[Fluid and electrolyte disorders]

OBJECTIVE: To review the major concepts involving electrolyte disorders in pediatrics, with special emphasis on the diagnosis and treatment.METHOD: Systematic literature review, searching through classic pediatric textbooks, periodic electronic databases, such as Medline, Lilacs and other sources. RESULTS: Electrolyte disorders are among the most common events in pediatric medical practice, specially in emergency care, where, depending upon the magnitude, they may represent significant risk to patient life or to the development of permanent sequelae. Dehydration, independent of etiology, has its importance defined by the severity of water deficit (mild, moderate or severe) and by the proportion of sodium waste in relation to water deficit (isotonic, hypotonic and hypertonic), and should be correctly recognized to guide adequate treatment. Sodium disorders have major risks of central nervous system compromise and potassium disorders are specially linked to cardiac arrhythmia, always deserving special attention and care. On the other hand, calcium, phosphorus and magnesium disorders are more related to neuromuscular function alterations and, although less threatening, they need adequate recognition and management.CONCLUSION: Knowledge of the several mechanisms involved in water and electrolyte metabolism is crucial to the correct comprehension, diagnosis and management of fluid and electrolyte disorders in pediatrics.