A 68-year-male is in the midst of a prolonged ICU stay for respiratory failure, ARDS, and gram-negative bacteremia. He initially presented with shock requiring high-dose vasopressors and stress-dose steroids as well as severe hypoxemia requiring mechanical ventilation and paralytics. By ICU day 10 he has repeatedly failed spontaneous breathing trials with low tidal volumes. His exam is notable for reduced strength in b/l upper and lower extremities without rigidity. Laboratory studies including creatine kinase are within normal limits. Head CT is normal and CSF studies are normal. Electrophysiologic testing is notable for significantly decreased sensory and motor nerve amplitudes in multiple nerves, prolonged compound muscle action potentials, and decreased motor amplitudes.
Which of the following is an appropriate next step in management?
A. Dantrolene 2.5 mg/kgCorrect Answer: B
This patient is likely suffering from critical illness polyneuropathy and myopathy (CIP/CIM). CIP/CIM is a form of generalized weakness that results from skeletal muscle dysfunction and peripheral neuropathy. Risk factors include prolonged ICU stay, sepsis, use of steroids and neuromuscular blocking agents, and hyperglycemia during ICU stay. The etiology of CIP/CIM is not entirely understood, but it is thought to result from some combination of nerve ischemia, decreased muscle protein synthesis, disordered inflammatory signaling. Typical clinical features include failure to wean from mechanical ventilation, peripheral limb weakness, and the described features on electrodiagnostic testing. Patients with CIP/CIM can experience prolonged weakness and resolution, if it occurs, typically occurs over weeks to months. Treatment is primarily supportive with aggressive physical therapy and potentially prolonged mechanical ventilation. The differential diagnosis of CIP/CIM includes rare neuromuscular disorders such as the Guillain-Barre syndrome (GBS), but GBS more typically presents with an elevated CSF protein (with normal CSF cell count). Plasma exchange and IVIG are used in GBS and myasthenic crisis associated with Myasthenia Gravis, but there is no role for either in CIP/CIM. Dantrolene has been used in neuroleptic malignant syndrome (NMS), but in this case there is no mention of the use of neuroleptics nor is there fever of rigidity on exam.
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