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P D Wimberley

Publications and source records attributed to P D Wimberley.

At least 19 recordsLinked to original sources
PubMed2002

A new transcutaneous bilirubinometer, BiliCheck, used in the neonatal intensive care unit and the maternity ward.

UNLABELLED: Transcutaneous bilirubin (TcB) was measured with a new bilirubinometer, BiliCheck, in 261 jaundiced infants in the neonatal intensive care unit (NICU) [gestational age (GA) 25-43 wk] (group 1) and in 227 healthy jaundiced term and near-term infants (GA 35-43 wk) (group 2). Imprecision of a single determination of TcB measured on the forehead [TcB(h)], expressed as 1 standard deviation, was 15-18 micromol l(-1). No statistically significant difference between intraoperator and interoperator imprecision was found. There was a good correlation between TcB(h) and total serum bilirubin (TSB) in both groups of infants, although TcB(h) was on average lower than TSB. In the NICU infants, TcB(h), other things being equal, was lower in males than in females, and decreased with increasing postnatal age, for the same TSB level. In the infants in both groups who had a GA > or = 35 wk, sick infants had a higher TcB(h) than healthy infants for the same TSB level. The differences were statistically significant, but small and of minor clinical significance. Blood haemoglobin concentration, GA and ethnic origin were not found to influence TcB(h), i.e. BiliCheck corrects sufficiently for these factors. In all 488 infants, TcB was measured at four different body sites. Measurements on the forehead and sternum [TcB(s)] correlated well with TSB, while measurements on the knee and foot correlated less well. In the NICU infants TcB(h) predicted TSB statistically significantly better than TcB(s), while in the healthy term and near-term infants TcB(h) and TcB(s) predicted TSB equally well. Therefore, the preferable body site for measurement of TcB under routine conditions is the forehead. By retrospective analysis of the data, a screening model is presented whereby TcB(h) can be used to screen infants who require phototherapy. We found that using screening limits for TcB(h), which are 70% of the currently used phototherapy limits for TSB, 80% of blood samples in healthy term and near-term infants, and 42% of NICU infants with GA > or = 32 wk, could be avoided. CONCLUSION: BiliCheck is suitable for screening both NICU and healthy newborn infants with jaundice, with regard to the need for phototherapy. The authors recommend using a TcB(h) limit which is 70% of the currently recommended TSB limits for phototherapy, to decide whether TSB needs to be measured.

Bilirubin↗
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↗
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

Oxygen monitoring in the newborn.

Current techniques for measuring oxygenation in newborn infants with respiratory insufficiency are reviewed, as well as the consequences of variable and high fetal hemoglobin (HbF) fractions on both the measurement of sO2 and FCOHb and the application of Siggaard-Andersen's oxygen status algorithm to newborn infants. A procedure involving tonometry of blood is described for measuring FHbF in newborn infants' blood.

Blood Gas Analysis↗
PubMed1991

Congenital dyserythropoietic anaemia with novel intra-erythroblastic and intra-erythrocytic inclusions.

A hitherto undescribed form of congenital dyserythropoietic anaemia is reported. The patient was severely anaemic and hydropic at birth and is now 8 years old. She has a moderate normochromic normocytic anaemia. HbF level of 50%, reticulocyte count of 5-12% and hyperbilirubinaemia. Bone marrow smears showed intense normoblastic erythroid hyperplasia with morphological evidence of dyserythropoiesis; the most common dysplastic features were basophilic stippling of polychromatic erythroblasts and erythrocytes and marked abnormalities of nuclear shape in polychromatic erythroblasts. Electron microscope studies showed that some polychromatic erythroblasts and several erythrocytes contained inclusions which were rounded, elongated or irregular in outline or were doughnut-shaped. These inclusions consisted of compact masses of tubules and saccules which may represent smooth endoplastic reticulum together with Golgi cisternae. The ultrastructural studies also revealed peculiar membrane-bound cylindrical structures in a rare late erythroblast, and phagocytosed erythroblasts within some macrophages. The technique of combined Feulgen microspectrophotometry and 3H-thymidine autoradiography demonstrated a pile-up of early polychromatic erythroblasts in the G1 and G2 phases of the cell cycle, indicating a prolongation of, or an arrest at, these phases. Furthermore, nearly a quarter of all erythroblasts failed to incorporate 3H-leucine into protein. Thus the anaemia appeared to be due to a combination of disordered erythroblast function, increased ineffectiveness of erythropoiesis and peripheral haemolysis. The primary defect may be an excessive synthesis or impaired degradation of intracytoplasmic membranes.

Anemia, Dyserythropoietic, Congenital↗
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↗
PubMed1990

Direct reading glucose electrodes detect the molality of glucose in plasma and whole blood.

