3/98medslides.com1 orthostatic hypotension: causes, mechanisms, and influencing factors christopher...
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3/98 medslides.com 1
Orthostatic Hypotension:causes, mechanisms, and influencing factors
Christopher J Mathias, DPhil, FRCPNeurology 1995; 45:S6-S11
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Control of Blood Pressure
• autonomic nervous system
• heart’s resistance and capacitance
• intravascular volume
• hormones– renin-angiotensin-aldosterone system– aldosterone– local endothelin or nitric acid
Neurology 1995; 45:S6-S11
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Orthostatic hypotensionconsensus 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
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.”
Neurology 1995; 45:S6-S11
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Orthostatic hypotensionsymptoms
• 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
Neurology 1996; 46:1470
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Autonomic Nervous SystemNeurogenic causes of
orthostatic hypotension
• Primary autonomic failure
• Secondary autonomic failure
Neurology 1995; 45:S6-S11
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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
Neurology 1995; 45:S6-S11
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Secondary autonomic failure
• central
• spinal
• peripheral
• miscellaneous
• drugs
• neurally mediated syncope
Neurology 1995; 45:S6-S11
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Secondary autonomic failure1. central
• brain tumors, especially of the 3rd ventricle or posterior fossa
• multiple sclerosis
• syringobulbia
• age-related
Neurology 1995; 45:S6-S11
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Secondary autonomic failure2. spinal
• spinal transverse myelitis
• transverse myelitis
• syringomyelia
• spinal tumor
Neurology 1995; 45:S6-S11
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Secondary autonomic failure3. 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)
Neurology 1995; 45:S6-S11
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Secondary autonomic failure4. miscellaneous
• autoimmune and collagen disorders
• renal failure
• neoplasia
• human immunodeficiency virus infection
Neurology 1995; 45:S6-S11
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Secondary autonomic failure5. drugs
• centrally acting – clonidine, methyldopa, reserpine,
barbiturates, anesthetics
• peripherally acting– guanethidine, bethanadine– phenoxybenzamine, prazosin– propranolol, timolol
Neurology 1995; 45:S6-S11
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Secondary autonomic failure6. neurally mediated syncope• vasovagal syncope
• carotid sinus hypersensitivity
• micturition syncope
• glossopharyngeal neuralgia and syncope
Neurology 1995; 45:S6-S11
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Neurogenic orthostatic hypotensionpathophysiology
• 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
Neurology 1995; 45:S6-S11
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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
Neurology 1995; 45:S6-S11
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Rise in plasma norepinephrine after 10 min Head-up tilt to 450
050
100150200250300350400450500
Controls MSA PAF DBH
Supine
Tilt
Nor
adre
nal
ine
(pg/
mL
)
Multiple system atrophy
Pure autonomic failure
Dopamine ß-OHdeficiency
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Nonneurogenic causesof hypotension
• cardiac impairmentmyocardial impaired ventricular filling
impaired output cardiac arrhythmia
• vasodilatation
• low intravascular volumeblood / plasma loss fluid / electrolytes
• miscellaneous
Neurology 1995; 45:S6-S11
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Nonneurogenic Hypotension1. cardiac impairment
• myocardialmyocarditis, myocardial infarction
• impaired ventricular fillingatrial myxoma, constrictive pericarditis
• impaired outputaortic stenosis, hypertrophic cardiomyopathy
• cardiac arrhythmiabradycardia, tachydysrhythmias
Neurology 1995; 45:S6-S11
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Nonneurogenic Hypotension2. vasodilatation
• drugs-nitrates
• alcohol
• heat, pyrexia
• hyperbradykinism
• systemic mastocytosis
• extensive varicose veins
Neurology 1995; 45:S6-S11
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Nonneurogenic Hypotension3. low intravascular volume
• Blood / plasma losshemorrhage, burns, hemodialysis
• Fluid / electrolyteinadequate intake (anorexia, vomiting)
diarrhea (including ileostomy)
renal/endocrine (salt losing nephropathy,
Addison’s, diabetes insipidus, diuretics
Neurology 1995; 45:S6-S11
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Nonneurogenic Hypotension3. miscellaneous
• Sepsis
• Endotoxic shock
Neurology 1995; 45:S6-S11
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Factors influencingpostural hypotension
• speed of positional change
• prolonged recumbency
• time of day (morning on rising)
• warm environment (hot weather, central heating, hot bath)
Neurology 1995; 45:S6-S11
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Factors influencingpostural hypotension
• food and alcohol (1)
• physical exertion (2)
(bending forward, abdominal compression, leg crossing, squatting)
• increased intrathoracic pressure(micturition, cough, defication)
1. Mathias CJ, et al. 1992; Autonomic Failure2. Smith GDP, et al. 1993; BHJ 1993; 69:359-361
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