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Biomedical subjects

O Siggaard-Andersen

Publications and source records attributed to O Siggaard-Andersen.

At least 73 records · Page 4Linked to original sources
PubMed1984

On the reliability of the Henderson-Hasselbalch equation in routine clinical acid-base chemistry.

This paper deals with the variability of the practical coefficient of the first ionisation equilibrium of carbonic acid as related to the CO2 in the liquid phase (Henderson-Hasselbalch equation) (Formula: see text) and that of the practical coefficient of the first ionisation equilibrium of carbonic acid as related to the CO2 in the gas phase (modified Henderson-Hasselbalch equation) (Formula: see text).

Acid-Base Imbalance↗
PubMed1984

Serum ionized calcium, nephrogenous and total urinary cyclic AMP and urinary phosphate in normal subjects.

Total urinary cyclic AMP (UcAMP) and nephrogenous cyclic AMP (NcAMP) were measured in 4, 20 and 24 h urine in forty-eight healthy volunteers. There were no significant differences between 4, 20 and 24 h excretion rate of UcAMP and NcAMP whether it was corrected for the glomerular filtration rate [( UcAMP]GF, [NcAMP]GF), creatinine corrected (UcAMP/Crea)U, or expressed as actual excretion rate (NcAMP,n), nor any sex differences. Mean values +/- one standard deviation (SD) for these parameters: [UcAMP]GF: 30.4 +/- 9.4 nmol/l; 27.7 +/- 7.0 nmol/min; 28.1 +/- 6.9 nmol/l in 4, 20 and 24 h urine, respectively. [NcAMP]GF: 13.4 +/- 8.5 nmol/l; 10.6 +/- 7.7 nmol/l; and 11.1 +/- 7.2 nmol/l in 4, 20 and 24 h urine, respectively. (NcAMP,n): 1.45 +/- 0.90 nmol/min; 1.14 +/- 0.80 nmol/min; 1.17 +/- 0.73 nmol/min in 4, 20 and 24 h urine, respectively, NcAMP accounts for about 40% of UcAMP. A positive correlation was found between plasma cyclic AMP and [UcAMP]GF (r = 0.41, P less than 0.001), whereas this relationship could not be demonstrated between plasma cyclic AMP and [NcAMP]GF (r = -0.008, P greater than 0.1). The calculation of [NcAMP]GF therefore corrects for unsuspected high or low plasma cyclic AMP values, and is therefore the preferred parameter of the PTH effect on the kidney tubular cells. No correlation could be demonstrated between [NcAMP]GF and concentration of ionized calcium in plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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

A mathematical model of the hemoglobin-oxygen dissociation curve of human blood and of the oxygen partial pressure as a function of temperature.

A mathematical model is described giving the oxygen saturation fraction (s) as a function of the oxygen partial pressure (p): y - y0 = x - x0 + h X tanh [k X (x - x0)], where y = kn[s/(1-s)] and x = ln(p/kPa). The parameters are: y0 = 1.875; x0 = 1.946 + a + b; h = 3.5 + a; k = 0.5343; b = 0.055 X [T/(K - 310.15)]; a = 1.04 X (7.4 - pH) + 0.005 X Cbase/(mmol/L) + 0.07 X [[CDPG/(mmol/L)] - 5], where Cbase is the base excess of the blood and CDPG is the concentration of 2,3-diphosphoglycerate in the erythrocytes. The Hill slope, n = dy/dx, is given by n = 1 + h X k X [1 - tanh2[k X (x - x0)]]. n attains a maximum of 2.87 for x = x0, and n----1 for x----+/- infinity. The model gives a very good fit to the Severinghaus standard oxygen dissociation curve and the parameters may easily be fitted to other oxygen dissociation curves as well. Applications of the model are described including the solution of the inverse function (p as a function of s) by a Newton-Raphson iteration method. The po2-temperature coefficient is given by dlnp/dT = [A X alpha X p + CHb X n X S X (1 - s) X B]/[alpha X p + CHB X n X s X (1 - s)], where A = -dln alpha/dT approximately equal to 0.012 K-1; B = (lnp/T)s = 0.073 K-1 for y = y0; alpha = the solubility coefficient of O2 in blood = 0.0105 mmol X L-1 X kPa-1 at 37 degrees C; CHb = concentration of hemoglobin iron in the blood. Approximate equations currently in use do not take the variations of the po2-temperature coefficient with p50 and CHb into account.

Chemical Phenomena↗
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

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

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

The concentration of free calcium ions and total calcium in pregnancies at term.

The concentration of free calcium ions (cCa2+), total calcium (ctCa) and pH was measured in 46 normal pregnancies at term. Measured with a combined Ca2+-pH electrode system in whole blood, maternal plasma cCa2+ was 1.18 +/- 0.03 mmol/l, and the corresponding plasma pH was 7.37 +/- 0.05 (mean +/- SD). In the cord vein, plasma cCa2+ was 1.44 +/- 0.07 mmol/l and pH 7.37 +/- 0.05. In the cord artery, plasma cCa2+ was 1.47 +/- 0.07 mmol/l and pH 7.29 +/- 0.07.

Calcium↗
PubMed1982

Evaluation of a new semiautomatic electrode system for simultaneous measurement of ionized calcium and pH.

The instrument (ICA 1 Radiometer, Copenhagen) measures the activity of calcium ion and hydrogen ion and displays the estimated concentration of free calcium ion (cCa2+) and pH at 37 degrees C in 110 microliter of whole blood or serum. The cCa2+ at pH 7.40 is calculated by means of a fixed relationship between cCa2+ and pH. The results are indicated on a display approximately 1 min after sample introduction. The measuring cycle plus automatic rinsing takes 3 min. The apparatus is equipped with a number of control functions. The sensitivity of the calcium electrode showed a fall from 100% to 92% over 20 weeks. The cell potential of the calcium cell showed a slow drift of--0.02 mV per day over a 20-week period while the pH cell which employs the same reference electrode showed no drift. Interference of Na+, K+, Li+, Mg2+ and H+ on the calcium measurement in whole blood is estimated to be at most +0.1%. The effect of erythrocytes on the static liquid junction potential is minimized by a special extrapolation procedure. The analytical standard deviation for cCa2+ in serum was 0.008 mmol/l within series, 0.017 mmol/l between days. The mean value for cCa2+ (at pH 7.4) in serum for 53 healthy adults was 1.249 mmol/l with a standard deviation of 0.036 mmol/l. cCa2+ in capillary blood at the actual pH from 20 healthy volunteers gave a mean value of 1.215 +/- 0.047 mmol/l (+/- 2SD) with pH 7.428 +/- 0.031 (+/- 2 SD). The slopes delta lgcCa2+/delta pH measured after equilibration at two different PCO2 values in venous blood (n = 20) and in serum (n = 104) gave a mean value of -0.221 +/- 0.040 (+/- 2 SD). The semi-automatic combined Ca2+ - pH electrode system makes the measurement of ionized calcium for clinical use a reliable and accurate analysis.

Calcium↗