Myopathy following mechanical ventilation for acute severe asthma - The role of muscle relaxants and corticosteroids

Background: Acute myopathy following mechanical ventilation for near-fatal asthma (NFA) has been described recently, and some researchers have suggest ed that this complication is related to the use of neuromuscular blocking a gents (NMBAs) and corticosteroids (CSs). Objectives: To determine the incidence of acute myopathy in a group of pati ents and to examine the most important predictors of its development. Design and methods: A retrospective cohort study. over a 10-year period (19 85 to 1995) of all asthma patients who received mechanical ventilation at t wo centers in Vancouver (designated center 1 and center 2). Results: In center 1, there were 58 patients who had 64 episodes of NFA, an d in center 2, there were 28 patients who had 30 episodes. NMBAs were used in 30 of 86 admissions for acute severe asthma (35%). The mean (+/- SD) dur ation of muscle paralysis was 3.1 +/- 2.3 days. A total of 9 patients (10.4 %) developed significant myopathy. The incidence of myopathy was 9 of 30 (3 0%) among patients who received NMBAs. In a multiple logistic regression mo del, the development of myopathy was only significantly associated with the duration of muscle relaxation. The odds ratio for the development of myopa thy increased by 2.1 (95% confidence interval, 1.4 to 3.2) with each additi onal day of muscle relaxation. The dose and the type of the CS were not sig nificantly associated with the myopathy in the multiple logistic regression analysis. Conclusion: Our study showed that there is a high incidence of acute myopat hy when NMBAs are used for NFA. The incidence of myopathy increases with ea ch additional day of muscle relaxation.