1. Duchenne’s muscular dystrophy (MD) (pseudohypertrophic MD) is inherited as a sex-linked recessive trait, clinically evident in males. It is characterized by painless degeneration and atrophy of skeletal muscle. Progressive skeletal muscle weakness develops between ages 2 and 5 years and worsens progressively. Death usually occurs between ages 15 and 25 due to pneumonia or congestive heart failure (CHF).

2. Cardiac manifestations of Duchenne’s MD involve cardiac degeneration:

Abnormalities are usually confined to the lateral and posterobasal walls of the left ventricle. Obstruction of the right ventricular outflow tract leads to right-sided heart failure.

3. Pulmonary manifestations of Duchenne’s MD involve degeneration of respiratory muscles, leading to a restrictive pattern on pulmonary function testing (PFT); decreased muscle strength leads to an ineffective cough → retention of secretions; this may lead to pneumonia and death.

4. Anesthetic implications of Duchenne’s MD include the following:

5. Cardiac manifestations of myotonic dystrophy involve progressive decrease in the function of cardiac, skeletal, and smooth muscles. Ventricular systolic function and the cardiac conduction system (in particular, the His-Purkinje system) deteriorate very rapidly, which may lead to cardiac dysrhythmias and atrioventricular block. Twenty percent of patients demonstrate mitral valve prolapse; they also have restrictive lung disease with mild arterial hypoxemia and diminished ventilatory responses to hypoxia and hypercapnia. This makes them prone to aspiration pneumonia.

6. Anesthetic implications of myotonic dystrophy include the following:

1. The main defect in myasthenia gravis (MG) is a disorder of the neuromuscular junction. It is characterized by weakness and fatigability of the voluntary muscles, with improvement following rest. The basic abnormality is a decrease in the number of postsynaptic ACh receptors at the endplates of affected muscles. It is an autoimmune disorder, and most patients have circulating antibodies to ACh receptors. The hallmark of MG is exacerbations of skeletal muscle weakness, which respond to cholinesterase inhibitors. Focal myocarditis or respiratory failure may develop. Pregnancy may produce either exacerbation or remission. Neonates (15% to 20% of patients) may have transient myasthenia from passive placental transfer of anti-ACh-receptor antibodies.

Treatment consists of cholinesterase inhibitors, thymectomy, corticosteroids, and immunosuppressants.

2. Myasthenic (Eaton-Lambert) syndrome is an autoimmune disease associated with cancer (particularly small cell carcinoma of lung). Immunoglobulin G (IgG) antibodies to presynaptic calcium channels cause a disorder of neuromuscular transmission, with decreased release of ACh in response to nerve stimulation and increased muscle strength with exercise (in contrast to MG). There is no improvement with administration of anticholinesterases. The difference in anesthetic management of Eaton-Lambert syndrome patients is their sensitivity to both depolarizing and nondepolarizing muscle relaxants (NDMRs).

3. Treatment of MG includes anticholinesterases, immunosuppressive drugs (steroids, azathioprine [Imuran], cyclosporine [Sandimmune]) (as it is considered an immunologic disease), plasma exchange/plasmapheresis, and thymectomy.

4. Anesthetic management considerations in patients with MG include the following:

5. Regional analgesia and general anesthesia have successfully been used in patients with MG, but they must be carefully monitored for hypoventilation due to skeletal muscle relaxation.

1. Familial periodic paralysis (FPP) involves episodes of skeletal muscle weakness or paralysis. It is believed to be caused by an abnormality in membrane transport of potassium and sodium, rendering skeletal muscle unexcitable. There are three types of FPP: hypo-, hyper-, and normokalemic.

2. Implications of FPP for anesthetic management:

3. Characteristics of Guillain-Barré Syndrome (GBS) include acute or subacute onset of skeletal muscle weakness, progressing cephalad within a few days; it may lead to difficulty in swallowing and ventilating. It is caused by immunologically mediated (antigen-virus) nerve demyelination. Plasmapheresis is the treatment of choice.

4. Autonomic dysfunction occurs in many GBS patients. It may produce wide fluctuations in blood pressure (BP), tachycardia, cardiac dysrhythmias, and cardiac arrest. Physical stimulation may produce hypertension, tachycardia, and cardiac dysrhythmias.

1. Multiple sclerosis (MS) is an acquired disease characterized by multiple sites of demyelination in the brain and spinal cord. Patients are usually aged between 15 and 40 years. Currently, the cause is thought to be viral, with initiation of an autoimmune response. Symptoms depend on the area of demyelination and include visual disturbances, bowel or bladder incontinence, diplopia, trigeminal neuralgia, respiratory failure, and so on.

2. Anesthetic management in MS patients includes the following:

Some reports indicate that anesthesia may exacerbate symptoms of MS, especially regional anesthesia. This should be carefully explained to patients and parturients. Spinal anesthesia should be reserved for special situations.

3. Initial treatment of grand mal seizure involves the following:

Status epilepticus represents seizure activity that continues unabated for at least 30 minutes. The best treatment is the use of diazepam. A muscle relaxant may be needed for intubation if a secured airway is needed.

4. Anesthetic management in a patient with a history of seizures:

5. Ketamine (Ketalar) and methohexital sodium (Brevital) have been implicated in producing seizures. Enflurane (Ethrane) produces seizure activity on electroencephalogram, particularly with hypocarbia.

6. Parkinson’s disease (PD) is a degenerative disease of the central nervous system (CNS), in which loss of dopaminergic fibers in the basal ganglia leads to unopposed action of ACh in the brain. Symptoms include increase in spontaneous movements, cogwheel rigidity of the extremities, facial immobility, rhythmic tremor at rest, mental depression, seborrhea, pupillary abnormalities, diaphragmatic spasm, and oculogyric crises.

Treatment is with carbidopa/levodopa (Sinemet). Side effects of PD therapy include myocardial norepinephrine store depletion, peripheral vasoconstriction, and decreased intravascular volume → orthostatic hypotension.

7. Considerations in the anesthetic management of patients with CNS disease include the following:

1. Physiologic responses to anemia include increases in the following:

At maximum levels of 2,3-DPG, oxygen (O₂) delivery is increased by 30%. Typically, in otherwise healthy patients, anemia does not become symptomatic until hemoglobin is <7 g/dL.

2. N₂O inactivates the vitamin B₁₂ component of methionine synthase. Prolonged exposure to N₂O may cause megaloblastic anemia and neurologic changes similar to those seen in pernicious anemia.

3. Folic acid deficiency may be caused by the following:

4. Hemolytic anemia may be caused by a structural erythrocyte abnormality, an enzyme deficiency, or an immune hemolytic anemia (hemolytic disease of the newborn by Rh sensitization). It is exacerbated by infection or exposure to oxidant chemicals or drugs (analgesics, antibiotics, sulfonamides, and antimalarials).

5. Sickling in sickle cell anemia (SCA) is caused by decreased O₂ tension (Po₂ <50 mm Hg; most pronounced at Po₂ <20 mm Hg), vascular occlusion, vascular stasis, hypothermia, and acidosis.

6. Clinical manifestations of SCA include chronic anemia, chronic hemolysis, infarction of multiple organs, generalized pulmonary fibrosis with significant pulmonary dysfunction (increased alveolar-to-arterial O₂ difference), cor pulmonale, cardiac dysfunction (decreased ventricular filling and ejection fraction), decreased glomerular filtration rate with nephrotic syndrome, and cholelithiasis.

7. Considerations in the anesthetic management of SCA patients include the following:

Supplemental O₂