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Biomedical subjects

A H Maas

Publications and source records attributed to A H Maas.

At least 19 recordsLinked to original sources
PubMed2001

[Hormonal supplement therapy in women: effects on the cardiovascular system].

Coronary heart disease develops on average 10-15 years later in women than in men and is uncommon before menopause. 17 beta-estradiol has atheroprotective properties through rapid vasodilatory effects on the endothelium by stimulating nitric monoxide production and longer-term actions by modulating changes in gene expression. Cardioprotective effects of hormone replacement therapy in postmenopausal women have been suggested by observational data but not proved in randomized trials. Recent data indicate that oestrogens have regenerative effects on the vascular wall after acute injury, like a percutaneous transluminal coronary angioplasty. As endothelial reactivity declines with age, more studies are needed to investigate the benefits of hormone replacement therapy in the younger category of postmenopausal women.

Age Factors↗
PubMed2001

IFCC recommendation on reporting results for blood glucose.

In human beings, glucose is distributed like water between erythrocytes and plasma. The molality of glucose (amount of glucose per unit water mass) is the same throughout the sample. Different water concentrations in calibrator, plasma, and erythrocyte fluid can explain some differences that are dependent on sample type, methods requiring sample dilution, and direct reading biosensors detecting molality. Different devices for the measurement of glucose detect and report fundamentally different analytical quantities. The differences exceed the maximum allowable error of glucose determinations for diagnosing and monitoring diabetes mellitus, and they complicate the treatment. The goal of the International Federation of Clinical Chemistry, Scientific Division, Working Group on Selective Electrodes (IFCC-SD WGSE) is to reach a global consensus on reporting results. The document recommends harmonizing to the concentration of glucose in plasma (with the unit mmol/l), irrespective of sample type or technology. A constant factor of 1.11 will convert measured concentration in whole blood to the equivalent concentration in plasma.

Biosensing Techniques↗
PubMed2000

Use of ion-selective electrodes for blood-electrolyte analysis. Recommendations for nomenclature, definitions and conventions. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). Scientific Division Working Group on Selective Electrodes.

This paper will familiarize the reader with the terms used to describe the behavior of ion-selective electrodes, particularly in relation to their use in clinical chemistry for determination of blood electrolyte cations. It serves as an introduction to a series of papers dealing with important cations in blood, namely calcium, sodium, and potassium. The detailed relationships between the ion activity determined by means of ion-selective electrode potentiometry in undiluted specimens, and the total substance concentration measured by flame atomic-emission spectrometry are described by flow chart and equations. Adoption of a convention for reporting results is recommended. The Working Group on Selective Electrodes has taken into account recent revisions of IUPAC recommendations on nomenclature and selectivity coefficient determinations for ion-selective electrodes, and benefited from the experience of a member of the WG, who was also involved in the IUPAC discussions. Nomenclature for determined quantities follows previous IUPAC/IFCC joint recommendations.

Electrodes↗
PubMed2000

Recommendations for measurement of and conventions for reporting sodium and potassium by ion-selective electrodes in undiluted serum, plasma or whole blood. International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). IFCC Scientific Division Working Group on Selective Electrodes.

Ion-selective electrodes (ISEs) respond to ion-activity and therefore do not sense substance concentration directly. However, it is recognized that sodium and potassium in plasma will continue to be expressed for clinical purposes in terms of substance concentration (mmol/l). A convention is proposed whereby for routine clinical purposes results of ISE measurements of sodium and potassium in undiluted plasma should be reported in terms of substance concentration (mmol/l). In specimens with normal concentrations of plasma water, total CO2, lipids, protein and pH, the values will concur with the total substance concentration as determined for example by flame atomic emission spectrometry (FAES) or ISE measurements on diluted samples. In specimens with abnormal concentrations of plasma water, the results will differ. However, under these circumstances, measurements of sodium and potassium by ISE in the undiluted sample will more appropriately reflect the activity of sodium and potassium and are therefore clinically more relevant than the determination in diluted samples. Detailed recommendations are made about practical procedures to achieve this. The recommended name for this quantity is the substance concentration of ionized sodium or ionized potassium in plasma, as opposed to total sodium or total potassium determined by, e.g. FAES, or ISE measurements on diluted samples.

