Does this patient have hypocalcemia?

Abnormal calcium metabolism is one of the components of the laboratory abnormalities in the CKD-MBD syndrome. Decreased conversion of storage form of vitamin D, 25-hydroxyvitamin D, to calcitriol, 1,25-dihydroxyvitamin D, results in decreased gastrointestinal calcium absorption and may be accompanied by hypocalcemia without treatment.

Key elements in the history

  • Evaluate in conjunction with other laboratory components of CKD-MBD

  • Recognize that correction to total calcium for decreased albumin may need to be made and if hypocalcemia is persistent, ionized calcium should be measured

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  • Ascertain history of blood transfusions

  • Consider disturbances in acid base status

  • Understand the effects of changing dialysis calcium bath on serum calcium levels

  • Understand the consequences of parathyroidectomy and pathophysiology of hungry bone syndrome

Key symptoms

  • Usually asymptomatic unless drop is severe and or acute

  • Generalized weakness, confusion

  • Perioral numbness, carpopedal spasms in hands and feet, tetany, seizures

  • Hypotension, heart failure

Key signs and physical findings

  • Chvostek’s sign

  • Trousseau’s sign

  • Prolonged QT interval

Other diseases or syndromes with similar appearances

  • Rule out hypoalbuminemia

  • Consider

    Citrate-induced decrease in ionized calcium following blood transfusions

    Acute respiratory alkalosis

    Hungry bone syndrome

    Sepsis

    Acute pancreatitis

    Rhabdomyolysis

    Tumor lysis syndrome

    Medications

    Cinacalcet

    Fleet’s phospho-soda

    Bisphosphonates

    Denosumab

What tests to perform?

Lab testing

Which tests do I order?

  • Serum albumin, phosphate, and PTH

  • Ionized calcium if hypocalcemia is persistent

  • Magnesium levels

  • If vitamin D deficiency is being considered and repletion is to be undertaken, 25-hydroxyvitamin D levels may be obtained

  • In the intensive care unit (ICU) setting, review acid-base status

  • First, hypoalbuminemia as a cause of low total calcium levels should be ruled out with calculation of corrected calcium levels

  • Ionized calcium levels may also be useful in confirming true hypocalcemia

How often do I order test?

  • In the outpatient dialysis setting monthly routine lab tests are sufficient for monitoring and if hypocalcemia is not severe

  • For more severe and symptomatic hypocalcemia and in the inpatient setting more frequent assessments may be needed

What are the next steps?

  • Review medication history

  • Review recent medical/surgical history (transfusions, surgeries, acute intercurrent illnesses)

Overall interpretation of test results

  • Diagnosis can be confirmed by measuring ionized calcium levels

  • Prognosis depends on severity of decrease, presence of symptoms, and rate of and response to correction

How should patients with hypocalcemia be managed?

Key treatment concepts

  • Confirm diagnosis

  • Ascertain severity of symptoms

  • Correct hypomagnesemia, if present

  • Stop offending medications: cinacalcet, bisphosphonates, iron chelators

  • Oral calcium based-binders and vitamin D should correct moderate hypocalcemia

  • Severe symptomatic cases may need IV calcium

What happens to patients with hypocalcemia?

  • Hypocalcemia may exacerbate secondary hyperparathyroidism

  • Hypocalcemia has been linked with sudden cardiac death

How to utilize team care?

  • Nurses can assist in review of laboratory values and alert physicians to changes.

  • Pharmacists can review medications for potential contributing factors.

  • Dietitians can review dietary intake.

What is the evidence?

Moe, SM. “Disorders involving calcium, phosphorus, and magnesium”. Prim Care. vol. 35. 2008. pp. 215-237. (This article provides a review of mineral disorders with clinical applications to commonly detected laboratory abnormalities.)

Yusuf, B. “Hypocalcemia in a dialysis patient treated with deferasirox for iron overload”. Am J Kidney Disease. vol. 52. 2008. pp. 587-590. (This is a case report of hypocalcemia in a dialysis patient treated with deferasirox.)

Kim, ED, Parekh, RS. “Calcium and Sudden Cardiac Death in End-Stage Renal Disease”. Semin Dial. vol. 28. 2015 Nov-Dec. pp. 624-35. (This review article summarizes the evidence on the association of hypocalcemia with cardiac events in patients undergoing dialysis.)

Block, GA, Bone, HG, Fang, L, Lee, E, Padhi, D. “A single-dose study of denosumab in patients with various degrees of renal impairment”. J Bone Miner Res. vol. 27. 2012. pp. 1471-9. (This study documents the effects of denosumab on calcium levels in patients undergoing dialysis.)

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