Autonomics and Orthostatic Hypotension
Faria Khimani
Background
- Orthostatic Hypotension (OH): SBP ↓ > 20 mmHg, DBP ↓ > 10 mmHg), or within 3 min of standing up or head-up tilt to 60 degrees on a tilt table
- Etiologies: Neurogenic OH (nOH) vs non-neurogenic OH
- nOH associated with autonomic failure, often seen in conditions like Parkinson's disease, multiple system atrophy, and pure autonomic failure. Characterized by a blunted heart rate response during hypotension (heart rate rise <15 beats per minute
- Non-neurogenic caused by dehydration, medications, acute blood loss
Evaluation
- Orthostatic vitals signs- Perform a bedside simplified Schellong test: Measure blood pressure and heart rate after five minutes in the supine position and three minutes after standing.
- Labs: CBC, CMP, EKG, TSH, B12, LFTs,
- Consider SPEP/UPEP, paraneoplastic panel, autonomic function testing depending on clinical context
Management
- Conservative:
- TED hose and abdominal binder for ambulation
- Drink 16oz of fluid 15 min prior to standing
- If they have supine HTN, keep HOB 30-45 degrees at all times
- Add 2.3-4.6g of salt per day to diet (if no contraindications)
- Avoid high temperatures (which cause peripheral vasodilation)
Drug |
Dose |
Mechanism |
Side Effects |
|---|---|---|---|
| Fludocortisone (Florinef) |
0.1mg QD ↑ by 0.1 mg Max: 0.3 mg QD |
Mineralocorticoid → increase blood volume. Enhances sensitivity to circulating catecholamines |
Edema HTN HypoK Do not use in CHF |
| Midodrine |
2.5mg TID ↑ by 2.5mg Up to 10mg TID |
Peripheral-selective α1 agonist → constricts both aa & vv |
Supine HTN Pilomotor reactions Pruritus GI sx Avoid w/uncontrolled HTN, urinary retention, heart dz |
| Droxidopa |
100mg ↑ by 100mg Max: 600mg TID |
NE precursor → carboxylated to NE. Can cross BBB | Supine HTN, less than midodrine |
| Atomoxetine | 10mg or 18mg | SNRI | Do not use w/ glaucoma or MAOI |
Supine HTN treatments: transdermal nitroglycerin (preferred); minoxidil, hydralazine, or clonidine in select pts