Some mention of disorders of calcium metabolism is relevant as both hyper- and hypocalcaemia can produce profound clinical pictures.
Hypocalcaemia can be a part of any severe illness, particularly septicaemia. Other specific conditions that may give rise to hypocalcaemia are severe rickets, hypoparathyroidism, pancreatitis, or rhabdomyolysis, and citrate infusion (in massive blood transfusions). Acute and chronic renal failure can also present with severe hypocalcaemia. In all cases hypocalcaemia can produce weakness, tetany, convulsions, hypotension, and arrhythmias. Treatment is that of the underlying condition. In the emergency situation, however, intravenous calcium can be administered. As most of the above conditions are associated with a total body depletion of calcium and as the total body pool is so large, acute doses will often only have a transient effect on the serum calcium. Continuous infusions will also often be required, and must be given through a central venous line as calcium is so irritant in peripheral veins. In renal failure, high serum phosphate levels may prevent the serum calcium from rising. The use of oral phosphate binders or dialysis may be necessary in these circumstances.
Hypercalcaemia usually presents as long-standing anorexia, malaise, weight loss, failure to thrive and vomiting. Causes include hyperparathyroidism, hypervitaminosis D or A, idiopathic hypercalcaemia of infancy, malignancy, thiazide diuretic abuse and skeletal disorders. Initial treatment is with volume expansion with normal saline. Following this, investigation and specific treatment are indicated.
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