Q: When is IV calcium contraindicated in symptomatic hypocalcemia?

Answer: Hypocalcaemia induced by severe life-threatening hyperphosphatemia

Essential to the treatment of phosphate toxicity is increasing urinary excretion. In patients with normal renal function, expansion of the extracellular space with saline have shown to increase renal phosphate excretion. Therefore, aggressive hydration is the mainstay of treatment, guided by urine output. Dialysis is usually not required but should be considered given the clinical situation, as hemodialysis can clear phosphate at a significantly higher rate than that achieved by normal kidneys.

IV calcium infusion in hypocalcemia from severe hyperphosphatemia can be dangerous because of the possibility of metastatic calcifications when the calcium-phosphate concentration product is >70 mg2/dL2.

References:

1. Orias M, Mahnensmith RL, Perazella M. Extreme hyperphosphatemia and acute renal failure after a phosphorus-containing bowel regimen. Am J Nephrol.1999;19 :60– 63

2. Sutters M, Gaboury CL, Bennett WM. Severe hyperphosphatemia and hypocalcemia: a dilemma in patient management. J Am Soc Nephrol.1996;7 :2056– 2061

3. Knobel B, Petchenko P. Hyperphosphatemic hypocalcemic coma caused by hypertonic sodium phosphate (Fleet) enema intoxication. J Clin Gastroenterol.1996;23 :217– 219

4. Feig PU, Hirszel P, Galen MA, Rosenworcel E, Raisz LG. Hemodialysis in the treatment of life-threatening hyperphosphatemia. Clin Exp Dial Apheresis.1982;6 :105– 111