Fluid and Electrolyte Imbalance in the Elderly
Fluid and Electrolyte Imbalance in the Elderly
A 79-year-old woman with chronic renal failure was admitted to a nursing home for physical therapy following open reduction external fixation for a hip fracture. On evaluation, the PT was surprised to find profound general weakness, no movement against gravity at the affected hip and knee, and inability to stand erect or ambulate. The charge nurse explained, "Her potassium is low."
Many elderly patients, especially those who are postoperative or who have chronic diseases, are at risk for fluid and electrolyte imbalances. Increased weakness is one symptom common to many of these conditions.
Water and Sodium Balance
Sodium is the major ion in extracellular fluid. It controls and regulates water balance. In an older person, the maintenance of fluid balance is more difficult for several reasons: Older people have a lower percentage of water in their bodies due to a higher percentage of body fat, which contains very little water. The ability of the kidneys to concentrate urine is compromised, response to antidiuretic hormone (ADH) is not as efficient, and thirst sensation may be diminished or even absent.1
After being deprived of fluid intake for 24 hours, healthy elderly people are less thirsty and drink less than younger people. Therapists should offer water before and after activity even if the patient denies thirst. In hot, humid weather, fluid replacement is particularly important.
Hypovolemia refers collectively to both volume depletion and dehydration. Volume depletion is a loss of body water and sodium and can cause sodium loss, or hyponatremia. Patients with congestive heart failure who have fluid overload can develop hyponatremia as the blood becomes more dilute.
Dehydration is a depletion of water alone and causes an excess of sodium, or hypernatremia. Early symptoms of dehydration are dry mouth and sticky saliva and reduced urine output with dark yellow urine. Later symptoms may include lethargy, tachycardia and hypotension. Predisposing factors are decreased food or fluid intake, fever, diabetes mellitus, vomiting, diarrhea, chronic renal disease, use of diuretics or nasogastric suction.2
An excess of potassium, hyperkalemia, often accompanies renal failure. This occurs when the kidneys lose their ability to excrete enough potassium. Diabetes mellitus or severe tissue damage from burns and large hematomas can also lead to hyperkalemia. Signs and symptoms of hyperkalemia include vague muscle weakness or decreased energy of movement, irritability, slurred speech, decreased deep tendon reflexes, nausea and diarrhea. Hyperkalemia becomes a medical emergency if there are EKG changes.3
Hypokalemia can develop when patients are malnourished, but more commonly it is caused by diuretics such as Lasix. Diarrhea, frequent vomiting and nasogastric suction are other common causes. Hypokalemia decreases the contractility of smooth, skeletal, and cardiac muscles, so patients may have signs and symptoms of leg and general body cramps, weakness, constipation, abdominal distention, anorexia, nausea, paralytic ileus, confusion and lethargy. At very low levels, cardiac arrhythmias such as ventricular tachycardia may occur.4 Physical therapy is contraindicated when potassium levels are below 3.0 mEq/L or above 5.1 mEq/L.
Calcium is necessary for muscle contraction, blood coagulation and transmission of neural impulses. Hypercalcemia can be caused by overuse of antacids and conditions that cause movement of calcium out of the bones and into the extracellular fluid, such as bone tumors, multiple fractures, osteoporosis and certain tumors. Signs and symptoms include anorexia, abdominal pain, constipation, confusion, pathological fractures and cardiac arrest.
Hypocalcemia can be caused by not eating enough calcium rich foods. Elderly patients who don't exercise regularly or get outdoors where they are exposed to Vitamin D (necessary for calcium use), will become hypocalcemic even faster, so the likelihood of osteoporosis is greatly increased.5
Magnesium plays a key role in maintaining the correct level of electrical excitability in the nerves and muscle cells. Magnesium deficiency--hypomagnesemia--is usually seen in older people who eat poorly, use diuretics, have prolonged diarrhea, or who chronically abuse alcohol. An excess of magnesium--hypermagnesemia--is rare and almost always linked to renal failure or the overuse of antacids containing magnesium or cathartics, such as Milk of Magnesia. Hypermagnesemia can cause hypotension, slow, weak pulse, cardiac arrhythmias and respiratory depression.6
Because therapists spend extended one-to-one time with patients, they can notice changes in health and function from one day to the next. By bringing a change in status to the attention of nurses and physicians, therapists can help the patient to receive tests and treatments without delay. Correction of fluid or electrolyte imbalances will give the patient a better chance of recovery. In the case of the woman with profound weakness following hip surgery, correction of her potassium levels allowed her to recover enough strength to begin gait training.
1. Stanley, M., & Beare, P.G. (1995). Gerontological nursing. Philadelphia: F.A. Davis Company, pp. 230-234.
2. Abrams, W.B., Beers, M.H., & Berkow, R. (1995). The Merck manual of geriatrics (2nd ed.). Whitehouse Station, NJ: Merck Research Laboratories, pp. 17-33.
3. Perez, A. (Nov. 1995). Restoring electrolyte balance: Hyperkalemia. RN, 58, 33-36.
4. Perez, A. (Dec. 1995). Restoring electrolyte balance: Hypokalemia. RN, 58, 33-35.
5. Bove, L.A. (March 1996). Restoring electrolyte balance: Calcium and phosphorus. RN, 59, 47-51.
6. Ferrin, M.S. (May 1996). Restoring electrolyte balance: Magnesium. RN, 59, 31-34.
Bob Thomas serves as director of the ancillary division of Avamere Health Services in Oregon and Washington. He also lectures nationally for Great Seminars on Rehab Solutions for the Institutionalized Elderly.
Emi Storey is employed by Rehab Specialists, Inc. and serves as PT at Porthaven Care Center and Marquis Care at Piedmont in Portland, OR.