Autonomic disorders Flashcards
Autonomic disorder assessments
- autonomic function test
- liquid challenge meal test
- modified exercise test
- catecholamine level
- Thermoregulatory sweat test
- dynamic sweat test
Types of autonomic cardiovascular testing
NON- invasive
- tilt table test
- blood pressure test
- blood pressure and recordings
Liquid meal test (normal vasodilation supports digestive system)
- necessary for postprandial hypotension)
Modified exercise test (increased demand for blood, exercise requires increased output)
- reduced exercise tolerances and exercise induced hypotension
PoTS
-increased after exercise
- reduce exercise
Pupillometry, what is it and why do we use it?
Pupillary fatigue as signature of seropositive AAG
- redilation (quicker than health control)
- prem pupillary redilation within an intense 2 sec light stimulus
- virtually no light/ near response
- bilateral (para/symp)
- pupillary fatigue may present as impairment of synaptic transfusion
Physiology of Thermoregulation and Types of sudomotor testing
Thermoregulation is a vital process involving central nervous system through endocrine, autonomic and behavioural mechanisms
The sympathetic cholinergic system (scs) is the main pathway involved.
- vasodilator (ACh)
- sudomotor (ACh) sweatgland
Local factors = temperature
Hypo/hyperactivity of the sudomotor pathway (hypo = hypohidrosis, anhidrosis / hyper = hyperhidrosis)
- heat intolerance
- collapse triggered by warm environment
- lack of sweating
- hyperhidrosis
QSART
(quantitative sudomotor axon reflex test)
Dynamic sweat test
(Both QSART and dynamic test can identify areas of entire pathway)
QDIRT
(Quantitative direct and indirect test of sudomotor function)
Thermoregulatory Sweat test
(Global assessment of sudomotor function)
What is QSART ?
Quantitative sudomotor axon reflex test
(Validated in mayo clinic)
- acetylcholine solution filled into compartment c
- iontophoresis
- axon reflex and antidromic stimulation (stimulate area A, stimuli can travel back to other layer)
- sweat response recorded from compartment A
What is the dynamic sweat test and how does it work?
- acetylcholine solution/ pilocarpine
- iontophoresis
- sweat gland density
- distribution of active glands
- sweat rate
Impairment:
- poor sweat gland activation
What is a Thermoregulation sweat test and what might we see in autonomic dysfunction?
Thermoregulatory sweat test is a global assessment of sudomotor function
- temp and humidity controlled
- air temp 48-50°c; 35-38% rel humidity
- skin temp 38.5-39.5°c
- core (oral temp), increase to 38°c, or at least 1°c of throats is greater than 38°c
- indicator powder, alizarin red, corn starch, sodium carbonate.
Findings:
Pure autonomic failure
- whole body anhidrosis
Assessing BP circadian rhythm- ambulatory 24 BP and HR monitoring
- post prandial hypotension
- exercise induced OH
- worsening of OH in the morning
- reversed circadian rhythm
- prominent supine hypertension
Clinical indication- autonomic neuropathies
- immune mediated
- metabolic
- infectious
- toxic
- systemic disorders
- hereditary
Autoimmune autonomic neuropathy
Autoimmune autonomic ganglionopathy(AAG)
- a severe and treatable form of autonomic failure with evidence of post ganglionic denervation
- (patients showed objective evidence of widespread sympathetic and parasympathetic autonomic failure, with improvements after immunotherapy)
Non-pharmacological treatment measures
- TO BE AVOIDED
- High environmental temperature
- large meals/ alcohol
- drugs with vasodepressor properties - TO BE INTRODUCED
- high salt intake
- water repletion
- small, frequent meals
- judicious regular exercise
- physical counter manoeuvres - TO BE CONNSIDERED
- elastic stockings
- abdominal binders
Treatments for neurogenic OH
ACh
Cholinesterase Inhibitor
- pyridostigmine
NE
Agonist
- midodrine
NE precursor
- Droxidopa
Reuptake inhibitor
- atomoxetine
Peptide release inhibitor
- somatostatin analogue : octreotide
Autoimmune Autonomic disorder treatment
Immunotherapy for AAG
(Majority of patients require immunotherapy treatment, also, most severely affected patients may benefit from combined therapy with immunosuppressant agents)
- intravenous immunoglobulin
(Generally first line therapy) - plans exchange
(First line therapy) - corticosteroids
(Not often mono therapy choice, may provide benefit as part of combi immunotherapy) - rituximab
- mycophenolate mofetil
(Benefits to several patients, both mono (after first line failure) and combi immunotherapy) - combination therapy
(Additional immunotherapy may provide additional benefit even first line theories alone fail)
Diagnostic evaluation and management of PoTS
Neuropathic PoTS +/- collagen IV pathology
- non pharma treatment
Standard autonomic function test AFT
- non pharma treatment
Positive splanchnic hyperemia (following liquid meal challenge test)
- non pharma treatment
Positive deconditioning (following modified exercise test)
- non pharma treatment
- Avoided
- Introduced
- considered
If non pharma works, maintaine current treatment
Low BP ( 1. Fludro 2. Midodrine. If these do not work liquid meal challenge test, Ocreotide)
Normal/high BP (1. Propanalol, clonidin, bisoprolol, If these do not work liquid meal challenge test, Ocreotide)
PoTS
Most common form of orthostatic intolerance
15-50 yrs
Palpitations, dizziness, lightheadedness, syncope
Symptoms with HR rise of >30 bpm or >120 bpm within 10 minutes of HUT
Allied features
- bladder dysfunction
- cognitive affective symptoms
- EDS
- nausea, bloating etc
- migraine
Pathways
- hyperadrenergic
- anxiety
- autoimmunity
- neural mechanisms
- intravascular volume
Venous pooling in periphery when upright.
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