Hypocalcemia

Hypocalcemia is a diminished calcium level, below 8.2 mg/dL, in the bloodstream. Calcium is vital to the body for the formation of bones and teeth, blood coagulation, nerve impulse transmission, cell permeability, and normal muscle contraction. Although 98% of the body's calcium is found in the bones, three forms of calcium exist in the serum: free or ionized calcium (50% of serum total), calcium bound to protein (45% of serum total), and calcium complexed with citrate or other organic ions (5% of serum total). Ionized calcium is reabsorbed into bone, absorbed from the gastrointestinal mucosa, and excreted in urine and feces as regulated by the parathyroid glands. Ionized calcium is the active, physiological component of total calcium fraction. Parathyroid hormone (PTH) is necessary for calcium absorption and normal serum calcium levels.

Hypocalcemia is a more common clinical problem than hypercalcemia and may occur as frequently as 15% to 50% in acutely ill patients. Some experts estimate that over half of critically ill patients in intensive care units have hypocalcemia. Alkalosis can induce hypocalcemia because it leads to increased calcium-protein binding and decreased ionized calcium; acidosis protects from hypocalcemia because it leads to decreased calcium-protein binding and increased ionized calcium. When calcium levels drop, neuromuscular excitability occurs in smooth, skeletal, and cardiac muscle, causing the muscles to twitch. The result can lead to cardiac dysrhythmias. Hypocalcemia can also cause increased capillary permeability, pathological fractures, and decreased blood coagulation. Most severe cases result in tetany (condition of prolonged, painful spasms of the voluntary muscles of the fingers and toes [carpopedal spasm] as well as the facial muscles), which, if left untreated, leads to carpopedal and laryngeal spasm, seizures, and respiratory arrest.

Causes ⬆ ⬇

The most frequent cause of hypocalcemia is a low albumin level, but if serum ionized (free) calcium is normal, then no disorder of calcium metabolism is present and no treatment is needed. In the clinical setting, the most common cause of hypocalcemia is acute/chronic kidney failure followed by vitamin D deficiency (vitamin D is needed for calcium absorption). Causes of low ionized calcium, which is needed for enzymatic reactions and neuromuscular function, also include hypoparathyroidism, severe hypomagnesemia, hypermagnesemia, and acute pancreatitis. It is also associated with thyroidectomy and radical neck dissection when there is postoperative ischemia to the parathyroid glands.

Low serum calcium levels can also occur after small bowel resection, partial gastrectomy with gastrojejunostomy, and Crohn disease. Severe diarrhea or laxative abuse may also cause hypocalcemia; when intestinal surfaces are lost, less calcium is absorbed. A transient low calcium level can result from massive administration of citrated blood. Some drugs that can result in hypocalcemia include loop diuretics, phenytoin, phosphates, caffeine, alcohol, antimicrobials (pentamidine, ketoconazole, aminoglycosides), antineoplastic agents (cisplatin, cytosine arabinoside), and corticosteroids.

Genetic Considerations ⬆ ⬇

Gain of function mutations in the calcium-sensing receptor (CASR) are associated with type 1 autosomal dominant familial hypocalcemia with hypercalciuria. Type 2 familial hypocalcemia with hypercalciuria is rarer and occurs from mutations in the GNA11 gene.

Persistent low blood calcium levels are also seen in DiGeorge syndrome, which results from a deletion of several genes on chromosome 22 (22q deletion). Other features of 22q deletion include cleft palate, cardiac defects, characteristic facial features, and underdevelopment of the thymus.

Sex and Life Span Considerations ⬆ ⬇

Hypocalcemia can occur in all people at any age, but infants, children, and older adults are at high risk. In infants, it occurs with the use of cow's milk formula with a high concentration of phosphate. The large bone turnover during growth spurts accounts for hypocalcemia in children, especially if their calcium intake is deficient. Osteoporosis in older adults is associated with a lifetime low intake of calcium, which leads to a total body calcium deficit. Those older adults with osteoporosis who spend prolonged time on bedrest also have a risk for hypocalcemia.

Health Disparities and Sexual/Gender Minority Health ⬆ ⬇

Ethnicity, race, and sexual/gender minority status have no known effect on the risk for hypocalcemia.

Global Health Considerations ⬆ ⬇

Hypocalcemia occurs in all global regions from acute and chronic renal failure, nutritional deficiencies (vitamin D, calcium, and magnesium), parathyroid disease, and pancreatitis.

