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Sodium | Potassium | Chloride | Magnesium | Phosphorus | Serum CO2

Normal levels:                               

Calcium - albumin relationship

Since 1/2 of the calcium is bound to albumin, when the albumin level is low, the serum calcium level is also low. Total serum calcium decreases by about 0.8 mg for every 1 gram decrease in albumin. Serum albumin needs to be measured every time calcium is measured. Then a determination can be made if the calcium is elevated or decreased due to the albumin level.

Ionized (free) calcium is unaffected by changes in albumin.

Calcium and phosphorus

An inverse relationship exists between calcium and phosphorus in the body. Serum calcium levels are controlled by calcitonin, parathormone, and vitamin D. Phosphorus levels are controlled by intake and renal function. People take in large amounts of phosphorus daily. Diets to increase calcium need to decrease phosphorus. Try for a 1:1 ratio.

In renal failure, the kidneys do not excrete phosphorus, leading to hyperphosphatemia and hypocalcemia. The hypocalcemia causes bone demineralization. Serum calcium is increased at the expense of the bones. The mobilized calcium and high phosphorus levels results in soft tissue calcification. Phosphorus binding antacids are given with meals to help balance phosphorus and calcium.

Other problems in renal failure is lack of activation of vitamin D. This also decreases calcium absorption.

Hypocalcemia

Signs and symptoms:

• Nervousness
• Excitability, irritability
• Tetany, cramps
• Decreased cardiac output
• Bleeding
• Fractures
• Seizures
• Laryngospasm
• Confusion
• Dry skin, brittle nails

Causes:  the most common cause is hypoalbuminemia

• Hypoalbuminemia: Malnutrition - alcoholics; large volume IV infusions
• Large volume banked blood transfusions - citrate in banked blood binds with calcium
• Intesinal malabsorption
• Renal failure - vitamin D not activated, hyperphosphatemia
• Rhabdomylosis
• Alkalosis - high pH causes calcium to move intracellularly
• Acute pancreatitis
• Hypomagnesemia - cause refractory hypocalcemia
• Burns
• Hypoparathyroidism
• Osteomalacia
• Drugs: acetazolamide, anticonvulsants, asparaginase, aspirin, calcitonin, cisplatin, corticosteroids, heparin, laxatives, loop diuretics, magnesium salts, thiazide diuretics, estrogens, albuterol and oral contraceptives.

Treatment: Replacement by diet, po supplements, IV supplements

Hypercalcemia

The most common cause of hypercalcemia is hyperparathyroidism. Parathormone increases calcium levels by increasing GI absorption, decreasing urinary excretion and increasing bone absorption. Malignancy is the second cause of hypercalcemia and works in two ways:
Tumor metastasis to the bone can destroy bone , causing reabsorption.
The cancer can produce a parathormone-like substance.

If albumin is low and serum calcium is normal - suspect hypercalcemia.

Signs and symptoms:

• anorexia
• nausea and vomiting
• abdominal and bone pain
• thirst
• somnolence, lethargy
• muscle weakness, flaccidity
• confusion
• heart blocks
• coma

Causes:

• Parathyroid hyperplasia: primary, secondary
• Some cancers
• Excess vitamin D ingestion - increased renal and GI absorption
• Sarcoidosis
• Tuberculosis
• Immobilization
• Hypophosphatemia
• Hyperthyroidism
• Adrenal insufficiency
• Paget's disease
• Milk-alkali syndrome
• Lymphoma
• Acromegaly
• Drugs: calcium salts, hydralazine, lithium, thiazide diuretics, PTH, thyroid hormone, alkaline antacids, ergocalciferol, adnrogens and vitamin D.

Treatment:

Careful handling of extremities to prevent pathological fractures
Hydration and diuretics to excrete via urine. Fluids up to 4 liters per day.
Early mobilization
Calcitonin
Oral or IV phosphorus - Calcium and phosphorus are inversely related