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PubMed2000

Clostridial gas gangrene. II. Phospholipase C-induced activation of platelet gpIIbIIIa mediates vascular occlusion and myonecrosis in Clostridium perfringens gas gangrene.

Clostridium perfringens gas gangrene is a fulminant infection, and radical amputation remains the single best treatment. It has been hypothesized that rapid tissue destruction is related to tissue hypoxia secondary to toxin-induced vascular obstruction, and previous studies demonstrated that phospholipase C (PLC) caused a rapid and irreversible decrease in skeletal muscle blood flow that paralleled the formation of intravascular aggregates of activated platelets, fibrin, and leukocytes. In this study, flow cytometry demonstrated that PLC stimulated platelet/neutrophil aggregation in a gpIIbIIIa-dependent fashion. Pretreatment of animals with heparin or depletion of leukocytes reduced blood-flow deficits, and aggregate formation caused by PLC. It is concluded that fulminant tissue destruction in gas gangrene results from profound attenuation of blood flow caused by PLC-induced, gpIIbIIIa-mediated formation of heterotypic platelet/polymorphonuclear leukocyte aggregates. Therapeutic strategies that target gpIIbIIIa may prevent vascular occlusion, maintain tissue viability, and provide an alternative to radical amputation for patients with this infection.

Animals↗

PubMedDate not supplied

Simultaneous identification of amphetamine and methamphetamine using solid-phase extraction and gas chromatography/nitrogen phosphorous detection or gas chromatography/mass spectrometry.

A method for the simultaneous detection and quantitation of amphetamine and methamphetamine in urine is described. Using solid-phase extraction, amphetamine, methamphetamine, and n-propylamphetamine (internal standard) are extracted from urine samples. Drugs in their free form are identified using gas chromatography/nitrogen-phosphorous detection (GC/NPD), whereas their heptafluorobutyric anhydride derivatives are detected by gas chromatography/mass spectrometry (GC/MS) in the selected ion monitoring (SIM) mode. Limits of detection for both amphetamine and methamphetamine are approximately 35 ng/mL. The procedure is simple, rapid, and suitable for a large number of specimens (25 or more).

Amphetamine↗

PubMed2001

Ventilation-perfusion inhomogeneity increases gas uptake: theoretical modeling of gas exchange.

Ventilation-perfusion (VA/Q) inhomogeneity was modeled to measure its effect on gas exchange in the presence of inspired mixtures of two soluble gases using a two-compartment computer model. Theoretical studies involving a mixture of hypothetical gases with equal solubility in blood showed that the effect of increasing inhomogeneity of distributions of either ventilation or blood flow is to paradoxically increase uptake of the gas with the lowest overall uptake in relation to its inspired concentration. This phenomenon is explained by the concentrating effects that uptake of soluble gases exert on each other in low VA/Q compartments. Repeating this analysis for inspired mixtures of 30% O(2) and 70% nitrous oxide (N(2)O) confirmed that, during "steady-state" N(2)O anesthesia, uptake of N(2)O is predicted to paradoxically increase in the presence of worsening VA/Q inhomogeneity.

Models, Biological↗

PubMed2006

Prediction of arterial blood gas values from venous blood gas values in patients with acute exacerbation of chronic obstructive pulmonary disease.

Arterial blood gas (ABG) analysis has an important role in the clinical assessment of patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). However, arterial puncture or insertion of an arterial catheter has many drawbacks. The aim of this study was to evaluate whether venous blood gas (VBG) values of pH, partial pressure of carbon dioxide (PCO(2)) and oxygen (PO(2)), bicarbonate (HCO(3)), and oxygen saturation (SO(2)) can reliably predict ABG levels in patients with AECOPD. One hundred and thirty-two patients with a prior diagnosis of COPD presenting with acute exacerbation according to AECOPD criteria were included in this prospective study. AECOPD is defined as a recent increase in cough, wheezing, the volume and purulence of sputum or shortness of breath necessitating a change in regular medication, including corticosteroids or antibiotics. ABG samples were taken immediately after venous sampling, and both were analyzed. Linear regression analysis was performed and equations were established for the estimation of arterial values. The Pearson correlation coefficients for pH, PCO(2), HCO(3), PO(2), and SO(2) were 0.934, 0.908, 0.927, 0.252, and 0.296, respectively. There was a significant correlation between ABG and VBG values of pH, PCO(2), and HCO(3) (p < 0.001). Linear regression equations for the estimation of pH, PCO(2), and HCO(3) were as follows: arterial pH = 1.004 x venous pH; arterial PCO(2) = 0.873 x venous PCO(2); and arterial HCO(3) = 0.951 x venous HCO(3). VBG analysis can reliably predict the ABG values of pH, PCO(2) and HCO(3) in patients with AECOPD.

