Recognizing fluid and electrolyte imbalances is essential to safe nursing care. Fluid volume deficit presents with thirst, dry mucous membranes, decreased skin turgor, tachycardia, hypotension, weak pulse, and decreased urine output. Fluid volume overload produces bounding pulse, elevated blood pressure, dyspnea, crackles, jugular venous distension, edema, weight gain, and an S3 heart sound.
Normal serum potassium is 3.5 to 5.0 mEq/L. Hypokalemia causes muscle weakness, cramps, constipation, and ECG changes including flattened T waves, prominent U waves, ST depression, and ventricular dysrhythmias. Hyperkalemia presents with muscle weakness, paresthesias, and characteristic ECG findings of peaked T waves, widened QRS, prolonged PR interval, and eventual sine-wave pattern. First-line treatment for severe hyperkalemia is IV calcium gluconate to stabilize the cardiac membrane, followed by insulin with dextrose, sodium bicarbonate if acidotic, and potassium-removing therapies such as kayexalate or dialysis.
Normal serum sodium is 135 to 145 mEq/L. Hyponatremia in SIADH produces low sodium with concentrated serum but dilute urine, while diabetes insipidus causes hypernatremia with massive polyuria and severe dehydration. Treatment of hypernatremia involves replacing water gradually with hypotonic fluids to avoid cerebral edema. Normal serum magnesium is 1.5 to 2.6 mEq/L, and early signs of excess include decreased deep tendon reflexes, flushing, drowsiness, and slurred speech, progressing to hypotension, respiratory depression, and cardiac arrest; calcium gluconate is the antidote.
Calcium imbalances are identified through clinical signs. Hypocalcemia produces perioral numbness, tingling, muscle cramps, Trousseau's sign (carpal spasm with BP cuff inflation), Chvostek's sign (facial twitch on tapping the facial nerve), prolonged QT interval, and tetany. Severe symptomatic hypocalcemia is treated with IV calcium gluconate peripherally or calcium chloride through a central line, given slowly while monitoring cardiac rhythm. Hypercalcemia manifests as kidney stones, bone pain, abdominal groans, and psychiatric overtones, with shortened QT interval on ECG. Acid-base assessment uses the formula Na − (Cl + HCO₃) for anion gap, normally 8 to 16 mEq/L; elevated values suggest metabolic acidosis from causes remembered by the mnemonic MUDPILES.