Long-path second-harmonic interferometer with nanosecond time resolution: reliable diagnostic tool for electron density measurement in pulsed plasma devices.

We describe the performance of a second-harmonic interferometer (SHI) to measure, on an optical path exceeding 12 m, the electron plasma density of two plasmoids formed in separate theta-pinch chambers and then merged in a central compression chamber after undergoing acceleration and compression. The excellent mechanical stability and a time resolution better than 50 ns suggest the application of SHI, especially in pulsed plasma devices with limited optical accesses.

Prevalence of arterial and venous thromboembolic events in diabetic patients with and without the metabolic syndrome: a cross sectional study.

BACKGROUND: Metabolic syndrome (MS) is associated with an increased risk of cardiovascular events. Recent studies have found a higher prevalence of the MS in patients with idiopathic venous thromboembolic events (VTE) compared to controls suggesting a role of the MS in the pathogenesis of VTE. The presence of MS was shown to further increase the risk of arterial cardiovascular diseases (CVD) in diabetic patients. Conversely, there are no studies that have compared the risk of VTE in diabetic patients with and without the MS. METHODS: A cross sectional study comparing the prevalence of arterial cardiovascular events and VTE in diabetic patients with and without the MS was conducted. RESULTS: Nine hundred and fifty three patients were included in the study; 85.7% of patients had MS. Patients with the MS had an increased prevalence of CVD as compared with those without (23.4% vs. 11.8%) and the MS was an independent predictor of CVD in diabetic patients (OR 3.16, 95%CI 1.78, 5.59) after multiple logistic regression analysis. The prevalence of VTE was higher in patients with the MS in comparison to patients without the MS, but this association was not statistically significant (3,43% vs 1.47%; OR 2.38, 95% CI 0.56, 10.10%). CONCLUSION: Our study confirms the role of MS as an adjunctive cardiovascular risk factor in patients with diabetes. There is insufficient evidence to evaluate the role of the as an adjunctive risk factor for VTE in these patients. Further studies are necessary to confirm or refute these preliminary findings.

Doppler spectroscopy and D-alpha emission diagnostics for the C-2 FRC plasma.

Two Doppler spectroscopy diagnostics with complementary capabilities are developed to measure the ion temperatures and velocities of FRC plasmas in the C-2 device. First, the multichord ion doppler diagnostic can simultaneously measure 15 chords of the plasma using an image intensified camera. Second, a single-chord fast-response ion Doppler diagnostic provides much higher faster time response by using a 16-channel photo-multiplier tube array. To study the neutral density of deuterium under different wall and plasma conditions, a highly sensitive eight-channel D-alpha diagnostic has been developed and calibrated for absolute radiance measurements. These spectroscopic diagnostics capabilities, combined with other plasma diagnostics, are helping to understand and improve the field reversed configuration plasmas in the C-2 device.

Dynamic formation of a hot field reversed configuration with improved confinement by supersonic merging of two colliding high-ß compact toroids.

A hot stable field-reversed configuration (FRC) has been produced in the C-2 experiment by colliding and merging two high-ß plasmoids preformed by the dynamic version of field-reversed θ-pinch technology. The merging process exhibits the highest poloidal flux amplification obtained in a magnetic confinement system (over tenfold increase). Most of the kinetic energy is converted into thermal energy with total temperature (T{i}+T{e}) exceeding 0.5 keV. The final FRC state exhibits a record FRC lifetime with flux confinement approaching classical values. These findings should have significant implications for fusion research and the physics of magnetic reconnection.

Fluid and volume monitoring.

BACKGROUND: Fluid resuscitation is not only used to prevent acute kidney injury (AKI) but fluid management is also a cornerstone of treatment for patients with established AKI and renal failure. Ultrafiltration removes volume initially from the intravascular compartment inducing a relative degree of hypovolemia. Normal reflex mechanisms attempt to sustain blood pressure constant despite marked changes in blood volume and cardiac output. Thus, compensated shock with a normal blood pressure is a major cause of AKI or exacerbations of AKI during ultrafiltration. METHODS: We undertook a systematic review of the literature using MEDLINE, Google Scholar and PubMed searches. We determined a list of key questions and convened a 2-day consensus conference to develop summary statements via a series of alternating breakout and plenary sessions. In these sessions, we identified supporting evidence and generated clinical practice recommendations and/or directions for future research. RESULTS: We defined three aspects of fluid monitoring: i) normal and pathophysiological cardiovascular mechanisms; ii) measures of volume responsiveness and impending cardiovascular collapse during volume removal, and; iii) measured indices of each using non-invasive and minimally invasive continuous and intermittent monitoring techniques. The evidence documents that AKI can occur in the setting of normotensive hypovolemia and that under-resuscitation represents a major cause of both AKI and mortality ion critically ill patients. Traditional measures of intravascular volume and ventricular filling do not predict volume responsiveness whereas dynamic functional hemodynamic markers, such as pulse pressure or stroke volume variation during positive pressure breathing or mean flow changes with passive leg raising are highly predictive of volume responsiveness. Numerous commercially-available devices exist that can acquire these signals. CONCLUSIONS: Prospective clinical trials using functional hemodynamic markers in the diagnosis and management of AKI and volume status during ultrafiltration need to be performed. More traditional measure of preload be abandoned as marked of volume responsiveness though still useful to assess overall volume status.

