Pediatric Nutrition in Practice

1 Specific Aspects of Childhood Nutrition

Key Words

Fluids · Electrolytes · Rehydration

Key Messages

• Maintenance of body water is principally governed
  by the kidney, except in pathologic states such as
  diarrheal disease


• Intestinal transportation of water and electrolytes is
  a finely tuned phenomenon regulated by complex
  interaction between endocrine, paracrine, immune,
  and enteric nervous systems


• Cotransportation of Na + with glucose by SGLT-1 is
  preserved in most diarrheal diseases and forms the
  basis for the oral rehydration solution


• Breastfed infants, including low-birth-weight in-
  fants, in hot climates do not require supplemental
  water


• An oral rehydration solution should be used for re-
  hydration and accomplished rapidly over 3–4 h, ex-
  cept in severe dehydration or intolerance of enteral
  fluids © 2015 S. Karger AG, Basel

Introduction

Maintenance of body water and electrolytes is a
tightly regulated balance of intakes and outputs
mediated by elaborate physiologic mechanisms.

Sodium (Na + ) retention causes volume expansion,

and Na + depletion causes volume contraction. A

net negative sodium balance results in a clinical

state of extracellular fluid (ECF) volume contrac-

tion, the most common cause worldwide being in-

fectious diarrheal disease resulting in dehydration.

Unlike sodium, whose distribution in the body

is uneven because of active transport of the ion,

water movement is passively determined in re-

sponse to osmotic gradients. Body water, being

freely diffusible, is therefore in equilibrium in rela-

tion to the distribution of its nondiffusable solutes.

Maintenance of body water involves the con-

trol of intake/absorption governed by the gastro-

intestinal tract and excretion, but principally by

excretion controlled by the kidney. Under normal

conditions, losses via the gastrointestinal tract

are small but can greatly increase in pathologic

states such as diarrheal disease.

Over 1.7 billion episodes of diarrhea occur an-

nually, accounting for 700,000 deaths of children

younger than 5 years, with most deaths in devel-

oping countries and from dehydration [1]. The

severity of dehydration is graded by clinical signs

and symptoms that ref lect f luid loss and that de-

termine the treatment regimen to correspond to

the degree of severity. Regardless of the etiology,

more than 90% of dehydration can be safely and

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 56–61
DOI: 10.1159/000367869

1.3 Nutritional Needs

1.3.6 Fluid and Electrolytes

Esther N. Prince  George J. Fuchs