Neuromuscular interaction of sevoflurane--cisatracurium in a myasthenic patient.

PURPOSE

To describe the influence of sevoflurane anesthesia on cisatracurium neuromuscular block in a myasthenic patient undergoing thymectomy.

CLINICAL FEATURES

A myasthenic patient (Osserman IIB) was managed for one year before surgery with 60 mg pyridostigmine qid, 50 mg immuran tid and 30 mg prednisone therapy. Pyridostigmine was interrupted three months before surgery, and five sessions of plasmapheresis were done within 13 days before surgery. The neuromuscular response was monitored by Datex electromyographic response to train-of-four stimulation of the ulnar nerve. Sevoflurane 4% decreased the T1/C ratio by 20%. Administration of 0.025 mg x kg(-1) cisatracurium, during sevoflurane anesthesia, was followed by complete neuromuscular block for 45 min. Discontinuation of sevoflurane resulted, after 10 min, in recovery of the T which reached T1/C ratio of 50% after 30 min.

CONCLUSION

The marked sensitivity of this myasthenic patient to 0.5 x ED95 of cisatracurium can be attributed to potentiation of cisatracurium neuromuscular block by sevoflurane, as evidenced by the reappearance of the first twitch of the train-of-four response 10 min after sevoflurane was discontinued.