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S5 - Advanced Patho > MG, MD, MD > Flashcards

MG, MD, MD Flashcards

1
Q

Most prevalent neuromuscular disorder

A

Myasthenia gravis

Ranges 3-30 per 1,000,000 people

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2
Q

Demographics of myasthenia gravis patients

A

Common in elderly

If less than 50, more women than men at a 3:2 ratio

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3
Q

What is myasthenia gravis?

What are the manifestations?

A

Chronic disease of neuromuscular junction

  • Increasing skeletal muscle weakness
  • Fatigue of muscles with effort
  • Partial restoration of strength/function with rest
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4
Q

Which type of acetylcholine receptors are affected in myasthenia gravis?

Which are normal?

A

Decreased number of ACh receptors postsynaptically

Prejunctional ACh pool normal

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5
Q

What is found in 80- 85% of myasthenia gravis patiens

A

Antibodies

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6
Q

Which of these does myasthenia gravis effect?

Motor, sensory, ANS, cognition

A

Motor only

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7
Q

Which of the motor diseases has increased prevalence when living near the equator?

A

Myasthenia gravis

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8
Q

How does thymectomy affect myasthenia gravis?

A

Improve symptoms but not curative

Because there is an unknown promotion pdouction of IgE antibodies that the thymus gland seems to play a central role in

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9
Q

Hallmark sign of myasthenia gravis

A

Generalized weakness that impoves with rest

Inability to sustain/repeat muscular contractions

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10
Q

In myasthenia gravis, more movement =

A

more weakness

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11
Q

Myasthenia gravis has a wide range of symptoms

from what to what?

A

Slight ptosis to respiratory failure

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12
Q

What muscles are most affected in myasthenia gravis?

A
  • Eyes
  • Mouth
  • Pharynx
  • Proximal limb
  • Shoulder girdle
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13
Q

What is myasthenia gravis exacerbated by?

A
  • Infection
  • Stress
  • Surgery
  • Electrolyte imbalances
  • Some medications
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14
Q

What unique effects can myasthenia gravis have in pregnant women?

A

Exacerbated in 33% of pregnant women and can produce transitory symptoms in newborns (<20%)

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15
Q

Treatment options for myasthenia gravis

A
  • Pyridostigmine (60 mg, tid= 2 mg IV)
  • Immunosuppressants
  • Thymectomy
  • Plasmapheresis
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16
Q

two possible complications of treatment of myasthenia gravis

A

cholinergic crisis and myasthenic crisis

(cholinergic crisis = overdosing, myasthenic crisis = undertreatment)

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17
Q

What complication can occur from overdosing of anticholinesterase?

A

cholinergic crisis

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18
Q

What can occur from underdosing of anticholinesterase?

A

Myasthenic crisis

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19
Q

signs of muscarinic stimulation with cholinergic crisis

A
  • excessive salivation
  • diarrhea
  • excessive tearing
  • bradycardia
  • miosis
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20
Q

eye signs in myasthenic crisis

A
  • pupils normal size
  • ptosis
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21
Q

what s/s can both cholinergic and myastenic crisis lead to?

A

weakness and respiratory failure

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22
Q

If a myasthenia gravis patient is on an anticholinesterase DOS, what effects will this have?

A
  • Increased vagal reflex
  • Interferes with muscle relaxants
  • Inhibits plasma cholinesterase
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23
Q

Myasthenia gravis patients should take their anticholinesterase several days before and right before surgery

What happens if they dont?

A
  • Aspiration risk
  • At risk for respiratory failure
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24
Q

In myasthenia gravis patients its important to review electrolytes and correct as needed

Which one in particular?

A

Hypokalemia because it can potentiate muscle weakness

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25
Q

What should be considered in plan of care for myasthenia gravis patient?

A
  • Pharyngeal/laryngeal muscle weakness
  • Oral secretions- difficulty eliminating
  • Increased risk of pulmonary aspiration
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26
Q

What accounts for much of the morbidity of myasthenia gravis?

A

Swallowing and respiratory muscle dysfunction

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27
Q

Preferred anesthetic plans in myasthenia gravis patiens

A
  • Regional or local anesthesia preferred
  • GA- inhalational agents may decrease muscle tone enough for intubation so that muscle relaxants are not needed
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28
Q

What NMB are myasthenia gravis patients sensitive to?

A

non-depolarizing NMBA

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29
Q

Consideration with reversing NMB in myasthenia gravis pt

A

Reverse cautiously to avoid cholinergic crisis

Sugammadex 2-4 mg/kg if available

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30
Q

Where to assess NM blockade in myasthenia gravis patients?

