HyperPhosphatemia



- Diff Dx:
    - Renal Failure
    - Secondary Hyperparathyroidism
    - Hypoparathyroidism (surgical, psuedo)
    - Immobilization
    - Addison's dz
    - Bone dz (Healing frx)
    - Factitious increase (hemolysis of specimen)
    - Vit D toxicity
    - Tumoral Calcinosis

- Discussion:
    - Adult nl value: 2.3-4.7 mg/dL; Child 4.0-7.0 mg/dL;
    - w/ concomitant hypercalcemia:
         - if serum phosphate concentration is markedly elevated in severe hypocalcemia, correction of hyperphosphatemia must be carried out with IV glucose and insulin before calcium is given in order to avoid metastatic calcification;
         - renal failure with hypocalcemia and hyperphosphatemia:

- Management:
    - when serum phospate concentration > 6 mg/dl, Mg free phospate binding antacids should be prescribed with meals to minimized elevations in calcium phospate product and attenuate soft tissue depositon of calcium-phospate crystals;
    - ionized Calcium in acute renal failure is usually near normal, owing to acidosis, uremic state, and hypoalbuminemia;
           - infusion of calcium is therefore unnecessary unless carpopedal spasm or tetany develops;
    - in other pts, the major clinical findings in hyperphosphatemia include hypocalcemia and ectopic calcification, both due to formation of calcium phosphate complexes;
    - pts w/ diabetic ketoacidosis commonly have hyperphophatemia at time of presentation despite total body Pi depletion;
         - insulin, fluid, and acid base therapy is accompanied by shift of Pi back into cells and development of hypophosphatemia;

- Tumor Lysis
    - massive tumor lysis results from release of intracellular phosphate during massive cell destruction;
    - commonly occurs during chemo for ALL in children;
    - serum Pi levels typically rise w/in 1-2 days after initiating treatment;
    - rising serum Pi concentration often is accompanied by hypocalcemia, hyperuricemia, hyperkalemia, and renal failure



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Wednesday, September 5, 2012 8:25 pm