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Biomedical subjects

A Houston

Publications and source records attributed to A Houston.

At least 19 recordsLinked to original sources
PubMed1992

A new standard for sterility testing for autoclaved surgical trays.

Sterility testing on autoclaved surgical trays provides scientific information on the duration for which an item can be safely stored. Previous studies were performed by sampling at various time-points after storage and did not take into account potential injuries (moving, lifting etc.) to these trays as they occur in a clinical setting. A standardized protocol was developed by an expert panel based on events which were frequently observed in the Central Sterilization area. We tested 600 samples in 100 surgical trays that were moved and transported according to the standardized protocol. Moved surgical trays were contaminated in 8.3% of tests, a figure much higher than that reported by previous studies. These data suggest that current standards for sterility testing of autoclaved surgical trays can be improved by the addition of event-related testing.

Central Supply, Hospital↗
PubMed1991

Perceptual and statistical analysis of cardiac phase and amplitude images.

A perceptual experiment was conducted using cardiac phase and amplitude images. Estimates of statistical parameters were derived from the images and the diagnostic potential of human and statistical decisions compared. Five methods were used to generate the images from 75 gated cardiac studies, 39 of which were classified as pathological. The images were presented to 12 observers experienced in nuclear medicine. The observers rated the images using a five-category scale based on their confidence of an abnormality presenting. Circular and linear statistics were used to analyse phase and amplitude image data, respectively. Estimates of mean, standard deviation (SD), skewness, kurtosis and the first term of the spatial correlation function were evaluated in the region of the left ventricle. A receiver operating characteristic analysis was performed on both sets of data and the human and statistical decisions compared. For phase images, circular SD was shown to discriminate better between normal and abnormal than experienced observers, but no single statistic discriminated as well as the human observer for amplitude images.

Analysis of Variance↗
PubMed1990

Effect of serum on the in vitro activities of 11 broad-spectrum antibiotics.

We evaluated the effect of serum on the in vitro activities of 11 antimicrobial agents against gram-negative isolates obtained from 100 patients with nosocomial bacteremia. The test organisms included 25 stains of Pseudomonas aeruginosa and 75 strains of the family Enterobacteriaceae. MICs were determined by broth microdilution with Mueller-Hinton broth alone or supplemented with 25 or 50% pooled, heat-inactivated human serum (25S or 50S, respectively). Among the antibiotics evaluated, the protein binding ranged from 9 to 95%. The antibiotics tested and their MICs for 90% of the strains tested in 50S included ciprofloxacin (0.12 micrograms/ml), ceftazidime (1 micrograms/ml), imipenem (1 micrograms/ml), aztreonam (4 micrograms/ml), cefpirome (4 micrograms/ml), cefotaxime (16 micrograms/ml), cefoperazone (16 micrograms/ml), desacetylcefotaxime plus cefotaxime (32 micrograms/ml), ceftriaxone (greater than 32 micrograms/ml), ticarcillin (128 micrograms/ml), and desacetylcefotaxime (greater than 128 micrograms/ml). MICs for 90% of the strains tested were calculated with 95% confidence intervals to show the precision of the MICs for these strains. With the exceptions of ceftriaxone (greater than 95% protein bound) and cefoperazone (90% protein bound), serum had no significant effect on the in vitro activities of various agents. A fourfold-or-greater increase in the MIC of ceftriaxone was observed in 45 of 100 isolates with 50S and in 30 of 100 isolates with 25S. With cefoperazone, 17 of 100 isolates demonstrated more than 2 twofold dilution increases in 50S. Testing of antibiotics which were less protein bound illustrated minor effects primarily with members of the Enterobacteriaceae. The presence of serum did not adversely affect the in vitro activities of broad-spectrum agents against these nosocomial isolates.

Anti-Bacterial Agents↗
PubMed1990

Reproducibility of measurements of cardiac output in newborn infants by Doppler ultrasound.

Interobserver reproducibility in deriving cardiac output by measuring aortic blood flow velocity and diameter with imaging and Doppler ultrasound was investigated in 20 healthy infants born at full term. Aortic diameter was measured in three ways. Mean blood flow velocity was measured at three sites with both continuous wave and pulsed Doppler. Two observers carried out each study independently. Intraobserver reproducibility was investigated in 12 infants using the suprasternal site for measuring blood flow velocity. The most reproducible determination of cardiac output was found when the suprasternal site with continuous wave Doppler was used for measurement of blood flow velocity and M mode trailing edge to leading edge echocardiography was used for diameter. Normal mean (2 SD) cardiac output is 231 (77) ml/kg/min. Technical difficulties in measuring aortic diameter accurately limit direct comparison between infants.

Cardiac Output↗
PubMed1990

Red cell volume and cardiac output in anaemic preterm infants.

To test the hypothesis that haemoglobin concentration is a poor predictor of benefit from transfusion in preterm infants, and that red cell volume is the most important indicator of anaemia, 24 preterm infants receiving red cell transfusions had red cell volume, haemoglobin concentration, and cardiac output measured before and after transfusion. Red cell volume was measured either using dilution of autologous fetal haemoglobin with donor adult haemoglobin, or with a new technique using biotin as a red cell label. The two techniques give similar results. Mean (SD) values before transfusion were 27.4 (13.3), and after transfusion 45.0 (13.7) ml/kg. Cardiac output was measured using imaging and Doppler ultrasonography, and fell with transfusion from mean 286 (121) to 251 (95.6) ml/kg/min. The red cell volume before transfusion correlated well with changes in cardiac output following transfusion, infants with a red cell volume before transfusion of less than 25 ml/kg showing a fall in cardiac output, and those with a red cell volume of greater than 25 ml/kg not showing a significant fall. There was no correlation between haemoglobin concentration, packed cell volume, or change in packed cell volume with changes in cardiac output after transfusion. A red cell volume of 25 ml/kg seems to be critical in preterm infants with anaemia, and infants with values below this are those most likely to benefit from transfusion.

