Magnesium in serum

Stewart et al. (S8) estimated magnesium in serum and urine. Of four different methods of sample preparation (i.e., wet-ashing, deproteiniza-tion, simple dilution with water, and dilution with hydrochloric acid), deproteinization with trichloroacetic acid was found to be most satisfactory. No interference was seen from sodium, potassium, or phosphate, but sulfate produced depression. With protein a 6% decrease in the apparent magnesium concentration was seen. Calcium and sulfate were added to standards and samples to control sulfate depression. 

Zettner and Seligson (Z4) determined magnesium in serum, using an air-acetylene flame. A study of interferences showed that phosphate and... 

Dastych M, Jezek P, Richtrova M. Der Einfluss einer PenidUamintherapie auf die Konzentration von Zink, Kupfer, Eisen, Kalzium und Magnesium in Serum und auf deren Ausscheidung in Urin. [Effect of penicillamine therapy on the concentration of zinc, copper, iron, calcium and magnesium in the serum and their excretion in urine.] Z Gastroenterol 1986 24(3) 157-60. 

E400 Toffaletti, J. and Abrams, B. (1987). Analysis of magnesium in serum and urine by the Kodak Ektachem analyzer. Clin. Chem. 33, 1006-1007, Abstr. 618. 

E494 Toffaletti, J., Abrams, B., Bird, C. and Schwing, M. (1988). Clinical validation of an automated thin-film reflectance method for measurement of magnesium in serum and urine. Magnesium 7,84-90. 

Fujita T, Kawakami Y, Kohda S> Takata S> Sunahara Y, Arisue K. Assay of magnesium in serum and urine with use of only one enzyme, isocitrate dehydrogenase CNADP+). Clin Chem 1995 41 1302-5. 

Liedtke RJ, Kroon G. Automated calmagite complexi-metric measurement of magnesium in serum, with sequential addition of EDTA to eliminate endogenous interference. Clin Chem 1984 30 1801-4. 

Savory J, Margrey KS, Shipe JR Jr, Savory MG, Margrey MH, Mifflin TE, et al. Stabilization of cal-magite reagent for automated measurement of magnesium in serum and urine, Clin Chem 1985 31 487-8. 

Tabata M, Kido T, Totani M, Murachi T. Direct spectrophotometry of magnesium in serum after reaction... 

Tsang WM, Howell Mf Miller AL. A simple enzymic method for the measurement of magnesium in serum and urine on a centrifugal analyzer. Ann Chn Biochem 1988 25 162-8. 

J.M. Fernandez-Romero, M.D. Luque de Castro, M. Valcarcel, R. Quiles-Zafra, Spec-trophotometric determination of magnesium in serum by using a flow-injection system with an immobilized enzyme reactor, Anal. Chim. Acta 283 (1993) 447. 

Thienpont LM, Van Nuwenboeg JE, Reinauee H and Stockl D (1996) Validation of candidate reference methods based on ion chromatography for determination of total sodium, potassium, calcium and magnesium in serum through comparison with flame atomic emission and absorption spectrometry. Clin Biochem 29 501-508. 

T. Uchida, C. S. Wei, C. lida, and H. Wada, Simultaneous Determination of Calcium and Magnesium in Serum with Flow Injection-Atomic Absorption System [in Japanese]. Nagoya Kogyo Daisako Gakuho, 33 (1982) 97. 

B. F. Rocks, R. A. Sherwood, and C. Riley, Direct Determination of Calcium and Magnesium in Serum Using Flow Injection Analysis and Atomic Absorption Spectroscopy. Ann. din. Biochem., 21 (1984) 51. 

Magnesium concentration can be determined in physiological samples such as serum and urine by FAAS, FAES, and UV-visible spectrophotometry. Urine must be acidified (pH 1.0) by hydrochloric acid to release magnesium from salts of the sediment. Recently, potentiometry has become available for the measurement of ionized (free) magnesium in serum and blood. 

