HYPERCALCAEMIA

    DEFINITION

    Abnormally high concentration of calcium in the blood (serum calcium
    > 2.58 mmol/L or > 10.3 mg/dL). 

    The ionized calcium is a more accurate reflection of calcium status,
    especially in patients with low serum albumin. The normal ionized
    calcium is 1.12 to 1.23 mmol/L (4.48 to 4.92 mg/dL). 

    TOXIC CAUSES

    Hypercalcaemia is observed most often in chronic intoxications and is
    a consequence of one or more of the following mechanisms:

         Increased bone resorption of calcium
         Increased intestinal resorption of calcium
         Impaired renal excretion of calcium

    Most frequent causes:

         Vitamin D overdose
         Milkalkali syndrome (Burnett syndrome)
         Calcium salts intoxication

    Occasional causes:

         Theophylline 
         Thiazide diuretics

    NON-TOXIC CAUSES

    Hyperparathyroidism
    Some neoplasms and bone metastases

    CLINICAL FEATURES

    Mild hypercalcaemia may be asymptomatic. Moderate to severe toxicity
    may cause constipation, anorexia, abdominal cramps, nausea, vomiting,
    polyuria, polydipsia, dehydration, delirium, stupor, psychotic states,
    asthenia, muscular weakness, shortening of QT interval on the ECG, and
    cardiac arrest.  Acute renal failure may result from calcium
    deposition in the kidney.

    RELEVANT INVESTIGATIONS

    Total serum calcium and ionized serum calcium 
    Other serum electrolyte concentrations including magnesium, phosphate,
      sodium, and potassium 
    Renal function (creatinine, urea)
    Electrocardiograph (QT interval)

    DIFERENTIAL DIAGNOSIS

    Other causes of coma and metabolic encephalopathy
    Polyuria and dehydration from diabetes insipidus or diabetes mellitus

    TREATMENT

    Cease administration of, or exposure to, the causative agent.

    Correct dehydration by administering intravenous fluids.  To promote
    calcium excretion, administer intravenous  normal saline (3 to 4
    L/day in adults).   Furosemide (20 to 80 mg IV in adults) may be
    given following correction of hypovolaemia. Monitor urine output and
    match renal losses with additional intravenous fluids.

     Corticosteroids: Prednisone (1 mg/kg orally) or  hydrocortisone 
    (300 mg intravenously) is recommended for patients with hypercalcaemia
    caused by Vitamin D overdose.

     Calcitonin (5 to 10 units/kg IM every 8 hours) promotes calcium
    uptake in bone, and is mainly used in patients with severe
    hyperparathyroidism.

    Haemodialysis may be indicated if renal failure develops.

    CLINICAL COURSE & MONITORING

    Urine output and fluid and electrolyte balance
    Serum calcium and ionized calcium concentration
    Renal function
    Electrocardiogram (QT interval)

    LONG-TERM COMPLICATIONS

    Hypercalcaemia by itself may cause nephrocalcinosis and/or renal
    insufficiency

    AUTHOR/REVIEWERS

    Author:             Dr V. Danel, Unité de Toxicologie Clinique,
                        Grenoble, France.

    Peer Reviewers:     Cardiff 9/96: V. Afanasiev, M. Burger, T. Della
                        Puppa, L. Fruchtengarten, K. Olsen, J. Szajewski.