Abnormalities of Body Water, Sodium, Potassium, and magnesium: Pathogenesis, Clinical Manifestations, and Treatment

I. CLASSIFICATION  The classification of abnormalities of water volume and/or sodium concentration is presented in Table 1.¹ From the standpoint of pathogenesis, the abnormalities may be di- vided into two groups: (a) conditions characterized by a primary alteration in extracellular volume or sodium concentration and a secondary shift of water between interstitial tissue and cells to effect equilibrium of osmotic pressure;* (b) conditions characterized by a primary cellular disturbance, with alteration in the content or concentration of osmotically active intracellular electrolytes and a parallel change in the osmolarity of the extracellular compartment. The pathogenesis and clinical manifestations of these two groups are presented separately.

II. PATHOGENESIS OF PRIMARY 

ABNORMALITIES  Pathogenesis of primary abnormalities of water volume and sodium concentration is given in Table 2.† The basic predisposing factor in the dehydration syndrome is fluid loss.‡ If losses continue unchecked, the syndrome likely to develop will depend partly upon the