Editing Reduction of Risk Potential (section)

=== Serum Electrolytes ===

;Sodium, 135 to 145 mEq/L
Sodium is primarily a water problem, not a salt problem. '''Hyponatremia''' (below 135) is seen with excess free water, syndrome of inappropriate antidiuretic hormone, heart failure, cirrhosis, adrenal insufficiency, thiazide diuretics, psychogenic polydipsia, and irrigation with hypotonic fluids. Findings progress from headache, nausea, and lethargy to confusion, seizures, and coma as cerebral edema develops. Nursing application: institute seizure precautions, monitor neurologic status hourly when the level is falling quickly, and correct slowly. Overly rapid correction of chronic hyponatremia risks osmotic demyelination. '''Hypernatremia''' (above 145) reflects water deficit or sodium excess from dehydration, insensible losses, fever, diabetes insipidus, tube feedings without free water, or hypertonic saline. Findings include thirst, dry sticky mucous membranes, restlessness, agitation, and twitching (Ignatavicius et al., 2021; Pagana et al., 2022).

;Potassium, 3.5 to 5.0 mEq/L
The most consequential electrolyte for cardiac safety. '''Hypokalemia''' arises from loop and thiazide diuretics, vomiting, nasogastric suction, diarrhea, insulin therapy, corticosteroids, and alkalosis. Findings include muscle weakness, leg cramps, decreased deep tendon reflexes, paralytic ileus with hypoactive or absent bowel sounds, and electrocardiogram changes of flattened T waves, ST depression, and a U wave. '''Hyperkalemia''' arises from renal failure, potassium-sparing diuretics, angiotensin converting enzyme inhibitors and angiotensin receptor blockers, crush injury, burns, tumor lysis, acidosis, and blood transfusion of older units. Findings include muscle weakness, paresthesias, and peaked T waves progressing to a widened QRS and cardiac arrest. Nursing application: intravenous potassium is '''never''' given by intravenous push or bolus and is not given intramuscularly. It must be diluted and infused by pump, generally not exceeding 10 mEq per hour on a general unit, with confirmation of adequate urine output before administration. Report a potassium above about 5.5 mEq/L or below about 3.0 mEq/L promptly, and check the level before giving digoxin (Ignatavicius et al., 2021; Pagana et al., 2022).

;Chloride, 98 to 106 mEq/L
Moves with sodium and shifts inversely with bicarbonate. Loss through vomiting or gastric suction contributes to metabolic alkalosis (Pagana et al., 2022).

;Total calcium, 9.0 to 10.5 mg/dL (ionized calcium approximately 4.5 to 5.6 mg/dL)
Total calcium is bound to albumin, so a low albumin falsely lowers the total calcium while the physiologically active ionized fraction is normal. '''Hypocalcemia''' follows thyroid or parathyroid surgery, acute pancreatitis, chronic kidney disease, vitamin D deficiency, massive transfusion with citrated blood, and alkalosis. Findings include perioral and digital numbness and tingling, muscle twitching, a positive Chvostek sign (facial twitch on tapping the facial nerve), a positive Trousseau sign (carpal spasm with blood pressure cuff inflation), tetany, and laryngospasm. Nursing application: after thyroidectomy or parathyroidectomy, keep intravenous calcium gluconate and emergency airway equipment available and assess for these signs on every shift. '''Hypercalcemia''' follows hyperparathyroidism, malignancy with bone metastases, prolonged immobilization, and excessive calcium or vitamin D intake. Findings include lethargy, confusion, constipation, decreased deep tendon reflexes, polyuria, and kidney stones (Harding et al., 2023; Pagana et al., 2022).

;Magnesium, 1.3 to 2.1 mEq/L (approximately 1.8 to 2.6 mg/dL)
'''Hypomagnesemia''' accompanies alcohol use disorder, malnutrition, diarrhea, and diuretic therapy, and it produces hyperexcitability, tremor, positive Chvostek and Trousseau signs, and dysrhythmias including torsades de pointes. Hypokalemia that will not correct is often a hidden magnesium deficiency. '''Hypermagnesemia''' occurs with renal failure and with magnesium sulfate therapy in obstetrics; the earliest reliable warning is loss of the patellar deep tendon reflex, followed by respiratory depression, hypotension, and cardiac arrest. Nursing application: during magnesium sulfate infusion, monitor deep tendon reflexes, respiratory rate, level of consciousness, and urine output, and keep calcium gluconate at the bedside as the antidote (Ignatavicius et al., 2021; Pagana et al., 2022).

;Phosphorus, 3.0 to 4.5 mg/dL
Varies inversely with calcium. Elevated in renal failure; low in refeeding syndrome, alcohol use disorder, and respiratory alkalosis (Pagana et al., 2022).