Chemistry: analytical and immunological testing – Metal or metal containing – Li – na – k – rb – cs – fr – be – mg – ca – sr – ba – ra
Patent
1992-11-05
1995-03-14
Redding, David A.
Chemistry: analytical and immunological testing
Metal or metal containing
Li, na, k, rb, cs, fr, be, mg, ca, sr, ba, ra
427 213, 436164, 436169, 436171, 436176, 422 56, G01N 3352
Patent
active
053977106
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the preparation of a testing methodology utilizing a chemical reaction for the colorimetric measurement of magnesium in biological fluids, such as blood or urine. More particularly, it relates to a stabilized complexometric reaction in alkaline buffer that determines magnesium concentration by color change in a dry chemistry strip format amenable to performance at the bedside or in the office.
The body of an adult contains 20-30 grams of magnesium, of which 5% is in the extracellular fluids such as blood plasma. Magnesium, compared to other cations, ranks fourth in plasma quantity after sodium, potassium and calcium. Magnesium influences the stability and osmotic equilibrium of cell membranes. This bivalent metal also activates several enzymes concerned with energy transfer. In particular, it is involved with the correct functioning of Na+/K+ ATPase of the neuron membrane and thereby has a protecting function against spontaneous depolarization and neuronal excitability, especially at the neuro-muscular junction.
Magnesium in pharmacological doses has a curariform action on the neuro-muscular junction. Magnesium sulfate has been used for a number of years in obstetrical practice in two clinical situations. First, it is the drug of choice to prevent seizures in preeclampsia. Second, in premature labor or uterine hyperstimulation, magnesium is used for tocolysis. The biggest problem is that the therapeutic serum level is close to the toxic level. The normal range for magnesium in serum is 1.3-2.1 meq/L. The ideal therapeutic level in treating preeclampsia is 6-8 meq/L. However, deep tendon reflexes become hypoactive at 8-10 meq/L and respiratory paralysis develops at 13-15 meq/L.
Most clinicians monitor the patient using reflexes, respiration, and urine output as parameters. Deep tendon reflexes and respirations need to be monitored hourly, and urine output should exceed 100 ml every 4 hours. A more meaningful standard of care would be achieved if the actual serum magnesium level could be determined rapidly and directly. However, the methods now available are not practical for the usual clinical setting since they require timely transport of blood specimens to a central laboratory, careful manipulation of the specimen and execution of the methodology, and report of results back to the delivery suite, all of which may take hours to complete. These results commonly become available long after their clinical pertinence has ceased.
Thus, the instant invention represents an important advance in the treatment of two major therapeutic problems in obstetrics, namely, preeclampsia (toxemia) and premature labor. In these situations magnesium sulfate is the drug of choice. However, because of its toxic potential, this agent needs to be monitored closely and frequently. Heretofore, in the absence of a convenient method for expeditiously testing patients at the bedside, no means have been available to fine tune, on an ongoing basis, the management of conditions which change quickly and frequently. Indirect testing created the possibility of undertreatment or overtreatment, both of which had serious, undesirable consequences. On the other hand, the instant invention now permits the frequent, rapid testing of the blood magnesium level where it is most immediately needed, under the control of the obstetrician at the bedside.
Other than atomic emission spectroscopy, the usual methods now used for determining magnesium in biological specimens involve chelatometry. The original technique involved titration with chelating agents and pH electrodes. This was improved by the advent of the colored indicator methods of Schwarzenbach in 1948 (Helv. Chim. Acta, 31:678), whereby dyes bearing chelatable dihydroxy functions were included. Such dyes either marked the end point of the titration or were in fact the bidentate complexometric agents acting to bind all of the bivalent cations present in the test specimen, thus allowing a direct photometric determination.
As noted above, the methods for serum magn
REFERENCES:
patent: 3798000 (1974-03-01), Helger
patent: 4215995 (1980-08-01), Turk et al.
patent: 4303610 (1981-12-01), Sardisco et al.
patent: 4386053 (1983-05-01), Motobayashi
patent: 4425427 (1984-01-01), Luderer
patent: 4753890 (1988-06-01), Smith-Lewis et al.
patent: 4966784 (1990-10-01), Tanaka et al.
patent: 5089420 (1992-02-01), Albarella et al.
patent: 5215922 (1993-01-01), Artiss et al.
Schwarzenbach et al., "Komplexone X. Erdalkalikomplexe von o,o'Dioxyzofarbstoffen," Helvetica Chemica ACTA, vol. XXXI, Ed. III (1948).
"Spectrophotometric Determination of Small Amounts of Magnesium and Calcium Employing Calmagite," F. Ingman and A. Ringbom, Microchemical Journal, 10, 545-553 (1966).
Kodak Clinical Products brochure "Kodak Ektachem DT Slides" released Aug., 1991.
"Dry Reagent Chemistries," B. Walter, Analytical Chemistry, 1983, 55, 498A.
David Diagnostics, Inc.
Redding David A.
LandOfFree
Process for measuring magnesium in biological fluids does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for measuring magnesium in biological fluids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for measuring magnesium in biological fluids will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-713303