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Physiology I F2015 > 21. Dysautonomia > Flashcards

21. Dysautonomia Flashcards

1
Q

What are the two limbs of ANS signal loop?

A
  1. Sensors sense changes in internal environ.
  2. Afferent neuron from sensing apparatus transmits signal to some sort of processing center (ganglion in SNS or higher processing center like medulla)
  3. Processing center decides what response is required of the body (PNS or SNS response)
  4. Efferent neuron from processing center to stimulate/effect effector systems
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2
Q

When does dysautonomia occur?

A

Dysfxn of sensing app, afferent or efferent nerve, processing center

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3
Q

What is most common example of primary ANS dysfxn?

A

Parkinson’s syndrome w autonomic failure

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4
Q

What is secondary ANS dysfxn?

A

Disease not directly affecting ANS but has ANS impacts

  • Guillain Barre - body’s immune system attacks PNS initially resulting in weakness + tingling in upper body and may eventually lead to paralysis
  • Myasthenia Gravis - breakdown in communication between nerves + muscle
  • Rheumatoid Arhtritis - autoimmune disorder –> can cause peripheral neuropathy
  • Diabetes Mellitus - common’y causes diabetic neuropathy –> numbness, tingling, pain, and altered pain sensation
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5
Q

Sx of dysautonomia?

A
  1. Orthostatic hypotension = dizziness or near blacking up when moving from lying or seated to standing
  2. Inability to increase heart rate w exercise or stress
  3. Sweating abnormalities
  4. Slow digestion –> loss of appetite, bloating, diarrhea, constipation, hard to swallow
  5. Sexual probs
    • Erectile dysfunction
    • Diff ejactulation
  6. Urinary probs
    • Incontinence
    • Recurring UTI’s due to bladder not emptying
    • Diff start urination
  7. Vision probs
    • Failure of pupils to react to changes in light
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6
Q

What causes orthostatic hypotension?

A
  1. When going from supine/sitting to standing –> drop in venous return of blood to heart –> decreased CO –> drop BP
    • 500-1000mL blood pool in feet
  2. NORM: Baroreceptors (carotid arteries + aorta) sense BP drop –> effector stimulation –> sympathetic resp + catechol surge –> maintain cerebral perfusion
    ORTHO HYPO: cerebral hypoperfusion –> faint to restore supine position + sympathetic surge
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7
Q

How to test to orthostatic hypotension?

A
  1. Ask pt to move from sitting/supine to standing position (best to check starting from supine)
  2. Measure BP
    • SBP decrease > 20mmHg
    • DBP decrease > 10mmHg
    • HOWEVER, BP drop not definitive, could also be due to hypovolemia, anemia…
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8
Q

Increase in ___ can compensate for orthostatic hypotension, despite no changes in BP.

A

HR.

POTS = postural orthostatic tachycardia syndrome –> good prognosis

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9
Q

What’s supposed to happen when moving from supine to standing position?

A
  1. Stand up quickly
  2. Drop in BP
  3. Aortic arch + carotid sinus baroreceptors sends sympathetic signal to medulla oblongata
  4. Sends sympathetic signals to veins, arteries, heart + SA node
    1. Increased F of contraction
    2. Increased HR
    3. Decreased venous pooling
    4. Increased tone + vascular resistance
  5. Overall increase in BP to maintain perfusion
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10
Q

What are three types of orthostatic conditions?

A
  1. Orthostatic hypotension - ineffective CV reflex –> hypotension –> bad prognosis
  2. Postural tachycardia - no changes in BP but abnorm increase in HR –> good prognosis
  3. Reflex syncope - passing out as reflex to some other physiologic signal (e.g. standing urination, exaggerated response to pain) –> sudden decrease in BP + HR
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11
Q

(T/F) Hypotension is sure sign of dysautonomia.

A

False

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12
Q

What happens during denervation hypersensitivity?

A
  • Denervation/nerve dysfxn –> denervation hypersensitivity
  • NORM: innervation = baseline tone/regulation
  • When remove nerve stim., muscle responds by gen. more receptors to try to regain baseline tone–> exagg. responses when giving meds
    • Careful when giving pressors to hypoT pt
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13
Q

What should be considered during preop eval in pt suspected of dysautonomia?

A
  1. Check for orthostasis
  2. Specialized evals
    • Table tilt test: pt placed on a table that can go head + feet down –> measure sp BP responses
    • Valsalva test: forced baring down to see CV resp
    • Cold pressor test: hand in cold water doesn’t cause increased BP/HR for pt w/ ANS probs
    • Deep breathing: looks at HR modulation or sinus arrhymthia during inhalation
    • Hyperventilation: drop in CO2 –> systemic vasodilation, but SIG. fall in BP = ANS failure
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14
Q

(T/F) Some HR variability is normal in healthy pt

A

True.

Variability = sign of good parasympathetic tone. This is low frequency variability.

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15
Q

(T/F) High frequency variability tests over longer period of time.

A

True.

Show balances b/w sympathetic + parasympathetic reflexes

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16
Q

Describe Bainbridge study.

A
  • Infused fluids directly into dog hearts –> saw increase in CVP + end diastolic P
  • When denervated heart from sympathetic + parasympathetic nerves –> stopped this reflex
  • Postulated increased HR due to downregulation of PNS as opposed to upregulation of SNS
  • Not applicable in humans
17
Q

What is Bezold-Jarish Reflex?

A
  • Abnormal resp to changes in BP as move from supine to sitting
  • Stimulus leads to initial sympathetic response (very forceful contractions) followed by vagal response thinking heart is overloaded
  • Results in bradycardia + hypotension + vasodilation–> inadequate perfusion –> syncopal episode
18
Q

Bezold-Jarish Reflex most commonly seen in pt w…

A
  • AMI
  • Spinal anesthetics that accidentally take out cardiac accel. nerves (SNS output) –> cardiac arrest if not treated w catecholamines
  • Interscalene/brachial plexus block
19
Q

What is autonomic dysreflexia?

A
  • Occurs in high spinal cord injuries (above T6), includes both normal + abnormal responses
  • Sympathetic response can be activated below injury but parasympathetic response can’t –> causes strong sympathetic outflow
    • Usually stimuli = distended bladder or colon
  • Brain detects hypertensive crisis –> sends parasympathetic response, but can’t get thru injury
  • Continued sympathetic response w/o parasympathetic balance
  • Vagus nerve intact to heart –> brady but HTN remains
20
Q

How to prevent autonomic dysreflexia?

A
  1. During surgery still need anesthesia for procedures below spinal cord injury (ANS still sensing the stimulus)
  2. Remove inciting stimulus (e.g. distended bladder/rectum)

Physiology I F2015 (13 decks)

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