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A H Maas

Publications and source records attributed to A H Maas.

At least 19 recordsLinked to original sources
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↗
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↗
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

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↗
PubMed1990

International Federation of Clinical Chemistry (IFCC). Scientific Division. Committee on pH, Blood Gases and Electrolytes. Guidelines for transcutaneous pO2 and pCO2 measurement.

This document provides guidelines in the terminology, methodology, and in the interpretation of data obtained from the use of skin (transcutaneous) pO2 and pCO2 electrodes. The transcutaneous technique has found special application in newborn infants. The causes of analytical bias with respect to arterial blood gas values and imprecision obtained with transcutaneous pO2 and pCO2 electrodes are reviewed. Electrode temperatures above 44 degrees C should not be used routinely, and at a measuring temperature of 44 degrees C, the measuring site should be changed at least every 4 h to avoid skin burning.

Blood Gas Monitoring, Transcutaneous↗
PubMed1990

Guidelines for routine measurement of blood hemoglobin oxygen affinity. International Federation of Clinical Chemistry, 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 p50, and requires only 200 microL to 400 microL 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 p50 is discussed in relation to evaluation of patients with hemoglobinopathies and as a parameter in estimating availability of oxygen to the tissues.

Abbreviations as Topic↗
PubMed1990

International Federation of Clinical Chemistry (IFCC). Scientific Division. Committee on pH, Blood Gases and Electrolytes. Guidelines for transcutaneous PO2 and PCO2 measurement.

This document provides guidelines in the terminology, methodology, and in the interpretation of data obtained from the use of skin (transcutaneous) P02 and PCO2 electrodes. The transcutaneous technique has found special application in newborn infants. The causes of analytical bias with respect to arterial blood gas values and imprecision obtained with transcutaneous P02 and PCO2 electrodes are reviewed. Electrode temperatures above 44 degrees C should not be used routinely, and, at a measuring temperature of 44 degrees C, the measuring site should be changed at least every 4 hours to avoid skin burning.

Bias↗
PubMed1989

IFCC document stage 3, draft 1, dated 1989 02 01. An approved IFCC recommendation. IFCC method (1988) for tonometry of blood: reference materials for pCO2 and pO2. International Federation of Clinical Chemistry Scientific Division. Committee on pH, Blood Gases and Electrolytes.

A reference method for tonometry of blood is described. The document covers the theory of tonometry, the materials and equipment needed, and essential aspects of the tonometry procedure for blood. The partial pressures of oxygen and carbon dioxide in tonometered blood are accurately known and therefore this blood is recommended for assessing the accuracy of blood gas analyzers. Tonometry of blood samples from patients may also be used in the determination of acid-base quantities and hemoglobin-oxygen affinity, e.g. p50.

Blood Gas Analysis↗
PubMed1989

International Federation of Clinical Chemistry (IFCC), Scientific Division. Committee on pH. Blood Gases and Electrolytes. IFCC method (1988) for tonometry of blood: reference materials for pCO2 and pO2.

A reference method for tonometry of blood is described. The document covers the theory of tonometry, the materials and equipment needed, and essential aspects of the tonometry procedure for blood. The partial pressures of oxygen and carbon dioxide in tonometered blood are accurately known and therefore this blood is recommended for assessing the accuracy of blood gas analyzers. Tonometry of blood samples from patients may also be used in the determination of acid-base quantities and hemoglobin-oxygen affinity e.g. p50.

Blood Gas Analysis↗
PubMed1987

Evaluation of a quality control material containing hemoglobin for blood gas and pH measurement.