Acute Disease↗

PubMed1992

The effect of respiratory care department management of a blood gas analyzer on the appropriateness of arterial blood gas utilization.

We investigated the effects of establishing a blood gas analysis service controlled by respiratory care practitioners (RCPs) on the appropriateness of arterial blood gas (ABG) sampling. An ABG analyzer was placed outside the surgical intensive care unit (SICU) and only RCPs were permitted to process samples on it. In 1-month and 1-year follow-up audits of appropriateness of ABG analysis, the nursing staff improved from 42% appropriate to 73% appropriate in both follow-up periods. RCPs maintained a high degree of appropriateness in all periods (90%, 87%, and 91%), although the percentage of the total ABGs performed by RCPs increased. Additional benefits included a better mutual understanding of each caregiver's role and work load, more collaboration among caregiver groups, and caregiver's perception of improved patient care.

Blood Gas Analysis↗

PubMed1978

Enlarged acid-base and blood gas calculations by electronical data computing in the blood gas laboratory.

A rapid anaysis of parameters of the acid-base equilibrium and blood gases during open heart surgery and emergency therapy is absolutely necessary. Computing of the several parameters of the acid-base status by slide rules or nomograms is time consuming and can be shortened by computer applications. The central blood gas laboratory consists of a blood gas analyzer for PO2, PCO2 and pH, an electronic desktop calculator, a four color X-Y-plotter and two data lines to the cardiac surgery unit and to the intensive care unit. The time needed for computing and feedback of the parameters could be decreased to one quarter. In addition to numerical data printout, a graphical representation of the several parameters is possible on a X-Y-plotter and includes the Rahn-Fenn-O2-CO2-Diagram with venous admixture, ventilation perfusion ratio, alveolar dead space ventilation and the standard and actual oxygen dissociation curve as well as the pH/HCO3- Acid-Base nomogram. Furthermore, a computer diagnosis of the actual disturbances can be plotted.

Acid-Base Equilibrium↗

PubMedDate not supplied

Determination of desaminosulfamethazine, sulfamethazine, and N4-acetylsulfamethazine by gas chromatography with electron capture detection and confirmation by gas chromatography-chemical ionization mass spectrometry.

An electron capture gas chromatographic method for the determination of sulfamethazine was modified to separate and quantitate simultaneously sulfamethazine and 2 of its metabolites, N4-acetylsulfamethazine and desaminosulfamethazine. The modified method was applied to incurred residues in a veal calf depletion study and to incurred residues in swine tissues. With capillary column gas chromatography-positive ion chemical ionization mass spectrometry, confirmation of the identities of incurred desaminosulfamethazine, N4-acetylsulfamethazine, and sulfamethazine in tissues was obtained from a single injection.

Animals↗

PubMed1979

Adsorption of organic acids from amniotic fluid and urine onto silica gel before analysis by gas chromatography and combined gas chromatography/mass spectrometry.

We describe a method for adsorbing organic acids from amniotic fluid and urine specimens onto a column of silica gel before analysis by gas chromatography and by combined gas chromatography/mass spectrometry. Analytical recoveries of individual organic acids by our adsorption method compare favorably with those obtained by a more laborious manual extraction with ethyl acetate. Results for specimens of amniotic fluid and urine show that our method gives better recoveries of most of the organic acids. Furthermore, because citric acid is also extracted in our method without extracting significant amounts of sulfate or phosphate, the method is a suitable alternative to methods involving the use of DEAE-Sephadex for concentrating these acids.

Amniotic Fluid↗

PubMed1977

[Gas-chromatographic determination of insecticidal chlorinated hydrocarbons using the GCHF 18.3-6 gas chromatograph with an attached electron detector].

