Magnesium phosphate functionalities

The special nature of H is discussed below in the section about acid-base physiology. The special functions of calcium, magnesium, phosphates, amino acids, iron, and the trace elements are considered separately in Chapters 20 and 30. 

Bone is a porous tissue composite material containing a fluid phase, a calcified bone mineral, hydroxyapatite (HA), and organic components (mainly, collagen type). The variety of cellular and noncellular components consist of approximately 69% organic and 22% inorganic material and 9% water. The principal constiments of bone tissue are calcium (Ca ), phosphate (PO ), and hydroxyl (OH ) ions and calcium carbonate. There are smaller quantities of sodium, magnesium, and fluoride. The major compound, HA, has the formula Caio(P04)g(OH)2 in its unit cell. The porosity of bone includes membrane-lined capillary blood vessels, which function to transport nutrients and ions in bone, canaliculi, and the lacunae occupied in vivo by bone cells (osteoblasts), and the micropores present in the matrix. 

Saline laxatives containing magnesium, potassium, or phosphates should be used cautiously in persons with reduced kidney function. Monitor appropriate serum electrolyte concentrations in patients with unstable renal function evidenced by changing serum creatinine or creatinine clearance. 

Electrolytes that are included routinely in PN admixtures include sodium, potassium, phosphorus (as phosphate), calcium, magnesium, chloride, and acetate. When determining electrolytes in PN admixtures, the patient s renal function always must be taken into account. Typical daily electrolyte maintenance requirements for adults with normal renal function are listed in Table 97-3. 

Renal function impairment Up to 20% of the magnesium in magnesium salts may be absorbed. Do not use products containing phosphate, sodium, magnesium, or potassium salts in the presence of renal dysfunction. 

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