It’s common for patients to say they at times get light headed immediately after standing up, but is that enough to diagnose them with orthostatic hypotension? Well, no. So how does one definitively diagnose orthostatic hypotension, and how is it further classified? This post will seek to shine light on these questions.

Orthostatic hypotension is defined by either a drop in systolic blood pressure or diastolic blood pressure by 20 mmHg or 10 mmHg, respectively. But how do we measure this and which blood pressure do we use as the baseline? Well, to take orthostatic vitals we first start with having the patient lay supine for 5 minutes. We then take the supine blood pressure and use that as the baseline blood pressure. Next, we have the patient stand and wait at least for at least a minute and take the blood pressure again. If only 1 standing blood pressure reading will be taken, it is best to wait at least 2 minutes. This standing blood pressure is then subtracted from the supine blood pressure. 

Now let’s say a patient was found to have a drop in diastolic blood pressure upon standing of 12 and we diagnose them with orthostatic hypotension – do we stop there? No. Once we have a diagnosis of orthostatic hypotension we next want to classify it as either cardiogenic or neurogenic. What do we look at to determine this classification? Heart rate. A patient who has orthostatic hypotension should physiologically attempt to compensate by raising the heart rate a noticeable amount, and if it doesn’t, it should clue you in that there may be a neurologic component to the patient’s hypotension.  

The criteria to classify orthostatic hypotension is fairly simple, but does vary between resources. When looking at the heart rate between supine and standing, the heart rate should increase by at least half as much as the blood pressure dropped. For example, our theoretical patient with a drop of 12 mmHg in blood pressure should have a heart rate increase upon standing of at least half that amount – 6 bpm. If this patient had a heart rate increase of only 5, it would be classified as neurogenic instead of cardiogenic. 

But why does it matter which classification of orthostatic hypotension a patient has? Well, it matters in that neurogenic orthostatic hypotension can potentially be the first manifestation of a major neurological condition. For example, it could be a manifestation of Parkinson’s, Multi-system atrophy, or dementia with lewy bodies to name a few. It can also be a sign of unmanaged or undiagnosed diabetes. So while it may seem nit-picky to further classify such a common condition, it can significantly decrease the time it takes for your patient to be diagnosed with a serious pathology.

Sources:

Kaufmann H, MD & Palma J, MD, PhD. Mechanisms, causes, and evaluation of orthostatic hypotension. Post TW, ed. UpToDate. Waltham, MA: UpToDate Inc. http://www.uptodate.com. (Accessed on August 9, 2023.)

Metzler M, Duerr S, Granata R, Krismer F, Robertson D, Wenning GK. Neurogenic orthostatic hypotension: pathophysiology, evaluation, and management. J Neurol. 2013 Sep;260(9):2212-9. doi: 10.1007/s00415-012-6736-7. Epub 2012 Nov 20. PMID: 23180176; PMCID: PMC3764319.

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