Download Acute necrotizing myopathy

CRITICAL ILLNESS MYOPATHY
INTRODUCTION
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The most common causes of newly acquired weakness
arising in the ICU setting are critical illness myopathy and
critical illness polyneuropathy.
Critical illness myopathy is probably the major
contributor to severe ICU-acquired weakness, causing
most instances of failure to wean from a ventilator in
patients with severe systemic diseases in the ICU,
while critical illness polyneuropathy affects 70% to 80% of
patients with severe sepsis and multiorgan failure
DEFINITION
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The hallmark of critical illness myopathy is weakness that
is typically diffuse in distribution, affecting both limb and
neck muscles.
As is typical of most myopathic disorders, weakness tends
to have a proximal predominance in the limbs, but it may
also involve distal muscles profoundly
There may be facial muscle involvement, and rarely,
extraocular muscles are affected other muscles supplied
by cranial nerves are usually spared.
A serious and common complication of the myopathy is
failure to wean from a ventilator due to marked weakness
of the diaphragm
PATHOPHYSIOLOGY
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Myosin loss and muscle fiber necrosis probably contribute
to persisting weakness. Myosin loss is characteristic of
CIM and is essentially pathognomonic of the disorder.
Corticosteroids may cause the loss of myosin, but other
factors trigger the process, such as an abnormal
neuromuscular junction caused by pharmacologic
blockade
who are systemically ill, often with metabolic acidosis, can
also develop the myopathy. Acidosis may stimulate
glucocorticoid production, lead to an increase in muscle
protein degradation, and trigger thick filament loss
CLINICAL SIGNS
Mixed motor and sensory neuropathy but motor signs tend to
predominate.
 tends to cause proximal muscle weakness predominance,
particularly affecting limbs, diffuse, flaccid and usually
symmetrical weakness often presents with difficulty in weaning
 Respiratory difficulties can be caused by atrophy of the
intercostals muscles, atrophy of the diaphragm muscle, and
degeneration of the nerve that stimulates the diaphragm.This
can prolong the time the wean a person of a mechanical
ventilation by as much as 7 – 13 days.
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 Deep
tendon reflexes may be lost or diminished, and
there may be bilateral symmetric flaccid paralysis of the
arms and legs possibly due to a generalized reduction in
membrane excitability that occurs in sepsis.
 The nervous system manifestations are typically limited
to peripheral nerves.
 Muscles
spared.
innervated by cranial nerves are usually
RISK FACTORS
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Severe sepsis and septic shock
disturbances of glucose metabolism resulting in hyperglycaemia
Adminstration
of corticosteroids, vasopressors, catecholamines,
Aminoglycosides, Beta agonists
use of neuromuscular blocking agents
Electrolyte Imbalance : Hyperkalemia, Hypokalemia,
Hypermagnesemia
trauma,
prolonged immobility
status epilepticus, toxin and hypothermia and heat stroke.
D/D
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Spinal cord disorders,
Gullain-Barre syndrome
Chronic inflammatory demyelinating neuropathy,
Diabetic polyneuropathy,
Myasthenia gravis
Lambert-Eaton syndrome.
Metabolic Abnormalities
Hypothermia
DIAGNOSIS
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Electrophysiological studies (such as needle EMG or
nerve conduction studies) and muscle biopsy may both be
necessary to diagnose critical illness myopathy.
Muscle biopsy
Laboratory investigations.
i) Electrophysiological studies
 This
studies show reduced amplitude of nerve action
potentials but normal conduction velocities in patients
with CIM
 Advantages :
can be conducted in unconscious/sedated patients
 high sensitivity and specificity in mechanically ventilated,
sedated patients
 can differentiates between primary nerve or muscle
dysfunction
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Disadvantages :
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requires some expertise and certain devices to perform these
measurements
ii) Muscle biopsy :
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Features seen on biopsy include fibre atrophy and angulated
fibres, fatty degeneration and fibrosis with minimal necrosis
Thick filament myopathy
 Acute necrotizing myopathy
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 Thick
filament myopathy
characterised by selective loss of myosin filaments
 plasma creatinine kinase levels are often elevated, and
progression to diffuse myonecrosis (rhabdomyolysis) is possible
 can be produced by surgical denervation of muscle followed by
exposure of the muscle to corticosteroids  this causes an
upregulation in the number of steroid receptors and a
resultant steroid hypersensitivity
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 Acute
necrotizing myopathy
myonecrosis with vacuolisation and phagocytosis of muscle
fibres is prominent
 plasma creatinine kinase levels are frequently raised, and in a
minority of patients frank rhabdomyolysis may ensue
 has also been described in patients admitted to ICU with
status asthmaticus that were generally non-septic and received
high-dose corticosteroids, either alone or in combination with
muscle relaxants
 this rare type of myopathy has a poor outcome
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The CPK rise which is found in about 50% of affected
patients, only occurs early in the course of the illness,
Peaks within a few days of onset, and then declines back
into the normal range.
CPK will raise 10-100 folds to normal level
PREVENTION
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Symptomatic treatment of sepsis and controlling the most
important risk factor.
Corticosteroid and NMBAs (if indicated) should be used
at a minimal dose for as short a period as possible
The need for neuromuscular blocking agents should be
reviewed frequently and overdosing should be avoided by
the use of a peripheral nerve stimulator
Avoiding hyperglycemia using insulin therapy to maintain
strict glycemic control.
Lower incidence of CIM was Observed in pts who had
treated with IvIg.
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Patients that are prescribed neuromuscular blocking
agents and/or steroids should be monitored for the
development of neuropathy and myopathy, including serial
serum creatinine kinase measurements and repeated
electrophysiological testing.
Correct Electrolyte imbalance.
Early mobilization can prevent prolonged hospitalization
and associated immobilization risks
Therapeutic exercises are aimed to improve function and reduce
disabilities and complications
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Percutaneous neuromuscular electrical stimulation
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A method to induce skeletal muscle growth, to enhance
strength and endurance capacity in chronic critically ill patient
to prevent loss of muscle mass
May be considered to be an alternative treatment to active
exercise
Has shown to increase muscle strength and reduce the number
of hospital stays
Long term use have positive effect on tissue healing
Medical Research Council
Neuromusclar Score (MRC Score)
Movement Tested
Score For Each Movement
Arm Abduction
0 = No Visible Contraction
Elbow Flexion
1 = visible contraction but no limb movement
Wrist Extension
2 = active movement insufficient to overcome gravity
Hip Flexion
3 = active movement against gravity
Knee Extension
4 = active movement against gravity and resistance
Ankle Dorsiflexion
5 = normal strength
• Each Limb is assigned a score from 0 – 15
• Total score range from 0 (tetraplegia) to 60 (normal muscle strength)
• ICUAW defined as a score of less than 48
PROGNOSIS
 Associated
with increased mortality, prolonged
mechanical ventilation and prolonged rehabilitation
 majority of survivors have persistent functional disability,
decreases in health-related quality of life and restriction
of autonomy
 Due to decreased mobility it increases the risk
of pneumonia, deep vein thrombosis, and pulmonary
embolism.
 Modern critical care must therefore no longer solely
focus on survival, but particularly consider health-related
quality of life after ICU discharge.
Thank You.