Calibration↗
PubMed1998

Lyophilized bovine hemoglobin as a possible reference material for the determination of hemoglobin derivatives in human blood.

We investigated the suitability of a lyophilized bovine hemoglobin (LBH) preparation containing various fractions of oxyhemoglobin (O2Hb), carboxyhemoglobin (COHb), and methemoglobin (MetHb) for quality assessment in multicomponent analysis (MCA) of hemoglobin derivatives. It was demonstrated that a stable preparation of these components after reconstitution yields a hemoglobin solution that is spectrophotometrically equivalent with a fresh bovine hemoglobin solution. The preparation was found to be stable for at least 1 year when it is kept at 2-8 degrees C and for 1 h after reconstitution. We determined the fractions of O2Hb, COHb, and MetHb of several LBH preparations, using the complete spectra of 480-650 nm with 2-nm intervals and absorptivities as determined for pure LBH solutions. A field trial involving various types of multiwavelength hemoglobin photometers showed the suitability of LBH as a quality-control material. Computer models of the various common multiwavelength hemoglobin photometers may be useful for establishing more accurate target values of LBH preparations for each type of photometer and for studying the importance of the influence of specific factors such as wavelength selection, absorptivity values, and interfering dyes.

Animals↗
PubMed1997

International Federation of Clinical Chemistry (IFCC). Recommendation on mean molar activity coefficients and single ion activity coefficients of solutions for calibration of ion-selective electrodes for sodium, potassium and calcium determination.

In principle, flame photometry measures substance concentration, and ion-selective electrodes (ISEs) measure ion activity. However, the situation regarding the comparison of results from the two techniques when applied to blood plasma is complex. The problem can be approached experimentally from the point of view of calibration of ion-selective electrodes with concentration calibrators, and similar procedures are adopted for commercial ISE-based clinical analysers. Nevertheless, there is interest in the evaluation of single ion activities in blood plasma and solutions simulating its ionic composition. Solutions are proposed for calibrating ion-selective electrodes for the determination of sodium, potassium and calcium. It is recommended that the values for single ion activities derived from the Pitzer treatment of mixed electrolyte solutions be adopted, because, although this has some empirical features, it has a sounder theoretical basis than the previously used Stokes-Robinson-Bates hydration approach.

Calcium↗
PubMed1996

Definition, significance and measurement of quantities pertaining to the oxygen carrying properties of human blood.

A consistent set of definitions is given of the principal quantities pertaining to the oxygen transport by the blood, and of their mutual relationships, in relation to the methods used in their measurement. At the core is the correct definition of oxygen saturation, the deviation of which has recently been the cause of considerable confusion, especially concerning pulse oximetry. The occurrence, properties, determination, and pathophysiological and clinical significance of dyshaemoglobins, such as carboxyhemoglobin, methemoglobin, and sulfhemoglobin, are briefly described, together with possible consequences for diagnosis and therapy. In addition, attention is payed to the use of some haemoglobin derivatives, such as methaemoglobin and cyanmethaemoglobin, for clinical chemical and therapeutic purposes.

Blood Gas Analysis↗
PubMed1995

International Federation of Clinical Chemistry (IFCC), Committee on pH, Blood Gases and Electrolytes: approved IFCC recommendation on definitions of quantities and conventions related to blood gases and pH.

Terminology in blood pH and gas analysis can be confusing, both because more than one name has been used for the same quantity, and because the same name has been used for more than one quantity. In addition, several calculated quantities are commonly used, but in some cases many different algorithms have been published for a single quantity. This document contains definitions of the most useful quantities in blood pH and gas analysis, and presents algorithms for the most useful calculated quantities. Use of these should lessen confusion among users and should also result in data that are more comparable among laboratories.

Algorithms↗
PubMed1995

International Federation of Clinical Chemistry (IFCC). Scientific Division. Committee on pH, Blood Gases and Electrolytes. Approved IFCC recommendations on whole blood sampling, transport and storage for simultaneous determination of pH, blood gases and electrolytes.

