Fluid and Electrolyte Abnormalities in Children

Abstract

Infants and children have been recognized for many years as having more frequent episodes of fluid and electrolyte disturbances than do adults; these disturbances may alter the delicate homeostasis that is normally maintained by the growing and developing human. Several characteristics of the young infant that emphasize the importance of this normally tightly regulated “salt and water” balance include 1) a larger body surface area per unit of body mass, promoting evaporative and convective, as well as conductive, losses of water via the skin; 2) a larger percentage of total body weight composed of water; 3) a higher metabolic rate, requiring more water for energy dissipation and waste product excretion; 4) in the very young infant, immaturity of certain discrete renal functions; 5) rapid utilization of body fluids; and 6) a much greater likelihood of many different types of disease processes manifesting by alterations in hydration or electrolyte status. For example, a six-month-old infant with a fever of 39–40°C will have increases in metabolic rate with increased metabolic utilization of water and will have increased insensible losses of water through the skin and the respiratory tract (with increased rate of breathing); he or she may also have increased sensible losses of water through sweating. In addition, the same sick infant is likely to have a decreased appetite, with less fluid ingested, and may have diarrheal stools and/or vomiting, with further fluid losses.