Ventriculoperitoneal shunt malfunction diagnosis based on substance dilution.

OBJECTIVE: Current methods for the diagnosis of ventriculoperitoneal (VP) shunt malfunction lack specific standards; therefore, it may be missed or misdiagnosed. Hence, providing a reliable diagnostic method will help improve the accuracy of preoperative decision-making. Therefore, the aim of the study was to provide a new method for the diagnosis of VP shunt malfunction. METHODS: After in vitro testing, we enrolled a total of 12 patients with VP shunt malfunction. Before revision surgery, 0.1 mL of a 5% sodium valproate (SV) solution was injected into the reservoir; 0.1 mL of the cerebrospinal fluid (CSF) was withdrawn 20 minutes later from the reservoir to measure the SV concentration. The process was repeated on the seventh day after surgery and compared with the preoperative results. RESULTS: The mean ±â€Šstandard deviation preoperative SV concentration in the cerebrospinal fluid was greater than the postoperative concentration (5967.8 ±â€Š1281.3 vs 391.1 ±â€Š184.6 µg/mL, P = .001). CONCLUSION: The proposed method is a reliable, safe, and relatively simple alternative for the diagnosis of VP shunt malfunction and further provides a reference for treatment.

Evaluation of the accuracy and precision of a new generation indirect calorimeter in canopy dilution mode.

BACKGROUND & AIMS: Indirect calorimetry (IC) is the only way to measure in real time energy expenditure (EE) and to optimize nutrition support in acutely and chronically ill patients. Unfortunately, most of the commercially available indirect calorimeters are rather complex to use, expensive and poorly accurate and precise. Therefore, an innovative device (Q-NRG®, COSMED, Rome, Italy) that matches clinicians' needs has been developed as part of the multicenter ICALIC study supported by the two academic societies ESPEN and ESICM. The aim of this study was to evaluate the accuracy and intra- and inter-unit precision of this new device in canopy dilution mode in vitro and in spontaneously breathing adults. METHODS: Accuracy and precision of oxygen consumption (VO2) and carbon dioxide production (VCO2) measurements were evaluated in vitro and in 15 spontaneously breathing healthy adults by interchanging three Q-NRG® units in a random order. In vitro validation was performed by gas exchange simulation using high-precision gas mixture and mass flow controller. Accuracy was calculated as error of measured values against expected ones based on volume of gas infused. Respiratory coefficient (RQ) accuracy was furthermore assessed using the ethanol-burning test. To evaluate the intra- and inter-unit precisions, the coefficient of variation (CV% = SD/Mean*100) was calculated, respectively, from the mean ± SD or the mean ± SD of the three mean values of VO2, VCO2, RQ and EE measured by each Q-NRG® units. In vivo accuracy measurement of the Q-NRG® was assessed by simultaneous comparison with mass spectrometry (MS) gas analysis, using Bland-Altman plot, Pearson correlation and paired t-test (significance level of p = 0.05). RESULTS: In vitro evaluation of the Q-NRG® accuracy showed measurement errors <1% for VO2, VCO2 and EE and <1.5% for RQ. Evaluation of the intra- and inter-unit precision showed CV% ≤1% for VO2 and EE and CV% ≤1.5% for VCO2 and RQ measurements, except for one Q-NRG® unit where CV% was 2.3% for VO2 and 3% for RQ. Very good inter-unit precision was confirmed in vivo with CV% equal to 2.4%, 3%, 2.8% and 2.3% for VO2, VCCO2, RQ and EE, respectively. Comparison with MS showed correlation of 0.997, 0.987, 0.913 and 0.997 for VO2, VCO2, RQ and EE respectively (p ≤ 0.05). Mean deviation of paired differences was 1.6 ± 1.4% for VO2, -1.5 ± 2.5% for VCO2, -3.1 ± 2.6% for RQ and 0.9 ± 1.4% for EE. CONCLUSION: Both in vitro and in vivo measurements of VO2, VCO2, RQ and EE on three Q-NRG® units showed minimal differences compared to expected values and MS and very low intra- and inter-unit variability. These results confirm the very good accuracy and precision of the Q-NRG® indirect calorimeter in canopy dilution mode in spontaneously breathing adults.

