W. R. Külpmann

Bio: W. R. Külpmann is an academic researcher from Hochschule Hannover. The author has contributed to research in topics: Magnesium & Molality. The author has an hindex of 5, co-authored 7 publications receiving 55 citations.

Ionised and Total Magnesium Serum Concentrations in Renal and Hepatic Diseases

Abstract: Ionised and total magnesium concentrations were determined in the serum of different groups of patients suffering from renal or hepatic diseases Ionised magnesium was measured by Microlyte 6 (KONE, Espoo, Finland) and total magnesium by atomic absorption spectrometry In renal insufficiency ionised and total magnesium concentrations were almost equally increased In proteinuria with a normal glomerular filtration rate, "pseudohypomagnesaemia" was observed, ie decreased total magnesium concentration in parallel with a decreased albumin concentration with no significant change in the concentration of ionised magnesium Hypermagnesaemia occurred in liver diseases combined with renal insufficiency, whereas "pseudohypomagnesaemia" was most often found in the absence of renal failure Also treatment with an aldosterone antagonist was associated with a normal ionised magnesium concentration, but the total magnesium concentration was decreased; when additional magnesium was administered, the total magnesium concentration approached a normal value, while ionised magnesium slightly exceeded reference values Only during cyclosporin treatment did both ionised and total magnesium concentrations become lowered However, the decrease of total magnesium exceeded that of ionised magnesium due to concomitant hypoalbuminaemia with reduction of the protein-bound fraction It is concluded that especially low total magnesium concentrations should be investigated by measurement of ionised magnesium to exclude "pseudohypomagnesaemia"

A candidate reference method for the determination of magnesium in serum.

Abstract: A candidate reference method for the determination of magnesium in serum (analytical range 0.5 to 2.0 mmol/l) by flame atomic absorption spectrometry was commissioned. The relative standard deviation of the 4 replicates of each value ranged from 0.18 to 1.07%, and the standard error of the mean ranged from 0.63 to 8.34 mumol/l. In the analysis of 3 different standard solutions (prepared by weighing the analyte), which was performed in each of three different experiments the values recorded by the candidate reference method deviated by -0.15, 0.44 and 0.24%, respectively. The reference method value did not differ significantly from the definitive value. As the method seems to be as reliable as comparable reference methods for the determination of sodium, potassium or calcium, tests of transferability should now be undertaken.

A Comparison of Reference Method Values for Calcium, Lithium and Magnesium with Method-Dependent Assigned Values

Abstract: Commercially available control sera were analysed by the reference methods for calcium, lithium and magnesium. Calcium: The mean deviation of the target values for routine flame atomic absorption spectrometry from the reference method values was -1.2%, in the case of flame atomic emission spectrometry -0.1%. The assigned values of determinations by methylthymol blue and cresolphthalein showed a positive bias: +2.3 and +2.2%. Lithium: Target values for routine flame atomic absorption spectrometry and flame atomic emission spectrometry were in generally good agreement with the reference method values (deviation +1.7% and +0.7%), although the differences were dependent on concentration. Magnesium: The assigned values for routine flame atomic absorption spectrometry yielded a mean bias of -0.4% from the reference method value. The target values for absorption spectrometry after reaction with Magon and Calmagite, however, differed by +8.2% and +9.3% on average. These methods seem to be less suitable for the determination of magnesium in serum than FAAS and would have failed several times to meet the requirements of quality assessment.

Influence of protein on the determination of sodium, potassium and chloride in serum by Ektachem DT 60 with the DTE module; evaluation with special attention to a possible protein error by flame atomic emission spectrometry and ion-selective electrodes; proposals to their calibration.

