Electrolyte Imbalances

Sodium (Na)

Normal range: 136–145 mEq/L

Hyponatremia (<136 mEq/L)

Causes: SIADH, heart failure, cirrhosis, diuretics, excessive water intake, vomiting/diarrhea, adrenal insufficiency, hypothyroidism.

Signs & symptoms: Headache, confusion, lethargy, seizures, nausea, muscle cramps, weakness, coma (severe).

Nursing interventions: Restrict fluid intake; monitor I&O and daily weights; administer hypertonic saline (3%) for severe symptomatic hyponatremia per protocol; correct slowly to avoid osmotic demyelination; monitor neurologic status; implement seizure precautions if severe.

Hypernatremia (>145 mEq/L)

Causes: Dehydration, diabetes insipidus, excessive Na intake, fever, burns, osmotic diuresis, inadequate water intake.

Signs & symptoms: Thirst, restlessness, irritability, muscle twitching, seizures, coma, dry mucous membranes, decreased skin turgor.

Nursing interventions: Replace free water (oral or IV D5W/½NS); correct gradually to avoid cerebral edema; monitor serum Na and neurologic status; encourage oral fluids if able; assess for underlying cause.

Potassium (K)

Normal range: 3.5–5.0 mEq/L

Hypokalemia (<3.5 mEq/L)

Causes: Diuretics, vomiting/diarrhea, NG suction, alkalosis, insulin, beta-agonists, magnesium deficiency, Cushing syndrome.

Signs & symptoms: Muscle weakness, fatigue, leg cramps, constipation, ileus, dysrhythmias (PVCs, U waves), hyporeflexia, cardiac arrest (severe).

Nursing interventions: Administer K replacement (oral or IV); IV K never push—use infusion pump, max 10 mEq/hr in peripheral line; monitor ECG; check Mg (hypomagnesemia impairs K correction); encourage K-rich foods (bananas, oranges, potatoes).

Hyperkalemia (>5.0 mEq/L)

Causes: Renal failure, potassium-sparing diuretics, ACE inhibitors, acidosis, tissue breakdown (rhabdomyolysis, burns), Addison disease, excess K intake.

Signs & symptoms: Muscle weakness, paresthesias, peaked T waves, prolonged PR, widened QRS, ventricular fibrillation, cardiac arrest.

Nursing interventions: Hold K supplements and K-sparing drugs; administer calcium gluconate to stabilize cardiac membrane (emergency); insulin + dextrose to shift K into cells; sodium polystyrene sulfonate (Kayexalate); dialysis if severe; restrict dietary K; monitor ECG continuously.

Calcium (Ca)

Normal range: 8.6–10.2 mg/dL (total); ionized Ca: 4.5–5.6 mg/dL

Hypocalcemia (<8.6 mg/dL)

Causes: Hypoparathyroidism, vitamin D deficiency, hypomagnesemia, pancreatitis, massive blood transfusion (citrate), renal failure, loop diuretics.

Signs & symptoms: Paresthesias (perioral, fingers), tetany, Chvostek sign, Trousseau sign, seizures, prolonged QT, laryngospasm.

Nursing interventions: Administer IV calcium gluconate or chloride for acute symptomatic hypocalcemia; give slowly; correct magnesium first if low; monitor ECG; implement seizure precautions; ensure adequate vitamin D and calcium intake.

Hypercalcemia (>10.2 mg/dL)

Causes: Hyperparathyroidism, malignancy, thiazide diuretics, vitamin D toxicity, immobilization, Paget disease.

Signs & symptoms: Fatigue, weakness, constipation, nausea, polyuria, polydipsia, shortened QT, kidney stones, confusion, coma.

Nursing interventions: IV normal saline to promote renal excretion; loop diuretics (after volume repletion); calcitonin, bisphosphonates, or denosumab per protocol; encourage mobility; restrict calcium intake; monitor cardiac rhythm.

Magnesium (Mg)

Normal range: 1.7–2.2 mEq/L (1.3–2.1 mg/dL)

Hypomagnesemia (<1.7 mEq/L)

Causes: Alcohol use disorder, diarrhea, diuretics, malnutrition, refeeding syndrome, pancreatitis, PPI long-term use.

Signs & symptoms: Muscle tremors, tetany, dysrhythmias, hypokalemia, hypocalcemia (refractory until Mg corrected), seizures, positive Chvostek/Trousseau.

Nursing interventions: Administer Mg sulfate IV or oral; IV Mg given slowly; monitor deep tendon reflexes and respiratory rate (excess can cause respiratory depression); correct before treating refractory hypokalemia/hypocalcemia.

Hypermagnesemia (>2.2 mEq/L)

Causes: Renal failure, excessive Mg intake (antacids, laxatives, tocolytics), adrenal insufficiency, hypothyroidism.

Signs & symptoms: Hyporeflexia, muscle weakness, hypotension, bradycardia, respiratory depression, cardiac arrest (severe).

Nursing interventions: Hold Mg-containing medications; administer IV calcium gluconate for acute symptoms; dialysis if renal failure; support respirations; monitor ECG and reflexes.

Phosphorus (P)

Normal range: 2.5–4.5 mg/dL (adults)

Hypophosphatemia (<2.5 mg/dL)

Causes: Refeeding syndrome, alcoholism, DKA, respiratory alkalosis, phosphate-binding antacids, hyperparathyroidism, malnutrition.

Signs & symptoms: Muscle weakness, respiratory failure, cardiomyopathy, confusion, seizures, osteomalacia, hemolysis, impaired WBC function.

Nursing interventions: Administer phosphate replacement (oral or IV); IV phosphate given slowly to avoid hypocalcemia and precipitation; monitor Ca and Mg; gradual refeeding in malnourished patients to prevent refeeding syndrome.

Hyperphosphatemia (>4.5 mg/dL)

Causes: Renal failure, tumor lysis syndrome, rhabdomyolysis, hypoparathyroidism, phosphate-containing laxatives, vitamin D excess.

Signs & symptoms: Tetany (from secondary hypocalcemia), soft tissue calcification, pruritus, cardiac dysrhythmias, seizures.

Nursing interventions: Restrict dietary phosphate; administer phosphate binders (calcium acetate, sevelamer, lanthanum) with meals; dialysis if renal failure; treat underlying cause; monitor Ca (often low with high P).