Systematic comparison of post-column isotope dilution using LC-CO-IRMS with qNMR for amino acid purity determination.

Determination of the purity of a substance traceable to the International System of Units (SI) is important for the production of reference materials affording traceability in quantitative measurements. Post-column isotope dilution using liquid chromatography-chemical oxidation-isotope ratio mass spectrometry (ID-LC-CO-IRMS) has previously been suggested as a means to determine the purity of organic compounds; however, the lack of an uncertainty budget has prevented assessment of the utility this approach until now. In this work, the previously published ID-LC-CO-IRMS methods have not only been improved by direct gravimetric determination of the mass flow of 13C-labelled spike but also a comprehensive uncertainty budget has been established. This enabled direct comparison of the well-characterised ID-LC-CO-IRMS method to quantitative nuclear magnetic resonance spectroscopy (qNMR) for purity determination using valine as the model compound. The ID-LC-CO-IRMS and qNMR methods provided results that were in agreement within the associated measurement uncertainty for the purity of a sample of valine of (97.1 ± 4.7)% and (99.64 ± 0.20)%, respectively (expanded uncertainties, k = 2). The magnitude of the measurement uncertainty for ID-LC-CO-IRMS determination of valine purity precludes the use of this method for determination of purity by direct analysis of the main component in the majority of situations; however, a mass balance approach is expected to result in significantly improved measurement uncertainty.

Eliminating Preparation of Multisample External Calibration Curves and Dilution of Study Samples Using the Multiple Isotopologue Reaction Monitoring (MIRM) Technique in Quantitative LC-MS/MS Bioanalysis.

Preparation of multisample external calibration curves and dilution of study samples are critical steps in bioanalytical sample processing for quantitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) based bioanalysis of small-molecule compounds, biotherapeutics, and biomarkers, but they can be time-consuming and prone to error. It is highly desired to simplify or eliminate these two steps in order to improve the assay throughput and robustness. While multisample external calibration curve preparation using authentic matrices can be eliminated with a previously reported in-sample calibration curve (ISCC) approach using multiple isotopologue reaction monitoring (MIRM) of a stable isotopically labeled (SIL) analyte, dilution of study samples is still inevitable due to limited LC-MS/MS assay ranges. In this work, a one-sample multipoint external calibration curve and isotope sample dilution, both using MIRM of an analyte, for quantitative LC-MS/MS based bioanalysis are proposed and demonstrated. By spiking a known amount of an analyte into one blank authentic matrix sample, a one-sample multipoint external calibration curve in an authentic matrix can be established on the basis of the relationship between the calculated theoretical isotopic abundances (analyte concentration equivalents) and the MS/MS responses in the corresponding MIRM channels. This one-sample multipoint external calibration curve can be used in the same way as the traditional multisample external calibration curve for quantitative LC-MS/MS-based bioanalysis. As isotopic abundance in each MIRM channel can be calculated and measured accurately, isotope sample dilution can be achieved by simply monitoring one or a few of the MIRM channels of the analyte in addition to the most abundant MIRM channel for study samples. While the most abundant MIRM channel (isotopic abundance of 100%) is used for the quantitation of samples having concentrations within the assay calibration curve range, less abundant MIRM channels (isotopic abundance of IA%) can be used for the quantitation of samples having concentrations beyond the assay upper limit of quantitation (ULOQ), resulting in isotope dilution factors (IDF) of 100%/IA%. The approaches of one-sample multipoint external calibration curve and isotope sample dilution were evaluated and demonstrated in this work with an example of the quantitation of daclatasvir in human plasma extracted with liquid-liquid extraction. Using these approaches together with the MIRM-ISCC methodology, accurate and reliable LC-MS/MS bioanalysis can be achieved without the need of preparation of multisample external calibration curve and dilution of study samples.

Isotope-dilution mass spectrometry for exact quantification of noncanonical DNA nucleosides.

