Combination of histopathological and electromyographic patterns can help to evaluate functional outcome of critical ill patients with neuromuscular weakness syndromes

The aim of the study was to describe patterns of neuromuscular weakness using a combination of electromyography and histology, and to evaluate functional outcome in patients following complicated cardiovascular surgery. Fifteen adults requiring long-term mechanical ventilation (>15 days) following cardiovascular surgery associated with postoperative complications were prospectively included. Electrophysiological and histological analyses (muscle and nerve) were performed when failure to wean from mechanical ventilation associated with peripheral neuromuscular weakness was noticed. Functional disability was evaluated 12 months after surgery. Six patients had a predominantly axonal neuropathy, six presented with myopathy, and three patients had a combination of axonal neuropathy and myopathy. All of them presented with acute tetraparesis and failure to wean from mechanical ventilation. All of the study patients who received corticosteroids exhibited a myopathic pattern (with or without axonopathic changes) but never an axonopathic pattern only. Only two of the eight survivors at 12 months were not ambulatory. These two patients had no detectable compound muscle action potential on electrophysiological examination. The combination of electromyographic evaluation and neuromuscular histological abnormalities could help to identify the type and severity of neuromuscular weakness, in turn helping to evaluate the patient's potential functional prognosis.