The Polyneuropathy of Critical Illness
Polyneuropathy occurs in 70% of patients who have sepsis and multiple organ failure. It presents as limb weakness and difficulty in weaning from the ventilator. Clinical signs are often unreliable, and electrophysiological studies are necessary to establish the diagnosis. These studies show a primary axonal degeneration of predominantly motor fibers. Creatinine phosphokinase levels are normal or mildly elevated. Muscle biopsy shows predominantly denervation atrophy. Recovery occurs, except in the most severe cases, if sepsis and multiple organ failure can be successfully treated. Other neuromuscular conditions that may be associated with sepsis are disuse atrophy and, rarely, acute myositis or pyomyositis. Measurements of creatinine phosphokinase levels and muscle biopsy, in addition to electrophysiological studies, are necessary to establish the correct diagnosis in these conditions. Recent reports in the literature implicate use of neuromuscular blocking agents or steroids as a possible further mechanism for causing either an axonal polyneuropathy or a primary myopathy; however, the precise role of these drugs in this type of toxicity has not been established. Nonetheless, comprehensive investigation of these patients is worthwhile to aid respiratory and rehabilitation management and to establish a long-term prognosis.