Treatment of patients with cardiac surgery associated-acute kidney injury.

Members of the Acute Dialysis Quality Initiative (ADQI) participated in a 3-day conference in Vicenza in May 2007 to evaluate the available literature on this topic and draft consensus recommendations for research studies in this area. This report summarizes the available evidence and describes the key questions that will need to be addressed with the goal of standardizing the care of patients with cardiac surgery-associated acute kidney injury (CSA-AKI) and improving outcomes.

Mortality after acute renal failure: models for prognostic stratification and risk adjustment.

To adjust adequately for comorbidity and severity of illness in quality improvement efforts and prospective clinical trials, predictors of death after acute renal failure (ARF) must be accurately identified. Most epidemiological studies of ARF in the critically ill have been based at single centers, or have examined exposures at single time points using discrete outcomes (e.g., in-hospital mortality). We analyzed data from the Program to Improve Care in Acute Renal Disease (PICARD), a multi-center observational study of ARF. We determined correlates of mortality in 618 patients with ARF in intensive care units using three distinct analytic approaches. The predictive power of models using information obtained on the day of ARF diagnosis was extremely low. At the time of consultation, advanced age, oliguria, hepatic failure, respiratory failure, sepsis, and thrombocytopenia were associated with mortality. Upon initiation of dialysis for ARF, advanced age, hepatic failure, respiratory failure, sepsis, and thrombocytopenia were associated with mortality; higher blood urea nitrogen and lower serum creatinine were also associated with mortality in logistic regression models. Models incorporating time-varying covariates enhanced predictive power by reducing misclassification and incorporating day-to-day changes in extra-renal organ system failure and the provision of dialysis during the course of ARF. Using data from the PICARD multi-center cohort study of ARF in critically ill patients, we developed several predictive models for prognostic stratification and risk-adjustment. By incorporating exposures over time, the discriminatory power of predictive models in ARF can be significantly improved.

Extracorporeal ultrafiltration for acute exacerbations of chronic heart failure: report from the Acute Dialysis Quality Initiative.

This report from a work group affiliated with the Acute Dialysis Quality Initiative is a critical assessment of the use of extracorporeal ultrafiltration (UF) in the management of acutely decompensated heart failure (HF). In addition to assessing UF in this setting, the report also provides background information on HF, including classification, pathophysiology, and the importance of concomitant renal failure. A summary of important results from clinical trials in this area is provided, along with a discussion of technical considerations. Finally, specific recommendations for future clinical evaluations are given.

Cirugía fetal experimental en un modelo animal para la corrección de mielomeningocele / Experimental fetal surgery in an animal model for the correction of myelomeningocele