A

Orbicularis occuli

May overestimate degree of relaxation but best place to avoid undetected residual weakness

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31
Q

Consideration in evaluating myasthenia gravis patient post op

A

Evaluate fully

Muscle strength seems adequate in early recovery but can deteriorate a few hours later

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32
Q

Predictors that post-op ventilation may be needed in myastenia gravis pt

A
  • Transsternal thymectomy
  • Having disease >6 years
  • Daily pyridostigmine dose >750 mg
  • COPD
  • Pre-op VC <2.9 L
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33
Q

How will succinylcholine dose be affected in myasthenia gravis not treated?

A

More resistant to succinylcholine (2-3x more resistant)

RSI dose is 1.5-2 mg/kg vs 1-1/5 mg/kg

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34
Q

If myasthenia gravis pt on cholinesterase inhibitor, effect on succ

What other drugs have similar effects?

A

May be prolonged

Ester local anesthetics

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35
Q

What drugs should you decrease or avoid in myasthenia gravis pt?

A

Non-depolarizers

Could be 10-100x more sensitive

If need to use, small dose 1/2-1/3 normal dose of short acting

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36
Q

Why is it better to titrate dose of non-depolarizer in NMB in myasthenia gravis patients?

A

To allow for spontaneous recovery so that you don’t have to use a reversal

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37
Q

Long ass list of drugs that may worsen myasthenic weakness

A
  • Quinine, quinidine, and procainamide
  • antibiotics
    • Aminoglycosides (gentamycin, neomycin)
    • Quinolones (ciprofloxacin, levofloxacin)
    • Macrolides (erythromycin, azithromycin)
  • Beta-blockers- both systemic and ocular
  • Calcium channel blockers
  • Mag salts (including laxatives with high mg++)
  • Iodinated contrast
38
Q

Anticholinesterases effect on ester LA

A

Impair hydrolysis

Prolong blcok

39
Q

Anticholinesterases effect on amide class of LA

Which are included in this class?

A

No effect

Lidocaine, ropivacaine, bupivacaine

40
Q

Lambert Eaton Myastheinc Syndrome (LEMS) is more common in patients who have what other problem

Does everyone have both?

A

Small cell carcinoma of bronchi

1/3-1/2 of people do not have evidence of carcinoma

41
Q

Demographic characteristics of LEMS

A

Men between 50-70

42
Q

Pathophysiology of LEMS

A
  • Presynaptic Ca++ channels are “messed up” via autoantibodies
  • Reduction in Ca++ mediated exocytosis of ACh at NMJ
  • Post-junctional ACh receptors unaffected unlike MG
  • Similar to that of Mg++ toxicity or botulism poisoning
43
Q

Main clinical manifestations of LEMS

A
  • Muscle weakness
  • Fatigue
  • Hyporeflexia
  • Proximal limb muscle aches
44
Q

What important muscles may be effected in LEMS

A

Diaphragm and respiratory muscles

45
Q

Cause and effect of ANS dysfunction in LEMS

A

Cause: related to Ca++ channel

Effects:

  • Orthostatic hypotension
  • Impaired gastric motility
  • Urinary retention
46
Q

What does tetany cause in patients with LEMS?

A

Progressive strengthening of muscle

47
Q

What occurs with voluntary contraction in LEMS?

A

brief increase in strength

48
Q

Cure/treatment for LEMS

A

No cure

Treatment goal is to improve muscle strength and decrease ANS deficits

49
Q

How does 3,4 diaminopyridine help with LEMS

A

Helps some people because it improves Ca+ influx thus increasing amount of ACh released

50
Q

Other treatments options besides 3,4 diaminopyridine for LEMS

A
  • Plasmapheresis
  • Corticosteroids
  • IV immunoglobulin
  • Immunosuppressants
51
Q

What may you suspect in patient coming for anesthetic with muscle weakness and suspected diagnosis of carcinoma of lung?

52
Q

Effect of NMB + LEMS

A

Very sensitive to both depolarizing and non-depolarizing

53
Q

Alternative to NMB in LEMS

A

Inhalational agents alone for tracheal relaxation

54
Q

should you titrate NMB carefully to avoid having to reverse LEMS pt with anticholinesterase?

A

No its fine to reverse them

55
Q

What possibility should you discuss with LEMS patient regarding post-op possibilities?

A

May require post op intubation/ventilation

56
Q

What do all the myotonias have in common?

