[Hematocrit measurement: comparison of conductimetry to microcentrifugation]. / Mesure de l'hématocrite: comparaison de la conductimétrie à la microcentrifugation.

In general, blood gas analysers can also determine the value of haematocrite by measuring the blood's conductivity. The question to ask is whether this value is reliable. In this study, hematocrit obtained via conductivity from 6 different pieces of equipment were compared with those measured using the gold standard method, which is microcentrifugation. By interpreting the results of 320 arterial blood samples taken in the intensive care unit DAR "B" we can see that the reliability between two measurements on the same piece of equipment is very good, in general > 0.95 whatever the equipment. The reliability between the means of the two measurements and the gold standard is slightly lower but remains very satisfactory, most often between 0.8 and 0.9. The Gem Premier 3000 (IL) analyser and the Roche OMNI S gave the best reliability compared with centrifugation. The Spearman coefficients between the mean values of the analysers and those of centrifugation were high, with the exception of the Rapidpoint 405. They are all statistically different from zero (p<0.0001).

[Comparative study of six blood gas analysers]. / Etude comparative de six analyseurs de gaz du sang.

An evaluation process directed by the biochemistry department of the UHC of Montpellier about acquisition of blood gas analysers for a point of care testing in 10 different medical care services. The values obtained by the different measurement machines have been compared taking into account the intra and inter measures variabilities. In this work, the results of 4 machines tested: Rapid-point 405, GEM Premier 3000, i-STAT 1 (série 300) and ABL 77 are compared with one i-STAT (série 200) and one OMNI S already available in the laboratory. The study lasted one month (november 2004). Each week, the two machines of the laboratory was compared with a new analyser randomly chosen between the four machines tested. In this study, including 21000 values, the statistical tests have been applied under the hypothesis that none of the measurement machine could be a "gold standard". Beside the classical research of correlation between the different values, we added the research of concordance between machines and the application of imperfect gold standard method. A high level of statistic concordance was observed between the different analysers. So the equipment has been selected using biological, analytic and computing criteria.

[Sodium determination in biological fluids]. / Méthodes de dosage du sodium dans les liquides biologiques.

Electrolyte disorders are frequently observed in nephrology and intensive care unit department and Na determination is routinely performed in biochemistry laboratories. Three methods are currently available. Flame photometry remains the reference method. With this method the serum sample is diluted before the actual measurement is obtained. Results are expressed as molarity (per Liter of plasma). Potentiometric methods have an increasing importance due to the advances in ion sensitive (selective) electrodes (ISE). Whereas the instruments for routine chemical analysis typically use indirect potentiometry (involving te dilution of samples) to measure sodium levels, the equipment for measuring arterial blood gases use direct potentiometry without any dilution. Thus, results obtained with indirect potentiometry are expressed in molarity (per liter of plasma) while results obtained with direct potentiometry are initially given in morality (per kg of plasma water) then converted in molarity. Analytical performances are in all cases satisfactory and therefore all the methods could be used in both normal and pathological ranges. Methods involving sample dilution such as flame photometry or indirect potentiometry, the serum sodium value would be expected to be low in case of decrease plasma water (pseudohyponatremia). By contrast, with direct potentiometry where no sample dilution takes place, no interference would be expected since the activity of sodium in the water phase only is being measured. Thus, the classical pseudohyponatremia observed with hyperlipemia or paraproteinemia are not further observed with direct potentiometry. These differences in methodology should be taken into account to explain discrepancies between results obtained with classical biochemistry analyser and with blood gas apparatus.

NMR studies of primary and secondary sites of parvalbumins using the two paramagnetic probes Gd (III) and Mn (II).

The binding of cations by parvalbumins was studied by the proton relaxation enhancement (PRE) method using the paramagnetic probes Gd(III) and Mn(II). Gd(III) appears as a specific probe of the primary sites CD and EF with the following binding parameters: n = 2, KdGd = 0.5 x 10(-11) M and epsilon b = 2.3. The low value of epsilon b is the result of a nearly complete dehydration of the protein bound ions. Competition experiments between Gd(III) and various diamagnetic cations show the following order of affinity for the EF and CD sites: Mg2+ less than Zn2+ less than Sr2+ less than Ca2+ less than Cd2+ less than La3+ less than or equal to Gd3+. Mn 2+ is a specific probe of a secondary site with the following binding parameters: n = 1, KdMn = 0.6 x 10(-3) M and epsilon b = 17. The high value of epsilon b suggests that the protein bound Mn(II) has retained most of its hydration shell. Competition experiments between (Mn(II) and different cations show similar affinities for this site: Ca2+ less than or equal to Mg2+ less than or equal to Cd2+ less than or equal to Mn2+. This secondary site is located near the EF primary site.

[Bleeding after extracorporeal circulation and epsilon-aminocaproic acid]. / Saignement après circulation extracorporelle et acide epsilon amino-caproïque.

In order to assess the efficacy of epsilon aminocaproic acid in reducing bleeding after extracorporeal circulation for aorto-coronary bypass grafting, a double blind study was carried out in 57 patients. The efficiency of epsilon aminocaproic acid was assessed by the fibrinolytic activity as measured by a Von Kaulla test one hour after injection of protamine, by the amount of blood transfusions required and by the measurement of blood losses between the end of the injection of protamine and transfer of the patient to the intensive care unit, and then during the first 24 h following operation. No significant difference (p less than 0.05) between the group of treated patients and the group with placebo could be found concerning the postoperative bleeding, the amount of blood transfusions necessary and the occurrence of fibrinolysis. It was therefore concluded that there was no reason to routinely use epsilon aminocaproic acid after aorto-coronary bypass grafting.