Dye Dilution Technique Research Articles

Amniotic Fluid Volume Assessment: Eight Lessons Learned.

Actual AFV can be determined by a dye-dilution technique or be directly measured at cesarean. This allows investigators to correlate estimated and actual AFVs. Lessons learned by assessing the relationship of estimated to actual AFVs. 1) Ultrasound estimates normal actual AFVs well, but abnormal AFVs poorly. 2) Quantile regression is a better statistical methodology to create a normal AFV curve across pregnancy. 3) There is no difference in the accuracy of the subjective (visualization without measurements) compared with the objective (visualization with measurements) technique in identifying normal and abnormal AFVs. 4) Color Doppler use leads to the over-diagnosis of oligohydramnios. 5) Intravenous hydration increases actual AFVs. 6) The estimation of AFV can be done with the transducer held perpendicular to the floor or perpendicular to the uterine contour. 7) The single deepest pocket should be used for identifying low AFVs. 8) The AFI should be used for identifying high AFVs.

Non-invasive dye dilution method for measuring an atrial septal defect shunt size

AimsObjective of this study was to evaluate the feasibility of the non-invasive dye dilution method to quantify shunt size related to atrial septal defects (ASD).The diagnostic accuracy of shunt size...

Blood reservoir function in patients with Fontan circulation and asplenia syndrome.

Splanchnic circulation constitutes a major portion of the vasculature capacitance and plays an important role in maintaining blood perfusion. Because patients with asplenia syndrome lack this vascular bed as a blood reservoir, they may have a unique blood volume and distribution, which may be related to their vulnerability to the haemodynamic changes often observed in clinical practice. During cardiac catheterisation, the mean circulatory filling pressure was calculated with the Valsalva manoeuvre in 19 patients with Fontan circulation, including 5 patients with asplenia syndrome. We also measured the cardiac output index and circulatory blood volume by using a dye dilution technique. The blood volume and the mean circulatory filling pressure and the venous capacitance in patients with asplenia syndrome were similar to those in the remaining patients with Fontan circulation (85 ± 14 versus 77 ± 18 ml/kg, p = 0.43, 31 ± 8 versus 27 ± 5 mmHg, p = 0.19, 2.8 ± 0.6 versus 2.9 ± 0.9 ml/kg/mmHg, p = 0.86). Unexpectedly, our data indicated that patients with asplenia syndrome, who lack splanchnic capacitance circulation, have blood volume and venous capacitance comparable to those in patients with splanchnic circulation. These data suggest that (1) there is a blood reservoir other than the spleen even in patients with asplenia; (2) considering the large blood pool of the spleen, the presence of a symmetrical liver may represent the possible organ functioning as a blood reservoir in asplenia syndrome; and (3) if this is indeed the case, there may be a higher risk of hepatic congestion in patients with Fontan circulation with asplenia syndrome than in those without.

Analysis of the frequencies and functions of CD4+CD25+CD127low/neg, CD4+HLA-G+, and CD8+HLA-G+ regulatory T cells in pre-eclampsia

Most of the investigations on regulatory T cells (Treg) have focused on CD4+CD25+Foxp3+ Treg cells. Although new subsets of these cells such as CD4+CD25+CD127low/neg, CD4+HLA-G+, and CD8+HLA-G+ Treg cells have been introduced, documents regarding these populations are limited or controversial in case of pregnancy and pre-eclampsia (PE). Here, we investigated the frequencies of the three aforementioned Treg cell subsets in the peripheral blood of non-pregnant (n = 15), healthy pregnant, and preeclamptic women (n = 17 in each group) using flow cytometry. We also assessed the ability of the isolated CD4+CD25+CD127low/neg and CD4+HLA-G+ Treg cells to suppress responder T cells proliferation and cytokine secretion using CFSE dye dilution and ELISA technique. Our results showed that the frequency of CD4+CD25+CD127low/neg Treg cells was significantly lower in preeclamptic women (p = 0.001). Also, this subset negatively correlated with both systolic (R= - 0.401, p = 0.004) and diastolic (R= - 0.541, p = 0.001) blood pressures. Regarding CD4+HLA-G+ and CD8+HLA-G+ Treg cells, the mean percentages of these cells were significantly higher in the context of normal pregnancy (p < 0.01). Finally, our results in the functional assay experiments did not show statistically significant differences between groups (p ≥ 0.05), but they reveal a shift toward the lower suppressive capacity of CD4+CD25+CD127low/neg and CD4+HLA-G+ Treg cells in preeclamptic patients which might be clinically important. In conclusion, a significant decrease in the frequency of Treg cell subsets and also a shift toward the lower suppressive capacity of these cells in preeclamptic patients may lead to immunological maladaptation in the context of PE.

Thermodilution Cardiac Output: A Concept Over 250 Years in the Making.