The authors describe the gas chromatographic determination of residues of insecticidal chlorinated hydrocarbons in foods by means of the GCHF 18.3-6 gas chromatograph with electron attachment detector of the VEB Chromatron Berlin which is most frequently available in the GDR for routine work. Furthermore, the authors deal with possibilities of identifying and confirming residues of chlorinated hydrocarbons with the aid of chemical reactions.

Aldrin↗

PubMed1997

Gas chromatography in anaesthesia. I. A brief review of analytical methods and gas chromatographic detector and column systems.

Practical applications and relevant studies involving the anaesthetic gases, have been extensively described in the literature. Many eminent analytical methods have already been developed for medical practice where routine analysis of anaesthetics is frequently needed, particularly during anaesthesia, and in related and respiratory research programmes. The determination of halothane, isoflurane, enflurane and nitrous oxide concentrations from vaporizers, in exhaled and inhaled gas mixtures, in body fluids and tissues is necessary to control anaesthetic concentrations, and thus, the relevant and adverse effects successfully. Therefore, a literature review, with particular emphasis on gas chromatography would provide important information for investigators in the search for a suitable analytical method for the analysis of multi-component mixtures of anaesthetic gases.

Anesthesia↗

PubMed1997

Application of gas-liquid chromatography to the analysis of essential oils. Part XVII. Fingerprinting of essential oils by temperature-programmed gas-liquid chromatography using capillary columns with non-polar stationary phases. Analytical methods committee.

Problems in obtaining reproducible results when 'fingerprinting' essential oils by temperature-programmed gas-liquid chromatography have been reported on in Parts VII and VIII of this series. Those reports were concerned with the general problems and the use of packed columns. This report is concerned with the use of capillary columns and non-polar stationary phases. A collaborative study using capillary columns with non-polar stationary phases has resulted in a method which specifies the 'g-pack value' of a column and gives reproducible relative retention indices for the test compounds limonene, acetophenone, linalol, naphthalene, linalyl acetate and cinnamyl alcohol. The method has been applied successfully to the examination of oil of rosemary. A recommended method is given for the reproducible temperature-programmed gas-liquid chromatographic fingerprinting of essential oils using capillary columns with non-polar stationary phases.

Chromatography, Gas↗

PubMed1999

Analysis of alkenes by copper ion chemical ionization gas chromatography/mass spectrometry and gas chromatography/tandem mass spectrometry

A novel chemical ionization/fast atom bombardment (CI/FAB) source was used to analyse alkenes by chemical ionization mass spectrometry (CI-MS) using copper ions as the ionizing agent. The Cu(+)-CI mass spectra showed abundant pseudomolecular adduct ions [alkene-Cu](+) and characteristic fragment ions. Mass-analysed ion kinetic energy spectroscopy was used to study the product ions resulting from the decomposition of adduct ions and to eliminate background interferences derived from the copper ions. The major fragmentations permitted the localization of double bonds and minor fragments allowed the differentiation of alkene isomers. The CI/FAB source was coupled to a gas chromatograph and simple and complex mixtures of octene isomers were analysed by gas chromatography (GC)/Cu(+)-CI-MS and GC/Cu(+)-CI-MS/MS. Copyright 1999 John Wiley & Sons, Ltd.

Journal Article↗

PubMed2001

Determination of polychlorodibenzo-p-dioxins and polychlorodibenzofurans by gas chromatography/tandem mass spectrometry and gas chromatography/triple mass spectrometry in a quadrupole ion trap.

The determination of tetra- to octachlorodibenzo-p-dioxins and tetra- to octachlorodibenzofurans (PCCD/Fs) by high-resolution gas chromatography/tandem mass spectrometry (HRGC/MS/MS) and high-resolution gas chromatography/triple mass spectrometry (HRGC/MS(3)) in a quadrupole ion trap, equipped with an external ion source, is presented. MS/MS involves a typical four-step process, namely ionization, parent ion isolation, collision-induced dissociation (CID) and mass analysis of the daughter ions. For the MS(3) experiment, the MS/MS scan function is used with the addition of selected daughter ion isolation, their CID and the mass analysis of second-generation product ions called 'grand-daughter ions.' For both methods, the energies necessary for the CID of the 17 PCDD/Fs were determined and optimized using multiple scan functions with different CID amplitudes. The CID efficiency, defined as the signal ratio of fragment ions detected from the major dissociation channels to molecular ions isolated, was 1.15-2.40 V for parent ion dissociation (MS/MS) and 1.05-1.50 V for daughter ion dissociation (MS(3)) and for all the chloro congeners. The same sensitivity (1 pg microl(-1)) can be reached with both the MS/MS and MS(3) methods and linear responses were obtained between 1 and 100 pg microl(-1) injected.