DNA contains not only canonical nucleotides but also a variety of modifications of the bases. In particular, cytosine and adenine are frequently modified. Determination of the exact quantity of these noncanonical bases can contribute to the characterization of the state of a biological system, e.g., determination of disease or developmental processes, and is therefore extremely important. Here, we present a workflow that includes detailed description of critical sample preparation steps and important aspects of mass spectrometry analysis and validation. In this protocol, extraction and digestion of DNA by an optimized spin-column and enzyme-based method are described. Isotopically labeled standards are added in the course of DNA digestion, which allows exact quantification by isotope dilution mass spectrometry. To overcome the major bottleneck of such analyses, we developed a short (~14-min-per-sample) ultra-HPLC (UHPLC) and triple quadrupole mass spectrometric (QQQ-MS) method. Easy calculation of the modification abundance in the genome is possible with the provided evaluation sheets. Compared to alternative methods, the quantification procedure presented here allows rapid, ultrasensitive (low femtomole range) and highly reproducible quantification of different nucleosides in parallel. Including sample preparation and evaluation, quantification of DNA modifications can be achieved in less than a week.

Isotope dilution LC-ESI-MS/MS and low resolution selected reaction monitoring as a tool for the accurate quantification of urinary testosterone.

A new analytical method for the quantification of testosterone in human urine samples by isotope dilution mass spectrometry is proposed. A standard solution of 13C2-testosterone is added to the samples at the beginning of the sample preparation procedure and then the measurements are carried out by UHPLC-ESI-MS/MS. In the proposed method, the resolution of the first quadrupole of the tandem MS instrument is reduced to transmit the whole precursor ion cluster to the collision cell and measure the isotopic distribution of the in-cell product ions with a small number of SRM transitions. The construction of a methodological calibration graph is avoided using a labelled analogue previously characterised in terms of concentration and isotopic enrichment in combination with multiple linear regression. In this way, the molar fractions of natural and labelled testosterone are calculated in each sample injection and the amount of endogenous testosterone computed from the known amount of labelled analogue. Recovery values between 97 and 107% and precisions between 0.4 and 3.7% (as %RSD) were obtained for testosterone concentrations in urine in the range of 1 to 8 ng g-1. The proposed low resolution SRM methodology was compared for the analysis of human urine samples with the traditional IDMS method based on a calibration graph and the IDMS method based on multiple linear regression combined with standard resolution SRM. A similar accuracy and precision was obtained by the three tested approaches. However, using the low resolution SRM method there was no need to resort to calibration graphs or to specific dedicated software to calculate isotopic distributions by tandem MS and a higher sensitivity was obtained. The proposed low resolution SRM method was successfully applied to the analysis of the certified freeze-dried human urine NMIA MX005.

Journal of Clinical Monitoring and Computing 2017 end of year summary: cardiovascular and hemodynamic monitoring.

Hemodynamic monitoring provides the basis for the optimization of cardiovascular dynamics in intensive care medicine and anesthesiology. The Journal of Clinical Monitoring and Computing (JCMC) is an ideal platform to publish research related to hemodynamic monitoring technologies, cardiovascular (patho)physiology, and hemodynamic treatment strategies. In this review, we discuss selected papers published on cardiovascular and hemodynamic monitoring in the JCMC in 2017.

Exclusive Breastfeeding Is More Common Among HIV-Infected Than HIV-Uninfected Kenyan Mothers at 6 Weeks and 6 Months Postpartum.