Pre-analytical variables, e.g., specimen collection, transport, and storage, can contribute significantly to inaccurate pH, blood gas, and electrolyte values. The International Federation of Clinical Chemistry (IFCC), through its Committee on pH, Blood Gases and Electrolytes, has developed specific recommendations to minimize the undesirable effects of pre-analytical variables. The Committee has drawn upon the experiences of its own members as well as published data by others. Specifically, the Committee has included pertinent guidelines and suggestions by the IFCC Working Group on Selective Electrodes (WGSE), the National Committee on Clinical Laboratory Standards (NCCLS), and the Electrolyte/Blood Gas Division of the American Association for Clinical Chemistry (AACC). This paper will familiarize the reader with the effect of different types of specimen containers and anticoagulants. It discusses important aspects of specimen collection procedures including patients status and special precautions during specimen collection from indwelling catheters or cannulae. The paper also identifies different requirements in storage and transport of specimens for blood gas and electrolyte analysis.

Anticoagulants↗
PubMed1994

Recommendations on whole blood sampling, transport, and storage for simultaneous determination of pH, blood gases, and electrolytes. International Federation of Clinical Chemistry Scientific Division.

Pre-analytical variables, e.g., specimen collection, transport, and storage, can contribute significantly to inaccurate pH, blood gas, and electrolyte values. The International Federation of Clinical Chemistry (IFCC), through its Committee on pH, Blood Gases and Electrolytes, has developed specific recommendations to minimize the undesirable effects of pre-analytical variables. The Committee has drawn upon the experiences of its own members as well as published data by others. Specifically, the Committee has included pertinent guidelines and suggestions by the IFCC Working Group on Selective Electrodes (WGSE), the National Committee on Clinical Laboratory Standards (NCCLS), and the Electrolyte/Blood Gas Division of the American Association for Clinical Chemistry (AACC). This paper will familiarize the reader with the effect of different types of specimen containers and anticoagulants. It discusses important aspects of specimen collection procedures including patient status and special precautions during specimen collection from indwelling catheters or cannulae. The paper also identifies different requirements in storage and transport of specimens for blood gas and electrolyte analysis.

Anticoagulants↗
PubMed1993

IFCC reference methods and materials for measurement of pH, gases and electrolytes in blood.

The Scientific Division Committee on pH, Blood Gases and Electrolytes (SD-CBGE) and Working Group on Selective Electrodes (SD-WGSE) of the International Federation of Clinical Chemistry (IFCC) produced recommendations to attempt to make the results of pH, blood gas and electrolyte analysis from different clinical chemistry laboratories internationally compatible. The aim of this paper is to present an updated version of a previous review of the essential aspects of: 1. the IFCC approved (1986) reference method for pH measurement in blood, 2. the IFCC approved (1988) reference method for tonometry of blood, 3. the provisionally proposed recommendations on the expression of results obtained with Ion-Selective Electrodes (ISE's) for sodium, potassium and ionized calcium measuring in serum, plasma or blood and 4. the provisionally proposed reference method for the determination of ionized calcium in serum, plasma or blood. Also reference materials for quality control of pH, blood gas and electrolyte measurements are discussed.

Blood Gas Analysis↗
PubMed1992

Recommendation on sampling, transport, and storage for the determination of the concentration of ionized calcium in whole blood, plasma, and serum. IFC Scientific Division, Working Group on Ion-Selective Electrodes (WGSE).

The substance concentration of ionized calcium (cCa 2+) in blood, plasma, or serum preanalytically may be affected by pH changes of the sample, calcium binding by heparin, and dilution by the anticoagulant solution. pH changes in whole blood can be minimized by anaerobic sampling to avoid loss of CO 2, by measuring as soon as possible, or by storing the sample in iced water to avoid lactic acid formation. cCa 2+ and pH should be determined simultaneously. Plasma or serum: If centrifuged in a closed tube and measured immediately, the pH of the sample will be close to the original value. If there has been a delay between centrifugation and measurement, causing substantial loss of CO 2, equilibration of the sample with a gas mixture corresponding to pCO 2 = 5.3 kPa prior to the measurement is recommended. Conversion of the measured values to cCa 2+ (7.4) is only valid if the pH is in the range 7.2-7.6. Ca 2+ binding by heparin can be minimized by using either of the following: 1) a final concentration of sodium or lithium heparinate of 15 IU/mL blood or less; or 2) calcium-titrated heparin with a final concentration of less than 50 IU/mL blood. Dilution effect can be avoided by use of dry heparin in capillaries or syringes.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Chemical Analysis↗
PubMed1991

IFCC reference methods for measurement of pH, gases and electrolytes in blood: reference materials.

