Hypocalcemia
Adult-Gerontology Acute Care Practice Guidelines
Definition
A.Total serum calcium less than 8.6 mg/dL or ionized calcium less than 1.1 mmol/L (see Box 5.2).
Incidence
A.The incidence of hypocalcemia is difficult to quantify.
B.In intensive care patients, hypocalcemia is estimated between 15% and 88% of all patients.
Pathogenesis
A.Calcium is necessary for bone mineralization, nerve conduction, muscle relaxation, and cardiac conduction.
Predisposing Factors
A.Renal failure.
B.Advancing age.
C.Volume depletion.
D.Hepatic insufficiency.
E.Chronic heart failure.
Subjective Data
A.Common complaints/symptoms.
1.Most specific symptoms are perioral numbness and spasms of upper and lower extremities.
2.Severe hypocalcemia can lead to tetany and seizures.
3.Other neuromuscular, central nervous system (CNS), and cardiovascular symptoms may be present, even with mild to moderate hypocalcemia.
a.Prolonged QT interval.
b.Paresthesia.
4.Chronic hypocalcemia may present with skin manifestations such as brittle and grooved nails, hair loss, dermatitis, and eczema.
Physical Examination
A.Cardiac examination.
B.Neurological examination (reflexes).
C.Possible bleeding.
D.Chvostek’s sign or Trousseau’s sign: Increased neuromuscular activity can be demonstrated by tapping over the facial nerve.
Diagnostic Tests
A.Total and ionized serum calcium.
B.Serum phosphorus.
C.Serum magnesium.
D.25-hydroxyvitamin D.
E.Intact parathyroid hormone (PTH).
Differential Diagnosis
A.Hypoparathyroidism.
B.Pseudohypoparathyroidism (low calcium with low phosphorus also known as iPTH resistance).
C.Hypomagnesemia.
D.Vitamin D deficiency.
1.Poor intestinal absorption (e.g., short bowel, poor nutritional intake).
2.Lack of sun exposure.
3.Decreased activation of vitamin D (e.g., cirrhosis).
E.Tissue consumption of calcium.
1.Acute severe pancreatitis.
2.Sepsis.
3.Acute malignancies/blastic bone metastases (excess bone formation).
4.Hungry bone syndrome
post parathyroidectomy in chronic kidney disease (CKD) or end-stage renal disease (ESRD) patients with history of hyperparathyroidism.
5.Acute hyperphosphatemia (i.e., rhabdomyolysis, tumor lysis syndrome).
6.Citrate infusion (citrate binds to ionized calcium decreasing unbound, active calcium).
a.Transfusion of blood products preserved with citrate.
b.Circuit anticoagulation for dialysis/apheresis.
Evaluation and Management Plan
A.Step 1—Replace acute calcium needs.
1.Intravenous administration used when rapid correction is required.
2.Initial dose: 1 g calcium chloride or 3 g calcium gluconate.
a.Repeat dose as needed.
b.Calcium chloride contains three times more elemental calcium than calcium gluconate.
3.Caution: Intravenous calcium can cause vascular and tissue necrosis if extravasation occurs as both calcium chloride and calcium gluconate. A central intravenous line is recommended for all calcium infusions.
B.Step 2—Assess for ongoing calcium replacement needs and replace as indicated.
1.Use intravenous or oral calcium replacement.
2.Oral calcium supplements used in asymptomatic patients and patients with chronic hypocalcemia.
a.Calcium carbonate contains maximum elemental calcium compared to other formulations.
b.Typical dose is calcium carbonate 1,250 mg (equivalent to 500 mg elemental calcium) twice daily.
c.Take on empty stomach to maximize absorption of calcium.
3.Administer vitamin D to increase intestinal absorption of calcium if vitamin is deficient.
a.NOTE: Patients with renal failure need activated formulas of vitamin D replacement. Consult nephrology for assistance.
C.Step 3—Treat other electrolyte and acid–base disorders (i.e., hypomagnesemia).
Follow-Up
A.Follow-up with an outpatient provider to monitor labs would be advised.
Consultation/Referral
A.Consider consults based on the underlying cause of hypocalcemia and the severity of the condition.
Special/Geriatric Considerations
A.Severe hypocalcemia may result in seizures, tetany, refractory hypotension, or arrhythmias that require a more aggressive approach.
Bibliography
Goltzman, D. (2000, updated 2016). Approach to hypercalcemia. In K. R., Feingold, B. Anawalt, & B, A. Boyce et al (Eds.), Endotext, South Dartmouth, MA: MDText.com. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK279129/
Kraft, M. D., Btaiche, I. F., Sacks, G. S., & Kudsk, K. A. (2005, August). Treatment of electrolyte disorders in adult patients in the intensive care unit. American Journal of Health System Pharmacy, 62(16), 1663–1682. doi:10.2146/ajhp040300
Moe, S. M., & Daoud, J. R. (2014). Disorders of mineral metabolism: Calcium, phosphorous, and magnesium. In D. S. Gipson, M. A. Perazella, & M. Tonelli (Eds.), National Kidney Foundation’s primer on kidney diseases (6th ed., pp. 100–112). Philadelphia, PA: Elsevier Saunders.