Acquired neuromuscular disorders in critically ill patients: a systematic review
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OBJECTIVE: To summarize the prospective clinical studies of neuromuscular abnormalities in intensive care unit (ICU) patients. STUDY IDENTIFICATION AND SELECTION: Studies were identified through MEDLINE, EMBASE, references in primary and review articles, personal files, and contact with authors. Through duplicate independent review, we selected prospective cohort studies evaluating ICU-acquired neuromuscular disorders. DATA ABSTRACTION: In duplicate, independently, we abstracted key data regarding design features, the population, clinical and laboratory diagnostic tests, and clinical outcomes. RESULTS: We identified eight studies that enrolled 242 patients. Inception cohorts varied; some were mechanically ventilated patients for > or = 5 days, others were based on a diagnosis of sepsis, organ failure, or severe asthma while others were selected on the basis of exposure to muscle relaxants, or because of participation in muscle biochemistry studies. Weakness was systematically assessed in two of the eight studies, concerning patients with severe asthma, with a reported frequency of 36 and 70%, respectively. Electrophysiologic and histologic abnormalities consisted of both peripheral nerve and muscle involvement and were frequently reported, even in non-selected ICU patients. In a population of patients mechanically ventilated for more than 5 days, electrophysiologic abnormalities were reported in 76 % of cases. Two studies showed a clinically important increase (5 and 9 days, respectively) in duration of mechanical ventilation and a mortality twice as high in patients with critical illness neuromuscular abnormalities, compared to those without. CONCLUSIONS: Prospective studies of ICU-acquired neuromuscular abnormalities include a small number of patients with various electrophysiologic findings but insufficiently reported clinical correlations. Evaluation of risk factors for these disorders and studies examining their contribution to weaning difficulties and long-term disability are needed.