Electrolyte imbalances

Electrolyte imbalances occur when the concentration of an electrolyte in the blood rises above or falls below its normal range. The major electrolytes are sodium, potassium, calcium, magnesium, chloride, and phosphate, and each imbalance is named with the prefix hyper- (too high) or hypo- (too low) — hyponatremia for low sodium, hyperkalemia for high potassium, and so on.

Each electrolyte has a characteristic clinical picture. Sodium disturbances primarily affect the brain: hyponatremia causes confusion, seizures, and cerebral edema. Potassium disturbances affect cardiac conduction — both hyperkalemia and hypokalemia can trigger dangerous arrhythmias and ECG changes, such as peaked T waves in hyperkalemia and flattened T waves with U waves in hypokalemia. Calcium and magnesium disorders alter neuromuscular excitability, producing tetany, cramping, or weakness and hyporeflexia.

Common causes include vomiting, diarrhea, kidney disease, diuretics and other medications, endocrine disorders, burns, and eating disorders — purging and malnutrition are classic sources of hypokalemia. Because the kidneys regulate both fluid and electrolyte levels, fluid status and electrolyte status are assessed together, and correction must be careful: overly rapid correction of hyponatremia, for instance, can itself injure the brain.

The NCLEX tests electrolyte imbalances heavily under reduction of risk potential — expect questions on normal lab ranges, ECG changes, and nursing priorities for each imbalance. The NPTE for physical therapists and physical therapist assistants also covers electrolyte disturbances in its renal, GI, and multisystem content, since imbalances affect a patient's safety during exercise and rehabilitation.