The need to quantify blood flow through the heart has led to the development of different techniques for its measurement. The 3 main approaches are the Fick method, dye dilution, and thermodilution techniques. The latter 2 are based on the use of indicators that indirectly quantify blood flow. These have slowly been developed over centuries, from the concept of measuring blood flow, to a technique, and its clinical utility. Thermodilution is the most popular dilution method used for measuring cardiac output (CO) in the clinical setting. The information obtained during this procedure is relevant in the process of clinical decision making in patients with critical illness, valvular heart disease, and congestive heart failure. The technique increased in popularity in the early 1970's after Swan and Ganz invented the pulmonary artery catheter that simplified thermodilution enough to utilize it as a bedside procedure. This was only possible with simple yet clever engineering methods that are not commonly known in the medical community. Despite these advancements, the concept of measuring CO by dilution techniques is one where its optimal use in the clinical setting continues to be an area of investigation. The thermodilution concept and the mechanism of measuring CO will be discussed in the following review.

Three-dimensional culture system enhances anti-inflammatory characteristics in human trophoblast cells

Most of the investigations on regulatory T cells (Treg) have focused on CD4+CD25+Foxp3+ Treg cells. Although new subsets of these cells such as CD4+CD25+CD127low/neg, CD4+HLA-G+, and CD8+HLA-G+ Treg cells have been introduced, documents regarding these populations are limited or controversial in case of pregnancy and pre-eclampsia (PE). Here, we investigated the frequencies of the three aforementioned Treg cell subsets in the peripheral blood of non-pregnant (n = 15), healthy pregnant, and preeclamptic women (n = 17 in each group) using flow cytometry. We also assessed the ability of the isolated CD4+CD25+CD127low/neg and CD4+HLA-G+ Treg cells to suppress responder T cells proliferation and cytokine secretion using CFSE dye dilution and ELISA technique. Our results showed that the frequency of CD4+CD25+CD127low/neg Treg cells was significantly lower in preeclamptic women (p = 0.001). Also, this subset negatively correlated with both systolic (R= - 0.401, p = 0.004) and diastolic (R= - 0.541, p = 0.001) blood pressures. Regarding CD4+HLA-G+ and CD8+HLA-G+ Treg cells, the mean percentages of these cells were significantly higher in the context of normal pregnancy (p < 0.01). Finally, our results in the functional assay experiments did not show statistically significant differences between groups (p ≥ 0.05), but they reveal a shift toward the lower suppressive capacity of CD4+CD25+CD127low/neg and CD4+HLA-G+ Treg cells in preeclamptic patients which might be clinically important. In conclusion, a significant decrease in the frequency of Treg cell subsets and also a shift toward the lower suppressive capacity of these cells in preeclamptic patients may lead to immunological maladaptation in the context of PE.

Methods for blood loss estimation after vaginal birth.

Methods for blood loss estimation after vaginal birth.

The Importance of Aquaporin 1 in Pancreatitis and Its Relation to the CFTR Cl- Channel.

Aquaporins (AQPs) facilitate the transepithelial water flow involved in epithelial fluid secretion in numerous tissues; however, their function in the pancreas is less characterized. Acute pancreatitis (AP) is a serious disorder in which specific treatment is still not possible. Accumulating evidence indicate that decreased pancreatic ductal fluid secretion plays an essential role in AP; therefore, the aim of this study was to investigate the physiological and pathophysiological role of AQPs in the pancreas. Expression and localization of AQPs were investigated by real-time PCR and immunocytochemistry, whereas osmotic transmembrane water permeability was estimated by the dye dilution technique, in Capan-1 cells. The presence of AQP1 and CFTR in the mice and human pancreas were investigated by immunohistochemistry. Pancreatic ductal HCO3- and fluid secretion were studied on pancreatic ducts isolated from wild-type (WT) and AQP1 knock out (KO) mice using microfluorometry and videomicroscopy, respectively. In vivo pancreatic fluid secretion was estimated by magnetic resonance imaging. AP was induced by intraperitoneal injection of cerulein and disease severity was assessed by measuring biochemical and histological parameters. In the mice, the presence of AQP1 was detected throughout the whole plasma membrane of the ductal cells and its expression highly depends on the presence of CFTR Cl- channel. In contrast, the expression of AQP1 is mainly localized to the apical membrane of ductal cells in the human pancreas. Bile acid treatment dose- and time-dependently decreased mRNA and protein expression of AQP1 and reduced expression of this channel was also demonstrated in patients suffering from acute and chronic pancreatitis. HCO3- and fluid secretion significantly decreased in AQP1 KO versus WT mice and the absence of AQP1 also worsened the severity of pancreatitis. Our results suggest that AQP1 plays an essential role in pancreatic ductal fluid and HCO3- secretion and decreased expression of the channel alters fluid secretion which probably contribute to increased susceptibility of the pancreas to inflammation.

