Bedside test for autonomic dysfunction
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bedside tests autonomic dysfunction Ewing tests orthostatic blood pressure heart rate authoritative
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https://pmc.ncbi.nlm.nih.gov/articles/PMC5351249
Bedside tests for autonomic dysfunction mainly assess cardiovascular sympathetic and parasympathetic reflexes. The standard bedside battery is often called Ewing’s cardiovascular autonomic reflex tests.
| Test | How to perform | Normal response | Predominantly assesses |
|---|---|---|---|
| Postural BP response | Measure BP after 5 minutes supine, then at 1 and 3 minutes standing | No significant sustained fall. Orthostatic hypotension is a fall of ≥20 mmHg systolic or ≥10 mmHg diastolic within 3 minutes | Sympathetic vasoconstrictor and baroreflex function |
| Heart-rate response to standing (30:15 ratio) | Record ECG continuously on standing. Calculate R-R interval around beat 30 divided by R-R interval around beat 15 | 30:15 ratio ≥1.04 | Parasympathetic (cardiovagal) function |
| Deep-breathing test | Six deep breaths/minute, with ECG monitoring. Measure maximum minus minimum HR during each cycle | HR variation typically ≥15 beats/min or E:I ratio about ≥1.2 | Parasympathetic function |
| Valsalva manoeuvre | Blow against a manometer at 40 mmHg for 15 seconds while monitoring ECG/BP | Valsalva ratio ≥1.4 in younger adults, with an appropriate BP overshoot after release | Cardiovagal and sympathetic baroreflex pathways |
| Sustained handgrip test | Maintain handgrip at about 30% maximal voluntary contraction for 3 to 5 minutes | Rise in diastolic BP of about ≥15 mmHg | Sympathetic efferent function |
| Cold pressor test | Immerse hand in ice water, if appropriate | Rise in BP and HR | Sympathetic adrenergic response |
Additional bedside examination:
- Pupils: size, anisocoria, light and near responses, and dilation lag in darkness.
- Sweating and skin vasomotor signs: dry skin/anhidrosis, excessive or asymmetric sweating, mottling, dependent color change, cold extremities.
- Supine and standing pulse/BP pattern: In neurogenic orthostatic hypotension, BP falls with an inadequate HR rise. A marked tachycardia with standing suggests volume depletion, drug effects, or POTS rather than pure autonomic failure.
- Bladder, bowel, and sexual history: urinary retention/incontinence, constipation, early satiety, erectile dysfunction.
Practical minimum screen: orthostatic BP plus pulse, deep-breathing HR variability, and the 30:15 response. Abnormal results should be interpreted with age-adjusted norms and medication review, as beta-blockers, anticholinergics, antidepressants, antihypertensives, dehydration, arrhythmia, and diabetes can alter results.
Avoid or modify Valsalva/handgrip testing in unstable cardiac disease, recent myocardial infarction, significant retinopathy, or when the manoeuvre is otherwise unsafe.
Source: Adams and Victor’s Principles of Neurology, 12th ed., p. 551.
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