A 45-year-old woman with cirrhosis due to autoimmune hepatitis comes to her hepatologist for routine follow-up. She has been feeling well and complains only of mild fatigue. Her medical history is otherwise unremarkable. Her medications include lactulose, spironolactone, propranolol, and furosemide. Vital signs are within normal limits. The remainder of her physical examination is consistent with compensated cirrhosis. Laboratory results are as follows: Which of the following is the most appropriate next step in managing this patient's low serum calcium?

Question

A 45-year-old woman with cirrhosis due to autoimmune hepatitis comes to her hepatologist for routine follow-up.  She has been feeling well and complains only of mild fatigue.  Her medical history is otherwise unremarkable.  Her medications include lactulose, spironolactone, propranolol, and furosemide.  Vital signs are within normal limits.  The remainder of her physical examination is consistent with compensated cirrhosis.  Laboratory results are as follows:  Which of the following is the most appropriate next step in managing this patient's low serum calcium?

Quizplus · Accepted Answer

Explanation: Calcium homeostasis involves blood transport as albumin-bound calcium (45%), ionized calcium (40%), or calcium bound to inorganic and organic anions (15%). Patients with hypoalbuminemia can have decreased total plasma calcium. However, the ionized serum calcium (physiologically active form) is hormonally regulated and remains stable. As a result, these patients may be asymptomatic as the measured total plasma calcium does not correlate with the physiologically active calcium. The serum calcium concentration decreases by 0.8 mg/dL for every 1 g/dL decrease in the serum albumin concentration. The corrected serum calcium level is calculated with the formula below (normal albumin is 4.0 g/dL): Corrected calcium in mg/dL = (measured total calcium) + 0.8 (4.0 g/dL - measured serum albumin in g/dL). This patient's corrected serum calcium is 8.7 mg/dL (7.5 mg/dL + 0.8 [4.0 - 2.5]). Because the normal calcium ranges from 8.5-10.5 mg/dL, this patient requires no further intervention. The corrected calcium is usually accurate in most patients. However, direct measurement of ionized calcium is usually more accurate in patients with acid base disorders (acidosis increases ionized calcium, alkalosis decreases ionized calcium), primary hyperparathyroidism, chronic kidney disease, and multiple myeloma (elevated proteins can increase corrected calcium). (Choice A) Intravenous calcium gluconate is used to treat acutely symptomatic hypocalcemia (eg, oral paresthesias, carpopedal spasm, tetany, seizures). However, this patient is asymptomatic with normal corrected calcium. (Choices B and C) Measuring serum parathyroid hormone level is usually required in patients with true hypocalcemia to evaluate for hypoparathyroidism. Similarly, vitamin D deficiency can also cause hypocalcemia, metabolic bone disease (eg, osteomalacia), and myalgias. However, this asymptomatic patient's normal corrected serum calcium makes these etiologies less likely. (Choice E) Oral calcium citrate or carbonate is indicated for patients with mild acute hypocalcemia (corrected calcium of 7.5-8.5 mg/dL) or chronic hypocalcemia. However, this patient's normal corrected calcium does not require therapy. Educational objective: Calcium homeostasis involves blood transport as albumin-bound calcium (45%), ionized calcium (40%), or calcium bound to inorganic and organic anions (15%). The serum calcium concentration decreases by 0.8 mg/dL for every 1 g/dL decrease in serum albumin concentration. References: Electrolyte quintet: Calcium. (http://www.ncbi.nlm.nih.gov/pubmed/9690425) Interpretation of serum calcium in patients with abnormal serum proteins. (http://www.ncbi.nlm.nih.gov/pubmed/4758544)

A 45-Year-Old Woman with Cirrhosis Due to Autoimmune Hepatitis Comes