Clinical approach to the weak patient in the intensive care unit

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Respir Care. 2006 Sep;51(9):1024-41.

Clinical approach to the weak patient in the intensive care unit.

Dhand UK.

Department of Neurology, University of Missouri, 1 Hospital Drive,

M178, Columbia MO 65212.

Motor weakness in a patient in the intensive care unit (ICU) may be

related to (1) pre-existing neuromuscular disorder that leads to ICU

admission, (2) new-onset or previously undiagnosed neurological

disorder, or (3) complications of non-neuromuscular critical illness.

Neuromuscular syndromes related to ICU treatment consist of critical

illness polyneuropathy, critical illness myopathy, and prolonged

neuromuscular blockade, and are now recognized as a frequent cause of

newly acquired weakness in ICU patients. Clinical features include

quadriparesis, muscle wasting, and difficulty weaning from the

ventilator. Evaluation of these patients is based on knowledge of

clinical setting and predisposing factors, focused neurological

examination, detailed electrophysiological investigation, serum

creatine kinase level, other laboratory studies as needed, and

histological examination of muscle biopsy. If a central nervous

system (brain or spinal cord) lesion is suspected, neuroimaging

studies are required. In addition to conventional nerve conduction

and needle electromyography, phrenic nerve conduction, diaphragm

electromyography, blink reflex, and (recently) the technique of

direct muscle stimulation have been employed. Critical illness

polyneuropathy is an axonal motor and sensory neuropathy that often

follows sepsis and multiorgan failure. Risk factors for critical

illness myopathy are corticosteroids and neuromuscular blocking

drugs, acute respiratory illness, and organ transplant. Three

subtypes (acute necrotizing myopathy, thick myosin filament loss

myopathy, and type II fiber atrophy) are recognized. Major

differential diagnoses of critical illness related paralysis are

incidental Guillain-Barre syndrome and unmasked myasthenia gravis.

Rarely, atypical presentation of amyotrophic lateral sclerosis,

polymyositis or other myopathies, and precipitation of porphyria or

rhabdomyolysis due to drugs used in the ICU have been described.

Recently a poliomyelitis-like flaccid paralysis due to West Nile

virus infection was reported. A subgroup of patients with myasthenia

gravis with muscle-specific tyrosine kinase antibody is noted to

present as respiratory crisis. Muscle biopsy in ICU paralysis

syndromes may be helpful in arriving at a specific diagnosis or to

classify the type of critical illness myopathy. Nerve biopsy is only

rarely indicated.