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Rare inherited enzymatic disorder characterized by severe hyperammonemia. Affected infants clinically present with vomiting, lack of appetite and failure to thrive, progressive lethargy, severe hypotonia, and coma. This entity is part of a group of disorders called urea cycle disorders (described later).

Arginosuccinic Aciduria; ASL Deficiency; Arginino Succinase Deficiency; ASA Deficiency.

Inherited as an autosomal recessive genetic transmission.

Argininosuccinate lyase is one of six enzymes that play a role in the metabolism of nitrogen from the body, preventing accumulation of amino acids from metabolic protein waste and development of hyperammonemia.

Severity varies among patients. A severe form of the disorder, characterized by complete absence of the enzyme, usually is present in the neonatal period and is called the severe form. A milder form of the disorder, characterized by partial absence of the enzyme, affects infants later during infancy or early childhood. A late-onset form, which occurs in adults, has been identified. Hyperammonemia is the main characteristic of this disease. The severe form of argininosuccinic aciduria occurs 24 to 72 hours after birth, usually after feeding. This form of the disease is clinically characterized by refusal to eat, severe failure to thrive, lethargy, vomiting, and neurologic irritability, often suggesting seizures. Affected infants may experience respiratory abnormalities, cerebral edema, and hepatomegaly. Hyperammonemic coma has been reported. If it is left untreated for more than 72 hours, neurologic abnormalities such as severe developmental delays and mental retardation are trademarks of surviving infants. Death is always inevitable for those not treated immediately. In infants with partial enzyme deficiency, onset of the disorder usually occurs later during infancy or childhood. Clinically, the symptomatology includes failure to grow and thrive, protein-free diet, ataxia, lethargy, and vomiting. Other features include dry brittle hair that may result in alopecia. These infants may alternate between periods of wellness and hyperammonemia. Hyperammonemic coma and life-threatening complications are potential complications.

Considerations are several. The children may require anesthesia while they are in systemic failure. Careful preoperative assessment of cardiovascular and neurologic status is important. Acute metabolic encephalopathy, associated with severe cerebral edema and significant raised intracranial pressure, may be present at induction. The possibility of subclinical seizure activities during anesthesia must be considered. Administration of intravenous antiepilepsy medication should be kept in mind. Severe hepatomegaly and respiratory abnormalities are among the anesthetic considerations. Administration of high-calorie fluid, without protein, must be given preoperatively. The potential risks of pulmonary aspiration after gastrointestinal surgery may lead to acute respiratory decompensation because of high protein load. Severe metabolic acidosis must be treated immediately. The decision to administer general anesthesia can be made based only on the patient's general health condition. The most important precautions must be taken to prevent sudden cardiovascular depression and loss of systemic vascular resistance in patients already presenting without any systemic reserve.

Urea Cycle Disorders are a group of rare disorders that affect the urea cycle. The consequence ...

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