitting up from lying down, standing up from sitting). It is commonly used for the diagnosis of volume depletion

Orthostatic Vital Signs

  • A reduction of systolic blood pressure (SBP) of at least 20 mm Hg
  • A reduction in diastolic blood pressure (DBP) of at least 10 mm Hg
  • An increase in heart rate (HR) by > 30 beats per minute

One of the above criteria must be met while measured 3 minutes after standing from a supine position.

Clinical Question: Are orthostatic vital signs useful in finding patients with occult volume loss? Do they add to our standard clinical assessment of patients?

Review of the Evidence

Background on Orthostatics

  • The development of orthostatic criteria appear to be derived from measuring blood pressure and HR before and after young, healthy patients donate blood
  • Baseline OH in Adolescents
    • Orthostatic HR changes common (Skinner 2010)
    • Transient OH common (Stewart 2002)
    • Blood pressure changes usually fall within normal adult ranges
  • Baseline OH in the Elderly
    • Positional SBP changes occur in 11 – 50% of patients > 65 years of age (Ooi 1997, Aronow 1988)
    • Varies based on time of day and irrelevant of accompanying symptoms

Orthostatic Hypotension Take Home Point: At baseline, orthostatic vital signs are common and increases in frequency with age.

Orthostatics in Blood Loss

Witting MD et al. Defining the positive tilt test: a study of healthy adults with moderate acute blood loss. Ann Emerg Med 1994; 23(6): 1320-3. PMID: 8198307

What they did: Measured postural BP and HR changes after blood donation (450 ml) by healthy volunteers

McGee S et al. The rational clinical examination. Is this patient hypovolemic. JAMA 1999; 281(11): 1022-9. PMID: 10086438

Orthostatics in Non-Blood Volume Loss (i.e. vomiting, diarrhea)

Johnson DR et al. Dehydration and orthostatic vital signs in women with hyperemesis gravidarum. Acad Emerg Med 1995; 2(8): 692-7. PMID: 7584747

Orthostatic Hypotension Take Home Point: Orthostatic measurements had poor sensitivity for diagnosing moderate blood loss or significant dehydration. Performance characteristics were improved in large blood loss but, these patients are unlikely to be missed

Orthostatic Symptoms

Question: If the utility of the vital sign changes with position aren’t useful, what about simply using symptoms (I.e. the patient feels lightheaded when they stand.)?

Moderate volume loss: symptoms have limited predictive value

Severe volume loss (McGee 1999)

  • Excellent performance characteristics of inability to stand for vital signs to be measured
    • Sensitivity: 97%
    • Specificity: 98%
    • (+) LR = 48.5
    • (-) LR = 0.03
  • However, likely that diagnosis of severe volume loss can be made without this test

Summary: Based on the limited available evidence, it’s unlikely orthostatic vital sign measurement can be used to determine which patients have volume loss and which do not. The baseline prevalence of orthostatic vital signs is common and patients will not always develop orthostatic vital signs in response to volume loss. Therefore, there will both be patients who are orthostatic by numbers without volume loss and there will be patients with volume loss who are not orthostatic by numbers. Symptoms, with the exception of inability to stand to have orthostatics performed, are not useful either.

Bottom Line: Based on the low overall sensitivity of orthostatic vital sign measurements, they should not be used to influence clinical decision making.

References:

  1. Skinner JE et al. Orthostatic heart rate and blood pressure in adolescents: reference ranges. J Child Neuro 2010; 25(10): 1210-5. PMID: 20197269
  2. Stewart JM. Transient orthostatic hypotension is common in adolescents. J Pediatr 2002; 140: 418-24. PMID: 12006955
  3. Ooi WL et al. Patterns of orthostatic blood pressure change and the clinical correlates in a frail, elderly population. JAMA 1997; 277: 1299-1304. PMID: 9109468
  4. Aronow WS et al. Prevalence of postural hypotension in elderly patients in a long-term health care facility. Am J Cardiology 1988; 62(4): 336-7. PMID: 3135742
    Witting MD et al. Defining the positive tilt test: a study of healthy adults with moderate acute blood loss. Ann Emerg Med 1994; 23(6): 1320-3. PMID: 8198307
  5. McGee S et al. The rational clinical examination. Is this patient hypovolemic. JAMA 1999; 281(11): 1022-9. PMID: 10086438
  6. Johnson DR et al. Dehydration and orthostatic vital signs in women with hyper emesis gravidarum. Acad Emerg Med 1995; 2(8): 692-7. PMID: 7584747

Post Peer Reviewed By: Salim R. Rezaie (Twitter: @srrezaie)

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Anand Swaminathan

Clinical Assistant Professor of Emergency Medicine at St. Joe's Regional Medical Center (Patterson, NJ)
REBEL EM Associate Editor and Author
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2 replies
  1. Natalie OH says:

    Just a question on your last statement “should not be used to influence clinical decision making”. Obviously sensitivity is poor, but specificity looks quite high.
    Postural BP is usually part of my syncope screen. And having a persistent drop >20mmHg would exclude an elderly patient from going home. I notice Ooi states that it’s quite common in the elderly, however in those who have just had a fall, I would be reluctant to send them home with persistent drop.
    Would be interested to know if someone has compared this to frequency of falls…

    Reply
    • Anand Swaminathan says:

      Natalie, Fantastic questions and you bring up some great points.
      I’m not very concerned with specificity in this case. Orthostatics are most commonly used as a screening test; to pick up those who have occult blood or volume loss. Sensitivity here is key and, as you noted, the sensitivity is quite low.
      For blood loss, I agree that specificity isn’t bad and so maybe there’s a role there. The limitations are that all of this data is in the setting of healthy volunteers who were phlebotomized as opposed to patients who actually had trauma and blood loss or GI bleeds and blood loss. We have no idea how orthostatics would perform in those settings.
      As for non-blood volume loss, the limited evidence we have speaks to orthostatics having poor performance characteristics.
      As for long term outcomes, we have little on it except for this study:
      Raiha I et al. Prevalence, predisposing factors and prognostic importance of postural hypotension. Arch Intern Med 1995; 155: 930-935.
      Raiha performed a prospective random sample cohort study with 10-year follow up. The data showed neither systolic nor mean blood pressure changes with standing predicted mortality at 10 years follow up, however a diastolic drop of 10 mmHg with standing was associated with increased vascular mortality (odds ratio 2.7, 95% CI, 1.3 to 5.6). When further analyzed this association disappeared in multivariate analysis after adjusting for background factors such as underlying cardiovascular disease. The thought being those patients with a more labile diastolic pressure likely had underlying risk factors that predisposed them to increased vascular mortality such as stroke and MI.

      Reply

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