Pediatric toxic ingestions are often unwitnessed and are usually complicated by the young patient’s inability to provide information on the quantity or identity of the substance ingested (see Chapter 102 Toxicologic Emergencies ) Table 17.2 lists many drug classes that cause coma with overdose Exogenous toxins may impair neuronal function directly or by causing hypoxia, acidosis, enzyme inhibition, hypoglycemia, or seizures ALOC can occur after direct intrathecal injection of medication such as baclofen resulting from intrathecal pump malfunction Metabolic Alterations Abnormal serum concentrations of any substrate or product involved in neuronal metabolism can produce ALOC leading to coma Hypoglycemia is the most common disorder in this category, especially in infants and young children, whose capacity for hepatic gluconeogenesis is limited Disorders known to produce hypoglycemia include serious bacterial infections, sepsis, dehydration, and toxic ingestions (especially ethanol, beta blockers, and oral hypoglycemics) Diabetes mellitus, especially of new onset, may present with profoundly depressed consciousness from the combination of hyperosmolarity, dehydration, hypotension, and metabolic acidosis Patients under treatment for diabetic ketoacidosis may also develop cerebral edema and ALOC Patients with type diabetes may have coma as part of hyperglycemic hyperosmolar nonketotic syndrome, which can be complicated by malignant hyperthermia Metabolic acidosis or alkalosis of sufficient degree produces ALOC The most common disorder of this type in children is severe dehydration leading to metabolic acidosis Abnormal concentrations of any serum electrolyte, including sodium, calcium, magnesium, and phosphorus, can also produce altered mental status Hyponatremia, from either dehydration or dilution from excess water, and hypernatremic dehydration, are among the most common causes of ALOC in infants The degree of resulting neurologic compromise will be affected by the duration and severity of the electrolyte disturbance and concurrent disorders Severe dehydration alone may also produce profound lethargy in infants and children, even in the absence of significant electrolyte abnormalities Other causes of metabolic coma in the pediatric age group include kidney or hepatic failure, both of which may result in progressive apathy, confusion, and lethargy Urea cycle defects may present with ALOC and hyperammonemia in young infants (see Chapter 95 Metabolic Emergencies ) Acute toxic encephalopathy (Reye syndrome) is a rare but devastating illness caused by mitochondrial injury of unknown origin that affects all organs of the body,