Dehydration in infancy and childhood.

Abstract

1. Laurence Finberg, MD* 1. *Clinical Professor of Pediatrics, University of California at San Francisco and Stanford University School of Medicine, San Francisco, CA After completing this article, readers should be able to: 1. List the conditions under which dehydration can occur. 2. Describe the first step in therapy of dehydration. 3. Explain how to treat isonatremic and hypernatremic dehydration. 4. Delineate when oral hydration may be started and why. The concept of dehydration did not enter clinical medicine until the 1830s and was not scientifically defined for some years after that. Although the word dehydration in general English usage means loss of water, in physiology and medicine, the unmodified word means a loss of water and salt or extracellular fluid (ECF), the most common of the clinically recognized types of dehydration. Depending on the type of pathophysiologic process, water and salts (primarily sodium chloride) may be lost in physiologic proportion or lost disparately, with each type producing a somewhat different clinical picture. We have found it useful to designate these types as isonatremic (classical), hypernatremic (hypertonic), or hyponatremic (hypotonic). The differential losses produce different clinical features because of the functional impermeability of the Na+ and Cl− ions of the ECF to the adjacent intracellular fluid (ICF). We use sodium rather than chloride in the nomenclature because chloride ions are simultaneously involved in a reciprocal relationship with bicarbonate ions. Such classification of the clinical entities has proved useful for understanding of the pathogenesis and especially for treatment. Dehydration is a physiologic disturbance that occurs in a wide variety of circumstances affecting water and salt losses. The most common associated disease group among infants is the infectious diarrheas caused by viral and bacterial agents. The most frequent pathogens in the United States are the several rotavirus species, which are most prevalent in the winter months. Bacterial diarrhea, currently seen less commonly over the past 40 years, occurs more often in the summer months, as do some types of disease …