It is the activity that determines the direction of chemical processes, transport, etc. and thus provides the clinically more relevant information. Direct reading glucose electrodes consume glucose at a rate proportional to the glucose activity in the sample. The activity equals the molality (mmol glucose per kg water), so results from direct reading glucose electrodes must differ from the conventionally measured glucose concentration. This was observed in 159 whole blood samples which gave higher results from a direct reading glucose electrode than by our conventional method (y = 1.21x - 0.37 mmol/l). However, adjustment for the different water concentration due to salt, plasma proteins, and hemoglobin occupying space, gave results equal to the concentrations (y = 1.00x - 0.28 mmol/l, r = 0.997). Furthermore, results for samples with constant glucose concentration and varying albumin concentration correlated with the albumin concentration (r = 0.989), but not after adjustment for water concentration (r = 0.037, n.s.).

Blood Chemical Analysis↗
PubMed1990

The oxygen status of the arterial blood revised: relevant oxygen parameters for monitoring the arterial oxygen availability.

The new generation of very accurate multi-wavelength oximeters, e.g. OSM3, for in vitro measurement of the hemoglobin oxygen saturation, total hemoglobin concentration, and carboxy- and methemoglobin fractions opens new aspects of oxygen monitoring. Combined with the data from the blood gas analyzer (e.g. ABL300) these very accurate measurements allow the calculation of several derived oxygen parameters on the basis of a set of newly developed calculation algorithms. The traditional parameters obtained from an arterial sample are the oxygen tension (pO2) and the hemoglobin oxygen saturation (sO2). Clinical examples illustrate that the pO2 and the sO2 even in combination may give misleading information. The new algorithm calculates three extra oxygen parameters. 1) The oxygen extraction tension, px, defined as the tension required to extract 2.3 mmol of oxygen per liter blood. It signals the mixed venous pO2 level on the assumption that the arterio-venous oxygen difference is normal (2.3 mmol/L). 2) The concentration of extractable oxygen, cx, defined as the concentration of oxygen extracted at a tension of 5.0 kPa. 3) The oxygen compensation factor, Qx, derived as (2.3 mmol/L)/cx. It may be interpreted as the increase in cardiac output necessary to maintain a normal mixed venous pO2 of 5 kPa. These three parameters indicate the oxygen availability of the blood and summarize important properties of the arterial blood in relation to oxygen supply of the tissues, including the arterial pO2, the 'active' hemoglobin concentration (equivalent to the oxygen capacity), and the hemoglobin oxygen affinity (p50). The set of data measured with the blood gas analyzer, e.g. the ABL300 combined with the data measured with the OSM3 contains much more information than is routinely utilized. This information is extracted and summarized by our calculation algorithm. Omitting the calculation of the extra oxygen parameters involves a risk of losing valuable information.

Arteries↗
PubMed1990

Arterial oxygen status determined with routine pH/blood gas equipment and multi-wavelength hemoximetry: reference values, precision, and accuracy.

We measured pH, pCO2, pO2, oxygen saturation, total hemoglobin concentration, and fractions of carboxy- and methemoglobin in arterial blood samples from 35 healthy adults. We used a new algorithm to calculate active hemoglobin concentration, total oxygen concentration, actual half-saturation tension, 2,3-diphosphoglycerate concentration, estimated functional shunt, oxygen extraction tension px (for extracting 2.3 mmol of oxygen per liter of blood, values below 4.5 kPa indicating risk of tissue hypoxia), and the oxygen compensation factor Qx (the factor by which the cardiac output should rise to maintain a normal mixed venous pO2 of 5.0 kPa, factors above 1.5 indicating an extra burden on the heart). Analytical precision was evaluated by duplicate determinations. The accuracy of the half-saturation tension was evaluated by comparison with values for simultaneously drawn venous blood, the accuracy of the calculated concentration of 2,3-diphosphoglycerate by comparison with direct enzymatic measurements. We conclude that all the variables may be determined with sufficient accuracy and precision in healthy adults, provided the oxygen saturation is less than 0.97 and the measurements are performed according to the highest state of the art.

2,3-Diphosphoglycerate↗
PubMed1990

Accurate measurements of hemoglobin oxygen saturation, and fractions of carboxyhemoglobin and methemoglobin in fetal blood using Radiometer OSM3: corrections for fetal hemoglobin fraction and pH.

The differences in the visible absorption spectra between fetal and adult oxyhemoglobin and carboxyhemoglobin result in errors in the measurements og hemoglobin oxygen saturation (SO2) and carboxyhemoglobin fraction (FCOHb) in fetal blood, if not corrected for the actual fetal hemoglobin fraction (FHbF) in the sample. In 11 fully oxygenated umbilical cord blood samples (mean FHbF = 77%), we found a mean positive bias in SO2 of 4.7%, and in FCOHb of 2.7%, when measured with a dedicated spectrophotometer (OSM3, Radiometer A/S, Denmark), and using the matrix of absorption coefficients for adult hemoglobin. Accurate measurements were obtained by using OSM3's correction for FHbF in the blood specimen after measurement of FHbF by OSM3. The effects of plasma pH on the measurements of SO2 and FCOHb in fully oxygenated fetal blood were found to be similar to those found for adult blood. From plasma pH 7.05 to 8.02, measured SO2 increased 1.3% and FCOHb 0.6%. Correction for the pH of fetal blood samples should be considered when calibrating OSM3 and in connection with research studies. The effects of FHbF and pH on the measurement of methemoglobin fraction (FMetHb) were less than 0.2%, and can be ignored. FHbF measured by OSM3 at pH 7.4 is about 14% too high compared to alkali denaturation rate method. However, the presence of a metabolic acidemia, which is common in fetal blood specimens, decreases this bias, so that for example in our study, FHbF, measured by OSM3 and uncorrected for pH changes was on average only 6% too high. We recommend that OSM3's factor of 18.6 is reduced to 16.4, and that correction is made for pH.