Abstract: The reliability of the Ektachem DT 60 with the DTE module was evaluated. The precision of the determination of sodium, potassium and chloride in serum was adequate. The relative standard deviation for precision between days was Na+ 0.7%, K+ 1.5% and Cl- 1.0%. The means of the Ektachem results for 7 control sera differed from those of the reference method values by 0.9% (Na+), -0.9% (K+) and +4.4% (Cl-). Similar results were obtained for the analysis of patient sera. The influence of protein was investigated, using sera of increasing protein concentration prepared by ultracentrifugation. The results from the Ektachem corresponded to the values obtained by flame atomic emission spectrometry, even at high protein concentrations, although Ektachem measurements are performed by ion-selective electrodes without predilution. In paraproteinaemia, the Ektachem and flame atomic emission spectrometry results disagreed. Chloride determinations by Ektachem distinctly differed from measurements of the chloride concentration in total serum. It is proposed that ion-selective electrodes should be calibrated and linearized with respect to sodium chloride, in order to obtain an accurate value for the concentration of electrolyte in serum water. Concentrations are easier to interpret than "activities" for therapeutical purposes, and they can be used to define protein- and lipid-independent reference intervals for these electrolytes. With this calibration procedure, the results from ion-selective electrodes are never lower than values obtained by flame atomic emission spectrometry. The accuracy of ion-selective electrode measurements should be evaluated by applying reference methods for sodium, potassium and chloride to the ultracentrifugation supernatant of the corresponding serum. This approach can help to settle the dispute concerning the influence of protein on the residual liquid junction potential.

Reference methods for the determination of sodium, potassium, pH and blood gases with ion-selective electrodes.

Abstract: The determination of sodium and potassium in serum will be performed in the near future mainly by ion-selective electrodes. When the samples are highly diluted before measurement, a demonstrably accurate value of the electrolyte concentration in serum can be obtained. Accuracy control by using the pertinent reference methods of the National Institute of Standards and Technology (NIST) is well established for this purpose. In undiluted samples a potential is measured by ion-selective electrodes, which is dependent on the relative molal activity of the electrolyte, from which free molal concentration can be estimated. Usually, the total molal concentration of e.g. sodium is about 1.5% higher than that of free sodium, as it includes portions bound to e.g. carbonate and proteins. Accuracy control is hampered, because reference methods for either relative molal activity or free molal concentration are not yet available. Reference method values for total molal concentration will differ systematically from an accurate value for free molal concentration. When ion-selective electrodes are calibrated by using "normal" sera, accuracy control can be based on the reference method of the NIST; but this is valid only for a very narrow, at best "normal", concentration range of proteins and lipids, assuming, of course, that binding is normal. The greater the variation of the concentration of macromolecules from normal (lower or higher), the greater the difference between the values obtained by the two methods. Calibration of ion-selective electrodes by using sera (this is the least desirable approach for calibration) requires the introduction of a new unit of measurement, which is not compatible with the rational system of quantities and units.(ABSTRACT TRUNCATED AT 250 WORDS)

Dynamics and Consequences of Potassium Shifts in Skeletal Muscle and Heart During Exercise

Abstract: Since it became clear that K+ shifts with exercise are extensive and can cause more than a doubling of the extracellular [K+] ([K+]s) as reviewed here, it has been suggested that these shifts may c...

Hypomagnesemia, oxidative stress, inflammation, and metabolic syndrome.

Abstract: Background Although hypomagnesemia, oxidative stress, and inflammation are involved in the pathogenesis of cardiovascular diseases, there is not a previous description concerning their potential interaction; thus, the aim of this study was to examine the relationship between metabolic syndrome (MetS), hypomagnesemia, inflammation, and oxidative stress. Methods Case-control design study. Incident cases of MetS (84 women and 63 men) were compared with healthy control subjects (163 women and 131 men) matched by age and gender. MetS was diagnosed according to the Adult Treatment Panel III (ATP III) criterion. Oxidative stress was defined by serum malondialdehyde concentration (MDA) ≥50 mg/dL, low-grade chronic inflammation by C-reactive protein (CRP) serum levels ≥3 mg/L, and hypomagnesemia by serum magnesium concentrations ≤1.8 mg/dL. Results Multivariate analysis adjusted by age, sex, body mass index, waist-to-hip ratio, and total adiposity showed a strong association between MetS and hypomagnesemia (OR 1.9; 95% CI 1.3–7.1), inflammation (OR 1.7; 95% CI 1.4–8.4), and oxidative stress (OR 1.4; 95% CI 0.9–12.6). Additional adjustment by CRP levels showed that MetS remained associated to hypomagnesemia (OR 1.4; 95% CI 1.1–5.9) but not to oxidative stress (OR 1.1; 95% CI 0.9–5.9), and adjusted by MDA levels, MetS remained strongly associated to hypomagnesemia (1.6; CI 95% 1.1–7.4), but not to inflammation (OR 1.05; 95% CI 0.97–14.2). Adjusted by serum magnesium levels, inflammation (OR 1.2; 95% CI 1.1–9.1) and oxidative stress (OR 1.1; 95% CI 1.1–9.7) were slightly associated to MetS. Conclusions The interaction of inflammation and oxidative stress is related and increases the risk for MetS, whereas serum magnesium levels and MetS are independently associated. Copyright © 2006 John Wiley & Sons, Ltd.

