title: Thymectomy in myasthenia gravis: proposal for a predictive score of postoperative myasthenic crisis.
abstract: OBJECTIVE
  Thymectomy plays an important role in patients with myasthenia gravis (MG). This study aimed to explore predictors of postoperative myasthenic crisis (POMC) after thymectomy and to define a predictive score of respiratory failure.
  
  
  METHODS
  The clinical data of 177 patients with MG undergoing thymectomy from January 1995 to December 2011 were retrospectively reviewed. The following factors were analysed in relation to the occurrence of myasthenic crisis: gender, age, body mass index (BMI), anti-acetylcholine receptor-antibody level, bulbar symptoms, comorbidities, duration of symptoms, Osserman-stage, Myasthenia Gravis Foundation of America (MGFA) stage, history of myasthenic crisis, use of immoglobulins or plasmapheresis, kind of therapy, spirometric and blood gas parameters, histology, kind of surgery, non-myasthenic complications and duration of intubation.
  
  
  RESULTS
  Twenty-two patients experienced postoperative respiratory failure after thymectomy. Univariate analysis revealed a correlation with age >60 years (odds ratio (OR) = 1.79, 95% confidence interval (CI) = 1.04-6.78; P = 0.040); Osserman-stage (IIB- OR = 5.16, 95% CI = 1.10-24.18; P = 0.037, III-IV- OR = 8.75, 95% CI = 1.53-50.05; P = 0.015); bulbar symptoms (OR = 7.42, 95% CI = 1.67-32.84; P = 0.008); BMI >28 (OR = 3.99, 95% CI = 1.58-10.03; P = 0.003); preoperative plasmapheresis (OR = 2.97, 95% CI = 1.18-14.04; P = 0.021); duration of symptoms >2 years (OR = 4.00, 95% CI = 1.09-14.762; P = 0.036); extended surgery (OR = 2.52, 95% CI = 1.02-6.22; P = 0.045); lung (OR = 4.05, 95% CI = 1.44-11.42; P = 0.008), pericardial (OR = 3.78, 95% CI = 1.45-9.82; P = 0.006) or pleural resection (OR = 3.23, 95% CI = 1.30-8.03; P = 0.012); Vital Capacity % <80% (OR = 0.20, 95% CI = 0.05-0.82; P = 0.025) and PaCO2 >40 mmHg (OR = 3.76, 95% CI = 1.12-12.68; P = 0.032). Multivariate logistic regression analysis showed that Osserman-stage (IIB- OR = 5.69, 95% CI = 1.09-29.69; P = 0.039 (III-IV- OR = 11.33, 95% CI = 1.67-76.72; P = 0.013), BMI >28 (OR = 3.65, 95% CI = 1.10-12.15; P = 0.035), history of myasthenic crisis (OR = 24.10, 95% CI = 2.34-248.04; P = 0.007), duration of symptoms >2 years (OR = 5.94, 95% CI = 1.12-31.48; P = 0.036) and lung resection (OR = 8.48, 95% CI = 2.18-32.97; P = 0.002) independently predict POMC. Excluding history of preoperative myasthenic crisis (statistically associated with Osserman-stage), we built a scoring system according to the OR of Osserman-stage (I-IIA, IIB, III-IV), BMI (<28, ≥ 28), duration of symptoms (<1, 1-2, >2 years) and association with a pulmonary resection. This model helped in creating four classes with increasing risk of respiratory failure (Group I, 6%; Group II, 10%; Group III, 25%; Group IV, 50%).
  
  
  CONCLUSIONS
  Our model facilitates the stratification of patient risk and prediction of the occurrence of POMC. Moreover, it could help to guide the anaesthesiologist's decision on the duration of intubation. Further studies based on larger series are needed to confirm these preliminary data.
authors: Department of Surgical Oncology, Thoracic Surgery Unit, IRCCS Regina Elena National Cancer Institute, Rome, Italy.
authors: Giovanni
authors: G
authors: Leuzzi
authors: Elisa
authors: E
authors: Meacci
authors: Giacomo
authors: G
authors: Cusumano
authors: Alfredo
authors: A
authors: Cesario
authors: Marco
authors: M
authors: Chiappetta
authors: Valentina
authors: V
authors: Dall'armi
authors: Amelia
authors: A
authors: Evoli
authors: Roberta
authors: R
authors: Costa
authors: Filippo
authors: F
authors: Lococo
authors: Paolo
authors: P
authors: Primieri
authors: Stefano
authors: S
authors: Margaritora
authors: Pierluigi
authors: P
authors: Granone
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009157:Myasthenia Gravis / Q000453:epidemiology / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications / Q000145:classification / Q000453:epidemiology / Q000209:etiology; D012131:Respiratory Insufficiency / Q000453:epidemiology; D012189:Retrospective Studies; D013934:Thymectomy / Q000009:adverse effects / Q000379:methods* / Q000706:statistics & numerical data
keywords: Intubation; Myasthenia gravis; Myasthenic crisis; Scoring system