NCLEX Review: Fluid and Electrolytes

Sodium (135-145 mEq/L)

  • The major cation in the ECF. It has a water retaining effect. When there is excess Na+ in the ECF, more water will be reabsorbed by the kidneys.
  • Functions: maintains body fluids, conduction of neuromuscular impulses via pump, regulates acid-base balance by combining with Cl- or HCO3-.

Hyponatremia

  • Causes: vomiting, diarrhea, NG suction, excessive perspiration, kidney disease, water intoxication, IV D5W, SIADH, burns
  • Signs and Symptoms: apprehension, muscular weakness, postural hypotension, N/V, dry mucous membranes, tachycardia
  • Treatment: water restriction, normal saline IV

Hypernatremia

  • Causes: excessive salt intake, dehydration, CHF, hepatic failure (excess aldosterone secretion), diabetes insipidus
  • Signs and Symptoms: extreme thirst, sticky mucous membranes, dry tongue, fever, postural hypotension, restlessness/agitation/irritability, increased fluid retention/edema, decreased urine output, convulsions
  • Treatment: stop IV normal saline, replace water loss

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Potassium (3.5-5.0 mEq/L)

  • The major ICF electrolyte, 80%-90% is excreted by the kidneys.
  • When tissue breaks down, K+ leaves the cells and enters the ECF and is excreted by the kidneys
  • The body does not conserve K+
  • Influences both skeletal and cardiac muscle activity

Hypokalemia

  • ** The most common electrolyte imbalance
  • Causes: vomiting/diarrhea, renal disorder, sweating, crash diets, diuretics
  • S/S: fatigue, anorexia, N/V, muscle weakness, decreased bowel motility, cardiac dysrhythmias, paresthesia or tender muscles
  • Treatment: administer KCl (never give K+ undiluted or IV push. concentrated solutions should be administered through central veins. Use IV pump!)

Hyperkalemia

  • Causes: renal failure, potassium supplements, digoxin toxicity, potassium sparing diuretics, acidosis (DKA), fluid volume deficit. 
  • S/S: anxiety, cardiac arrhythmias (bradycardia, heart block, peaked T wave, widened QRS), muscle weakness, abdominal cramps, diarrhea
  • Treatment: dialysis, Kayexalate, stop supplements

Calcium (4.5-5.3 mg/dL)

  • Ionized (free Calcium) is Calcium not attached to proteins.
  • 99% is located in skeletal system, 1% in serum
  • Necessary for bone and teeth formation
  • Necessary for the transmission of nerve impulses and contraction of the myocardium and skeletal muscles
  • Causes blood clotting by converting prothrombin into thrombin
  • Strengthens capillary membranes

Hypocalcemia

  • Causes: lack of Ca and Vit D in diet, extensive infection, hypoparathyroidism, pancreatitis, chronic renal failure (Phosphorus rises/calcium declines)
  • S/S: Related to diminished neuromuscular and cardiac function – positive Trousseau’s sign, positive Chvostek’s sign, numbness of fingers and around mouth, hyperactive reflexes, tetany, convulsion, spasms/muscle cramps, arrhythmia/ventricular tachycardia. (CATS: convulsions, arrhythmias, tetany, spasms)
  • Treatment: Oral/IV replacement, correct underlying cause

Hypercalcemia

  • Causes: hyperparathyroidism, neoplasm, osteoporosis, prolonged immobilization
  • S/S: anorexia, N/V, lethargy, flank pain from kidney stones, cardiac arrhythmias (heart block, eventual cardiac arrest), muscle flaccidity
  • Treatment: Calcitonin, discontinue antacids, treatment of underlying cause


Phosphate (2.7-4.5 mg/dL)

  • buffer found primarily in ICF
  • functions: acid-base regulation, phosphate and calcium help with bone and teeth development, promotes normal neuromuscular action and participates in CHO metabolism, conversion of glycogen to glucose
  • normally absorbed in the GI tract, regulated by diet, renal excretion, intestinal absorption and PTH

Hypophosphatemia

  • Cause: excretion
  • Symptoms: disorientation, bruising, numbness, bone pain, muscle weakness
  • Treatment: increase dietary intake, IV replacement

Hyperphosphatemia

  • Causes: decreased intake or increased excretion
  • S/S: same as hypocalcemia
  • Treatment: limit phosphate intake, administer aluminum-based antacids.

Chloride (98-106 mEq/L)

  • anion found mostly in ECF, maintains body water balance, plays a role in acid-base balance, combines with H+ to produce acidity in the stomach
  • follows Na+ up or down

Hypochloremia

  • Causes: vomiting, diarrhea, excessive NG drainage, hypokalemia, hyponatremia, adrenal gland deficiency
  • S/S: hyperexcitabilty of the nervous system and muscles, tetany
  • Treatment: treat underlying cause

Hyperchloremia

  • Causes: dehydration, hypernatremia, kidney dysfunction, head injury, hyperparathyroidism
  • S/S: deep, rapid, vigorous breathing, lethargy, weakness
  • Treatment: decrease intake, correct underlying cause
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Magnesium (1.5-2.5 mEq/L)

  • Most plentiful in the cells
  • Needed for neuromuscular activity
  • Responsible for the transport of Na and K across the cell membrane

Hypomagnesemia

  • Causes: protein malnutrition, alcoholism/cirrhosis of the liver, aldosterone excess, inadequate absorption (chronic diarrhea, vomiting, NG drainage)
  • S/S: muscle tremors, hyperactive tendon reflexes, confusion, tachycardia
  • Treatment: treat underlying causes, IV replacement if necessary.

Hypermagnesemia

  • Causes: severe dehydration, renal failure, leukemia, antacids/laxatives
  • S/S: flushing, muscular weakness, increased perspiration, cardiac arrhythmias (bradycardia, prolonged QT intervals, AV block)
  • Treatment: treat underlying cause

Helpful Tidbits

  • 4 electrolytes that impact cardiac functioning: K, Mg, Ca, Ph
  • 3 imbalances that contribute to digoxin toxicity: hypokalemia, hypercalcemia, hypomagnesmia
  • 4 imbalances that contribute to seizures: hyponatremia, hypocalcemia, hypomagnesmia, hyperphosphatemia
  • Electrolytes associated with alkalosis: hypomagnesemia, hypokalemia
  • Clinical Dehydration = ECV Deficit + Hypernatremia

Source: Texas Woman’s University College of Nursing, Fundamentals of Nursing – Perry & Potter 2016




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