A

inability of skeletal muscle to relax after stimulation (chemical or physical)

57
Q

Steinart’s disease is another name for

A

myotonic dystrophy

multisystem disease

58
Q

How to describe skeletal muscles in myotonic dystrophy

A

Hypoplastic

Dystrophic

Weak

Yet persistently contract

59
Q

When does myotonic dystrophy usually occur?

A

20-30 years old

60
Q

Is myotonic dystrophy fast?

Is it localized?

A

No and no

Slow progressive deteroriation of all muscle groups

61
Q

What is the definition of myotonia?

Is it seen early or late in disease?

A

Persistent contracture of muscle after stimulation

Seen early in disease

62
Q

What drugs are used to treat myotonic contractures?

How do they work?

A

Drugs

  • Phenytoin
  • Procainamide
  • Tocainide

They delay return of membrane excitation aka block sodium influx

63
Q

What drugs do not help with myotonia?

64
Q

Is there any treatment for muscle weakness in myotonic dystrophy?

65
Q

myotonic dystrophy effect on sleep

A
  • hypersomnolent
  • sleep apnea
66
Q

cardiac effects of myotonic dystrophy

A
  • conduction defects (50-90%)
  • most commonly first degree AV block
  • also see bradycardia, atrial flutter/fib
67
Q

myotonic dystrophy effect on face/neck

A

Hypoplastic, weak skeletal muscles of face and neck

68
Q

respiratory effects of myotonic dystrophy

how would you classify respiratory dsyfunction associated?

A

pharyngeal and resp muscle weakness

restrictive type impairment

69
Q

GI effects of myotonic dystrophy

A
  • intestinal hypomotility
  • gastric atony
70
Q

anesthetic implications of myotonic dystrophy

A
  • abnormal swallowing makes them vulnerable to pulm aspiration
  • avoid hypothermia/shivering
  • preop EKG and close intraop monitoring
  • RA- good choice but doesnt prevent contractures
  • be gentle with airway and use careful positioning
71
Q

what NMB to use in myotonic dystrophy

A

Avoid succ

NDMR ok but recognize muscle wasting

72
Q

What is duchenne’s MD?

A

progressive, painless degeneration and necrosis of muscle fibers

73
Q

what muscles are effected first in duchennes?

A

Calf, pelvic girdle, and muscle of thighs

74
Q

Patho of duchenne’s MD

A

Mutant gene identified on “X” chromosome that causes an error in coding dystrophin

75
Q

Difference in Duchenne’s and Beckers

A

Duchenne’s has no dystrophin while Becker’s has decreased levels of dystrophin

76
Q

Which muscular disorder only occurs in males?

Why?

A

Duchenne’s MD

Because it is x-linked recessive

77
Q

What is the most common and most severe of all the dystrophies?

A

Duchenne’s MD

78
Q

What causes necrosis of muscle fibers in Duchenne’s?

A

Infiltration of fat and fibrous tissue in muscle

79
Q

Effect of degeneration of skeletal muscle in Duchenne’s MD?

What about cardiac muscle?

Smooth muscle?

A

Skeletal= degeneration of respiratory muscles

Cardiac= cardiomyopathy, mitral regurgitation, ventricular dysrhythmias

GI

80
Q

EKG changes in Duchenne’s MD

A
  • Tall R waves (R)
  • Deep Q waves (L)
81
Q

What may mask issues in Duchenne’s MD?

A

Limited activity may mask cardio-pulm condition

82
Q

Progression of Duchenne’s MD

A

Presents early 2-6 y/o and progresses to wheelchair by 12

Death usually in late teens to early adulthood

83
Q

usually cause of death in Duchenne’s MD

A

Pneumonia or CHF

84
Q

What are good anesthesia options for Duchenne’s MD?

A
  • Local/regional anesthesia ideal
  • TIVA
85
Q

Why is careful titration of fluids important in Duchenne’s MD?

A

risk of CHF

86
Q

Hypotension + tachycardia in Duchenne’s MD

A

Heart failure

87
Q

why should we consider using an NG tube in Duchenne’s MD

A

Aspiration risk

88
Q

What is Gowers sign?

What is it associated with?

A

Using hands to push on legs to stand

Associated with Duchenne’s MD

89
Q

Which patients may commonly present for surgery on their tight heel cord?

A

Duchenne’s MD

90
Q

what drug should be avoided in Duchenne’s MD?

A

Succinylcholine - contraindicated

91
Q

caution with what anesthetic agents in Duchenne’s MD patients? why?

A
  • Opioids, sedatives, GA - very sensitive to these so use smallest amount possible
  • NDMR - have prolonged effect (3-6x longer) so carefully titrate/monitor

S5 - Advanced Patho (6 decks)

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