Restoring electrolyte balance: a shift up. A shift down. Either way, an imbalance in electrolytes spells trouble for your patients. Averting a crisis hinges on your clinical skills. This review will help you sharpen them

Electrolytes, or ions, are the charged particles in body fluids that help transmit electrical impulses for proper nerve, heart, and muscle function. (1,2) The number of positive ions, called cations, and negative ions, called anions, is supposed to be equal. Anything that upsets this balance can have life-threatening consequences.

There's a long list of conditions that lead to electrolyte imbalances, including dehydration, diabetic ketoacidosis, cancer, and even head injury. But renal disease is at the top of the list. (1-3) It's the kidneys' job to control fluid, electrolyte, and acid-base balance.

Because too much or too little of any one of the electrolytes quickly becomes a major problem of its own, doing everything possible to maintain the proper balance is a vital component of patient care. Therefore, monitoring electrolytes and checking for signs of an imbalance should be an integral part of your nursing assessment.

Here, then, is a review of the role each electrolyte plays, the causes of imbalances, and the corrective measures required.

Understanding sodium's effect on water balance

Sodium (Na), the most abundant cation in extracellular fluid, plays a key role in transmitting nerve impulses. It also helps maintain serum concentration, or osmolality. (1)

Water follows salt in the body, so a gain or loss in sodium results in a gain or loss in water. For instance, when you eat too much salt, the rise in serum osmolality triggers thirst and the release of antidiuretic hormone (ADH) from the pituitary gland. Thirst leads you to drink, while ADH signals the kidneys to hang onto water. (1,2)

The opposite is also true: Low serum osmolality from too little salt stops thirst and inhibits ADH release, allowing more water to be excreted by the kidneys. (2)

Hypernatremia occurs when either too much water is lost or too much salt is taken in. (You'll find a list of normal values and causes of electrolyte imbalances in the box on page 37). The elderly are particularly at risk for hypernatremia following surgery or a fever because of volume depletion, and because of a diminished thirst mechanism. (4) All patients on fluid restrictions and those receiving diuretic therapy, hypertonic IV solutions, or tube feedings are at risk, as well. (1,4) So, too, are patients with diabetes, because of dehydration related to their hyperglycemia. (3)

Regardless of the cause, patients with hypernatremia may appear thirsty, tachycardic, and lethargic. (1,2) As their cells become more dehydrated, patients may develop disorientation, weakness, irritability, and muscle twitching. Urine output is generally low as the body tries to compensate by hanging onto water. The exception is untreated diabetes insipidus, where a lack of ADH results in a high urine output--possibly as much as 20 liters in 24 hours. (1,2) Regardless, though, of whether urine output is high or low, seizures, coma, or death may result if hypernatremia is left untreated. (1,2)

Correcting the situation requires that you focus on the underlying cause. That may be as simple as replacing volume orally or by the IV administration of...