Orthostatic Vital Signs: Have They Fallen Out of Favor?

A 46-year-old female presents to the emergency department with a chief complaint of syncope, continuing to feel unwell and lightheaded.

Her vitals upon arrival are: blood pressure 138/84; pulse 74; respirations 16; and oxygen saturation 98% on room air. The patient was working outside, serving hotdogs at a concession stand during the summer. She has a history of depression and hypercholesterolemia, but otherwise an unremarkable history. Are orthostatic vital signs useful in the workup of this patient?

Background
When performed correctly, orthostatic vital signs measure blood pressure and pulse changes in a sequence of lying, sitting, and standing, waiting 3 minutes between each position.¹ A person is said to be “orthostatic positive” if one of the following is true: a reduction of systolic blood pressure of at least 20mmHg; a reduction in diastolic blood pressure of at least 10mmHg; or an increase in heart rate by >30 beats per minute, when comparing lying to standing.^1,2

The pathophysiology of orthostatic hypotension is that people, when standing, have pooling of blood in both the lower extremities and splanchnic circulation. This initiates a cascade to quickly increase cardiac output to limit blood pressure decrease through increased sympathetic outflow. Orthostatic hypotension results when these compensatory mechanisms are inadequate, leading to decreased cerebral perfusion pressure and, subsequently, symptoms such as syncope and lightheadedness.³

When patients are found to be orthostatic positive, fluid loss or decreased volume status is assumed most likely, and the go-to treatment is usually fluids, most commonly intravenous.^1,3

Although this is the typical use of orthostatic vital signs, their utility has been debated in literature and in the emergency department for decades. Supporters point to orthostatic vital signs as being useful in determining fluid loss as a cause of syncope, lightheadedness, and vertigo.³ They further tout their use as a risk-stratification tool in the elderly population.^4,5 Those opposed say a patient can still be hypovolemic and in need of treatment for such, but not have orthostasis.¹ Another risk is the potential pitfall of orthostatic vital signs causing anchoring bias of hypovolemia as the cause of syncope.⁶

Support
With syncope, patients commonly present with multiple symptoms, such as lightheadedness, palpitations, tremulousness, generalized weakness, blurred vision, and fatigue.³ These can be vague symptoms, and orthostatics give objective data to accompany these subjective symptoms and to support the diagnosis. Proponents argue that obtaining orthostatic vitals can help differentiate orthostatic causes of syncope versus non-orthostatic causes, such as autonomic peripheral neuropathies, pure autonomic failure, multiple system atrophy, and more.^2,7,8 Positive orthostatic vital signs can help tailor treatments, such as more frequent hydration or medication review, particularly in those with polypharmacy or in the elderly, who may be more sensitive to medication changes .^2,3,6

The 2017 American Heart Association (AHA) Guidelines on syncope stress the importance and need for obtaining orthostatic vital signs along with a thorough medical history and physical exam, particularly in older patients.² One prospective single-center study of more than 800 ED patients by Cohen and colleagues showed that orthostatic vital signs can be helpful to risk-stratify the elderly population, as patients 75 years and older who were orthostatic positive in the ED had an increased risk of hospitalization, all-cause mortality, and falls.⁴ More support for orthostatic vitals, a cost-effective and non-invasive test, comes from a retrospective study in which 2100 patients 65 years and older underwent analysis of workups for syncope. Only 38% of the 2100 patients had orthostatic vital signs performed; however, when performed, the tests helped inform diagnosis, management and etiology of syncope in over 30% of cases.⁹ Compare those findings with CTs, which were obtained in 63% of cases, and electrocardiograms and cardiac enzymes, which were obtained in greater than 95% of cases; these diagnostics changed management and diagnosis in less than 5% of cases.⁹

Against
While support for orthostatic vital signs shows them to be cheap, non-invasive, and particularly useful to help differentiate causes of syncope, their use has been called into question.

Skeptics believe that orthostatic vital signs are not useful and can even be dangerous, as they may cause anchoring bias and lead the physician to stop looking for further causes of the patient’s symptoms. White and colleagues concluded that orthostatic vital signs have no role in diagnosing life-threatening causes of syncope, such as stroke or cardiac arrhythmia, and can lead to misattribution to orthostasis.¹⁰ White’s study, a prospective multi-center observational analysis of 11 emergency departments, evaluated adults 60 years and older presenting with syncope and near syncope and showed orthostatic vitals had no independent correlation with 30-day adverse outcomes such as mortality; this was in direct contrast to the study by Cohen, which showed increased mortality.^4,10 In the same study in which Cohen showed that orthostatic vital signs can be used to risk-stratify the elderly, it was also found that 25% of people presenting to the ED were orthostatic positive, regardless of their complaint.⁴

As discussed initially, orthostatic vital signs are used to determine fluid status; however, in one small single-center study, orthostatic vital signs were performed on 23 pregnant patients with hyperemesis gravidarum, and the tests were found to have inadequate sensitivity for determining volume status.¹¹

