Evidence Based Practice and Quality Assurance
Background and Goal of Study: Thymectomy as a standard procedure in patients with myasthenia gravis (MG) may be responsible for postoperative exacerbation of symptoms of MG. Only few studies concerning this subject were published and their results are controversial. The aim of the study was to identify factors associated with the increased incidence of myasthenic crisis in the postoperative period.
Materials and Methods: We analyzed retrospectively the postoperative course in 67 patients (age 34.8 ± 13.7 y, 46 women and 21 men) after thymectomy operated on between 1995-2002. The following factors were evaluated: age, sex, grade of symptoms (MGFA Clinical Classification and Osserman classification), presence of bulbar symptoms, time from the onset of symptoms to thymectomy, anticholinesterase and steroid use, preoperative lung function (VC, FEV1, FEV1/VC), Leventhal scoring system, methods of anesthesia (TIVA or balanced anesthesia with inhalation agent, with or without TEA, use of myorelaxants) and surgery (sternotomy or video-assisted thoracic surgery), presence of thymoma and coexisting diseases. Statistical analysis was performed using chi-square test and p < 0.05 was regarded as significant.
Results and Discussions: Extubation after surgery was delayed in 23 patients (34.3%). Eight patients (11.9%) developed myasthenic crisis on 4 ± 1.4 postoperative day, 4 of them (50%) needed ventilatory support for 96 ± 8.5h. Thymoma was found in 11 patients (16.4%). The statistical analysis showed that only MGFA clinical classification ≥ IIIA and VC < 80% were significant factors for development of myasthenic crisis in the post-operative period (p < 0.05). We found no correlation of preoperative status, anesthetic type or surgical approach with delayed extubation. Leventhal scoring system had no predictive value in this group of patients.
Conclusion: More advanced clinical stage of MG according to MGFA Clinical Classification and decreased vital capacity were identified as the risk factors for myasthenic crisis in postoperative period after thymectomy.
1. Jaretzki A et al. Ann Thor Surg 2000;70:327-334.
2. Leventhal SR et al. Anesthesiology 1979;51:S151.