We have found that the use of serum standards for standardizing the instrument in the laboratory is useful. However, the serum standards cannot be used for urines. In urines, one runs into other problems and needs to use aqueous standards. Therefore, at present, while atomic absorption is the instrument of choice, there is much to be desired for the determination of calcium and magnesium in the routine laboratory of clinical chemistry. 

Check parathyroid hormone (PTH), vitamin D and precursors, magnesium, and phosphate levels ° Pharmacological causes of decreased ionized calcium may include excess infusions of citrate, EDTA, lactate, fluoride poisoning, foscarnet, cinacalcet, bisphosphates, or unrelated increase in serum phosphate or decrease in serum magnesium levels... 

Because disturbances in fluid balance are routinely encountered in clinical medicine, it is essential to have a thorough understanding of body fluid compartments and the therapeutic use of fluids. Similarly, disturbances in serum sodium, potassium, calcium, phosphorus, and magnesium are ubiquitous and must be mastered by all clinicians. Dysregulation of fluid and/or electrolyte status has serious implications regarding the concepts of drug absorption, volumes of distribution, and toxicity. Similarly, many medications can disrupt fluid and/or electrolyte balance as an unintended consequence. 

Several recent determinations of the alkali and alkaline earth metals in serum or urine have been reported. Barrett 29) determined potassium, sodium, and calcium in semm by diluting the samples with lanthanum chloride solution. Suttle and Field 3°) used atomic absorption spectroscopy to determine potassium and magnesium in sheep plasma. 

Other Systemic Effects. Dalin and Kristoffersson (1974) reported elevated serum concentrations of potassium and magnesium in rats exposed to 26 ppm phenol vapor continuously for 15 days. While not necessarily adverse, this effect may be related to the muscle tremors and neurological effects observed following inhalation exposure to phenol (see Section 2.2.1.4). 

Many of the adverse effects of lithium can be ascribed to the action of lithium on adenylate cyclase, the key enz)nne that links many hormones and neurotransmitters with their intracellular actions. Thus antidiuretic hormone and thyroid-stimulating-hormone-sensitive adenylate cyclases are inhibited by therapeutic concentrations of the drug, which frequently leads to enhanced diuresis, h)rpoth)n oidism and even goitre. Aldosterone synthesis is increased following chronic lithium treatment and is probably a secondary consequence of the enhanced diuresis caused by the inhibition of antidiuretic-hormone-sensitive adenylate cyclase in the kidney. There is also evidence that chronic lithium treatment causes an increase in serum parathyroid hormone levels and, with this, a rise in calcium and magnesium concentrations. A decrease in plasma phosphate and in bone mineralization can also be attributed to the effects of the drug on parathyroid activity. Whether these changes are of any clinical consequence is unclear. 

Plasma volume and the extracellular fluid space have been observed to constrict 30% during reducing diets (300-600 calories per day) (B22). These changes can be accompanied by functional impairment of glomerular filtration and hepatic perfusion with transient increases up to 2 mg/100 ml in serum creatinine and BSP retention up to 40% (B22). In rare instances a significant fall in serum calcium, magnesium, or potassium was observed. Hyperuricemia was also observed, with concentrations as high as 9 mg/100 ml (B22). 

Elderly Geriatric patients often require reduced dosage because of impaired renal function. In patients with severe impairment, dosage should not exceed 20 g in 48 hours. Monitor serum magnesium in such patients. 

L A. Nephrotoxicity is the most common and most serious toxicity associated with amphotericin B administration. This is manifested by azotemia (elevated serum blood urea nitrogen and creatinine), and by renal tubular acidosis, which results in the wasting of potassium and magnesium in the urine (leading to hypokalemia and hypomagnesemia, requiring oral or intravenous replacement therapy). Normochromic normocytic anemia is also seen with long-term amphotericin B administration. Elevation of hver enzymes is not associated with the use of amphotericin B. 

Magnesium speciation (Section ni.A) in serum was carried out using an anion exchange column for protein separation, with mobile phase at pH 7.4 the effluent was collected in an automatic fraction collector. On-line quantitation of the protein fractions was carried out by DA-UVD, and Mg determination was carried out from the automatic sampler in a GFAAS apparatus, measuring at 202.8 nm . ... 

---