Introducción. El mielomeningocele representa una de las malformaciones congénitas más frecuentes y severas en humanos, que afecta aproximadamente a 1 de cada 2.000 recién nacidos en el mundo. Tiene una enorme significación médica y social, por la importante morbilidad a que se asocia, con gran cantidad de secuelas y un elevado coste en salud. Existe sólida evidencia que apoya la necesidad de tratamiento precoz. Dentro de las posibilidades de tratamiento actuales tiene especial interés la reparación quirúrgica durante la vida intrauterina. El trabajo con un modelo animal constituye el paso previo necesario a la intervención en humanos. Objetivos. En concordancia con otros grupos de investigadores, hemos elegido un modelo animal que permita conocer los resultados de la reparación de la columna vertebral en mielomenigoceles creados instrumentalmente. Material y métodos. Durante el período de mayo de 2002 hasta mayo de 2004 se ha reclutado un grupo de 23 ovejas de raza merina a las que se les realizó quirúrgicamente, a los 80 días de preñez, un mielomeningocele, realizando una laminectomía lumbar de 1 a 4 con apertura del canal medular y exposición del contenido al líquido amniótico. Las ovejas fueron aleatorizadas para ser incluidas en tres grupos: un grupo control y dos grupos de intervención. En uno de ellos se realizó una reparación neuroquirúrgica convencional y en el otro grupo se realizó una reparación colocando una membrana de tejido dérmico porcino acelular cultivado. Resultados. Los corderos del grupo control nacieron con manifestaciones clínicas severas de la enfermedad (tres de cinco corderos), con incapacidad en la deambulación e incontinencia de esfínteres; en los corderos de ambos grupos de intervención las manifestaciones clínicas de espina bífida fueron leves (cuatro de cinco corderos), con dificultad leve en la deambulación y continencia de esfínteres. Conclusiones. Los resultados alcanzados por el trabajo, debido al reducido número de intervenciones, no son concluyentes, pero muestran una tendencia a favor de la intervención de reparación intraútero del mielomeningocele. Las consecuencias de estos resultados en la práctica clínica deberán ser observadas a la luz de los resultados del Management of Myelomeningocele Study (MOMS) que se desarrolla actualmente en Estados Unidos en cuatro centros. Comentario final. La realización del presente trabajo ha tenido enorme significación para los autores ya que se ha reunido un equipo multidisciplinario que incluye anestesiólogos, neurocirujanos, neonatólogos, obstetras, veterinarios, enfermeros, neurólogos, etc., y se ha alcanzado el objetivo de adquirir nuevas destrezas que serán fundamentales para el manejo futuro de la cirugía fetal intraútero (AU)

Introduction. Myelomeningocele is one of the most frequent and severe congenital defects in humans, affecting approximately one in 2000 worldwide. This pathology is of great medical and social relevance due to its high morbidity, multiple sequela and high social cost. There is supporting evidence in favor of early treatment, particularly through intra uterine surgical correction. The work on animal models is a required preliminary step before intervention on humans. Objectives. In agreement with several other investigative groups we have chosen an animal model that allows us to know the results of spine correction in surgically induced myelomeningocele. Material and methods. Between may of 2002 and may of 2004 we recruited 23 sheep on which we induced myelomeningocele surgically at 80 days of gestational age, through 1 to 4 lumbar laminectomy with opening of bone marrow channel and exposure to amniotic fluid. AH sheep were randomized to be included in three groups: control group A, and intervention groups B (conventional intervention) and C (conventional plus noncellular porcine skin patch. Results. Neonate lambs (three out of five) in the control group presented with severe clinical disease related disabilities, namely walking impairment and incontinence. Lambs in B and C groups showed less severe impairment: slight walking handicap and lack of incontinence. Conclusions. Owing to the small sampling the results we reached are not conclusive, though they show a trend in favor of intrauterine correction of myelomeningocele. Relevance of these findings should be availed for clinical practice through the results from Management of Myelomeningocele Study (MOMS), currently ongoing in four UScenters. Final comment. The present trial represents an important advance for all participants in that it gathered a multidisciplinary team composed of anesthesiologists, neurosurgeons, pediatric neurosurgeons, obstetricians, pediatricians, vets, nurses, etc., and has led us to the acquisition of essential handskills for the future management of intra uterine fetal surgery (AU)

A preliminary survey of bacterial contamination of the dialysate circuit in continuous veno-venous hemodialysis.

AIMS: The problem of dialysate bacterial contamination has not been defined in continuous renal replacement therapy. We assessed the bacterial integrity of source bicarbonate dialysate (study 1) and the continuous veno-venous HD (CVVHD) bicarbonate dialysate circuit (study 2). METHODS: Study 1: 50 ml dialysate were collected from 41 bags randomly selected from 150 consecutively made dialysate bags, immediately after manufacture or after 24, 48 or 72 h. Study 2: 10 ml dialysate were drawn from 4 sample points ranged along the dialysate circuit in 18 therapies (mean duration 119.5 +/- 72.0 h). All points were sampled at therapy start then daily, bar the proximal point which was sampled after each dialysate bag change. All dialysate samples underwent Gram stain and aerobic/anaerobic culture. Samples over 10 ml were cultured after centrifugation (15 min, 4,000 rpm). A disseminated contamination (DC) involved > or = 1 sample point at a time and/or was sustained over time. RESULTS: Study 1: One bag was culture-positive (staphylococcal/diphtheroid growths; 48-h sample). Study 2: Six DCs developed in 6 therapies (1 at therapy end, 5 sustained to therapy end (duration 57.25 +/- 45.95 h), 5 with Gram-negative bacilli, all involving reported growths of > or = 1,000 cfu). Dialyzer-inclusive dialysate circuit changes were more frequent in non-DC therapies (change rate: DC, 0.08 +/- 0.12/day, non-DC, 0.34 +/- 0.23, p = 0.02, permutation tests with general scores) but did not entirely prevent DC or alter it once underway. CONCLUSIONS: Sustained bacterial contamination of bicarbonate-based CVVHD is common and could relate to the completeness of dialysate circuit change. The importance of technique and regular quality control is highlighted.