OBJECTIVE: To compare breastfeeding practices determined by mothers' own recall versus a stable isotope technique (deuterium oxide dilution) among human immunodeficiency virus (HIV)-infected and HIV-uninfected mothers at 6 weeks and 6 months postpartum. METHODS: Exclusive breastfeeding (EBF) rates were assessed cross-sectionally at 6 weeks and 6 months postpartum among 75 HIV-positive and 68 HIV-negative women attending postnatal care. EBF was derived from maternal 24-hour recall of foods that were fed to the infant and by objective measurement of nonhuman milk-water intake using deuterium oxide (DO) dilution technique. RESULTS: Multivariable logistic analyses were adjusted for infant sex, gravidity, maternal age, marital status, and maternal education. Using recall method, a greater proportion of HIV-infected mothers exclusively breastfed than HIV-uninfected mothers both at 6 weeks postpartum [94.1% versus 76.9%, respectively (adjusted odds ratio [aOR] 7.81; 95% confidence interval [CI] 1.9-31.6, p = 0.004)] and at 6 months postpartum [75% versus 59.7%, respectively (aOR 2.27; 95% CI 1.0-5.3, p = 0.058)]. At 6 weeks postpartum EBF rates from the DO technique were 23.5% and 13.8% for HIV-positive and HIV-negative mothers, respectively (aOR 0.35; 95% CI 0.11-1.04, p = 0.059). At 6 months postpartum, the DO technique determined EBF rates were 43.3% among HIV-positive and 24.2% among HIV-negative mothers, respectively (aOR 2.4; 95% CI 1.0-5.7, p = 0.048). CONCLUSIONS: HIV-infected mothers are more likely to exclusively breastfeed compared with HIV-uninfected mothers. In this resource-poor setting, maternal recall overestimates EBF rates as compared with the deuterium oxide dilution technique. Validating EBF recall data using the objective DO technique is highly recommended for accurate tracking toward global targets on breastfeeding practices.

Journal of Clinical Monitoring and Computing 2015 end of year summary: cardiovascular and hemodynamic monitoring.

Hemodynamic monitoring is essential in critically ill patients. In this regard, the Journal of Clinical Monitoring and Computing (JCMC) has become an ideal platform for publishing cardiovascular and hemodynamic monitoring-related research, as reflected by an increasing number of articles related to this topic and published in the recent years. To highlight this new progress, every New Year the journal prints a descriptive review on some important papers published last year in the JCMC and related to blood, cardiovascular function and hemodynamic monitoring.

Deuterium oxide dilution and body composition in overweight and obese schoolchildren aged 6-9 years / Diluição do óxido de deutério e composição corporal em escolares de seis a nove anos com sobrepeso e obesidade

ABSTRACT OBJECTIVE: To correlate different methods of body composition assessment in overweight or obese schoolchildren, using deuterium oxide (D2O) dilution as a reference. METHODS: Percentage of total body water (%TBW), fat free mass (%FFM), and body fat (%BF) were assessed by D2O and tetrapolar electrical bioimpedance analysis (BIA) in 54 obese and overweight students aged 6-9 years. Skinfold thickness (ST), body mass index (BMI), conicity index (CI), waist circumference (WC), waist-to-height ratio (WHtR), and waist-to-hip (WHR) ratio were also used. RESULTS: Mean values for body composition were 38.4% ± 8.4% BF, 44.9% ± 6.1% TBW and 61.6% ± 8.4% FFM. There was no significant difference in body weight, body fat mass (FM), TBW, and FFM between genders. Regarding D2O, ST underestimated %BF, and overestimated %FFM in both genders (p < 0.05). BIA overestimated %TBW in the group as a whole and in males (p < 0.05). The only positive and strong correlations occurred in females regarding the WC (s= 0.679), CI (r = 0.634), and WHtR (r = 0.666). CONCLUSIONS: In this sample of obese and overweight children, there were strong correlations between body composition measured by D2O and some indices and anthropometric indicators in females, but there was no positive and strong correlation of fat tissue with the indices/indicators at all ages and in both genders.

