Magnesium (Mg, Mg++) is an essential nutrient found in bone and muscle. In the blood, magnesium is most abundant in the red blood cells, with relatively little found in the serum. Magnesium functions in (1) control of sodium, potassium, calcium, and phosphorus; (2) utilization of carbohydrates, lipids, and proteins; and (3) activation of enzyme systems that enable B vitamins to function. Magnesium also increases intestinal absorption of calcium and is required for bone and cartilage formation. It is essential for oxidative phosphorylation, nucleic acid synthesis, and blood clotting.
Magnesium is so abundant in foods that dietary deficiency is rare. Decreased serum magnesium levels are seen, however, in chronic alcoholism. Elevated levels most commonly occur in renal failure. A variety of other disorders and drugs also are associated with altered magnesium levels (Table 5-29). Altered magnesium levels are associated with cardiac dysrhythmias, especially decreased levels, which may lead to excessive ventricular irritability.
| Conventional Units | SI Units | |
|---|---|---|
| Newborns | 1.4-2.9 mEq/L | 0.58-1.19 mmol/L |
| Children | 1.6-2.6 mEq/L | 0.65-1.07 mmol/L |
| Adults | 1.5-2.5 mEq/L | 0.61-1.03 mmol/L |
| 1.8-3.0 mg/dL | 0.74-1.23 mmol/L | |
| Critical values | <1 mg/dL or >4.9 mg/dL | <0.41 or >2.02 mmol/L |
Nursing Care Before the Procedure
Client preparation is the same as that for any study involving the collection of a peripheral blood sample (see Appendix I).
A venipuncture is performed and the sample collected in a red-topped tube. The sample should be handled gently to avoid hemolysis, which may falsely elevate levels, and transported promptly to the laboratory.
Nursing Care After the Procedure
Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.