The aging kidney - Defending a delicate balance of fluid and electrolytes

The aging kidney is characterized by reduced glomerular filtration rate, lo ss of tubular volume, and narrowed homeostatic control of water and electro lyte balance. It is unclear whether these physiologic changes represent nor mal aging or subclinical disease. With aging, there is an increased risk of hyper- or hypovolemia. Sluggish control of potassium concentration also ma kes hyperkalemia more common, particularly when the patient is using certai n drugs. Water metabolism is particularly vulnerable in older patients, res ulting in a frequent tendency toward dehydration and hyperosmolality. Under standing these : limitations on fluid and electrolyte homeostasis can help the clinician recognize and prevent complications when caring for older pat ients.