Acute myopathy associated with combined use of corticosteroids and neuromuscular blocking agents

To review the occurrence and pathophysiology of myopathy associated with combined use of neuromuscular blocking agents (NMBAs) and systemic corticosteroids.

A MEDLINE search (1985 to July 1995, English language) yielded case reports and clinical studies involving myopathy or weakness associated with the use of NMBAs and/or corticosteroids. References cited in those articles were reviewed.

Prolonged muscle weakness has been reported in intubated patients in the intensive care unit (ICU) who were receiving NMBAs and/or corticosteroids. Many cases involved the use of both agents in individuals with no underlying risk factors. The term "blocking agent-corticosteroid myopathy" (BACM) has been used to describe this myopathy when it develops following combined use of these agents. Features common to BACM include prolonged weakness, elevated creatine kinase concentrations, myopathic features on electromyography, normal nerve conduction and sensation, and reduced deep tendon reflexes. Muscle biopsy results vary, but tend to show type 1 and/or 2 fiber atrophy without inflammation. Some recently reported cases revealed thick myosin myofilament loss, which is consistent with findings in denervated rat muscle after exposure to corticosteroids. Two small prospective studies reported that 36-50% of mechanically ventilated patients receiving either one or both drugs developed prolonged weakness.

NMBAs and corticosteroids alone have both been reported to cause myopathy in patients in the ICU. When coadministered, these agents appear to confer an even greater risk of myopathy; the exact pathology is not understood. Concomitant use of NMBAs and corticosteroids should be avoided if possible. Guidelines for cautious use and careful monitoring are suggested when combined use is deemed necessary.