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Difference in sensitivity to vecuronium between patients with ocular and generalized myasthenia gravis
1Department of Anesthesiology and Intensive Care Medicine, Kanazawa University School of Medicine, Japan.
Abstract:
Patients with myasthenia gravis show sensitivity to non-depolarizing neuromuscular blocking drugs, but little is known about differences in this sensitivity between types of myasthenia. In 10 patients with ocular myasthenia gravis and 10 with generalized myasthenia gravis, twitch tension was monitored in the adductor pollicis muscle by supramaximal train-of-four stimulation of the ulnar nerve during anaesthesia with sevoflurane 2.5% and nitrous oxide 60%. After baseline measurement, an initial dose of vecuronium 10 microg kg(-1) was given. When the twitch height stabilized (maximum block after the first 10 microg kg(-1)), the next incremental dose of 10 microg kg(-1) was given and repeated until block, defined as [1-(first twitch/baseline first twitch)] x 100 reached 90%. Maximum block after the first dose of vecuronium in ocular patients was significantly less than that in generalized patients (median 51 vs 91%; P<0.05). Onset of block after the first dose of vecuronium was significantly slower in ocular than in generalized myasthenic patients (mean 300 vs 200 s; P<0.05). Doses required to attain a block of 90% or more were significantly higher in ocular than in generalized patients (median 20 vs 10 microg kg(-1); P<0.05). Clinicians should consider the type of disease according to the Osserman classification when using non-depolarizing neuromuscular. blocking drugs in patients with myasthenia gravis.
Insights
Patients with ocular myasthenia gravis require higher doses of neuromuscular blocking drugs compared to those with generalized myasthenia gravis. This difference in sensitivity impacts anesthetic drug management for myasthenia gravis patients.
Area of Science:
- Anesthesiology
- Neurology
- Pharmacology
Background:
- Myasthenia gravis (MG) patients exhibit variable sensitivity to non-depolarizing neuromuscular blocking drugs (NDNMBs).
- Limited data exists on differential sensitivity to NDNMBs between ocular myasthenia gravis (OMG) and generalized myasthenia gravis (GMG).
Purpose of the Study:
- To investigate and compare the sensitivity to vecuronium, a non-depolarizing neuromuscular blocking drug, between patients with ocular myasthenia gravis and generalized myasthenia gravis.
Main Methods:
- Twitch tension was monitored in 10 OMG and 10 GMG patients under sevoflurane and nitrous oxide anesthesia.
- Incremental doses of vecuronium were administered, and neuromuscular block was assessed using train-of-four stimulation.
- Dose-response relationships and onset of block were analyzed.
Main Results:
- Ocular MG patients showed significantly less maximal block (median 51%) compared to generalized MG patients (median 91%) after the initial vecuronium dose.
- The onset of neuromuscular block was significantly slower in ocular MG patients (mean 300s) versus generalized MG patients (mean 200s).
- Higher cumulative doses of vecuronium were required to achieve 90% block in ocular MG patients (median 20 µg/kg) compared to generalized MG patients (median 10 µg/kg).
Conclusions:
- Significant differences in vecuronium sensitivity exist between ocular and generalized myasthenia gravis subtypes.
- Anesthetic management involving neuromuscular blocking drugs should consider the specific type of myasthenia gravis, potentially using the Osserman classification.