Research Article: Outcomes after major surgery in patients with myasthenia gravis: A nationwide matched cohort study

Date Published: June 30, 2017

Publisher: Public Library of Science

Author(s): Yi-Wen Chang, Yi-Chun Chou, Chun-Chieh Yeh, Chaur-Jong Hu, Chih-Jen Hung, Chao-Shun Lin, Ta-Liang Chen, Chien-Chang Liao, Tobias Derfuss.


To validate the comprehensive features of adverse outcomes after surgery for patients with myasthenia gravis.

Using reimbursement claims from Taiwan’s National Health Insurance Research Database, we analyzed 2290 patients who received major surgery between 2004 and 2010 and were diagnosed with myasthenia gravis preoperatively. Surgical patients without myasthenia gravis (n = 22,900) were randomly selected by matching procedure with propensity score for comparison. The adjusted odds ratios and 95% confidence intervals of postoperative adverse events associated with preoperative myasthenia gravis were calculated under the multiple logistic regressions.

Compared with surgical patients without myasthenia gravis, surgical patients with myasthenia gravis had higher risks of postoperative pneumonia (OR = 2.09; 95% CI: 1.65–2.65), septicemia (OR = 1.31; 95% CI: 1.05–1.64), postoperative bleeding (OR = 1.71; 95% CI: 1.07–2.72), and overall complications (OR = 1.70; 95% CI: 1.44–2.00). The ORs of postoperative adverse events for patients with myasthenia gravis who had symptomatic therapy, chronic immunotherapy, and short-term immunotherapy were 1.76 (95% CI 1.50–2.08), 1.70 (95% CI 1.36–2.11), and 4.36 (95% CI 2.11–9.04), respectively.

Patients with myasthenia gravis had increased risks of postoperative adverse events, particularly those experiencing emergency care, hospitalization, and thymectomy for care of myasthenia gravis. Our findings suggest the urgency of revising protocols for perioperative care for these populations.

Partial Text

Myasthenia gravis, an autoimmune disorder, mainly presents as diplopia, ptosis, fluctuating muscle weakness, and even respiratory failure [1]. Global estimates note its incidence and prevalence between 1950 and 2007 were about 5 and 77.7 per 100,000 persons, and mortality was 0.1–0.9 per 100,000 persons [2]. Annual medical costs for myasthenia gravis in the United States were found to be as high as $15,675 per patient [3]. Mental disorders, limited physical activity, and poor quality of life are significant problems for this socially vulnerable population [4,5]. Thymectomy was considered as an invasive but definite treatment procedure for patients with myasthenia gravis [6–11]. With the increasing incidence of myasthenia gravis in elderly people due to longer life expectancy and improved diagnostic methods, myasthenia gravis patients may be receiving increasing numbers of surgeries other than thymectomy [12].

After matching procedure by propensity score (Table 1), the baseline characteristics showed no significant differences between surgical patients with and without myasthenia gravis in terms of age, sex, low income, operation in teaching hospital or not, type of surgery or of anesthesia, or preoperative coexisting mental disorders, hypertension, diabetes, chronic obstructive pulmonary diseases, hyperlipidemia, liver cirrhosis, congestive heart failure, and renal dialysis.

This nationwide retrospective population-based study shows myasthenia gravis as an independent risk factor increasing postoperative adverse outcomes after major surgery. Risks of pneumonia, septicemia, postoperative bleeding, and intensive care unit admission were found higher in those with myasthenia gravis, although 30-day in-hospital mortality did not increase. Prolonged length of stay and increased medical expenditure after surgery were also noted in patients with myasthenia gravis. Women, patients under age 60, and those without other medical conditions had higher incidences of postoperative adverse events. We also provided some parameters which could be easily obtained from personal history that could be helpful in predicting risks of postoperative adverse events. Unlike other investigations [7–11], this study is unique in its large sample size, selection of control group by matching procedure with propensity score and multivariate adjustment for potential confounding factors.

Our study found increased postoperative pneumonia, septicemia, bleeding, stay in intensive care unit, prolonged stay, and increased medical expenditure for patients with myasthenia gravis receiving major surgery compared with control. In particular, postoperative adverse events significantly increased in myasthenia gravis patients with preoperative history of hospitalization, emergency visit, thymectomy, low income and high medical expenditure. These findings have important clinical implications, both for their predictive value and for showing the urgent need to improve management of surgical patients with myasthenia gravis.




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