Transcript Key Points from NCEP Guidelines

Orthostatic Hypotension:
causes, mechanisms,
and influencing factors
Christopher J Mathias, DPhil, FRCP
Neurology 1995; 45:S6-S11
3/98
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Control of Blood Pressure
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autonomic nervous system
heart’s resistance and capacitance
intravascular volume
hormones
– renin-angiotensin-aldosterone system
– aldosterone
– local endothelin or nitric acid
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Orthostatic hypotension
consensus definition (1)
• reduction of
– systolic BP of at least 20 mm Hg, or
– diastolic BP of at least 10 mm Hg
within 3 minutes of standing (some may
take more than 10 minutes)
• similar drop in blood pressure within
3 minutes in a head-up tilt table test
at an angle of at least 60 degrees
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1. Neurology 1996; 46:1470
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Orthostatic hypotension
“when associated with relevant
symptoms indicating impaired
perfusion, a smaller drop in blood
pressure may be equally important,
especially for further investigation.”
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Orthostatic hypotension
symptoms
• symptoms develop on assuming the
erect posture
– lightheadedness, dizziness, blurred
vision, weakness, fatigue, cognitive
impairment, nausea, palpitations,
tremulousness, headache, neck ache
• some patients may be asymptomatic
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Neurology 1996; 46:1470
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Autonomic Nervous System
Neurogenic causes of
orthostatic hypotension
• Primary autonomic failure
• Secondary autonomic failure
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Primary autonomic failure
• chronic
– pure autonomic failure
– Shy-Drager syndrome
• with parkinsonian features
• with cerebellar and pyramidal features
• with multiple system atrophy (combination)
• acute or subacute dysautonomias
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Secondary autonomic failure
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central
spinal
peripheral
miscellaneous
drugs
neurally mediated syncope
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Secondary autonomic failure
1. central
• brain tumors, especially of the 3rd
ventricle or posterior fossa
• multiple sclerosis
• syringobulbia
• age-related
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Secondary autonomic failure
2. spinal
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spinal transverse myelitis
transverse myelitis
syringomyelia
spinal tumor
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Secondary autonomic failure
3. peripheral
• afferent
– Guillain-Barre syndrome, Tabes dorsalis,
Holmes-Adie syndrome
• efferent
– diabetes mellitus, amyloidsis, surgery,
dopamine-b-hydroxylase deficiency
• afferent / efferent
– familial dysautonomia (Riley-Day synd)
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Secondary autonomic failure
4. miscellaneous
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autoimmune and collagen disorders
renal failure
neoplasia
human immunodeficiency virus
infection
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Secondary autonomic failure
5. drugs
• centrally acting
– clonidine, methyldopa, reserpine,
barbiturates, anesthetics
• peripherally acting
– guanethidine, bethanadine
– phenoxybenzamine, prazosin
– propranolol, timolol
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Secondary autonomic failure
6. neurally mediated syncope
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vasovagal syncope
carotid sinus hypersensitivity
micturition syncope
glossopharyngeal neuralgia and
syncope
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Neurogenic orthostatic hypotension
pathophysiology
• major abnormality is the lack of
neurally mediated vasoconstriction
in large vascular beds (skeletal
muscle and the splanchnic bed)
• gravitational pooling in the periphery
with lack of compensatory change
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Plasma norepinephrine level
• measure of sympathetic activity
• in neurogenic OH, the sympathetic
nervous system is not activated, the
rise in NE level is minimal or absent
despite a marked fall in BP
• basal NE level cannot determine the
site of lesion
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Rise in plasma norepinephrine
after 10 min Head-up tilt to 450
500
450
400
350
300
250
200
150
100
50
0
Multiple system atrophy
Pure autonomic failure
Dopamine ß-OH
deficiency
Controls
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Supine
Tilt
MSA
PAF
DBH
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Nonneurogenic causes
of hypotension
• cardiac impairment
myocardial
impaired output
impaired ventricular filling
cardiac arrhythmia
• vasodilatation
• low intravascular volume
blood / plasma loss
fluid / electrolytes
• miscellaneous
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Nonneurogenic Hypotension
1. cardiac impairment
• myocardial
myocarditis, myocardial infarction
• impaired ventricular filling
atrial myxoma, constrictive pericarditis
• impaired output
aortic stenosis, hypertrophic cardiomyopathy
• cardiac arrhythmia
bradycardia, tachydysrhythmias
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Nonneurogenic Hypotension
2. vasodilatation
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drugs-nitrates
alcohol
heat, pyrexia
hyperbradykinism
systemic mastocytosis
extensive varicose veins
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Nonneurogenic Hypotension
3. low intravascular volume
• Blood / plasma loss
hemorrhage, burns, hemodialysis
• Fluid / electrolyte
inadequate intake (anorexia, vomiting)
diarrhea (including ileostomy)
renal/endocrine (salt losing nephropathy,
Addison’s, diabetes insipidus, diuretics
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Nonneurogenic Hypotension
3. miscellaneous
• Sepsis
• Endotoxic shock
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Factors influencing
postural hypotension
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speed of positional change
prolonged recumbency
time of day (morning on rising)
warm environment (hot weather,
central heating, hot bath)
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Factors influencing
postural hypotension
• food and alcohol (1)
• physical exertion (2)
(bending forward, abdominal
compression, leg crossing, squatting)
• increased intrathoracic pressure
(micturition, cough, defication)
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1. Mathias CJ, et al. 1992; Autonomic Failure
2. Smith GDP, et al. 1993; BHJ 1993; 69:359-361
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