Faculty Bibliography

We evaluated the respiratory function of 32 patients with myasthenia gravis who had transsternal thymectomy. Preoperative clinical, pulmonary function, and respiratory muscle pressure data were submitted to stepwise logistic regression analysis to identify preoperative factors that correlated with duration of supported ventilation after surgery. Ten patients (31%) had postoperative supported ventilation for more than 3 days. The duration of ventilatory support correlated most closely with maximal static expiratory pressure (r = 0.714, p less than 0.001). Expiratory weakness, by reducing cough efficacy, seems to be the main determinant that predicts need for longer postoperative supported ventilation

In an analysis of myasthenia crises during the past 20 years, the incidence of crisis remained fairly constant at 12-16%, but the fatality rate of crises declined from 42% to 6%, and the overall mortality of myasthenia declined from 12% to 3.3%. Most crisis episodes were caused by aspiration pneumonia or occurred in patients with severe dysphagia, who were at risk of aspiration. Cholinergic drug therapy clearly was not useful during crisis, and should probably be discontinued while the patient is on a respirator. Fifteen of 28 patients with thymectomy had 21 episodes of crisis months or years after surgery. Ultimately, 42% of crisis survivors achieved a state of improved myasthenia or remission after one or more crises