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Updated May 2007 by Charles Gomersall

Difficult to distinguish between critical illness polyneuropathy and critical illness myopathy and it may be preferable to group the two together

• occurs in 25-63% of patients who have been mechanically ventilated for ≥1 week
  • 70-100% of those who are also septic
• rare in children
• twice as common in males
• associated with:
  • sepsis, SIRS
  • multiorgan dysfunction
  • neuromuscular blocking agents
  • corticosteroids
  • cytotoxics
  • status asthmaticus

• often presents with difficulty in weaning. (Note that time to successful discontinuation of ventilation is not reduced by respiratory muscle "training" and that it is determined by time to resolution of neuropathy)
• mixed motor and sensory neuropathy but motor signs tend to predominate
• tends to cause distal muscle weakness (as do inflammatory, diabetic, porphyria neuropathy), particularly affecting lower limbs
• cranial nerves unaffected (cf Guillain Barre) - in common with other axonal neuropathies. Discrepancy between facial grimacing and decreased limb movement on painful stimulus often striking
• reflexes usually disappear during the course of the illness but absent reflexes are not a prerequisite for diagnosis
• subclinical in 50%
• NB features may be modified by presence of co-existing septic encephalopathy

• EMG & nerve conduction
  • relative preservation of conduction velocities and latencies (primary axonal degeneration)
  • reduction of amplitude and duration of muscle compound action potentials
  • ±  decreased amplitured of sensory nerve action potentials
  • needle EMG show fibrillation potentials and positive sharp waves, particularly in distal muscles. Comprehensive needle EMG testing is necessary.
  • can give information on severity of polyneuropathy
• muscle biopsy
• CPK: normal or near normal in most patients
• CSF: at most mildly raised protein

• Guillain-Barre syndrome
• other causes of predominant motor neuropathy (eg lead poisoning)
• diabetic neuropathy
• porphyria
• acute quadriplegic myopathy
  • more common in patients with severe asthma treated with high dose corticosteroids but may occur in the absence of steroid use
  • sensation and reflexes relatively spared
  • may be distinguished from critical illness polyneuropathy and myopathy by EMG
  • CPK elevated

Prevention

• subgroup analysis suggests that intensive insulin therapy/tight glucose control may reduce the incidence

Treatment

• no specific treatment
• treat underlying condition

• associated with increased mortality, prolonged mechanical ventilation and prolonged rehabilitation
• majority of survivors have persistent functional disability, reduced quality of life and restriction of autonomy

© Charles Gomersall December 1999, May 2007

©Charles Gomersall, June, 2013 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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