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Biomedical subjects

N Fogh-Andersen

Publications and source records attributed to N Fogh-Andersen.

At least 109 records · Page 6Linked to original sources
PubMed1985

Measurement of ionized calcium with five types of instruments. An external quality assessment.

An external quality assessment for ionized calcium determinations was carried out in 24 laboratories in Northern Europe. Both protein-free and protein-containing test materials were included in the study. The average within-laboratory variation (CV) for all test materials was 3.1, 1.7, 1.2, 1.8 and 1.3% for the AVL 980 (AVL, Graz, Austria), the Microlyte (Kone, Espoo, Finland), the Nova 2 (Nova Biomedical, Newton, Ma USA), the Orion SS-20 (Orion, Cambridge, Mass., USA), and the ICA1 (Radiometer, Copenhagen, Denmark) respectively. The corresponding interlaboratory CV was 3.1, 2.9, 3.1 and 2.4%. The variation between types of instruments was even larger and caused differences of up to 33%. The results indicate a need for well-defined protein-containing control material.

Calcium↗
PubMed1984

Renal and hepatic extraction of carboxyl-terminal immunoreactive parathyrin in normal man.

We measured the carboxyl-terminal immunoreactive parathyrin (parathyroid hormone) in samples from twenty catheterized patients with hypertension. The radioimmunoassay reacted equally well with intact parathyrin and carboxyl-terminal parathyrin fragments. The renal arterio-venous extraction ratio (extraction ratio = arterio-venous concentration difference divided by the arterial concentration) of endogenous carboxyl-terminal immunoreactive parathyrin equalled that of inulin, with mean values for both of 0.17. The carboxyl-terminal parathyrin fragments have about the same molecular weight as inulin, and they are extracted exclusively by glomerular filtration, whereas intact parathyrin is extracted by both peritubular uptake and glomerular filtration. The findings therefore agree with a high proportion of circulating carboxyl-terminal parathyrin fragments in normal man. The mean extraction ratio of endogenous carboxyl-terminal immunoreactive parathyrin across nine livers was 0.16. Some of the hepatic extraction might be due to cleavage and uptake of intact parathyrin, which constitutes about 15% of the circulating immunoreactive parathyrin, but the findings suggest that the liver also extracts and metabolizes the circulating carboxyl-terminal parathyrin fragments in normal man.

Amino Acid Sequence↗
PubMed1984

Acid-base-induced changes in the distribution of water between plasma and erythrocytes, as measured with a sodium-ion-selective electrode.

aNa+ measured in whole blood changes with the pH of plasma, and the effect depends on the erythrocyte volume fraction (phi E). The relative change in aNa+ with pH, dlnaNa+/dpH, was -0.01 at phi E = 0 and -0.11 at phi E = 0.76. The observations agreed with the combined predicted effects of changes in phi E, in concentration of the NaHCO3 complex, and in liquid-junction potential. The pH-induced osmotic transfer of water between plasma and erythrocytes will affect the concentration of all components confined to plasma. Although the clinical importance of this may be limited, blood samples for research should either be dealt with immediately or stored anaerobically at 4 degrees C until separation, to avoid bias.

Body Water↗
PubMed1984

Calcium homeostasis in morbid obesity.

Calcium homeostasis in morbidly obese subjects has attracted little attention. Prompted by reports of elevated serum levels of parathyroid hormone in such patients, calcium homeostasis was investigated in 36 patients with morbid obesity and in 44 normal weight controls. Concerning serum immunoreactive parathyroid hormone (C-terminal), serum ionized calcium (Ca++) and serum albumin corrected magnesium no significant differences between the groups were detected. When albumin corrected, serum total calcium turned out to be significantly elevated (p less than 0.0001) in the obese subjects. Also, serum alkaline phosphatase activity was significantly raised in the obese state. The results demonstrate that calcium homeostasis, as expressed by the metabolically active serum Ca++, is normal in morbid obesity. But the results also point towards an abnormal calcium binding due to either an increased calcium binding to albumin or to calcium complexing small anions.

Adult↗
PubMed1984

Sex-dependent relation between ionized calcium in serum and blood pressure.

In an epidemiological study of 977 45-year-olds, both the mean concentration of ionized calcium in serum, [Ca2+]7.4, and arterial blood pressure were higher in men than in women. Among the men, there was a weak positive correlation between [Ca2+]7.4 and the systolic blood pressure, but no other significant correlation was found within each separate sex. Postmenopausal women had slightly increased [Ca2+]7.4 but normal blood pressure. Patients taking thiazide diuretics or beta-adrenergic blocking agents had normal [Ca2+]7.4.

Blood Pressure↗
PubMed1984

Determination of sodium and potassium with ion-selective electrodes.

