RT Book, Section A1 Smith, Silas W. A1 Ann Howland, Mary A2 Nelson, Lewis S. A2 Howland, Mary Ann A2 Lewin, Neal A. A2 Smith, Silas W. A2 Goldfrank, Lewis R. A2 Hoffman, Robert S. SR Print(0) ID 1163003336 T1 Calcium T2 Goldfrank's Toxicologic Emergencies, 11e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9781259859618 LK accessemergencymedicine.mhmedical.com/content.aspx?aid=1163003336 RD 2024/03/29 AB Calcium is a divalent cation that is essential to maintain the normal function of the heart, vascular smooth muscle, the skeletal system, the nervous system, and intracellular signaling. It is vital in enzymatic reactions, neurohormonal transmission, blood coagulation, and the maintenance of cellular integrity.12 The endocrine system maintains calcium homeostasis. Hypercalcemia raises the threshold for nerve and muscle excitation, resulting in muscle weakness, lethargy, cardiac conduction disturbances, and coma. Hypocalcemia can result in hyperreflexia, muscle spasms, tetany, seizures, and QT interval prolongation (Chaps. 12 and 15).12