RESUMO OBJETIVO: Correlacionar diferentes métodos para avaliação de composição corporal em escolares diagnosticados com sobrepeso e obesos com o uso como referência da diluição de óxido de deutério (D2O). MÉTODOS: O percentual de água corporal total (%ACT), massa livre de gordura (%MLG) e gordura corporal (%GC) foi obtido pelo D2O e pela bioimpedância elétrica tetrapolar (BIA), em 54 estudantes com sobrepeso e obesos, entre seis-nove anos. O método das dobras cutâneas (DC) com o uso de triciptal e panturrilha, índice de massa corporal (IMC), índice de conicidade (IC), circunferência de cintura (CC), relação cintura/estatura (RCE) e relação cintura/quadril (RCQ) também foi usado. RESULTADOS: Os valores médios para composição corporal aferidos pelo D2O foram 38,4 ± 8,4%GC, 44,9 ± 6,1%ACT e 61,6 ± 8,4%MLG. Não houve diferença significativa entre peso corporal, massa corporal de gordura (MG), ACT e MLG entre os sexos. Considerando o D2O, DC subestimou o %GC e superestimou o %MLG em ambos os sexos (p < 0,05); BIA superestimou %ACT no grupo como um todo e no masculino (p < 0,05). As únicas correlações fortes e positivas ocorreram no grupo feminino nas variáveis CC (s = 0,679), IC (r = 0,634) e RCE (r = 0,666). CONCLUSÕES: Nessa amostra de crianças obesas e com sobrepeso, houve fortes correlações entre a composição corporal mensurada pelo D2O e alguns índices e indicadores antropométricos nas meninas, mas nenhuma correlação forte e positiva do tecido adiposo foi encontrada com os índices/indicadores em todas as idades e ambos os sexos.

Deuterium oxide dilution and body composition in overweight and obese schoolchildren aged 6-9 years.

OBJECTIVE: To correlate different methods of body composition assessment in overweight or obese schoolchildren, using deuterium oxide (D2O) dilution as a reference. METHODS: Percentage of total body water (%TBW), fat free mass (%FFM), and body fat (%BF) were assessed by D2O and tetrapolar electrical bioimpedance analysis (BIA) in 54 obese and overweight students aged 6-9 years. Skinfold thickness (ST), body mass index (BMI), conicity index (CI), waist circumference (WC), waist-to-height ratio (WHtR), and waist-to-hip (WHR) ratio were also used. RESULTS: Mean values for body composition were 38.4%±8.4% BF, 44.9%±6.1% TBW and 61.6%±8.4% FFM. There was no significant difference in body weight, body fat mass (FM), TBW, and FFM between genders. Regarding D2O, ST underestimated %BF, and overestimated %FFM in both genders (p<0.05). BIA overestimated %TBW in the group as a whole and in males (p<0.05). The only positive and strong correlations occurred in females regarding the WC (σ=0.679), CI (r=0.634), and WHtR (r=0.666). CONCLUSIONS: In this sample of obese and overweight children, there were strong correlations between body composition measured by D2O and some indices and anthropometric indicators in females, but there was no positive and strong correlation of fat tissue with the indices/indicators at all ages and in both genders.

How to monitor vascular access in our hospital.

BACKGROUND: The number of dialysis patients in Japan has amounted to approximately 310,000. Most of the patients undergo hemodialysis. The reason why they can undergo hemodialysis is because maintaining and managing vascular access (VA) has improved. Recently, thanks to the progress of medical equipment, a variety of monitoring systems have been developed. It is important to make good use of these monitoring systems. RESULTS: In our hospital, we have been monitoring with an ultrasonic device and HD02. We measure blood flow of brachial artery with an ultrasonic device during nondialysis treatment. We examine real blood flow and blood recirculation with HD02 and evaluate the function of VA during dialysis. CONCLUSIONS: In order to provide good dialysis care, good use of monitoring devices of VA is significant.

Infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide.

The effects of temperature and density on retention of platinum(II) 2,4-pentanedionate in supercritical fluid chromatography were investigated at temperatures of 308.15-343.15K and pressure range from 8 to 40MPa by the chromatographic impulse response method with curve fitting. The retention factors were utilized to derive the infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide. The determined partial molar volumes were small and positive at high pressures but exhibited very large and negative values in the highly compressible near critical region of carbon dioxide.

Validation of a new method based on ultrasound velocity dilution to measure cardiac output in paediatric patients.

