Musculoskeletal diseases (muscular dystrophies) are characterized by a progressive loss of skeletal muscle function (cardiac and smooth muscle are also affected).
- Duchenne muscular dystrophy is caused by a lack of production of dystrophin, a major component of the skeleton of the muscle membrane characterized by painless degeneration and atrophy of skeletal muscle.
- The genetic defect is sex linked (manifests only in males), and symptoms manifest between 2 and 5 years of age (creatine kinase may be increased before symptoms appear). Death is usually secondary to congestive heart failure or pneumonia.
- Axial skeletal muscle imbalance produces kyphoscoliosis, which often requires surgical correction.
- Involvement of cardiac muscle is reflected by a progressive loss of the R-wave amplitude on the lateral precordial leads of the electrocardiogram (ECG). Routine echocardiography can provide important information about cardiac function. Progressive loss of myocardial tissue results in cardiomyopathy, ventricular dysrhythmias, and mitral regurgitation.
- Treatment of cardiac dysfunction includes angiotensin-converting enzyme inhibitors, β-adrenergic blockers, and dysrhythmia surveillance.
- Degeneration of respiratory muscles (reflected by spirometry) results in an ineffective cough with retention of secretions and pneumonia.
- Management of Anesthesia
- Significant complications from anesthesia in patients with muscular dystrophy are secondary to the effects of anesthetic drugs on myocardial and skeletal muscle.
- Reports of cardiac arrest associated with rhabdomyolysis and hyperkalemia have occurred with volatile anesthetics alone or in combination with succinylcholine (SCh).
- Susceptibility to malignant hyperthermia is unpredictable.
- It may be prudent to use intravenous anesthetics and avoid volatile anesthetics and SCh for patients with muscular dystrophy.
- Degeneration of gastrointestinal smooth muscle with hypomotility of the intestinal tract and delayed gastric emptying in conjunction with impaired swallowing mechanisms may increase the risk of perioperative aspiration.