Assessment ⬆ ⬇

ASSESSMENT

History

Ask about a prior diagnosis of hypoparathyroidism, renal failure, pancreatic insufficiency, or hypomagnesemia. Elicit a history of severe infections or burns. Ask if the patient has been under treatment for acidosis, which might lead to alkalosis. Determine if the patient has an inadequate intake of calcium, vitamin D, or both. Investigate causes of vitamin D or magnesium deficiency, such as a gastrointestinal disease associated with malabsorption, poor diet, gastrectomy, intestinal resection or bypass, or hepatobiliary disease. Ask about medication use associated with disordered calcium metabolism, such as phenytoin, estrogen, loop diuretics, or plicamycin.

Inquire about anxiety, irritability, twitching around the mouth, laryngospasm, or convulsions, all central nervous system signs and symptoms of hypocalcemia. Establish a history of tingling or numbness in the fingers (paresthesia) or around the mouth, tetany or painful tonic muscle spasms, abdominal cramps, muscle cramps, or spasmodic contractions. Determine if the patient has experienced mental status changes. Ask the patient about gastrointestinal symptoms such as diarrhea.

Physical Examination

The most common symptoms of severe hypocalcemia include neuromuscular excitability with muscle cramps, twitching and irritability, and laryngospasm. Assess airway, breathing, and circulation. Hypocalcemia can lead to wheezing, laryngospasm, dyspnea, and difficulty swallowing. Central nervous system signs include confusion, disorientation, hallucinations, dementia, and seizures. Auscultate for heart sounds. The patient may have heart failure and/or dysrhythmias, especially heart block and ventricular fibrillation. Tetany, increased neural excitability, accounts for the majority of signs and symptoms of hypocalcemia. Check for Trousseau sign (development of carpal spasm when a blood pressure cuff is inflated above systolic pressure for 3 minutes) and Chvostek sign (twitching facial muscles when the facial nerve is tapped anterior to the ear).

Inspect the patient's skin to see if it is dry, coarse, or scaly, which are signs of hypocalcemia. Note any exacerbation of eczema or psoriasis along with hair loss or brittle nails. Check for dental abnormalities. Inspect the patient's eyes for cataracts of the cortical portion of the lens, which may develop within a year after the onset of hypocalcemia.

Psychosocial

Severe hypocalcemia may produce mental changes, which is frightening for the patient and the family. Assess for depression, impaired memory, and confusion. As the condition continues, delirium and hallucinations may be present. In severe cases of hypocalcemia, psychosis or dementia may develop. Electrolyte disturbances that affect a patient's personality often increase the patient's and family's anxiety. Assess the patient's and family's coping mechanisms.

Diagnostic Highlights

Test	Normal Result	Abnormality With Condition	Explanation
Serum calcium: Total calcium, including free ionized calcium and calcium bound with protein or organic ions	8.4–10.2 mg/dL	<8.2 mg/dL; critical value: < 6.5 mg/dL	Deficit of calcium below normal levels in the extracellular fluid compartment; if ionized calcium cannot be measured, total serum calcium can be corrected by adding 0.8 mg/dL to the total calcium level for every 1 g/dL decrease of serum albumin below 4 g/dL; the corrected value determines whether true hypocalcemia is present. When calcium levels are reported as high or low, calculate the actual level of calcium by the following formula: Corrected total calcium (mg/dL) = (measured total calcium mg/dL) + 0.8 (4.4 measured albumin g/dL).
Serum ionized calcium: Unbound calcium; level unaffected by albumin level	4.6–5.3 mg/dL	<4.5 mg/dL; critical value: < 3.5 mg/dL	Ionized calcium is approximately 50% of circulating calcium and is the form of calcium available for enzymatic reactions and neuromuscular function; levels increase and decrease with blood pH levels; for every 0.1 pH decrease, ionized calcium increases 1.5%–2.5%
Serum PTH	10–65 mg/mL pg	Elevated in disorders other than hypoparathyroidism and magnesium deficiency	Determines presence or absence of hypoparathyroidism; determines the cause of hypocalcemia

Other Tests: Tests include electrocardiogram (prolonged ST segment and QT interval; in patients taking digitalis preparations, hypocalcemia potentiates digitalis toxicity), phosphorus (elevated in hypocalcemia resulting from most causes, although in hypocalcemia from vitamin D deficiency, it is usually low), magnesium, creatinine, and urine calcium. Note that alkalosis augments calcium binding to albumin and increases the severity of symptoms of hypocalcemia.