PURPOSE: To validate a novel method of ultrasound dilution (COstatus(®); Transonic Systems, Ithaca, NY) for measuring cardiac output in paediatric patients after biventricular repair of congenital heart disease. METHODS: Children undergoing biventricular repair of congenital heart disease were prospectively identified. Patients with significant intracardiac shunts were excluded. Postoperative cardiac output was measured by ultrasound dilution (COud) and concurrently calculated by the Fick equation (COrms) using measured oxygen consumption by respiratory mass spectrometry. RESULTS: Thirty-five patients were studied generating 66 individual data sets. Subjects had a median (interquartile range) age of 147 days (11, 216), weight of 4.98 kg (3.78, 6.90) and body surface area of 0.28 m(2) (0.22, 0.34). Of the patients, 66% had peripheral arterial catheters and 34% had femoral cannulation; peripheral arterial lines accounted for 6/8 of unsuccessful studies due to inability to generate sufficient flow. The site of the central venous cannula did not impact the feasibility of completing the study. A mean bias of 0.00 L/min [2 standard deviation (SD) ± 0.76 L/min] between COud and COrms was found with a percentage error of 97%. When comparing cardiac index, bias increased to 0.13 L/min/m(2) (2SD ± 2.16 L/min/m(2)). CONCLUSIONS: Cardiac output by ultrasound dilution showed low bias with wide limits of agreement when compared to measurement derived by the Fick equation. Although measurements through central and peripheral arterial lines were completed with minimal difficulties in the majority of patients, the application of COstatus(®) in neonates with low body surface area may be limited.

Determination of creatinine in human urine with flow injection tandem mass spectrometry.

BACKGROUND/AIMS: Excretion of urinary compounds in spot urine is often estimated relative to creatinine. For the growing number of liquid chromatography-tandem mass spectrometry (LC-MS/MS) assays of urine-excreted molecules, a fast and accurate method for determination of creatinine is needed. METHODS: A high-throughput flow injection tandem mass spectrometry method for exact quantitation of creatinine in urine has been developed and validated. Sample preparation used only two-step dilution for protein precipitation and matrix dilution. Flow injection analysis without chromatographic separation allowed for total run times of 1 min per sample. Creatinine concentrations were quantitated using stable isotope dilution tandem mass spectrometry. Selectivity and coelution-free quantitation were assured by qualifier ion monitoring. RESULTS: Method validation revealed excellent injection repeatability of 1.0% coefficient of variation (CV), intraday precision of 1.2% CV and interday precision of 2.4% CV. Accuracy determined from standard addition experiments was 106.1 ± 3.8%. The linear calibration range was adapted to physiological creatinine concentrations. Comparison of quantitation results with a routinely used method (Jaffé colorimetric assay) proved high agreement (R(2) = 0.9102). CONCLUSIONS: The new method is a valuable addition to the toolbox of LC-MS/MS laboratories where excretion of urinary compounds is studied. The 'dilute and shoot' approach to isotope dilution tandem mass spectrometry makes the new method highly accurate as well as cost- and time-efficient.

Influence of lung injury on cardiac output measurement using transpulmonary ultrasound dilution: a validation study in neonatal lambs.

BACKGROUND: Transpulmonary ultrasound dilution (TPUD) is a promising method for cardiac output (CO) measurement in severely ill neonates. The incidence of lung injury in this population is high, which might influence CO measurement using TPUD because of altered lung perfusion. We evaluated the influence of lung injury on the accuracy and precision of CO measurement using TPUD in an animal model. METHODS: In nine neonatal lambs, central venous and arterial catheters were inserted and connected to the TPUD monitor. Repeated lavages with warmed isotonic saline were performed to gradually induce lung injury. CO measurements with TPUD (COtpud) were compared with those obtained by an ultrasonic transit-time flow probe around the main pulmonary artery (COufp). An increase in oxygenation index was used as an indicator of induced lung injury during the experiment. Post-mortem lung injury was confirmed by histopathological examination. RESULTS: Fifty-five sessions of three paired CO measurements were analysed. The mean COufp was 1.53 litre min(-1) (range 0.66-2.35 litre min(-1)), and the mean COtpud was 1.65 litre min(-1) (range 0.78-2.91 litre min(-1)). The mean bias (standard deviation) between the two methods was 0.13 (0.15) litre min(-1) with limits of agreement of ±0.29 litre min(-1). The overall percentage error was 19.1%. The accuracy and precision did not change significantly during progressive lung injury. Histopathological severity scores were consistent with heterogeneous lung injury. The capability to track changes in CO using TPUD was moderate to good. CONCLUSIONS: The accuracy and precision of CO measurement using TPUD is not influenced in the presence of heterogeneous lung injury in an animal model.