Journal Article↗

PubMed2006

Combined use of gas chromatography and selected ion flow tube mass spectrometry for absolute trace gas quantification.

The value of the gas chromatography (GC) and selected ion flow tube mass spectrometry (SIFT-MS) combination for the analysis of trace gases is demonstrated by the quantification of acetone in air samples using the three precursor ions available to SIFT-MS, viz. H3O+, NO+ and O2+, and by the separation of the isomers 1-propanol and 2-propanol, and their analysis using H3O+ precursor ions. It is shown that the GC/SIFT-MS combination allows for accurate trace gas quantification obviating the regular, time-consuming calibrations that are usually required for the more commonly used detectors of GC systems, and the positive identification of isomers in mixtures that is often challenging using SIFT-MS alone. Thus, the GC/SIFT-MS combination paves the way to more confident analyses of complex mixtures such as exhaled breath.

Journal Article↗

PubMed1984

The wide-range ejector flowmeter: calibrated gas evacuation comprising both high and low gas flows.

The wide-range ejector flowmeter is an active scavenging system applying calibrated gas removal directly to the anaesthetic circuit. The evacuation rate can be adjusted on the flowmeter under visual control using the calibration scale ranging from 200 ml X min-1 to 151 X min-1. The accuracy of the calibration was tested on three ejector flowmeters at 12 different presettings. The percentage deviation from presetting varied from + 18 to - 19.4 per cent. The ejector flowmeter enables the provision of consistent and accurately calibrated extraction of waste gases and is applicable within a wide range of fresh gas flows.

Anesthesiology↗

PubMed1985

A mathematical model for gas exchange in the fish gill based on non-linear blood gas equilibrium curves.

A mathematical model for gas exchange in fish gills is presented, which makes allowance for the non-linear nature of the oxygen and carbon dioxide equilibrium curves of blood, for the uneven distribution of diffusion conductance along the secondary lamellae, and for coupling of oxygen and carbon dioxide exchange through the Bohr and Haldane effects. The model demonstrates that for oxygen loading in the gill the sigmoid equilibrium curve is superior to a linear one, whereas the non-linearity of the carbon dioxide equilibrium curve does not significantly affect carbon dioxide exchange and that the Bohr and Haldane effects have importance only for carbon dioxide exchange. It is also shown that the arterial and expired gas tensions and concentrations are unaffected by whether the bulk of the diffusion conductance is at either the afferent or the efferent end of the individual lamellae, provided that the total conductance is unchanged.

Animals↗

PubMed1988

Gas-phase protein sequencing: gas flow control by positive displacement.

A modification of an automatic gas-phase protein/peptide sequencing apparatus is described; this eliminates the effect of the sample on cell gas flow rates. Consistent sequencing chemistry is achieved, yielding data from material that is intractable using standard equipment.

Amino Acid Sequence↗

PubMed2005

Raman spectra of gas hydrates--differences and analogies to ice 1h and (gas saturated) water.

It is generally accepted that Raman spectroscopic investigations of gas hydrates provide vital information regarding the structure of the hydrate, hydrate composition and cage occupancies, but most research is focused on the vibrational spectra of the guest molecules. We show that the shape and position of the Raman signals of the host molecules (H(2)O) also contain useful additional information. In this study, Raman spectra (200-4000 cm(-1)) of (mixed) gas hydrates with variable compositions and different structures are presented. The bands in the OH stretching region (3000-3800 cm(-1)), the O-H bending region (1600-1700 cm(-1)) and the O-O hydrogen bonded stretching region (100-400 cm(-1)) are compared with the corresponding bands in Raman spectra of ice Ih and liquid water. The interpretation of the differences and similarities with respect to the crystal structure and possible interactions between guest and host molecules are presented.

Carbon Dioxide↗