Autonomics and Orthostatic Hypotension

Emily Walsh

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Background

• Orthostatic Hypotension (OH): 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)

Evaluation

• 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

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)

• Pharmacologic therapies (see table):

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

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