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The major cause of death in patients with neuromuscular disorders is respiratory insufficiency. Respiratory involvement varies considerably among the various neuromuscular disorders, and the extent of general muscle weakness does not necessarily correlate with the severity of respiratory muscle involvement.
Cardiovascular involvement may manifest as myocardial failure in patients with myopathic disorders and as autonomic dysfunction in patients with neuropathic disorders. Clinical signs of autonomic dysfunction include orthostatic hypotension, resting tachycardia, paralytic ileus, anhidrosis, and constricted pupils. The presence of these clinical signs may indicate profound hemodynamic instability that may manifest during the perioperative period, requiring invasive monitoring to manage intravascular volume status and myocardial contractility.
In patients with neuromuscular disorders, the severity of skeletal muscle involvement does not necessarily correlate with the severity of cardiac involvement.
Children with asymptomatic, undiagnosed muscular dystrophy are at significant risk for serious, life-threatening anesthetic complications. Specifically, these patients may develop intractable hyperkalemic cardiac arrest after receiving succinylcholine intravenously.
Spinal anesthesia has been associated with exacerbation of multiple sclerosis, although the mechanism is unclear. Speculation is that demyelinated areas of the spinal cord are more sensitive to the effects of the local anesthetic, resulting in a relative neurotoxicity.
Numerous anesthetics may exacerbate an acute attack of porphyria and should be avoided. Propofol, ketamine, local anesthetics, muscle relaxants, nitrous oxide, isoflurane, and opioids are considered safe.
Myasthenic crisis is a rapid deterioration of neuromuscular and respiratory function that may occur at any time perioperatively as a result of infection, stress, or an overdose with anticholinesterase drugs (cholinergic crisis).
Patients with myasthenia gravis and myasthenic syndrome are exquisitely sensitive to the effects of nondepolarizing muscle relaxants.
Succinylcholine should be avoided in patients with muscular dystrophies; it may further damage the already abnormal muscle membrane and cause the release of intracellular contents.
Succinylcholine produces an exaggerated contracture, and its use should be avoided in patients with myotonias. The myotonic response produced by succinylcholine may be so severe that ventilation and tracheal intubation are difficult and may be impossible.
Rheumatoid arthritis, osteoarthritis, and ankylosing spondylitis all are associated with possible cervical spine disease and may make airway management difficult.
Some musculoskeletal disorders are associated with an abnormal heat dissipation mechanism; central temperature monitoring is essential in these patients.
Many etiologies of high creatine kinase concentrations or rhabdomyolysis may be associated with malignant hyperthermia susceptibility.
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Perioperative management of patients with neuromuscular disorders is challenging because of the low incidence, diverse etiology, coexisting diseases, and variable responses to anesthetics that often are present. A safe anesthetic plan demands that the anesthesia provider assess the extent of disease and its progression. Despite distinct etiologies, all neuromuscular disorders may adversely affect the respiratory and cardiovascular systems. Unfortunately, the extent of peripheral muscle involvement does not always correlate with the extent of cardiovascular and respiratory system involvement. Indeed, during stressful intervals such as acute illness, anesthesia, or surgery, the patient with a neuromuscular disorder may have his or her reserve easily overwhelmed, resulting in unanticipated complications such ...