Etomidate and ECT.
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Anesthetics, Intravenous↗
Biomedical subjects
C Aldridge
Publications and source records attributed to C Aldridge.
The effects of astigmatism and working distance on optic nerve head images using a Heidelberg Retina Tomograph scanning laser ophthalmoscope.
PURPOSE: To determine effects of astigmatism and working distance on optic nerve head images in normal patients using the Heidelberg Retina Tomograph. METHODS: The optic disks of 51 normal healthy subjects, aged 19 to 44 years, were imaged through dilated pupils. Subjects with 0.75 DC or less of astigmatism were imaged without correction at a working distance of 15 mm. They were then re-imaged with a cylindrical correction of +3.00 DC at 90 degrees axis (n = 20). Naturally astigmatic subjects with more than 1.00 DC were imaged without correction and then re-imaged once this was neutralized with their appropriate spectacle prescription (n = 15). The effects of working distance were studied using subjects with 0.75 DC or less (n = 16). Two working distances were used, 15 and 25 mm. At each session the means of three topographic images were taken from which standard deviations and parameters were recorded. Parameters analyzed included cup shape measure, rim area, and inferior temporal rim volume. Z-profile full width at half maximum was calculated from one image per subject for each condition. RESULTS: No significant difference was found in the measured parameters of the optic disk for any astigmatic condition or changes in working distance (P >.05), (paired t test). Both the standard deviation of the mean topographic images and the Z-profile half-maximum width of the axial intensity profile were significantly greater with induced astigmatism of +3.00 DC (P values 0.3 and.00, respectively). CONCLUSIONS: Optic disk parameters are not significantly affected by uncorrected astigmatism (up to 2.50 DC) or working distance. The algorithm used by the Heidelberg Retina Tomograph to generate topographic maps is sufficiently robust that astigmatism up to 2.50 DC does not require correction.
Adult↗
Recirculation and the post-dialysis rebound.
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Blood Circulation↗
Haemodialysis recirculation detected by the three-sample method is an artefact.
The efficiency of haemodialysis may be limited by recirculation of blood between venous and arterial needles. Recirculation can be detected directly using a saline dilution method but is most commonly calculated from the urea concentrations of simultaneous samples from venous and arterial lines and a peripheral vein (three-sample method). The methods detect markedly different rates of recirculation in similar study populations. To investigate the possibility that the methods detect different phenomena, we performed both tests on 16 haemodialysis patients at various extracorporeal blood flow rates (Qb). The saline dilution method showed no recirculation in any of the patients, whereas the three-sample method indicated recirculation in all patients. The three-sample method indicated a mean recirculation fraction of 12.5% (SD 6.1) and was not influenced by changing Qb, suggesting that it was not detecting fistula recirculation. The three-sample method detects a solute concentration difference between arterial blood and peripheral blood during dialysis. There appears to be a disequilibrium between a central pool, represented by the arterial sample, and a poorly perfused peripheral pool, relatively isolated from the dialysis process, represented by the peripheral venous sample. The three-sample method for detecting recirculation should be abandoned.
Arteries↗
Interleukin-5 (IL-5) and IL-6 define two molecularly distinct pathways of B-cell differentiation.
Interleukin-5 (IL-5) and IL-6 have both been reported to act as B-cell differentiation factors by stimulating activated B cells to secrete antibody. However, it has not been possible to directly compare the effects of these two lymphokines because of the lack of a suitable B-cell line capable of responding to both. We have identified a clonal, inducible B-cell lymphoma, CH12, that has this property. Both IL-5 and IL-6 can independently stimulate increases in steady-state levels of immunoglobulin and J-chain mRNA and proteins, and they both induce the differentiation of CH12 into high-rate antibody-secreting cells. Nevertheless, there are significant differences in the activities of these two lymphokines. First, while IL-6 acts only as a differentiation factor, IL-5 also augments the proliferation of CH12 cells. Second, the differentiation stimulated by IL-5 but not by IL-6 is partially inhibited by IL-4. Inhibition of IL-5-induced differentiation was not at the level of IL-5 receptor expression, since IL-4 did not inhibit IL-5-induced proliferation. Third, IL-5 but not IL-6 stimulated increased mouse mammary tumor proviral gene expression in CH12 cells. These results demonstrate that while both IL-5 and IL-6 may act as differentiation factors for B cells, they induce differentiation by using at least partially distinct molecular pathways. Our results also establish that B cells characteristic of a single stage of development can independently respond to IL-4, IL-5, and IL-6.
Animals↗
Blood volume change during isolated ultrafiltration and combined ultrafiltration-dialysis.
Despite extensive study of the difference in the cardiovascular response to ultrafiltration in isolation and during haemodialysis, there is still disagreement in the literature as to whether or not there is a difference in the efficiency of plasma refilling between the two procedures. We believe that this results both from the use of inadequate techniques to measure change in blood volume and shortcomings in experimental design. We have employed novel methods in ten patients to study plasma refilling during isolated ultrafiltration and dialytic ultrafiltration. Measurement of blood pressure and heart rate confirmed the inferior cardiovascular tolerance to haemodialysis observed by others. However, no difference in the rate of plasma refilling could be demonstrated. Our observations suggest that the superior tolerance to isolated ultrafiltration is not explained by differences in vascular refilling.
