Potassium and Sodium Imbalances

Normal potassium is 3.5-5.0 mEq/L; hypokalemia causes weakness, flat/inverted T waves, U waves, and constipation, while hyperkalemia causes peaked T waves, weakness progressing to paralysis, and can cause fatal dysrhythmias — never give IV potassium as a bolus, always dilute and infuse via pump, never exceeding 10 mEq/hr peripherally. Normal sodium is 135-145 mEq/L; hyponatremia causes confusion, headache, and seizures as cells swell, while hypernatremia causes thirst, restlessness, and dry mucous membranes as cells shrink — correct both slowly to prevent neurologic injury from osmotic shifts.

Calcium and Magnesium Imbalances

Normal calcium is 9-10.5 mg/dL; hypocalcemia causes tetany, positive Chvostek's and Trousseau's signs, and perioral numbness, while hypercalcemia causes muscle weakness, constipation, kidney stones, and decreased deep tendon reflexes — remember 'bones, stones, groans, and moans.' Normal magnesium is 1.5-2.5 mEq/L; hypomagnesemia mimics hypocalcemia with tetany and hyperreflexia and often accompanies alcoholism, while hypermagnesemia causes loss of deep tendon reflexes, respiratory depression, and cardiac arrest — calcium gluconate is the antidote for severe magnesium toxicity, often seen with excessive magnesium sulfate treatment for preeclampsia.

Priority Nursing Actions and Safety

Always assess deep tendon reflexes and cardiac rhythm when an electrolyte imbalance is suspected, since cardiac and neuromuscular symptoms are the most dangerous consequences. For severe hyperkalemia with ECG changes, priority interventions include IV calcium gluconate to stabilize the cardiac membrane, followed by insulin with dextrose to shift potassium intracellularly, then options like sodium polystyrene sulfonate to remove potassium from the body. For magnesium sulfate toxicity, stop the infusion immediately if reflexes are absent or respirations drop below 12/min, and have calcium gluconate available at the bedside.