The end-stage renal disease program. Experience with a chronic disease capitated health plan.

The ESRD program has demonstrated the potential for a capitated, disease-oriented, total care method of patient support. Given both the increasing age and complexity of the patient population, not only has the cost per patient decreased over the life of the program, but the standardized mortality rates have also declined. Technology has bridged the gap and made the relative cost per treatment more affordable and science has developed medications and techniques that have enhanced both patient comfort and longevity. As more complex patients enter the fold of the ESRD program, an increased awareness of enhanced coordination of care needs to be recognized.

Role of the nephrologist in the intensive care unit.

Intensive care units (ICUs) are increasingly becoming a focal point for tension between medical specialists. In an extreme approach to this issue, some ICUs have become closed units managed by intensivists, with other specialists, such as nephrologists, having a restricted supportive role. The nephrologist, a subspecialist with broad skills in general internal medicine, has trained and appropriately can serve as the primary physician for patients with significant renal failure and end-stage renal disease in multiple hospital settings, including the ICU. Sick and complex hospitalized patients offer ample opportunity for a collaborative interaction between the nephrologist and intensivist in the ICU.

Growth kinetics and structure of fibrin gels.

The structure and kinetics of fibrin gels grown from fibrinogen solutions under quasiphysiological conditions, but in absence of Ca++, were investigated by means of elastic light scattering. By combining classical light scattering and low-angle elastic light scattering, an overall wave-vector range of about three decades was spanned, from q approximately 3 x 10(2) to q approximately 3 x 10(5) cm(-1). The scattered intensity distribution of the gels was measured in absolute units and fitted to a single function, which was able to reproduce accurately the data over the entire wave-vector range. From the fitting, it was possible to estimate the average diameter d of the fibrin fibers, the average crossover length xi of the gel, and establish the fractal nature of the gel structure, with a measure of its fractal dimension D(m). The measure of the intensity in absolute units also allowed the estimate of the density rho of the fibrin fibers and provided an independent measure of their size. The kinetics of formation of the gel was described in terms of a simple growth model: the scaffold of the network is formed very early in the course of the gelation process, at a "networking time," t(n), which is much smaller than the time required to form the final gel. At times t>t(n), the gel structure remains substantially unchanged and the successive growth consists only in a thickening of the gel fibers. Gels prepared under the same physical-chemical conditions, but at different fibrinogen concentrations, exhibited rather similar structures and kinetics, showing that the modalities of the gelation process are mainly governed by the solution conditions, and only secondarily by the fibrinogen concentration. For gels at fibrinogen concentration of approximately 0.24 mg/ml, the gel parameters were d approximately 130 nm, xi approximately 27 microm, D(m) approximately 1.3, and rho approximately 0.4 g/cm(3). Our d and rho values are in very good agreement with electron microscopy- and turbidity-derived literature data, respectively, while xi seems to be related to the mesh size of the initial scaffold formed at t(n), rather than to the mesh size of the final aged gel.

Instrument for long-path spectral extinction measurements in air: application to sizing of airborne particles.

A novel instrument that is capable of taking spectral extinction measurements over long optical paths (approximately 1-100 m) in the UV, visible, and IR ranges is described. The instrument is fully automated, and the extinction spectrum is acquired in almost real time (approximately 5-10 s) with a resolution of ~3 nm. Its sensitivity and accuracy were estimated by tests carried out in a clean room that showed that, for optical paths between 50 and 100 m, the extinction coefficient can be detected at levels of ~10(-5) m(-1). Tests carried out on calibrated latex particles showed that, when it was combined with an appropriate inversion method, the technique could be profitably applied to characterize airborne particulate distributions. By carrying out measurements over optical paths of ~100 m, the instrument is also capable of detecting extinction coefficients that are due to aerosol concentrations well below the limits imposed by the European Economic Community for atmospheric pollution (150 mug/m(3)). Scaled over optical paths of ~10 m, the limit imposed for particle emissions from industrial plants (10 mg/m(3)) can also be detected sensitively.

A fractional dialysate collection method to estimate solute removal in continuous venovenous hemodialysis.

