Fluid and Electrolyte Therapy

An understanding of pediatric fluid therapy is one of the most important advances in pediatric medicine and a cornerstone of current inpatient practice for children with a wide range of acute and chronic conditions. Before beginning to calculate deficit fluid replacement and manage electrolyte disturbances, it is important to understand the pathophysiology behind water homeostasis and maintenance fluid calculations. Body water and sodium retention are regulated by the hormones antidiuretic hormone (ADH) and aldosterone in response to reninangiotensin production. Renin and ADH are secreted in reaction to output from sensors detecting changes in circulating blood volume and serum osmolality. These volume receptors are located in the left atrium, carotids, and the aortic arch, and the osmolar receptors are located in the hypothalamus, as well as elsewhere in the body. There are also nonosmotic triggers of ADH secretion, such as pain, stress, vomiting, and a number of pulmonary processes, that in particular affect hospitalized patients. Because sodium is the predominant extracellular cation, its regulation is essential to maintaining water homeostasis. Disturbances in ADH, aldosterone, and sodium will therefore have significant effects on water and electrolyte homeostasis.