Calcium

Calcium is mostly found in the bones and teeth (99%).  The other one percent is the active form.  It is used in enzyme activation to stimulate chemical reactions, skeletal and heart muscle contractions, nerve transmission, blood coagulation, formation of bones and teeth, and maintaining cell membrane permeability.  When calcium is released from the bone it splits up.  Half is bound to albumin (a protein) and half is free and ionized.  The ionized, free form is the active form of calcium.  It is important for the two halves to remain in the same basic proportions at all times.

The normal range of calcium is 9-11 mg/dL.

Hypocalcemia, or low amounts of calcium (<9 mg/dL), is caused primarily by low albumin (because half of all calcium is bound to albumin).  It can also be caused by inadequate intake of calcium, renal failure, steroids, and loop diuretics.  Hypoparathyroidism can also cause hypocalcemia because calcium levels are regulated by the parathyroid hormone (PTH) and vitamin D.  The signs and symptoms of hypocalcemia are increased neuromuscular excitability (meaning muscle twitching and possible cardiac arrhythmias), numbness and tingling of extremities and lips, decreased blood coagulation, tetany (involuntary contraction of the muscles), irritability, and anxiety.  Watch for increased bleeding, especially on the gums, in urine, and at the IV site.  A very definitive sign of hypocalcemia is Trousseau’s or Chvostek’s sign.  These happen because of the increased excitably of the CNS.  Trousseau’s sign happens when a blood pressure cuff is inflated.  The hand and fingers will spasm, forming a claw.  Chvostek’s is a spasm of the upper lip when the facial nerve is touched.  See pictures below.  To treat hypocalcemia, administer calcium supplements and vitamin D.  Oral supplements are better absorbed and utilized, and vitamin D facilitates that absorption.  If the imbalance is severe, IV calcium gluconate can be administered.  This should be given slowly to avoid hypotension and bradycardia.  The patient should increase dietary consumption of calcium (dairy products, instant oatmeal, rhubarb, spinach, and tofu) and should exercise regularly.

https://i0.wp.com/img.tfd.com/mk/T/X2604-T-46.png

Trousseau’s Sign (http://img.tfd.com/mk/T/X2604-T-46.png)

https://i1.wp.com/www.medicalmystery.org/wp-content/uploads/2012/12/Chvosteks-sign-2.jpg

Chvostek’s Sign (http://www.medicalmystery.org/wp-content/uploads/2012/12/Chvosteks-sign-2.jpg)

High amounts of calcium (>11 mg/dL) is known as hypercalcemia.  This can be caused by metastatic malignancies, hyperparathyroidism, thiazide diuretics, prolonged immobility, excessive intake of calcium (often from ingestion of TUMS), and destruction of bone.  This is often accompanied by hypophosphatemia, because calcium and phosphate have an inverse relationship.  Signs and symptoms of hypercalcemia are muscle weakness, fatigue, lethargy, constipation, kidney stones, and increased risk of thrombus formation.  There is often a lack of coordination and abdominal pain or distention.  To treat hypercalcemia, give the patient phosphorus.  This will push calcium back into the bones.  Calcitonin can be given by intramuscular of subcutaneous injection, which will increase urinary calcium excretion and inhibit the effects of PTH.  Fluids should be increased in order to dilute the calcium, either orally or by IV (0.45% NS or NS).  The patient should also maintain acidic urine to prevent a urinary tract infection and kidney stones and restrict dietary calcium.

Ready for your questions?

What is the primary reason for hypocalcemia?

Differentiate between Trousseau’s and Chvostek’s signs.

References

McCarthy, M. (2011). Electrolyte imbalances [PowerPoint Slides].

White, B. (2009). Clients with electrolyte imbalances. In Black, J. M., & Hawks, J. H. (Eds). Medical-surgical nursing. Clinical management for positive outcomes, (Vol 1., 8th Ed), (pp. 151-167). St. Louis, MO: Elsevier Inc.

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