Primary Nursing Diagnosis ⬆ ⬇

Diagnosis

DiagnosisRisk for ineffective airway clearance as evidenced by wheezing, laryngospasm, and/or dyspnea

Outcomes

OutcomesHypocalcemia severity; Respiratory status: Airway patency; Respiratory status: Gas exchange; Respiratory status: Ventilation; Electrolyte & acid/base balance; Fluid balance

Interventions

InterventionsElectrolyte management: Hypocalcemia; Fluid management; Airway management; Airway insertion and stabilization; Airway suctioning; Anxiety reduction; Oxygen therapy; Mechanical ventilation management: Invasive or noninvasive; Respiratory monitoring

Planning and Implementation ⬆ ⬇

PLANNING AND IMPLEMENTATION

Collaborative

If the patient has an airway obstruction, endotracheal intubation and mechanical ventilation may be needed to manage laryngospasm. Hypocalcemia is treated pharmacologically. Acute hypocalcemia with tetany is a medical emergency that requires parenteral calcium supplements. Be aware of factors related to the administration of calcium replacement. A too-rapid infusion rate can lead to bradycardia and cardiac arrest; therefore, place patients who are receiving a continuous calcium infusion on a cardiac monitor and place the infusion on a controlled infusion device. The infusion rate should be adjusted to avoid recurrent symptomatic hypocalcemia and to maintain serum calcium levels between 8 and 9 mg/dL. Monitor the patient's serum calcium levels every 12 to 24 hours and immediately report a calcium deficit less than 8.5 mg/dL. When giving calcium supplements, frequently check pH levels because an alkaline state (pH < 7.45) inhibits calcium ionization and decreases the free calcium available for physiological reactions.

Chronic hypocalcemia can be treated in part by a high dietary intake of calcium. If the deficiency is caused by hypoparathyroidism, however, teach the patient to avoid foods high in phosphate. Vitamin D supplements are prescribed to facilitate gastrointestinal calcium absorption.

Pharmacologic Highlights

Medication or Drug Class	Dosage	Description	Rationale
Calcium supplements	Varies by drug	Electrolyte supplement; emergency supplementation: Calcium gluconate 2 g IV over 10 min followed by an infusion of 6 g in 500 mL D5W over 4–6 hr; oral calcium gluconate, calcium lactate, or calcium chloride; asymptomatic hypocalcemia can be alleviated with oral calcium citrate, acetate, or carbonate and vitamin D supplementation	Correct deficiency
Magnesium sulfate	1 g in 50 mL over 1 hr IV	Electrolyte supplement	Corrects magnesium deficiency; magnesium deficiency needs to be corrected in order to correct calcium deficiency; magnesium is needed to transport calcium across cell membrane

Independent

Monitor calcium supplements carefully. If calcium is given intravenously, the patient should have continuous cardiac monitoring attached and have calcium supplements on an infusion device to regulate dosage. If the patient has an altered mental status, institute the appropriate safety measures. Provide a quiet, stress-free environment for patients with tetany. Institute seizure precautions for patients with severe hypocalcemia. If tetany is a possibility, maintain an oral or a nasal airway and intubation equipment at the bedside. Initiate patient teaching to prevent future episodes of hypocalcemia.

Evidence-Based Practice and Health Policy

Lapointe, A., Moreau, N., Simonyan, D., Rousseau, F., Mallette, V., Préfontaine-Racine, F., Paquette, C., Mallet, M., St-Pierre, A., & Berthelot, S. (2021). Identification of predictors of abnormal calcium, magnesium and phosphorus blood levels in the emergency department: A retrospective cohort study. Open Access Emergency Medicine, 13, 13–21.

Because rising healthcare costs require judicious use of diagnostic tests, the authors sought to determine risk factors that could predict abnormal calcium, magnesium, and phosphorus serum levels, as well as to identify patients who may need corrective interventions. They conducted a retrospective cohort study evaluating variables in 1,008 cases with serum calcium and/or magnesium and/or phosphorus levels drawn in the emergency department.
The most significant risk factors for a hypocalcemia electrolytic abnormality were as follows: respiratory distress, diuretics (excluding loop and thiazide), antineoplastic medication, long QTc (cardiac dysrhythmia), and chronic kidney disease. Predictors of patients who needed an intervention included poor peripheral perfusion, nausea, and chronic obstructive pulmonary disease. Emergency physicians can possibly reduce unnecessary testing of calcium, magnesium, and phosphorus blood levels by targeting patients with high-acuity conditions or chronic comorbidities such as renal and pulmonary disease.

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DRG Information ⬇

Introduction ⬆ ⬇