Critical illness myopathy (CIM) is the most common cause of neuromuscular weakness in intensive care unit patients. It results from critical illness and treatments like glucocorticoids. CIM causes flaccid quadriparesis through selective loss of myosin. Diagnosis is based on onset after critical illness and features like electrical inexcitability on muscle stimulation. Treatment involves managing the underlying illness and discontinuing glucocorticoids. Recovery can take weeks to months. Critical illness polyneuropathy (CIP) also occurs through axonal injury, likely from ischemia. It causes limb weakness and sensory loss. Both CIM and CIP can occur together.

1. Presenter : Dr. Kumar
Neuromuscular weakness related
to critical illness

2. Introduction
 Neuromuscular weakness is a common occurrence in
patients who are critically ill, developing in ≥25 percent of
patients who are in the ICU and ventilated for at least
seven days.
 Weakness is partly a consequence of improved survival in
patients with multiorgan failure and sepsis, but is also a
consequence of treatments administered in the ICU,
including i.v glucocorticoids and paralytic agents.
 Neuromuscular weakness in the ICU is most often due to

3. CRITICAL ILLNESS MYOPATHY
 The most common form of intensive care unit
(ICU)-acquired myopathy is critical illness
myopathy (CIM).
 This disorder is also known by other names,
including acute quadriplegic myopathy and thick
filament myopathy.

4. Epidemiology and risk factors
 patients with status asthmaticus or COPD and 7
percent who receive a liver transplant develop CIM.
 Patients with other critical illnesses, such as ARDS,
may also be affected.
 Each of these disorders is typically associated with
intravenous (IV) glucocorticoid therapy.
 Triggering factors may include a higher illness
severity index, hyperglycemia, hyperthyroidism ,

5. Clinical features
 Critical illness myopathy usually begins several days
after IV glucocorticoid treatment is initiated.
 The time of onset of the myopathy may not be known
in patients who are comatose or encephalopathic.
 The most common presenting features of CIM are
1. Flaccid quadriparesis that may affect proximal more
than distal muscles
2. Failure to wean from mechanical ventilation

6. Laboratory and electrodiagnostic
findings in CIM
 The increase in serum CK peaked around four days
after initial treatment with glucocorticoids, and lasted
for as long as 16 days.
 major nerve conduction findings of CIM are normal to
low motor amplitudes with occasional broadening of
the compound muscle action potential .
 Phrenic motor amplitudes may also be low.
 Needle electromyography shows early or normal full
recruitment

7.  Direct muscle stimulation- muscles exhibit
electrical inexcitability
 This inexcitability is due to a defect in muscle
membrane depolarization, which may be related
to increased inactivation of sodium channels at
the resting potential

8. pathogenesis of CIM
 The major histopathologic finding in CIM is
relatively selective loss of myosin, which can be
identified as a lack of reactivity to myosin ATPase
in non-necrotic fibers.
 atrophy of myofibers, type 2 more than type 1

9. Diagnosis of CIM

10. By definition, patients are or were critically ill,
and weakness should have started after onset
of critical illness.
1. For a definite diagnosis of critical illness
myopathy , patients should have all four major
features and one or more supportive features.
2. For probable critical illness myopathy , patients
should have any three major features and one
or more supportive feature.
3. For possible critical illness myopathy , patients
should have either major features 1 and 3, or 2
and 3, and one or more supportive feature.

11. Treatment and prognosis of CIM
 Treatment of CIM is directed toward
1. discontinuation or reduction of glucocorticoids
as soon as possible,
2. aggressive management of medical conditions
3. avoidance of additional complications such as
venous thrombosis and
4. rehabilitation

12.  two studies have reported that intensive insulin
therapy (target blood glucose 80 to 110 mg/dL [4.4 to
6.1 mmol/L]) may lower the incidence of CIM and CIP
among critically ill patients who remain in the
intensive care unit for seven or more days.
 Critical illness myopathy is usually reversible over
weeks to months , but leads to prolonged ICU stays
and increased length of hospital stay overall

13. CRITICAL ILLNESS
POLYNEUROPATHY
1. second neuromuscular condition that is commonly
acquired in the intensive care unit (ICU)
2. Critical illness polyneuropathy appears to be a common
complication of severe sepsis
3. mechanism of axonal injury in CIP is unknown
4. speculation focuses on injury to the microcirculation of
distal nerves, causing ischemia and axonal
degeneration.
5. During the early stages of sepsis, electrical inexcitability
due to sodium channel inactivation may be present in

14. Clinical features of CIP
 Affected patients manifest a sensorimotor
polyneuropathy characterized clinically by
1. Limb muscle weakness and atrophy
2. Reduced or absent deep tendon reflexes
3. Loss of peripheral sensation to light touch and
pin prick
4. Relative preservation of cranial nerve function

15. Laboratory and electrodiagnostic
findings
 Nerve conduction studies in patients with CIP
typically reveal low motor and sensory
amplitudes.
 Needle EMG may show fibrillation potentials in
subacute to chronic patients.
 The serum CK levels are normal and muscle
biopsy shows findings consistent with neurogenic
atrophy

17. Treatment and prognosis of CIP
 CIP with mild or moderate nerve injury, recovery
of muscle strength generally occurs over weeks
to months
 Patients with severe CIP may remain
quadriplegic.
 treatment of CIP is supportive and includes
aggressive management of sepsis and underlying
medical conditions, avoidance of additional
complications such as venous thrombosis, and

18. COMBINED CRITICAL ILLNESS
MYOPATHY AND
POLYNEUROPATHY
 Combined CIM and CIP, sometimes called critical
illness polyneuromyopathy, is increasingly recognized
as a cause of neuromuscular weakness in the ICU.
 Sepsis and the systemic inflammatory response
syndrome may be a common pathologic mechanism
underlying the development of both CIM and CIP.
 Nerve conduction studies may be predictive of
neuromuscular dysfunction as early as 72 hours after
onset of critical illness.

19. PROLONGED NEUROMUSCULAR
JUNCTION BLOCKADE
 A rare disorder occurring in the ICU is prolonged
neuromuscular junction blockade.
 This disorder is related to prolonged use (days) of
paralytic agents, often in the setting of renal or
hepatic insufficiency, leading to prolonged circulation
of drug metabolites .
 These curare-like paralytic agents bind reversibly to
ach receptors on the motor end-plates of nmjs,
thereby inhibiting neuromuscular transmission

20.  The commonly used aminosteroid blocking agents,
such as pancuronium and vecuronium , are
normally cleared from the circulation within several
hours, primarily by the liver.
 in patients with decreased renal function (creatinine
clearance <30 mL/min), functionally active 3-hydroxy
metabolites of these drugs accumulate and persist in
the blood

21.  Affected patients have flaccid areflexic tetraplegia.
 Train-of-four stimulation may detect a major
neuromuscular junction defect, but formal repetitive
nerve stimulation is required for confirmation.
 Transient improvement in muscle strength after
administration of an anticholinesterase reversing
agent such as pyridostigmine supports prolonged
neuromuscular junction blockade as a cause of
weakness

22. DIFFERENTIAL DIAGNOSIS
 Other acute and subacute myopathies can occur
in critically ill patients, including
1. rhabdomyolysis
2. cachectic myopathy.
3. In addition, rare acute neuropathies such as
Guillain-Barré syndrome can also develop in
the ICU.