Risk Factors And Scoring Model Establishment Of Myasthenic Crisis After Thymectomy For Patients With Myasthenia Gravis

Objective: To investigate the risk factors of myasthenic crisis after thymectomy for patients with myasthenia gravis, to establish risk scoring model and evaluate its effectiveness for predicting myasthenic crisis after thymectomy for patients with myasthenia gravis. Methods: A retrospective study was conclude in 86 myasthenia gravis patients who underwent a thymectomy from June 2002 to June 2015. Logistic regression analysis was used to investigate the risk factors, The following factors were evaluated: sex, age at surgery, disease duration before thymectomy, history of myasthenic crisis, preoperative severity of gravis(Osserman-stage), bulbar symptoms, pyridostigmine dose before thymectomy, concomitant other diseases, preoperative pulmonary function, operation methods, operation time, intraoperative blood loss, postoperative pulmonary infection and pathological type. Related literatures published in English about the risk factors of myasthenic crisis after thymectomy for patients with myasthenia gravis were electronically searched comprehensively from 1980 through to August 2015. Two reviewers independently screened literature according to the inclusion and exclusion criteria extracted data,and assessed methodological quality. Then meta-analysis was performed using Stata 13.0 software. Risk scoring model was established according to the result of meta-analysis, and evaluate its effectiveness, accuracy, sensitivity and specificity for predicting myasthenic crisis after thymectomy for patients with myasthenia gravis. Results: 16 patients of myasthenia gravis after thymectomy developed myasthenic crisis(18.6%). Univariate statistical analysis showed history of myasthenic crisis, preoperative severity of gravis(Osserman-stage), bulbar symptoms, pyridostigmine dose before thymectomy,preoperative pulmonary function, postoperative pulmonary infection and intraoperative blood loss were the risk factors. Multivariate Logistic regression analysis showed that myasthenic crisis, preoperative severity of gravis(Osserman-stage) and bulbar symptoms were the independent risk factors of myasthenic crisis after thymectomy for patients with myasthenia gravis. A total of 10 studies involving 195 patients in case group and 941 patients in control group were include in meta-analysis. The result of meta-ananlysis showed that history of myasthenic crisis, bulbar symptoms, preoperative severity of gravis and postoperative complications(expect MCAT) were the major risk factors of myasthenic crisis after thymectomy for patients with myasthenia gravis. Two group were divided based on the risk scoring model and the incidence of MCAT in each group was 5.63% and 80.00%, respectively. Its effectiveness, accuracy, sensitivity, specificity was 75.00%, 95.71% and 91.86% respectively. The negative and positive predictive values were, respectively, 80.00% and 94.37%. Conclusion: Myasthenic crisis, preoperative severity of gravis(Osserman-stage) and bulbar symptoms are the independent risk factors of myasthenic crisis after thymectomy for patients with myasthenia gravis. History of myasthenic crisis, bulbar symptoms, preoperative severity of gravis and postoperative complications(expect MCAT) are the major risk factors of myasthenic crisis after thymectomy for patients with myasthenia gravis, and the risk scoring model based on it is reliable in predicting the occurrence of myasthenic crisis after thymectomy for patients with myasthenia gravis.