hypocalcemia after thyroidectomy

Although this patient has mild persistent asthma, he also recently had thyroidectomy, placing him at risk for hypocalcemia from hypoparathyroidism. Even without inadvertent parathyroid gland removal, transient hypoparathyroidism occurs in 10% of patients who undergo total thyroidectomy. Hypoparathyroidism results in hypocalcemia because, without parathyroid hormone, the body cannot mobilize calcium from bone or reabsorb calcium from the distal nephron. Hypocalcemia usually occurs in the first few days after surgery and can be asymptomatic. Although this patient could be having an exacerbation of his asthma, he does not have severe asthma at baseline and is not responding to aggressive treatments for asthma exacerbation. When other etiologies for respiratory distress were considered, serum total calcium was 4.5 (8.4-10.5) mg/dL (1.13 [2.10-2.63] mmol/L) and ionized calcium was 2.1 (4.5-5.3) mg/dL (0.53 [1.13-1.32] mmol/L). Hypocalcemia causes paresthesias, especially around the mouth and in the hands and feet, and can produce muscle cramps and spasms, or tetany. More serious effects include seizures, cardiac arrhythmias, laryngospasm, and bronchospasm, which may reflect tetany of the bronchial smooth muscle. Although hypocalcemia is a rare cause of refractory bronchospasm, it is the likely etiology in this patient. Severe hypocalcemia should be corrected rapidly, so a bolus of calcium chloride should be administered over 5 to 10 min, then followed by a continuous calcium infusion while monitoring levels. This patient was given IV calcium and within 30 min his wheezing, stridor, and respiratory distress had resolved.

Some patients who present with severe, refractory asthma exacerbations need mechanical ventilation; however, reversible causes of bronchospasm and stridor should be treated prior to intubation when able. The correction of hypocalcemia improved this patient’s condition rapidly and he did not need to be intubated.

Magnesium has mild bronchodilatory properties and is often used in exacerbations of asthma or COPD. However, the benefit is small, on the order of a 10% improvement in peak flows, and randomized trials have failed to show significant improvements in outcomes when it is added to acute asthma treatment regimens. It is unlikely to significantly improve the bronchoconstriction in this patient.

While corticosteroids help reduce inflammation and are clearly beneficial in patients with acute asthma exacerbations, the dose he received is adequate. Repeat or higher dosing is not needed at this time.1234

Footnotes

  1. SEEK Questionnaires ↩

  2. Goodacre S, Cohen J, Bradburn M, et al; 3Mg Research Team. Intravenous or nebulised magnesium sulphate versus standard therapy for severe acute asthma (3Mg trial): a double-blind, randomised controlled trial. Lancet Respir Med. 2013;1(4):293-300. PubMed ↩

  3. Joosen DA, van de Laar RJ, Koopmans RP, et al. Acute dyspnea caused by hypocalcemia-related laryngospasm. J Emerg Med. 2015;48(1):29-30. PubMed ↩

  4. Khan MI, Waguespack SG, Hu MI. Medical management of postsurgical hypoparathyroidism. Endocr Pract. 2011;17(suppl 1):18-25. PubMed ↩