We compared different sample-handling techniques for measurement of Na+ and K+ with ion-selective electrodes (ISE). Imprecision was less for venous blood (with a minimum of heparin) than for plasma, serum, or capillary blood. The results for K+ were higher for serum than for whole blood, and higher for whole blood than for plasma. The latter difference was apparently due to release of K+ during the analysis. Values were more stable for whole blood stored at 20 degrees C than at 4 degrees C or 37 degrees C. The molality of Na+ in the plasma of mixed whole blood changed by -10.5 mmol/kg per unit change in blood pH. This could be explained by the different H+ buffering capacities of plasma and erythrocyte fluid, because when the pH is changed, the concentration of small anions in erythrocytes changes more than it does in plasma, with a consequent osmotic movement of water across the erythrocyte membrane. When we took into account the residual liquid-junction potential and the mass concentration of water in each of 65 patients' sera, the molality determined for Na+ was 1% lower and that of K+ 3% lower by ISE than by flame photometry--differences that may be related to ionic binding or to a lower molal activity coefficient in serum than in the calibrator.

Capillaries↗
PubMed1983

Relation between ionised calcium and pH in infants with acute acid-base disturbances.

Plasma ionised calcium, [Ca2+], and pH were negatively correlated in 21 infants with disturbed acid-base homeostasis. The slopes of the individual regression lines indicated a mean decrease in [Ca2+] of 42% per pH increase. (Mean delta log[Ca2+]/delta pH = -0.184, SEM = 0.050, p less than 0.001). The value was not significantly different from the relation between [Ca2+] and pH in vitro, when whole blood or plasma was equilibrated with CO2-air mixtures. pH and [Ca2+] must be measured and considered together to allow a proper interpretation of the result.

Acid-Base Imbalance↗
PubMed1983

Decreased serum concentration of ionized calcium in insulin-dependent human diabetes mellitus.

Low serum ionized calcium concentrations were observed in twenty-five insulin dependent diabetic outpatients compared with twenty-three age-matched normal subjects: mean 1.16 mmol/l (SEM 0.01) versus 1.20 mmol/l (0.01), P less than 0.002. Despite this, there was no compensatory increase in serum concentrations of immunoreactive parathyroid hormone, nor was serum total calcium decreased in the diabetic patients. Serum magnesium was significantly decreased in the diabetics compared with normals: mean 0.75 mmol/l versus 0.83 mmol/l, P less than 0.001. No significant correlation could be demonstrated between serum magnesium and serum ionized calcium or parathyroid hormone in the diabetic patients. Since no significant correlations were observable between serum ionized calcium and indices of diabetes control, the etiology and pathogenesis of decreased serum calcium ion in insulin-dependent human diabetes mellitus remain unknown.

Adolescent↗
PubMed1983

Donnan effect or protein interference in ionised calcium measurements?

The observation that the ionised calcium concentration is higher if measured in the original serum sample than in an ultrafiltrate is examined by means of a theoretical model. It is concluded that this difference is a predictable consequence of the Donnan equilibrium and is not a result of protein interference with the calcium-specific electrode.

Blood Proteins↗
PubMed1983

Lowered serum ionized calcium in insulin treated diabetic subjects.

The concentration of ionized calcium at pH 7.40, [Ca2+]7.4, in serum from 43 insulin dependent diabetic patients was lowered in comparison with 47 healthy controls (p less than 0.001), and the difference was biggest in children under sixteen. Serum total calcium, phosphate, and parathyroid hormone were normal, and it is inexplicable why the parathyroid glands did not react by raising serum total calcium. The lowered serum ionized calcium may contribute to the development of diabetic bone loss.

Adolescent↗
PubMed1983

Transcutaneous and capillary pCO2 and pO2 measurements in healthy adults.

Transcutaneous carbon dioxide and oxygen tensions (tc-pCO2 and tc-pO2) were measured in seven healthy adult volunteers during hyperventilation in atmospheric air and during CO2 inhalation. Three skin sensors were applied to each subject: an O2 electrode, a CO2 electrode, and a combined O2-CO2 electrode, each heated to 44 degrees C. We observed close correlation between tc-pCO2 and capillary-pCO2, the relation being close to that calculated from the anaerobic temperature coefficient of pCO2 in blood. For O2, on the other hand, the relationship between transcutaneous and capillary values appeared more complex. Electrode drift during in-vivo monitoring was greater for pCO2 (up to 12%) than for pO2 (up to 7%), but generally we observed no differences in drift between the combined and the single electrodes. We conclude that tc-pCO2 measured with a single or a combined electrode reliably predicts capillary-pCO2 in healthy adults and that changes are rapidly observed. Our conclusions regarding tc-pO2 values are less definite because of uncertain interpretation of the capillary-pO2 values.

Adult↗
PubMed1983

What is "ionized calcium"?