Quantification of recirculation as an adjuvant to transthoracic echocardiography for optimization of dual-lumen extracorporeal life support.

PURPOSE: Proper cannula positioning in single site veno-venous extracorporeal life support (vv-ELS) is cumbersome and necessitates image guidance to obtain a safe and stable position within the heart and the caval veins. Importantly, image-guided cannula positioning alone is not sufficient, as possible recirculation cannot be quantified. METHODS AND RESULTS: We present an ultrasound dilution technique allowing quantification of recirculation for optimizing vv-ELS. CONCLUSION: We suggest quantification of recirculation in addition to image guidance to provide optimal vv-ELS.

Dispersion serial dilution methods using the gradient diluter device.

A solute aspirated into a prefilled tube of diluent undergoes a dilution effect known as dispersion. Traditionally the effects of dispersion have been considered a negative consequence of using liquid-filled fixed-tip liquid handlers. We present a novel device and technique that utilizes the effects of dispersion to the benefit of making dilutions. The device known as the Gradient Diluter extends the dilution range of practical serial dilutions to six orders of magnitude in final volumes as low as 10 µL. Presented are the device, dispersion methods, and validation tests using fluorescence detection of sulforhodamine and the high-performance liquid chromatography/ultraviolet detection of furosemide. In addition, a T-cell inhibition assay of a relevant downstream protein is used to demonstrate IC(50) curves made with the Gradient Diluter compare favorably with those generated by hand.

[Assessment of cardiac output and intrathoracic blood volume by means of transpulmonary thermodilution and ultrasound dilution: similarities and differences].

UNLABELLED: The aim of the study is to compare results of the assessment of cardiac output and intrathoracic blood volume by two methods--transpulmonary (TTD) and ultrasound (UTD) thermodilution. MATERIALS AND METHODS: The prospective study included 58 patients (sepsis, septic shock, acute respiratory distress syndrome, intracranial haemorrhages), which underwent femoral artery catheterization with "Pulsiocath" 5Fr catheter (PICCO technology). For the means of ultrasound the catheter was connected to the central venous catheter by an arteriovenous loop. Sensors on arterial and venous ends of the loop registered the time and the volume of the indicator, blood properties and the ultrasound curve. Cooled (0 to 8 C) 5% glucose solution was used as an indicator for TTD, while heated (up to 37C) 0.9% NaCl solution was used as an indicator for the ultrasound. The cardiac output (CO) was measured by TTD and UTD, the global end diastolic volume (GEDV) by TTD, its analogue total end diastolic volume (TEDV) by UTD, intrathoracic blood volume (ITBV) by TTD and central blood volume (CBV) by UTD. 218 pairs of measurements were conducted. Oscillations of CO (TTD) were 2.76-16.3 l/min (8.6 +/- 2.48 l/min) and of CO (UTD)--2.92-18.1 l/min (8.72 +/- 2.65 l/min). There was a strong correlation between CO (TTD) and CO (UTD). The systematic mistake was 0.12 l/min, percentage based mistake--20.9%. ITBV correlated with CBV. There was a big systematic mistake found, which measured as much as 323 ml, the percentage based mistake was 36.5%. The correlation between GEDV and TEDV was (r = 0.70, p < 0.01). The TTD ejection fraction (23.2 +/- 5.6%) was lower (p < 0.01), than by UTD (57.8 +/- 15.2%). RESULTS: Both methods demonstrate close values of CO. GEDV was higher than TEDV and physiological heart volume. The absolute values of GEDV and ITBV measured by TTD are higher than the actual ones, although they reflect the changes of blood volume and can be used as dynamic preload parameters.