Edema is typically marked by swelling of the face, fingers, abdomen, or ankles The three fundamental causes of edema are increased capillary filtration due to poor venous return, reduced capillary absorption due to albumin deficiency, and obstructed lymphatic drainage. Whatever the cause, edema can result in a loss of blood volume and pressure, which creates the potential for circulatory shock. Pulmonary edema presents a threat of suffocation. Cerebral edema produces headaches, nausea, and sometimes seizures and coma. Dietary deficiency of sodium is rare, and the primary concern is adequate renal excretion of the excess.
Aldosterone plays the primary role in adjustment of sodium excretion.
Hypernatremia is usually the result of administration of intravenous saline. Its major consequences are water retention, hypertension, and edema. Along with sodium, it produces the resting membrane potentials and action potentials of nerve and muscle cells. Potassium homeostasis is closely linked to that of sodium. Hyperkalemia can result from aldosterone deficiency, renal failure, or acidosis, and sometimes follows blood transfusions.