Magnesium in chronic kidney disease Stages 3 and 4 and in dialysis patients.

Abstract: The kidney has a vital role in magnesium homeostasis and, although the renal handling of magnesium is highly adaptable, this ability deteriorates when renal function declines significantly. In moderate chronic kidney disease (CKD), increases in the fractional excretion of magnesium largely compensate for the loss of glomerular filtration rate to maintain normal serum magnesium levels. However, in more advanced CKD (as creatinine clearance falls <30 mL/min), this compensatory mechanism becomes inadequate such that overt hypermagnesaemia develops frequently in patients with creatinine clearances <10 mL/min. Dietary calcium and magnesium may affect the intestinal uptake of each other, though results are conflicting, and likewise the role of vitamin D on intestinal magnesium absorption is somewhat uncertain. In patients undergoing dialysis, the effect of various magnesium and calcium dialysate concentrations has been investigated in haemodialysis (HD) and peritoneal dialysis (PD). Results generally show that dialysate magnesium, at 0.75 mmol/L, is likely to cause mild hypermagnesaemia, results for a magnesium dialysate concentration of 0.5 mmol/L were less consistent, whereas serum magnesium levels were mostly normal to hypomagnesaemic when 0.2 and 0.25 mmol/L were used. While dialysate magnesium concentration is a major determinant of HD or PD patients’ magnesium balance, other factors such as nutrition and medications (e.g. laxatives or antacids) also play an important role. Also examined in this review is the role of magnesium on parathyroid hormone (PTH) levels in dialysis patients. Although various studies have shown that patients with higher serum magnesium tend to have lower PTH levels, many of these suffer from methodological limitations. Finally, we examine the complex and often conflicting results concerning the interplay between magnesium and bone in uraemic patients. Although the exact role of magnesium in bone metabolism is unclear, it may have both positive and negative effects, and it is uncertain what the optimal magnesium levels are in uraemic patients.

Magnesium in disease: a review with special emphasis on the serum ionized magnesium.

Abstract: This review deals with the six main clinical situations related to magnesium or one of its fractions, including ionized magnesium: renal disease, hypertension, pre-eclampsia, diabetes mellitus, cardiac disease, and the administration of therapeutic drugs. Issues addressed are the physiological role of magnesium, eventual changes in its levels, and how these best can be monitored. In renal disease mostly moderate hypermagnesemia is seen; measuring ionized magnesium offers minimal advantage. In hypertension magnesium might be lowered but its measurement does not seem relevant. In the prediction of severe pre-eclampsia, elevated ionized magnesium concentration may play a role, but no unequivocal picture emerges. Low magnesium in blood may be cause for, or consequence of, diabetes mellitus. No special fraction clearly indicates magnesium deficiency leading to insulin resistance. Cardiac diseases are related to diminished magnesium levels. During myocardial infarction, serum magnesium drops. Total magnesium concentration in cardiac cells can be predicted from levels in sublingual or skeletal muscle cells. Most therapeutic drugs (diuretics, chemotherapeutics, immunosuppressive agents, antibiotics) cause hypomagnesemia due to increased urinary loss. It is concluded that most of the clinical situations studied show hypomagnesemia due to renal loss, with exception of renal disease. Keeping in mind that only 1% of the total body magnesium pool is extracellular, no simple measurement of the real intracellular situation has emerged; measuring ionized magnesium in serum has little added value at present.