"Ionized calcium", in clinical chemistry, designates the free calcium ions which are present in the biological fluids as hydrated ions: Ca2+, 12 H2O. The calcium ion selective electrode measures differences in activity, however, values are reported not as the activity, but as the activity divided by the activity coefficient (gamma) of Ca2+ in "normal plasma". The latter is assumed to be equal to the activity coefficient (gamma) in a calibration solution of CaCl2 + NaCl with an ionic strength of 0,16 mol X kg-1. We have estimated the activity coefficient in this calibration solution to be gamma Ca2+ = 0,3040 (molal basis) or gamma Ca2+ = 0,3048 (substance concentration basis). The derivation of gamma Ca2+ is based on a convention for derivation of the activity coefficient of the chloride ion. We have used the Debye-Hückel equation extended by the Stokes-Robinson hydration theory plus the Bates-Staples-Robinson convention that the hydration number for Cl- is zero. International consensus is needed concerning the convention to be used for deriving the activity coefficient of Ca2+ in the calibration solutions and concerning the most appropriate value for gamma Ca2+ in normal plasma.

Calcium↗
PubMed1983

Ionized calcium during dialysis and ultrafiltration.

The changes in ionized calcium during dialysis and ultrafiltration with albumin containing solutions were highly dependent on the total electrolyte concentration. Protein interference on the calcium electrode could not explain the observation, which was, however, consistent with the Donnan theory. The uneven distribution of sodium ion also agreed with a Donnan membrane potential.

Blood Proteins↗
PubMed1983

Elimination of the erythrocyte effect on the liquid junction potential in potentiometric measurements on whole blood using mixed salt bridge solutions.

An effect of erythrocytes on the liquid junction potential of the junction "concentrated KCl whole blood" has previously been described, the effect being a positive bias of +1,4 mV with a high erythrocyte volume fraction (0.75). We have studied the erythrocyte effect with different concentrated salt solutions, and found a similar positive bias with KBr, KJ, KNO3, K2SO4, but a negative bias with NaCl, NaNO3, LiCl and CaCl2. The erythrocyte bias may be eliminated by mixing salts with opposite effect, e.g. KCl + NaCl (1.0 + 7.0 mol/l), KNO3 + NaNO3 (1.0 + 3.0 mol/l) KNO3 + Li-acetate (0.15 + 4.0 mol/l). The use of a mixed salt bridge solution may be advantageous for eliminating the erythrocyte bias when measuring ionic activity (e.g. Na+, K+, Ca2+) directly in whole blood.

Blood Chemical Analysis↗
PubMed1983

Nomograms for calculating the concentration of ionized calcium of human blood plasma from total calcium, total protein and/or albumin, and pH.

Two nomograms are described. One is a Cartesian nomogram similar to the original McLean-Hastings nomogram but supplemented by an albumin scale and a pH scale to allow calculations in case of an abnormal albumin/globulin ratio or an abnormal pH. The other is an alignment nomogram. The underlying arithmetic equations, which are slightly different for the two nomograms are described. Both refer to 37 degrees C. Calculated and measured ionized calcium are compared for 24 specimens and it is concluded that the calculated value may be subject to a considerable bias amounting to 0.2 mmol/l in the worst cases. Nomograms size A4 and BASIC program are available on request.

Blood Proteins↗
PubMed1983

Relation between pH and ionized calcium in vitro and in vivo in man.

We investigated the in vitro and in vivo relation between pH and ionized calcium during acute respiratory pH changes. The in vitro slope delta 1gcCa2+/delta pH determined in 20 healthy volunteers after equilibration at two different pCO2 values was -0.22 +/- 0.04 (mean +/- 2 SD) for whole blood and -0.24 +/- 0.04 (mean +/- SD) for serum. The in vivo slope delta 1gcCa2+/delta pH during acute respiratory changes in 10 healthy volunteers was -0.17 +/- 0.04 (mean +/- 2 SD) for capillary blood. A mathematical formula which describes the relation between pH and ionized calcium is presented.

Adult↗
PubMed1982

Serum calcium fractions in diabetes mellitus.

Diabetes mellitus is associated with a decrease in bone mineral content and increased urinary excretion of calcium and phosphate. The purpose here was to elucidate the pathogenesis of these changes by comparing serum calcium fractions of diabetics and healthy controls. In a cross-sectional study, serum ionized calcium at pH 7.40, [Ca2+]7.4, of 46 insulin-treated diabetics was decreased in comparison with 44 healthy controls: mean 1.16 (SD 0.04) vs 1.21 (SD 0.03) mmol/L (p less than 0.001). The decreased [Ca2+]7.4 was associated with a higher concentration of complexed calcium in diabetic serum. The diabetics had higher concentrations of undetermined anions (p less tha 0.001) and this anion gap correlated negatively with [Ca2+]7.4 (r = -0.43, p less than 0.02). Serum [Mg2+] was decreased in the diabetics (p less than 0.001). Values for venous acid-base status, serum creatinine, total and ultrafiltrable calcium, parathyrin, and inorganic phosphate were the same in the two groups. [Ca2+]7.4, but not serum total calcium, had increased by 0.04 mmol/L (p less than 0.001) in the diabetics and by 0.02 mmol/L (p less than 0.01) in the controls by 90 min after breakfast, with and without subcutaneous insulin, respectively.

Adolescent↗