Alterations in body fluid volume–Causes of changes in body fluid volume can usually be determined by the history and physical examination. Volume overload is manifested by an increase in weight and peripheral edema or ascites. Edema from local obstruction of venous return must be differentiated from systemic processes (congestive heart failure, cirrhosis, and nephrotic syndrome). A history of increased dietary sodium intake and use of medications that affect the renin-angiotensin system (converting enzyme inhibitors, prostaglandin synthesis inhibitors, mineralocorticoids, calcium channel blockers) should be sought. Volume depletion is characterized by weight loss, excessive thirst, and dry mucous membranes. There may be resting tachycardia, orthostatic hypotension, or shock. Causes include vomiting or diarrhea, diuretic use, renal disease, diabetes mellitus or diabetes insipidus, dehydration from inadequate oral intake associated with altered mental status, and excessive insensible losses from sweating or fever.

Treatment of fluid and electrolyte disorders is based on assessment of total body water and its distribution, electrolyte concentrations, and serum osmolality. _ _ _ _ _ _ _ _ _ _