In another study, Aronow evaluated 476 patients older than 60 years of age, living in long-term care facilities. This population was found to have significant variations in orthostasis throughout the day, with higher likelihood of orthostatic hypotension presence in the morning before breakfast.¹² Aronow concluded that in the non-acutely ill, there are significant cofounders, many coexisting (such as antihypertensives and beta-blockers), that make orthostatic vital signs less useful in this population.¹²

In a prevalence study of more than 900 long-term nursing home residents, Ooi and colleagues also showed that older patients are more likely to have baseline abnormal orthostatic vital signs due to medications and autonomic dysfunction, and the finding of orthostasis in the ED may be unrelated to the cause of syncope.¹³

In adolescents, a descriptive population study of 307 high school students proved orthostatic heart rate changes are common in euvolemic teens, and their blood pressures tend to fall within normal adult limits even if they are hypovolemic.⁵ Another study looked at 23 healthy adolescents and found that transient orthostatic hypotension is common as well in this population, attributed to underdeveloped vasoconstriction, with standing.¹⁴

If a patient is found to have positive orthostatic vital signs, there is a significant concern of anchoring bias.^6,10 A physician could potentially treat the patient with intravenous fluids and not do further testing, potentially leading to a missed diagnosis.

Discussion
The argument, given the data, is whether orthostatic vitals add anything to the evaluation and treatment of patients in the emergency department. Do we need to perform them? The AHA supports the use of orthostatic vitals in its 2017 update, and Cohen and colleagues demonstrated risk stratification for the elderly population.^2,4

Despite this, as noted in a study by Mendu and colleagues, orthostatic vitals are not performed in even half of syncope cases.⁹ In contrast, Ooi, Skinner, and Stewart found that orthostatic hypotension was common in non-acutely ill patients belonging to various age groups. Cohen even noted that, despite increased risk in the elderly, 25% of all ED patients were orthostatic upon evaluation.^5,13,14

Despite these conflicting studies, we should likely err on the side of caution and perform orthostatic vital signs more often, in conjunction with other diagnostics, to form a more complete picture of a patient’s volume status and risk factors.

As research continues, better alternatives to the use of orthostatic vitals may be discovered or refined, such as the Shock Index.¹⁵ The Shock Index is defined as the heart rate (HR) divided by systolic blood pressure (SBP). A result of >1 has been widely found to predict increased risk for mortality; the normal range is 0.5 - 0.7. Koch discusses that while heart rate and blood pressure have been traditionally used to characterize shock, they can appear normal due to confounding factors such as medications, leading to a delay in treatment.¹⁵ Research is promising for the Shock Index; however, a limited number of studies performed leads to inadequate data to support its use as a replacement for orthostatic vitals, at this time.

Routine evaluation of patients’ hydration status through intake and output, as well as evaluation of medications for effect on blood pressure, could give more accurate and reliable data, but these methods are likely not possible for patients being discharged.³ Future research into orthostatic vitals and alternatives need to include further prospective studies. These could include using orthostatic vital signs and following outcomes when used versus not used in a patient’s evaluation and management.

Conclusion
Just as there are two sides to every coin, some medical literature supports taking patients’ orthostatic vitals when they present to the emergency department with syncope, lightheadedness, or similar complaints; other literature takes a different view. However, as a low-cost and low-resource test, orthostatic vital signs should be used more often to help inform diagnosis and management of syncope. If better alternatives, such as the Shock Index, are proven to help elucidate syncope etiology and inform management, then maybe use could fade. Caution must be taken not to anchor on hypovolemia as a cause of orthostasis; many emergent diagnoses can have orthostasis associated with them. Always keep your differential large and work up other causes before only giving fluid and discharging the patient.

Case resolution
You decide to obtain orthostatic vitals, ECG, BMP, and CBC. Orthostatic vitals before treatment are:

Lying - blood pressure 134/92, pulse 71

Sitting - blood pressure 130/84, pulse 83

Standing - blood pressure 108/76, pulse 97

EKG - NSR at 74 bpm

You decide to give the patient 1 L of normal saline IV. Her BMP and CBC were unremarkable. You recheck orthostatic vitals after treatment, and they are as follows:

Lying - blood pressure 130/90, pulse 74

Sitting - blood pressure 126/84, pulse 75

Standing - blood pressure 122/78, pulse 80

You re-evaluate the patient as she is no longer orthostatic. On re-evaluation, she is still complaining of lightheadedness and dizziness. You obtain a CT scan of the brain, which is normal. You give the patient meclizine, which improves her symptoms. You diagnose the patient with orthostatic hypotension secondary to dehydration, and she is discharged with strict return precautions and told to follow up with her family physician. This turned out to be a straightforward case of orthostatic hypotension related to dehydration, but it is important not to anchor and to consider electrolytes imbalance, cardiac arrhythmia, and more.

References

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