Water accounts for approximately half of an adult human’s body weight. Two thirds of body water is intracellular, and the remaining one third is contained in the extracellular fluid compartment, which includes intravascular (plasma) and interstitial fluid. Small amounts of water are also contained in bone, dense connective tissue, digestive secretions, and cerebrospinal fluid. To maintain the stability of the internal milieu, body fluids are processed by the kidney, guided by intricate physiologic control systems that regulate fluid volume and composition. This chapter reviews the regulation of body fluid volumes, cell volume regulation in hypotonicity and hypertonicity, disorders of water excess (hyponatremia), water deficiency (hypernatremia), water conservation (diabetes insipidus), saltwater excess (edematous states), and saltwater deficiency (volume depletion). Tables describe control of body fluid volumes, causes of nonhypotonic hyponatremia, causes and treatment of acute hyponatremia, causes of the syndrome of inappropriate release of antidiuretic hormone (SIADH), and causes of hypernatremia. Figures illustrate sodium reabsorption by the renal tubules, the relationship between plasma vasopressin levels, renal sodium handling, and dose-response curves for a loop diuretic in patients with normal and reduced renal function.
This chapter contains 4 highly rendered figures, 5 tables, 88 references, and 5 MCQs.
Blood volume and body fluid compartment changes soon after closed and open intracardiac surgery