Carboxyhemoglobin↗
PubMed1990

Guidelines for transcutaneous p O2 and p CO2 measurement.

This document provides guidelines in the terminology, methodology, and in the interpretation of data obtained from the use of skin (transcutaneous) p O2 and p CO2 electrodes. The transcutaneous technique has found special application for newborn infants. The causes of analytical bias with respect to arterial blood gas values and imprecision obtained with transcutaneous p O2 and p CO2 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↗
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

[Oxygen status of arterial blood including uncompensated mixed venous oxygen tension and cardial oxygen compensation factor. Reevaluation on the basis of 250 arterial punctures].

In arterial blood from 250 patients we measured pH, pco2, and po2 (electrochemically) together with total-hemoglobin concentration, oxygen saturation, carboxy- and methemoglobin fractions (spectrometrically). With a previously published algorithm we calculated the effective hemoglobin concentration, total-oxygen concentration, half saturation tension, erythrocyte 2,3-diphosphoglycerate concentration, and two new oxygen parameters: uncompensated mixed venous oxygen tension and cardiac oxygen compensation factor. 11% of the patients have normal arterial oxygen tension, but nevertheless risk of tissue hypoxia judged from the two new oxygen parameters. This is due to a low hemoglobin concentration and/or low half saturation tension (increased hemoglobin oxygen affinity). Some patients have decreased arterial oxygen tension but normal uncompensated mixed venous oxygen tension (15%) or normal cardiac oxygen compensation factor (9%). This is due to a high hemoglobin concentration and/or increased half saturation tension. The latter varies from 2.6 to 5.2 kPa (ref.: 3.3-3.9 kPa); 36% have decreased, 27% increased values. The 2,3-diphospho-glycerate concentration varies from 2.0 to 7.9 mmol/l (ref.: 3.6-5.1 mmol/l); 14% have decreased, 30% increased values. Uncompensated mixed venous oxygen tension varies from 1.8 to 5.7 kPa (ref.: 4.5-5.5 kPaf). The cardiac oxygen compensation factor varies from 0.9 to infinity (ref.: 0.8-1.6). We conclude that the variation in the different oxygen parameters is so significant that it justifies routine calculation for all arterial blood samples where the measurement on a conventional blood gas analyzer is supplemented with measurement on one of the new multi-wavelength hemoximeters. The calculation algorithm permits calculation of all the oxygen parameters for the majority of arterial samples (84%) where the oxygen saturation is less than or equal to 0.970.

Adult↗
PubMed1989

Chloride and bicarbonate transport in fetal red cells.

1. Chloride (JCl) and bicarbonate (JHCO3) self-exchange flux in fetal human red cells was studied at 0-38 degrees C as 36Cl- and [14C]HCO3- efflux. 2. Both at 0 and 38 degrees C JCl showed a bell-shaped pH dependence with a broad maximum at pH 7-8. JCl was 99.7% inhibited by the binding of 1.1 x 10(6) 4,4'-diisothiocyanostilbene-2,2'-disulphonate (DIDS) molecules per cell membrane. 3. By raising the temperature from 0 to 38 degrees C JCl, at external concentration (C0) = 150 mM, increased about 200 times to 5 x 10(-8) mol/(cm2 s), the half-time of the tracer efflux being 80 ms at 38 degrees C and pH 7.2. Under conditions where Co = (110 mM-Cl- + 25 mM-HCO3-), JCl also increased by about 200 times, while JHCO3 increased only about 100 times, as temperature was raised from 0 to 38 degrees C. 4. The apparent activation energy (EA) of Janion was not constant, but increased gradually with decreasing temperature. Assuming that the change of EA with temperature consists of two components JCl, under both experimental conditions, had average values of EA = 117-120 under and EA = 73-78 kJ/mol above a 'breaking' point at 15-20 degrees C, while JHCO3 showed an EA = 100 below and EA = 48 kJ/mol above 25 degrees C. 5. We conclude that the anion transport protein becomes built into the membrane at a very early stage of life, and that the kinetics of Janion in fetal red cells show characteristics that are similar to those of adult red cells. 6. Our results suggest that the CO2 transport capacity of the fetal blood can be exploited during rest nearly as efficiently as that of adult blood.

Bicarbonates↗