Orthostatic vitals

Figure 1

I hate assessing postural vitals! Personally, I think there's nothing more damaging to a clinicians credibility than to reflexively order postural vitals on all patients over the age of 70. Because I'm willing to vent my anger on this topic to anyone willing to listen, I feel the need to keep the stats that support my self righteous nerd-anger fresh in my mind. One of the best articles for this is a 2015 narrative review by James Frith "Diagnosing orthostatic hypotension: a narrative review of the evidence". While the article doesn't directly address the causes of orthostatic hypotension; it does, in my opinion, offer the best summation of the futility of performing postural vitals.  

As the title suggests this is narrative review of English language articles discussing orthostatic hypotension (OH). Unfortunately this isn't a systematic review, so we don't know the exact search strategy, inclusion or exclusion criteria, the number of articles reviewed, or the exact data extraction process. 

Frith starts by summarizing current guidelines on the diagnosis of OH which vary slightly depending on the national committee. The European Federation of Neurological Sciences (EFNS) guidelines (figure 1), although of poor quality (level C), are the most comprehensive and complete of the guidelines, and align well with the available evidence.

Figure 2

Frith reviewed and evaluated the evidence used to:

• define baseline blood pressure, 
• the method used to illicit the orthostatic challenge (sit to stand vs tilt table etc), 
• the frequency and duration of BP testing (how often to cycle the BP cuff, and how long to wait before starting and finishing the test), 
• and the cutoff for defining BP drop. 

Frith determined that all the data came from low quality heterogeneous studies. Frith points out that the diagnostic power of the tool is questionable: the sensitivity varies from 25- 37%, that the inter-rater reliability is low (kappa 0.12-0.32); and that the prevalence of OH is high (up to 59%). Based on the synthesized evidence he made the following recommendations for assessing OH (figure 2). The recommendations align well with, and add considerable clarity to, the EFNS guidelines.

I think the evidence presented in this article clarifies the finer points of how to "properly" assess postural vitals; but more importantly I think it does an excellent job of pointing out the fallibility of the test: it highlights the high prevalence of OH, the low sensitivity of postural vitals, and poor inter-rater reliability of the test. 

I would suggest that the most important take home point here is that the only "proper" way to assess for OH is to simply stand the patient up and see if they become dizzy!

Frith, J. (2015). Diagnosing orthostatic hypotension: a narrative review of the evidence. British medical bulletin, 115(1), 123-134.

If you're looking for additional FOAMed resources to fuel your postural BP hatred you may also like:

http://ccareanywhere.blogspot.com/2015/01/did-you-get-orthostatics-yet.html

https://lifeinthefastlane.com/futility-orthostatic-measurements/