Autonomic nervous system disorders

Bedside screening for neurogenic orthostatic hypotension

Evaluating blood pressure and heart rate changes upon standing helps screening for nOH at bedside.

Orthostatic hypotension (OH) is a fall of systolic blood pressure (BP) ≥ 20 mmHg and/or diastolic BP ≥ 10 mmHg within 3 minutes of standing or head-up tilt. OH is a common problem in the elderly and may be due to hypovolemia, BP lowering drugs or a problem with the sympathetic nerves that control blood pressure (which is called neurogenic OH or nOH). In clinical practice, it is important to establish the cause of OH, because the treatments are different. While hypovolemia can be easily corrected and BP lowering drugs adjusted, nOH is a chronic neurological condition which can signal a neurodegenerative brain disease like in Parkinson’s disease, multiple system atrophy and dementia with Lewy bodies (1).

Cardiovascular autonomic function tests use continuous heart rate (HR) and BP measurements to help distinguish neurogenic from non-neurogenic causes of OH. Norcliffe-Kaufmann et al. showed in 2018 that an increase in heart rate <0.5 beats-per-minute/mmHg of systolic blood pressure fall during head-up tilt captures  nOH with a high diagnostic accuracy (2).

A recent validation study showed that this HR/BP diagnostic ratio is also useful at the bedside and has an excellent sensitivity for detecting nOH during active standing (3). The nOH ratio is an important screening tool for nOH that can easily be performed when no tilt-test facilities are available by having the patient lie and stand for 3 minutes and taking measures using a standard arm cuff BP and HR monitor, (3).

 

References:

 

  1. Kaufmann H, Norcliffe-Kaufmann L, Palma JA. Baroreflex dysfunction. N Engl J Med. 2020;382(2):163–78. pubmed.ncbi.nlm.nih.gov/31914243/
  2. Norcliffe-Kaufmann L, Kaufmann H, Palma JA, Shibao CA, Biaggioni I, Peltier AC, et al. Orthostatic heart rate changes in patients with autonomic failure caused by neurodegenerative synucleinopathies. Ann Neurol. 2018;83(3):522–31. pubmed.ncbi.nlm.nih.gov/29405350/
  3. Fanciulli A, Kerer K, Leys F, Seppi K, Kaufmann H, Norcliffe-Kaufmann L, et al. Validation of the neurogenic orthostatic hypotension ratio with active standing. [published online ahead of print, 2020 Jun 28]. Ann Neurol. 2020;10.1002/ana.25834..pubmed.ncbi.nlm.nih.gov/32596818/