Electrolytes and acid-base: Common fluid and electrolyte disorders

Disturbances of fluid and electrolyte balance are common in clinical practice, especially in a hospital setting, and may be iatrogenic or compounded by inappropriate medical or surgical treatment. Their recognition and appropriate management are not necessarily difficult or complex; while specific formulae and standard protocols can be helpful at the bedside, there is no substitute for an understanding, and application, of some basic principles of renal and endocrine physiology, which is what this article tries to provide. Some knowledge of basic renal physiology (including transport function along the nephron and its regulation) is useful, because it makes it easier to work through, and understand, most clinical disorders of fluid and electrolyte balance. Unfortunately, patients seldom present with a single acid-base or fluid and electrolyte disturbance, so the real challenge is to determine which disorder came first, before rushing in and treating in isolation what might seem to be the major clinical abnormality. First, we need to consider the main homeostatic functions of the kidney and, more specifically, the essential workings of its functional unit, the nephron (glomerulus and renal tubule). © 2011 Elsevier Ltd. All rights reserved