BACKGROUND: Fractional direct dialysis quantification (fDDQ), whereby a known proportion of dialysate effluent is sampled, can reliably estimate total solute removal in intermittent hemodialysis (IHD). Our study aimed to develop and test the technique in continuous venovenous hemodialysis (CVVHD). METHODS: Twenty dialysate collections (mean duration 23.5 hours, range 17.25 to 26.6) were performed in 12 patients on CVVHD. An infusion pump diverted 10% of the total effluent volume to the fractional collection (fc), the remainder being channeled into the bulk collection (bc). Both fc and bc were collected on ice and assayed for urea nitrogen (UN) and creatinine (Cr). Actual solute removal (ASR) was calculated from the measured effluent volume and solute concentrations of the fc and bc. Estimated solute removal (ESR) was calculated from the product of the fc solute concentration and effluent volume. All fc/bc samples in 15 out of 20 collections underwent gram stain and aerobic/anaerobic culture. RESULTS: Bland-Altman analyses suggested good agreement between ASR and ESR [absolute values of percentage differences: 95% CI = 1.73, 5.17% (UN); 1.88, 4.31% (Cr)]. Favorable concordance correlation coefficients confirmed this [rc = 0.995 (UN), 0.997 (Cr)] and were apparently unaffected by heavy pseudomonal growths in 4 out of 7 culture positive collections [rc = 0.997 (UN), 0.997 (Cr); culture negative (N = 8), rc = 0.996 (UN), 0.997 Cr)]. CONCLUSION: fDDQ, using 24-hour, pump-assisted, cooled fractional dialysate sampling reliably estimates total solute removal and provides a practical alternative to total dialysate collection in assessing delivered dialysis dose.

Introduction of a switch that can reverse blood flow direction on-line during hemodialysis.

In several circumstances in hemodialysis, the regular direction of blood flow has to be reversed or changed, such as in access dysfunction or insufficient blood flow being obtained through the arterial port, as well as to measure actual access blood flow in fistulas or grafts by using the formula Qa = Qb((1-R)/R), where R represents recirculation in the reversed line configuration. We invented a disposable switch device made from standard blood line tubing that can be introduced into the dialysis circuit and allows for on-line reversal of lines, without needing to manually disconnect and reconnect tubing or interrupt the hemodialysis procedure. Over a period of eight months, 16 patients (8 arteriovenous fistula, 8 PTFE) underwent 193 hemodialysis sessions with the switch in place. Circuit pressures, pump, and actual blood flows measured with ultrasound dilution were monitored before and after reversing the lines. Switching was accomplished within 1-2 seconds. Arterial circuit (r = 0.99), venous circuit pressures (r = 0.6), and actual pump flow (364 +/- 56 vs. 350 +/- 57 ml/min; r = 0.73) correlated very well preswitching and postswitching (p < 0.0001). Dialysis circuit flow measured with an ultrasound dilution technique decreased from 364 +/- 56 (230-480) ml/min preswitching to 350 +/- 57 (220-490) ml/min postswitching (p < 0.001). No difficulties or complications were observed. This switch device is a useful addition to the technology of hemodialysis in that it greatly facilitates the procedure of reversing the lines in an extracorporeal circuit while not significantly interfering with circuit pressures and connections.

Abnormal electrical stimulus of an intra-aortic balloon pump with concurrent support with continuous veno-venous hemodialysis.

Malfunction of electronic medical support apparatus utilized in the ICU usually causes system failure. We report several occurrences of a potentially dangerous interaction between a continuous veno-venous hemodialysis (CVVHD) system and an intra-aortic balloon pump (IABP) counterpulsation device in four patients requiring both systems. The patients had acute renal failure in the face of multi-organ failure and were dependent upon the balloon pump for pressure support. Electrical interference created by the roller pump action of the CVVHD system was identified by the balloon pump as cardiac in origin, and it responded by inflation and deflation. As the blood pump rate was reduced, the interference reduced to the point of complete cessation when the blood pump was shut down. Whereas one patient transiently had a significant drop of mean arterial pressure (from 70 +/- 4 to 40 +/- 2 mm Hg) the other observed occurrences had no clinically significant sequelae. Electrocardiogram (ECG) tracings identified the abnormal stimulus and systematic review identified as potential sources for the creation of this interference static electricity buildup, piezoelectric properties of the polyvinyl chloride tubing, and, possibly but less likely, radiofrequency interference. A newer generation ECG cable and advanced cardiac rhythm recognition software (CardioSync) have been introduced with the Datascope System 98, and the ECG interference, although still occasionally present, does not cause erratic inflation and deflation of the intra-aortic balloon pump. Interference between different electrical support systems may occur, and we suggest that the systems be tested for compatibility before combined use and that older equipment be more rigorously tested for potential clinically significant interference.