ANESTHESIA AND NEUROMUSCULAR DISEASES

Risk factors for perioperative adverse events in children with myotonic dystrophy

BACKGROUND

This study was conducted to identify patient-related, surgical, and anesthetic factors that would help predict adverse events and allow for better planning of perioperative care in children with myotonic dystrophy.

METHODS

This is a retrospective chart review from a large tertiary pediatric hospital. Data were collected on demographics, disease severity, surgical procedure, and anesthetic technique. Perioperative adverse events were recorded.

RESULTS

Records on 27 patients having 78 anesthetics over a 17.5-year period were reviewed. The overall frequency of postoperative respiratory complications was 10%. Significant risk factors were high muscular impairment rating scale (MIRS) grade (P = 0.007), at least 2300 cytosine, thymine, guanine (CTG) repeats on the protein kinase gene of chromosome 19q (P = 0.009), a longer duration of surgery (RR = 14.0 for surgery lasting at least 1 h; P = 0.002), perioperative morphine use (RR = 7.7, 95% CI 2.2-12.8; P = 0.005), intubation (P = 0.02), and the use of muscle relaxant without reversal (RR = 15.5, P = 0.0002). Using a multivariate risk model, only MIRS grade and the use of muscle relaxant without reversal were shown to be significant independent risk factors (RR = 24.9, P < 0.0001).

CONCLUSIONS

The MIRS is a statistically significant and clinically useful tool for predicting high perioperative risk. Patients with a high MIRS grade should therefore be considered for postoperative intensive care. The use of muscle relaxant without reversal was also shown to be a significant risk factor. Patients who require morphine infusions postoperatively might also be most safely managed in a high dependency unit.

Preoperative Preparation of the Patient with Myasthenia Gravis

All patients who are to undergo a thymectomy should be evaluated thoroughly by a neurologist--ideally one with special training and interest in the diagnosis and management of MG. Confirmatory tests to diagnose MG and other potential diseases should be reviewed. The antibody test seems to be most specific, but there are rare cases of other diseases that are ACh-R antibody positive. In 10% of MG patients, serology is negative, and other tests are necessary to confirm the diagnosis. All patients should undergo a contrast-enhanced high-resolution CT scan with 5- to 8-mm slices because thymoma or thymic carcinoma may be present. Pulmonary function tests, including vital capacity, forced expiratory volume, maximal expiratory force, arterial blood gas, and a flow-volume loop, should be performed. Exercise testing to evaluate for hypoxia and hypotension with exercise and ambulation also may be appropriate. A thorough assessment for cardiac dysfunction, including echocardiography, nuclear medicine studies, or a formal cardiology evaluation, may be beneficial. Because MG is a complex autoimmune disease, preoperative blood tests should include thyroid function testing, antinuclear antibody, and rheumatoid factor in addition to routine preoperative studies. Plasmapheresis or intravenous immunoglobulin should be considered for patients with advanced disease, bulbar symptoms, or poor pulmonary function. Given these guidelines, careful selection of candidates for surgery should optimize the long-term results for patients with MG.

The prognostic value of pre-operative predicted forced vital capacity in corrective spinal surgery for Duchenne's muscular dystrophy

The majority of patients with Duchenne's muscular dystrophy require corrective spinal surgery for scoliosis to maintain seated balance and to slow the progression of respiratory compromise, thereby facilitating nursing and enhancing their quality of life. Traditionally patients with a pre-operative forced vital capacity (PFVC) of 30% or below predicted have been denied this surgery as it was thought that the incidence of postoperative complications was unacceptably high. We present data collected prospectively from 45 consecutive operations undertaken in our unit. These cases indicate that there is no clinically significant difference in operative and postoperative outcomes between patients with PFVC > 30% and < or =30%. However, the routine postoperative use of mask ventilation to facilitate early tracheal extubation is vital.

Perioperative management of patients with neurologic disease

Because many of the perioperative problems of the neurologic patient are predictable, they should be anticipated by the neurologist so that measures can be taken to prevent as many complications as possible and to recognize and manage those that cannot be prevented in a timely, efficient manner.

Preoperative preparation and anesthetic management of patients with myasthenia gravis

Patients with myasthenia gravis have specific clinical problems that must be addressed by the anesthesiologist when surgery is contemplated. Optimal perioperative management of myasthenia gravis patients undergoing thymectomy requires careful preoperative assessment and preparation. This assessment and preparation includes evaluation for concomitant autoimmune, respiratory, and cardiac disorders as well as optimization of medical management for myasthenia. There are important intraoperative concerns to be addressed including appropriate monitoring, premedication, and other agents used during surgery including muscle relaxants and anesthetic agents. Postoperatively, attention must be directed specifically to pain relief, ventilatory management, and the appropriate titration of reversal agents and anticholinesterase inhibitors. Optimal management of all these factors maximizes the chance for successful and uncomplicated hospitalization.