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result from airway obstruction, pulmonary disease, severe acute anemia, severe
methemoglobinemia, carbon monoxide poisoning, or asphyxia (e.g., drowning).
Permanent CNS dysfunction results from total anoxia lasting more than 4 to 5
minutes at normal body temperatures; lesser degrees of hypoxia may be tolerated
for longer periods. Submersion in near-freezing water may cool the brain
sufficiently to exert a neuroprotective effect, the magnitude of which is not
usually apparent in the emergency department. Hypercarbia may accompany
hypoxia and may contribute to neurologic depression and coma.
Cardiovascular Abnormalities
ALOC may be produced by poor cerebral perfusion resulting from insufficient
cardiac output or hypotension, as in hemorrhage, dehydration, septic shock,
dysrhythmia, and intoxication. Hypertensive encephalopathy is distinguished by
headache, nausea, vomiting, visual disturbance, ALOC, or coma in the presence
of a blood pressure greater than the 95th percentile for age and gender (see
Chapter 37 Hypertension ). The acute onset of severe hypertension may reflect
ongoing renal (e.g., unilateral renal artery stenosis, acute glomerulonephritis),
endocrine (e.g., pheochromocytoma), or cardiac (e.g., aortic coarctation)
pathology, or it may be the result of a toxic ingestion (e.g., cocaine).
Hypertension accompanied by bradycardia may be caused by increased ICP.
Disorders of Thermoregulation
Hypothermia or hyperthermia in the pediatric patient is usually caused by
prolonged environmental exposure to temperature extremes, such as those found
in cold water or in a closed car in sunlight (see Chapter 90 Environmental
Emergencies, Radiological Emergencies, Bites and Stings ). The child who
becomes comatose as a result of abnormal core temperature will have multiple
organ system abnormalities in addition to CNS dysfunction. Mental impairment is
progressive as body temperature is lowered, as each fall of 1°C produces a 6%
decline in cerebral blood flow. At 29° to 31°C, confusion or delirium is present,
as is muscular rigidity. Patients with core temperatures of 25° to 29°C are
comatose with absent deep tendon reflexes and fixed, dilated pupils. CNS
findings in hyperthermia include headache, vomiting, and obtundation, leading to

coma and/or seizures, especially above 41°C. Nonenvironmental causes of
hyperthermia include neuroleptic malignant syndrome, serotonin syndrome, and
malignant hyperthermia.
Toxic Ingestions