Autonomics and Orthostatic Hypotension¶

Leonard Chiu

Background¶

Orthostatic Hypotension: SBP ↓ > 20 mmHg, DBP ↓ > 10 mmHg), or HR Increase > 30 within 3 min of standing up or head-up tilt to 60% on a tilt table
Etiologies: Neurogenic OH (nOH) vs non-neurogenic OH
nOH associated with autonomic failure
- Blunted tachycardia during hypotension characteristic of autonomic failure
- nOH: If HR rise is \<15
- nOH also associated with periods of high BP (supine hypertension)
- Ex: Neurodegenerative disease, neuropathy (diabetes, amyloid, paraneoplastic, etc)
Other causes: volume depletion (most common), medications (diuretics, alpha-1 blockers, BB, etc), pump failure (severe AS, arrhythmia)

Orthostatic vitals signs (checking supine, sitting, and standing with 5-minute wait in each position)
Volume status exam
Labs: CBC, CMP, EKG, TSH, B12, , LFTs,
Consider SPEP/UPEP, paraneoplastic panel, autonomic function testing depending on clinical context
Autonomic Function Testing: Available at 4:15pm Tues, Wed, Thurs NPO 4 hours prior
Hold oral pressors and antihypertensives 12 hours prior

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)
Supine HTN therapies: transdermal nitroglycerin (preferred); minoxidil, hydralazine, or clonidine in select patients

Orthostatic hypotension pharmacologic therapies

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 upset Avoid in uncontrolled HTN, urinary retention, heart disease
Droxidopa	100mg ↑ by 100mg Up to 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

Last update: 2022-05-29 04:29:03