Electrolyte Imbalances: Sodium, Potassium, Calcium, Magnesium - Pathophysiology and Nursing Management

Sodium (Na+)

Norm: 136-145 mEq/L. Na+ imbalances typically associated with parallel changes in osmolality. Plays a major role in ECF volume and concentration, generation and transmission of nerve impulses, and muscle contractility.

Hypernatremia

Na+ > 145 mEq/L. Causes include low H2O intake, osmotic diuretics (e.g., mannitol), diabetes insipidus, excessive H2O loss, and high sodium intake from meds and meals.

Lab Findings in Hypernatremia

↑ Serum Na+, ↑ Serum Osmolality (more concentrated serum), ↑ Urine Osmolality, specific gravity >1.030, dark, concentrated urine.

Clinical Manifestations of Hypernatremia

Fried: Flushed; fever (low grade), Restless (irritable); progressing to confusion/seizure, Increased fluid retention (edema), Excited muscles (↑muscle irritability and twitching, ↑DTRs), Exhausted muscles (↑ volume), Decreased urine output, dry mouth, increased thirst (except in elderly).

Priority Nursing Interventions for Hypernatremia

Sodium intake ↓, Oral hygiene (due to dry mouth), Diuretics, Increase water intake, Use hypotonic or isotonic fluids, Monitor for inadequate renal output (I&O's).

Hyponatremia

Na+ < 136 mEq/L. Results from loss of sodium-containing fluids and/or from water excess.

Clinical Manifestations of Hyponatremia

Confusion, irritability, headache. Can progress to vomiting, seizures, or coma.

Decreased Lab Values in Hyponatremia

↓ Serum Na+, ↓ Serum Osmolality (less concentrated), ↓ Specific Gravity

Priority Nursing Interventions for Hyponatremia

Sodium intake & seizure precautions, Overload—restrict water intake, Daily weight, Intake & Output, Use isotonic fluids to restore ECF (higher in Na), Monitor postural hypotension.

Potassium Imbalances

Hyper/hypokalemia.

Magnesium Imbalances

Hypermagnesemia/hypomagnesemia.

Calcium Imbalances

Hyper/Hypocalcemia.

Phosphate Imbalances

Hyper/hypophosphatemia.

Extracellular Fluid Volume Imbalances

Fluid volume deficit and fluid volume excess.

Osmotic Diuretics

Example: mannitol (given to decrease ICP).

Diabetes Insipidus

An issue with ADH leading to excessive water loss.

Increased Fluid Retention

Associated with hypernatremia, leading to edema.

Decreased Urine Output

A symptom of hypernatremia, leading to dry mouth and increased thirst.

Specific Gravity in Urine

In hypernatremia, specific gravity is >1.030 indicating concentrated urine.

Fluid Volume Deficit

A condition characterized by a decrease in body fluid volume.

Potassium (K+)

Norm: 3.5-5.0 mEq/L; Major ICF cation; Necessary for transmission and conduction of nerve and muscle impulses, maintenance of cardiac rhythms.

Sources of Potassium (K+)

Fruits and vegetables, salt substitutes, potassium medications (PO, IV), blood transfusions; regulated by kidneys.

Hyperkalemia

↑K+: >5.0 mEq/L; Causes include impaired renal excretion, shift from ICF to ECF, massive intake.

Most common cause of Hyperkalemia

Renal failure.

Manifestations of Hyperkalemia

Restlessness, weak or paralyzed skeletal muscles, bilateral muscle twitching, leg pain/cramps, abdominal cramping, explosive diarrhea, slow irregular pulse, hypotension, dysrhythmias.

ECG Changes with Hyperkalemia

Dysrhythmias such as PVCs, V Fib, peaked/tented T waves, wide QRS.

Nursing Implementation for Severe Hyperkalemia

Monitor cardiac rhythm (telemetry), administer calcium gluconate IV, possibly dialysis.

Nursing Implementation for Moderate Hyperkalemia

Force K+ from ECF to ICF by IV regular insulin and glucose, sodium bicarbonate if patient is acidotic.

Nursing Implementation for Mild Hyperkalemia

Stop intake of K: IVF, PO (meds/foods); if no kidney dysfunction, give furosemide (Lasix) and Kayexalate.

Telemetry-Cardiac Monitoring

Used for monitoring cardiac rhythm in patients with potassium imbalances.

Hypokalemia

↓K+: < 3.6 mEq/L; Causes include GI losses, renal losses, skin losses, insufficient K+, intracellular shift.