Adult↗
Dialysis-induced change in erythrocyte volume: effect on change in blood volume calculated from packed cell volume.
Blood volume (BV) change during hemodialysis is often monitored by packed cell volume (PCV). This assumes erythrocyte volume is constant. We tested this by dialyzing 5 patients for 2 hours against high (154 mmol/l), normal (140 mmol/l) and low (126 mmol/l) dialysate sodium concentrations. Erythrocyte water content, calculated from measured blood and plasma water contents, decreased with high and increased with low dialysate sodium concentrations. Erythrocyte volume, calculated from mean corpuscular hemoglobin concentration (MCHC) decreased 3.8% with high concentration dialysate and increased 2.5% when dialysate concentration was low. These changes correlated significantly (r = 0.80, p less than 0.01) with alterations in plasma sodium. Mean corpuscular volume (MCV), measured with a Coulter-S Plus Counter did not alter because of a methodological artefact. BV change can be calculated from PCV when plasma concentrations of osmotically active substances are changed only if allowance is made for altered erythrocyte volume.
Adult↗
Continuous measurement of blood hydration during ultrafiltration using optical methods.
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Blood Volume Determination↗
Effect of dialysate composition on intercompartmental fluid shift.
Effect of dialysate composition on intercompartmental fluid shift and hemodynamics was studied in 12 patients during 1.5 or 2 hours of hemodialysis without net ultrafiltration, using high (H;Na 154 mmol/liter), normal (N;Na 140 mmol/liter) or low (L:Na 126 mmol/liter) concentration dialysate. H dialysate was associated with a small (0.9%) increase in blood volume, a larger increase in plasma volume and a decrease in erythrocyte volume. L dialysate resulted in a 2.3% decrease in blood volume, a larger decrease in plasma volume and an increase in erythrocyte volume. N dialysate gave results which were intermediately between the other two dialysis conditions. There was no difference in the post-dialysis mean arterial pressure between the groups, although heart rate increased more during H dialysis than during the other two conditions. Change in blood and erythrocyte volume correlated significantly with change in plasma Na concentration and osmolality, but not with change in plasma urea concentration. We conclude that dialysate composition affects the movement of water into and out of the plasma and erythrocytes in a manner that can be accounted for by altered plasma concentrations of osmotically active substances.
Adult↗
Assessment of arteriovenous fistulae from pressure and thermal dilution studies: clinical experience in forearm fistulae.
Knowledge of useful fistula flow (UFF), the maximum blood flow available using twin needles within acceptable pressure limits and without recirculation, is essential for the optimal management of patients receiving maintenance hemodialysis or hemofiltration. A technique for the measurement of UFF employing thermal dilution for the detection of recirculation has been developed. Using this technique, 94 studies were carried out in 69 forearm fistulae. UFF exceeded 400 ml/min in 45 fistulae. In these satisfactory fistulae a normal range was defined for basal intrafistula pressures (60 mmHg being the approximate upper limit of normal). Analysis of arterial and venous line pressure recordings with increasing extracorporeal blood flow and knowledge of the presence or absence of recirculation allowed us to define the functional problem in unsatisfactory fistulae. The functional diagnosis was supported in 16 of 24 fistulae by angiography or surgery or both. In all but two of the remainder, satisfactory UFF was obtained by repositioning the patients' needling sites. Fistulae were divided into different clinical groups. Of 35 fistulae which were thought to be clinically acceptable, 7 were found to be unsatisfactory. In 17 fistulae in patients with poor biochemical control, recirculation was detected in 8. Of 11 fistulae reported to produce poor flows on dialysis, 4 had UFF above 400 ml/min. Of 6 fistulae in patients experiencing needling difficulties, 5 had satisfactory UFF. These studies which take only a few minutes and can be carried out immediately preceding a routine dialysis session not only identify unsatisfactory fistulae, but yield valuable diagnostic information in these cases. This has reduced dependence on angiography and has led to more careful selection of patients for surgery.
Arteriovenous Shunt, Surgical↗
Serial blood water estimations and in-line blood viscometry: the continuous measurement of blood volume during dialysis procedures.
It has been shown in vitro that serial measurements of blood water during ultrafiltration accurately reflect changing blood volume. It has been shown that minute changes in blood hydration produce detectable changes in blood viscosity. An 'in-line' capillary viscometer has been constructed which can be placed in parallel with an extracorporeal circuit to give a continuous semi-quantitative measure of blood viscosity during ultrafiltration or haemodialysis. By making serial measurements of blood water each 'viscometer curve' can be corrected to permit calculation of blood volume provided that the starting blood volume is known. Blood volume changes of less than 1% can be detected in vitro and provided that blood volume changes solely as a result of the removal or influx of water it can be measured continuously to within an accuracy of 4% for volume changes up to 30% irrespective of starting packed cell volume or blood water.