Anemia, Neonatal↗
PubMed1989

Normal rat serum cytotoxicity against syngeneic oligodendrocytes. Complement activation and attack in the absence of anti-myelin antibodies.

The role of complement in mediating oligodendrocyte and myelin injury has been investigated by studying the effects of normal adult rat serum on syngeneic cultured neonatal glial cells. Rat serum has cytotoxic activity directed against oligodendrocytes but not astrocytes, the potency of which increases with cell maturation. The effects of heat inactivation, decomplemented rat serum, EGTA treatment, removal of any possible anti-myelin antibody by absorption using syngeneic myelin and absence of surface staining for immunoglobulins on serum-treated oligodendrocytes, C9 depletion and reconstitution, and oligodendrocyte staining for surface C9 demonstrate that this cytotoxicity is mediated by complement via antibody independent activation of the classical pathway and is membrane attack complex dependent. These findings significantly extend the previous demonstration of complement activation by extracted myelin, and may have significance for the pathogenesis of demyelinating diseases.

Animals↗
PubMed1989

Normal limits of the high-fidelity pediatric ECG. Preliminary observations.

A study of more than 1,780 neonates, infants, and children was carried out, using a digital electrocardiograph with a sampling rate of 500 per second, to revise the normal limits of the pediatric ECG. The 12-lead ECG was used with V4R replacing V3. All leads were recorded simultaneously off-line in digital form on magnetic tape and were subsequently analyzed using well-established computing techniques. The results showed that the upper 98 percentile limit of normal amplitudes could be up to 46% higher than previously published limits. Differences in some mean values were very much higher, though these are of less clinical significance. In addition, QRS durations were found to be wider than previously published data. Sex-related differences could be demonstrated in both amplitude and duration measurements, particularly in the early adolescent years. This study confirms that to record pediatric ECGs with high fidelity, it is necessary to use equipment that converts the ECG from analog to digital form at a rate of 500 samples/sec. Significant errors in amplitude and duration measurements may be expected if a much lower sampling rate is utilized.

Adolescent↗
PubMed1987

Psychiatric training for primary care residents: proposed standards.

Most of the nation's psychiatric care is provided by primary care physicians, and this trend is expected to continue. Primary care physicians see themselves as poorly trained in psychiatry, and evidence supports a high incidence of missed diagnosis and inadequate or inappropriate treatment. In addition, poor training may underlie the indifference to psychiatric problems often demonstrated by primary physicians. The Ohio Psychiatric Association Foundation has designated an annual award to be given to the primary care program which provides the best psychiatric training in the state, and the psychiatric training directors met to develop criteria for selecting the recipients. The resulting standards emphasize the importance of training which is relevant to a medical care setting, provided by psychiatrists, and supportive of the integration of psychiatric methods into medical care.

Curriculum↗
PubMed1984

Mitral valve replacement in the first three months of life.

Two infants, aged 2 and 3 months, underwent mitral valve replacement with Björk-Shiley mechanical valves for severe congenital mitral regurgitation not amenable to valve repair. Both infants survived the operation and left hospital taking a low dose aspirin anticoagulant regimen. One child survived for three years without incident, but the other died at 11 months of pneumonia after valve replacement for tissue ingrowth and subsequent thrombosis.

Graft Occlusion, Vascular↗
PubMed1984

A simple separator to generate half micron aqueous particles for lung imaging.

An aerosol of a radionuclide may be used for ventilation imaging as an alternative to radioactive rare gases. For good-quality images as few particles as possible must be deposited in the trachea and bronchi, which means that no, or very few, particles should have aerodynamic diameter of more than 2 micron. We have developed a separator to modify the output of an Acorn jet nebuliser. It reduced the proportion of particles in the aerosol with aerodynamic diameters of more than 2 micron from 60% for the unmodified output of the nebuliser to only 6%; it consisted of a cylinder of perspex with two compartments containing inert spheres, either stainless steel or glass, of diameter 3 mm (the first compartment contained two layers of spheres, and the main section was packed with spheres). To examine the efficiency of the separator system for routine clinical use we compared the images produced and the deposition of the particles in the modified aerosol (using 99TcmDTPA) with the distribution of ventilation of 81Krm in eight subjects. Despite the theoretical differences between the behaviour of a gas molecule and of a particle in the respiratory tree, the images produced using the modified aerosol delivery system were as good as those produced with 81Krm in normal subjects. In abnormal subjects the images produced were only distinguished following the calculation of a penetration index.

Adult↗
PubMed1983

Acute chlormethiazole poisoning in patients notified to the Poisons Unit, Guy's Hospital, 1978--1981.

1 Out of 493 patients with suspected acute chlormethiazole poisoning notified to the Poisons Unit, Guy's Hospital during 1978--1981, the diagnosis was confirmed either analytically or by detailed clinical information in 108 patients, 40 of whom had ingested chlormethiazole alone. 2 The principal signs reported indicate that the clinical features of acute chlormethiazole poisoning resemble those of barbiturate poisoning, with deep coma (n = 66), respiratory depression (n = 26) and hypotension (n = 17) in the severe cases. Five patients died as a result of early, profound respiratory depression. 3 In 53 survivors in whom toxicological analyses were performed, poisoning with chlormethiazole alone had a better prognosis than when ethanol or other drugs were also present, except in patients with hepatic or pulmonary disease or in the elderly. 4 These results emphasise that although patients poisoned with chlormethiazole who survive to reach hospital generally have a good prognosis, fatal respiratory complications often occur before the patient can be treated.

Adolescent↗