The Scientific Division Committee on pH, Blood Gases and Electrolytes of the International Federation of Clinical Chemistry (IFCC) produced recommendations to attempt to make the results of pH, blood gas and electrolyte analysis from different clinical chemistry laboratories internationally compatible. The aim of this lecture is to discuss the essential aspects of 1. the IFCC approved (1986) reference method for pH measurement in blood, 2. the IFCC approved (1988) reference method for tonometry of blood, 3. the provisionally proposed recommendations on the expression of results obtained with ion-selective electrodes for measuring sodium, potassium and calcium in serum, plasma or blood and 4. the reference method for the determination of ionized calcium in serum, plasma or blood. Also reference materials for quality control of pH, blood gas and electrolyte measurements are reviewed. Failures of several types of currently available quality control materials are discussed.

Blood Chemical Analysis↗
PubMed1991

Guidelines for routine measurement of blood hemoglobin oxygen affinity. IFCC Scientific Division, Committee on pH, Blood Gases, and Electrolytes.

Two methods for the routine determination of blood hemoglobin oxygen affinity are described. Both methods use whole blood and do not require special equipment, tonometry, or special gas mixtures. The first method consists of a one-point determination of p 50, and requires only 200 muL to 400 muL of whole blood, therefore making it suitable for the pediatric population. The second method uses multiple points, thereby establishing both the shape and position of the hemoglobin oxygen equilibrium curve between 10 and 99% oxygen saturation. Interpretation of p 50 is discussed in relation to evaluation of patients with hemoglobinopathies and as a parameter in estimating availability of oxygen to the tissues.

Blood Gas Analysis↗
PubMed1991

International Federation of Clinical Chemistry (IFCC) scientific division IFCC recommendation. Recommendation on sampling, transport and storage for the determination of the concentration of ionized calcium in whole blood, plasma and serum.

The substance concentration of ionized calcium (cCa2+) in blood, plasma or serum preanalytically may be affected by pH changes of the sample, calcium binding by heparin, and dilution by the anticoagulant solution. pH changes in whole blood can be minimized by anaerobic sampling to avoid loss of CO2, by measuring as soon as possible or by storing the sample in iced water to avoid lactic acid formation. cCa2+ and pH should be determined simultaneously. Plasma or serum: if centrifuged in a closed tube and measured immediately the pH of the sample will be close to the original value. If delay has occurred between centrifugation and the measurement, causing substantial loss of CO2, equilibration of the sample with a gas mixture corresponding to PCO2 = 5.3 kPa prior to the measurement is recommended. Conversion of the measured values to cCa2+ (7.4) is only valid if the pH is in the range 7.2-7.6 Ca2+ binding by heparin can be minimized by using either of the following: a final concentration of sodium or lithium heparinate of 15 IU/ml blood or less, by use of calcium titrated heparin with a final concentration less than 50 IU/ml blood. Dilution effect can be avoided by use of dry heparin in capillaries or syringes. When heparin solutions are used errors due to dilution or calcium binding can be reduced using syringes with a heparin solution containing free calcium ions corresponding to the mean concentration of ionized calcium in normal plasma. Conditions for blood collection, storage, and transport to avoid preanalytical errors are described.

Blood Chemical Analysis↗
PubMed1991

International Federation of Clinical Chemistry (IFCC), scientific division: IFCC recommendation on sampling transport and storage for the determination of the concentration of ionized calcium in whole blood, plasma and serum.

The substance concentration of ionized calcium (cCa2+) in blood, plasma or serum preanalytically may be affected by pH changes of the sample, calcium binding by heparin, and dilution by the anticoagulant solution. pH changes in whole blood can be minimized by anaerobic sampling to avoid loss of CO2, by measuring as soon as possible or by storing the sample in iced water to avoid lactic acid formation. cCa2+ and pH should be determined simultaneously.

Blood Coagulation↗