Preanesthetic Train-of-four Fade Predicts the Atracurium Requirement of Myasthenia Gravis Patients

Background: The most sensitive diagnostic criterion of myasthenia gravis is a decrement in the muscular response to repetitive stimulation. The authors hypothesized that myasthenia gravis patients who show a train-of-four ratio (T4/T1) 0.75 and to treat residual myasthenic symptoms. Results: In 14 patients, preanesthetic T4/T1 was ≥ 0.9 (normal), whereas 6 patients presented with T4/T1 < 0.9 (decrement). Decrement patients had a lower ED 95 of 0.07 ± 0.03 mg/kg atracurium (mean ± SD) compared with normal patients with an ED 95 of 0.24 ± 0.11 mg/kg atracurium (P = 0.002). All patients were extubated within 30 min after surgery. Postoperative pyridostigmine infusion did not differ significantly between groups. Conclusions: The requirement for atracurium is significantly reduced in myasthenia gravis patients with a T4/T1 ratio < 0.9 before anesthesia. This study indicates that routine neuromuscular monitoring in myasthenia gravis patients should be extended into the preinduction period to identify patients who require less atracurium.