A procedure for the preparation of a Stroma-Free Hemoglobin Solution (SFHS) is given. The stability of this SFHS containing Methemoglobin Reductase, can be improved by addition of NADH. The characteristics of the stable SFHS can be manipulated by varying independently the concentrations of bicarbonate and Inositol-Hexa-Phosphate. This way the desired acid-base behaviour and position of the Oxygen Hemoglobin Equilibrium Curve (OHEC) can be obtained. Three SFHS were prepared with acidotic, alkalotic or normal acid-base characteristics and all SFHS had an OHEC in the normal position (actual p50 3.33-3.87 kPa). Results show that: stability of SFHS is 1 year, xHi less than 2.5% after 1 year; p50 decreases about 15% per year; Hill's coefficient, nHill, is constant, but differed between levels; the mean values for nHill are 2.0 for the acidotic level, 2.2 for the normal and 2.4 for the alkalotic level; temperature coefficients for SFHS are: d(pH)/dt = -0.016 pH/degrees C, d(pCO2)/dt = 6.2%/degrees C and d(pO2)/dt = 7.2%/degrees C. Oxygen and carbon dioxide tonometered SFHS, of which the pH was measured with the reference method for pH measurement in blood was used on several blood gas analyzers to demonstrate the suitability for pH, pCO2 and pO2 measurement. The SFHS, which contained oxyhemoglobin, carboxyhemoglobin and methemoglobin, was also used as a control material for hemoglobin meters and CO-Oximeters. It is concluded that SFHS behaves blood-like with respect to pH, pCO2 and pO2 as well as total hemoglobin, oxygen saturation, carboxyhemoglobin and methemoglobin measurements. In contrast to hemoglobin-free aqueous control material, it buffers oxygen in a blood-like manner. Its shelflife is limited compared to the generally used aqueous control materials, but it is sufficient for repetitive use in clinical laboratories.

Blood Gas Analysis↗
PubMed1987

Quality control material containing hemoglobin for blood gas and pH measurement: preparation of stroma-free hemoglobin solution.

A method for the preparation of stroma-free hemoglobin solution suitable for quality control of blood gas and pH measurements as well as hemoglobinometry, is described. Several methods were compared for purification and lysis of red blood cells. For separation of stroma from hemoglobin solution tangential cross-flow filtration has been used. Diluted hemoglobin solutions were concentrated using various forms of ultrafiltration as well as other methods. A precipitate removing procedure is introduced in which the pH is increased temporarily to 8.0 and the ionic strength is enhanced by adding 130 mmol NaCl per litre stroma-free hemoglobin solution, to remove a precipitate that was observed during tonometry at 37 degrees C in the pH-range 7.4-8.0 and when electrolytes were added to create a plasma-like composition of stroma-free hemoglobin solution. Tests were designed to quickly detect turbidity and precipitate. During storage at 4 degrees C no methemoglobin was formed in contrast with two other types of stroma-free hemoglobin solution, which formed appreciable amounts of methemoglobin within 40 days.

Blood Gas Analysis↗
PubMed1987

Quality control material containing hemoglobin for blood gas and pH measurement: improvement of the stability of stroma-free hemoglobin solution.

In stroma-free hemoglobin solution (SFHS) formation of methemoglobin (hemiglobin; Hi) occurs over a period of some months, due to the fact that Hi reduction stops in hemolysates. SFHS should contain active hemoglobin (Hb), which is able to bind oxygen and should not contain inactive Hb (Hi, carboxyhemoglobin) which does not bind oxygen. Reversible binding of oxygen by Hb is only possible when the molecule is in its reduced (Fe++) form. In red blood cells (RBC) Hb is in the reduced form. The formation of Hi, which contains Fe as a result of Hb oxidation, is the first step in Hb degradation. This step is reversible in RBC. Previously, we have described the preparation of SFHS containing the methemoglobin reductase (MR) system of RBC. To improve the stability of SFHS, we first investigated the formation of Hi as a function of pH and ionic strength and quantified the MR activity in SFHS. Non-enzymatic Hi reduction was studied with substances as ascorbate and glutathione. Stimulation of MR by EDTA was tested. Inhibition of Hi formation was studied with nicotinic acid amide in the presence and absence of NADH. It is concluded that ascorbate and glutathione are not effective during extended periods of storage of SFHS, and that EDTA causes formation of large amounts of Hi. Nicotinic acid amide did not inhibit Hi formation. NADH, as a substrate for the MR system, is very effective in keeping Hi low.

Blood Gas Analysis↗