Blood↗
Voluntary Service Overseas.
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Community Health Nursing↗
Epidemiologic observations of influenza B virus infections in Houston, Texas, 1976-1977.
Influenza B virus infections were documented in Houston, Texas, in 726 patients with febrile respiratory illnesses who presented to representative primary care facilities during the 1976-1977 respiratory disease season. This epidemic followed a "herald wave" of illness associated with influenza B during the preceding spring. Over one-half the virus isolates were from children aged 5-19 years, and school absenteeism rates indicated that about 40 per cent of the students in the Houston area were ill enough to miss school during the epidemic. The rapid rise in the number of cases among students after the school holiday recess demonstrated the importance of school attendance for the rapid dissemination of influenza viruses. During the later phase of the epidemic, most of the cases were preschool children and adults. In addition to disease of the respiratory tract, the epidemic was accompanied by cases of Reye's syndrome at a rate expected for an urban area.
Absenteeism↗
Automated microbiological detection/identification system.
An automated, computerized system, the AutoMicrobic System, has been developed for the detection, enumeration, and identification of bacteria and yeasts in clinical specimens. The biological basis for the system resides in lyophilized, highly selective and specific media enclosed in wells of a disposable plastic cuvette; introduction of a suitable specimen rehydrates and inoculates the media in the wells. An automated optical system monitors, and the computer interprets, changes in the media, with enumeration and identification results automatically obtained in 13 h. Sixteen different selective media were developed and tested with a variety of seeded (simulated) and clinical specimens. The AutoMicrobic System has been extensively tested with urine specimens, using a urine test kit (Identi-Pak) that contains selective media for Escherichia coli, Proteus species, Pseudomonas aeruginosa, Klebsiella-Enterobacter species, Serratia species, Citrobacter freundii, group D enterococci, Staphylococcus aureus, and yeasts (Candida species and Torulopsis glabrata). The system has been tested with 3,370 seeded urine specimens and 1,486 clinical urines. Agreement with simultaneous conventional (manual) cultures, at levels of 70,000 colony-forming units per ml (or more), was 92% or better for seeded specimens; clinical specimens yielded results of 93% or better for all organisms except P. aeruginosa, where agreement was 86%. System expansion in progress includes antibiotic susceptibility testing and compatibility with most types of clinical specimens.
Bacteria↗
Fluid balance modelling in patients with kidney failure.
In patients with kidney failure, adequate control of fluid status remains one of the most difficult routine issues to be addressed in the modern style of dialysis. This is primarily due to the lack of quantitative methods for the assessment of fluid status and the reliance on subjective criteria. Fluid is removed from the blood during dialysis treatments using a process called ultrafiltration. The last decade has seen considerable developments in blood volume monitoring (BVM) technology which has enabled responses to ultrafiltration to be continually monitored on an individual basis. This has enabled feedback control of patients' blood volume to be applied with partial success, reducing the number of symptoms. The feedback control algorithms employed have been relatively unsophisticated, using simple proportional control with no attempt to include models of the patient fluid dynamics. This paper describes the development of some prototype fluid kinetic models which may be used in a more advanced control system. Initial results demonstrate the importance of active control processes in the patients' physiological compensatory mechanisms.
Blood Volume↗
Identification of focal viral infections by confocal microscopy for subsequent ultrastructural analysis.
A correlative microscopy method for the ultrastructural analysis of focal viral tissue infections is presented. Using a confocal scanning laser microscope, foci of infection are identified in tissue sections prior to embedment; a variety of techniques can be employed for viral detection, including staining with standard histochemical reagents and fluorescently labeled antibodies. Areas of infection identified using confocal microscopy are excised from the tissue sections, embedded, and examined by transmission electron microscopy. Applications of this technique in both diagnostic and basic research settings are described.
Animals↗
The assessment of arteriovenous fistulae created for haemodialysis from pressure and thermal dilution measurements.
A technique is described for the assessment of arteriovenous fistulae created for haemodialysis. This involves the measurement of intrafistula pressures and 'useful fistula flow' (UFF). The latter we define as the maximum blood flow available for twin needle haemodialysis without recirculation and without unacceptable pressures in the arterial ('A') and venous ('V') lines. The test circuit resembles that used for conventional haemodialysis except there is 'A' and 'V' line pressure and temperature monitoring and no dialyser. Intrafistula pressures are first measured at the time of insertion of the fistula needles. 'A' and 'V' line pressures are then recorded as the extracorporeal blood flow rate is increased in increments from zero to 500 ml/min. A check for recirculation is made at each flow rate. A bolus of cold saline injected into the 'V' line causes a momentary decrease in 'A' line temperature when recirculation is present; when there is no recirculation, 'A' line temperature remains constant. The blood flow rate at which recirculation is first detected will be above the useful fistula flow by definition. This technique allows identification of those patients who obtain high blood flows at the expense of recirculation and thus dialyse inefficiently. Combined pressure and thermal dilution measurements yield valuable information in the investigation of failing or problem fistulae.
Arteriovenous Shunt, Surgical↗