Manifestations of Hypokalemia

↓ BP, weak irregular pulse, altered mental status, flat T wave, various dysrhythmias, hypoactive bowel sounds, weakness, shallow breathing.

Nursing Implementation for Hypokalemia

KCl supplements orally or IV; always dilute IV KCl; NEVER give KCl via IV push or as a bolus; should not exceed 10 mEq/hr.

Potassium Deficit (Hypokalemia)

K+: < 3.6 mEq/L; Nursing interventions include dietary sources like potatoes, avocados, broccoli, and oral potassium supplements.

T waves in Hypokalemia

Depressed (flattened) T waves; monitor for arrhythmias.

Respiratory effects of Hypokalemia

Weak respiratory muscles leading to shallow breathing; may lead to respiratory arrest.

Older adults and Hypokalemia

Increased risk due to laxatives and diuretics.

Urine output

Must be 0.5 mL/kg per hr

Calcium (Ca++)

Norm: 9.0-10.5 mg/dL

Functions of Calcium

Transmission of nerve impulses, muscle contractions, myocardial contractions, formation of teeth and bone, blood clotting

Sources of Calcium

Obtained from ingested foods, need vitamin D to absorb, present in three forms: Ionized calcium is biologically active

Hypercalcemia

Defined as >10.5 mg/dL

Causes of Hypercalcemia

Hyperparathyroidism (two thirds of cases), prolonged immobilization, malignancy

Manifestations of Hypercalcemia

Lethargy, weakness, stupor, coma, depressed reflexes, muscle contractility issues, confusion, personality changes, psychosis, anorexia, nausea, vomiting, bone pain, fractures, polyuria, dehydration leading to risk of renal calculi

Nursing Implementation for Hypercalcemia

Excretion of Ca++ with loop diuretic, hydration with isotonic saline infusion, low calcium diet, mobilization, synthetic calcitonin, bisphosphonates

Hypocalcemia

Defined as < 9 mg/dL

Causes of Hypocalcemia

Decreased production of PTH, after thyroid/neck surgeries, acute pancreatitis, multiple blood transfusions, alkalosis, increased calcium loss

Manifestations of Hypocalcemia

Positive Trousseau's or Chvostek's sign, laryngeal stridor, tingling around the mouth or in the extremities, cardiac dysrhythmias

Nursing Implementation for Hypocalcemia

Treat underlying cause (primary goal), oral or IV calcium supplements (NOT IM to avoid local reactions), rebreathe into paper bag, treat pain and anxiety to prevent hyperventilation-induced respiratory alkalosis

Magnesium (Mg++)

Norm: 1.3-2.1 mEq/L

Functions of Magnesium

Coenzyme in metabolism of protein and carbohydrates, required for nucleic acid and protein synthesis, helps maintain calcium and potassium balance, necessary for sodium-potassium pump

Sources of Magnesium

Acts directly on myoneural junction, important for normal cardiac function, 50% to 60% contained in bone, absorbed in GI tract, excreted by kidneys

Hypermagnesemia

Defined as >2.1

Causes of Hypermagnesemia

↑ intake or ingestion of products containing magnesium (usually only creates a problem when renal insufficiency/failure is present), excess IV magnesium administration

Manifestations of Hypermagnesemia

Lethargy, nausea and vomiting (initial signs and symptoms of mild ↑), impaired reflexes, somnolence, respiratory and cardiac arrest as levels increase

Management of Hypermagnesemia

Prevention first—restrict Mg intake in high-risk patients, emergency treatment with IV CaCl or calcium gluconate to oppose the effects of Mg on cardiac muscle, oral and parenteral fluids and IV furosemide to promote urinary excretion of Mg, dialysis required if patient has impaired renal function

Hypomagnesemia

Defined as

Causes of Hypomagnesemia

Prolonged fasting or starvation, chronic alcoholism (most common cause), fluid loss from GI tract (NG suction, diarrhea or fistulas), prolonged parenteral nutrition without Mg supplementation, diuretics leading to renal excretion of Mg, hyperglycemic osmotic diuresis in uncontrolled DM

Manifestations of Hypomagnesemia

Confusion, hyperactive deep tendon reflexes (DTRs), muscle cramps, tremors, seizures, cardiac dysrhythmias (PVCs or Vfib), corresponding hypocalcemia and hypokalemia

Management of Hypomagnesemia

Primary goal is to treat underlying cause, oral supplements, increase dietary intake of Mg, parenteral IV or IM magnesium when severe