Experimental study of efficient mixing in a micro-fluidized bed

Micro-fluidized beds represent a novel means of significantly enhancing mixing and mass and heat transfer under the low Reynolds number flows that dominate in microfluidic devices. This study experimentally evaluates the mixing performance of a micro-fluidized bed and the improvements it affords over the equivalent particle-free system. The dye dilution technique coupled with standard top-view image analysis was used to characterize the mixing in a 400×175μm2 polydimethylsiloxane (PDMS) Y-microchannel. Overall, the micro-fluidized bed provided a mixing effectiveness and energetic efficiency of mixing that were up to three times greater than those of a particle-free channel of the same dimensions. The mixing performance is strongly affected by specific power input and bed voidage. The optimal operating voidage, which corresponds to the energetic efficiency of mixing being maximal, is around 0.77 for the smallest particle-to-channel size ratio considered here 0.121, and appears to increase beyond this with size ratio.

Amniotic Fluid Assessment: Amniotic Fluid Index Versus Maximum Vertical Pocket

Amniotic fluid assessment is vital to fetal well-being. Accurately diagnosing an amniotic fluid abnormality can aid in the proper management of a pregnancy at risk for an adverse outcome. Sonography is the most common way to assess amniotic fluid volume throughout a pregnancy; however, the most accurate technique, amniotic fluid index or maximum vertical pocket, is yet to be determined. Dye-dilution techniques are the most accurate way to measure amniotic fluid volume, but they are invasive and can be performed only at the time of a cesarean delivery. Multiple studies have been performed to determine the accuracy of the amniotic fluid index and maximum vertical pocket methods when diagnosing amniotic fluid volume abnormalities. Based on the studies reviewed in this article, neither method stands out as superior to the other when it comes to diagnosing amniotic fluid abnormalities during pregnancy. However, the maximum vertical pocket should also always be considered when an amniotic fluid abnormality is suspected because the amniotic fluid index overdiagnoses amniotic fluid abnormalities, leading to increased rates of pregnancy intervention and the potential for adverse pregnancy outcomes.

Left ventricular atrioventricular plane displacement is preserved with lifelong endurance training and is the main determinant of maximal cardiac output.

Age-related decline in cardiac function can be prevented or postponed by lifelong endurance training. However, effects of normal ageing as well as of lifelong endurance exercise on longitudinal and radial contribution to stroke volume are unknown. The aim of this study was to determine resting longitudinal and radial pumping in elderly athletes, sedentary elderly and young sedentary subjects. Furthermore, we aimed to investigate determinants of maximal cardiac output in elderly. Eight elderly athletes (63 ± 4 years), seven elderly sedentary (66 ± 4 years) and ten young sedentary subjects (29 ± 4 years) underwent cardiac magnetic resonance imaging. All subjects underwent maximal exercise testing and for elderly subjects maximal cardiac output during cycling was determined using a dye dilution technique. Longitudinal and radial contribution to stroke volume did not differ between groups (longitudinal left ventricle (LV) 52-65%, P = 0.12, right ventricle (RV) 77-87%, P = 0.16, radial 7.9-8.6%, P = 1.0). Left ventricular atrioventricular plane displacement (LVAVPD) was higher in elderly athletes and young sedentary compared with elderly sedentary subjects (14 ± 3, 15 ± 2 and 11 ± 1 mm, respectively, P < 0.05). There was no difference between groups for RVAVPD (P = 0.2). LVAVPD was an independent predictor of maximal cardiac output (R(2) = 0.61, P < 0.01, β = 0.78). Longitudinal and radial contributions to stroke volume did not differ between groups. However, how longitudinal pumping was achieved differed; elderly athletes and young sedentary subjects showed similar AVPD whereas this was significantly lower in elderly sedentary subjects. Elderly sedentary subjects achieved longitudinal pumping through increased short-axis area of the ventricle. Large AVPD was a determinant of maximal cardiac output and exercise capacity.

Tailored therapy for aggressive dilatation of systemic veins and arteries may result in improved long-term Fontan circulation

switch procedure. Pulmonary artery banding is not a benign procedure, and mechanical support after surgery can be unpredictable, with the potential for significant bleeding issues as a result of anticoagulation. In this particular case, the presence of a restrictive muscular VSD provided the opportunity to stent the VSD open to allow preparation of the left ventricle. Stenting the VSD obviated the need for initial palliative surgery and allowed easy monitoring of the progress of the left ventricle. One caveat with this technique is that not all VSDs are amenable to stenting, because the risk of inducing heart block is high in the more commonly seen perimembranous type of VSD. In this reported case, the VSD was muscular, however, which made the risk of heart block low. The use of interventional cardiology procedures for initial palliation is a relatively new and promising alternative. Some groups have explored stenting of the right

Drug effects in multiple rounds of cell division monitored by flow cytometry

Flow cytometry, and the more recently introduced imaging flow cytometry, are ideal tools for following the cell cycle in mammalian cells. One of the first applications of flow cytometry was looking at DNA content via single parameter fluorescence of a DNA-binding dye such as propidium iodide or DAPI but this only provides a snapshot of cells at one point in time. More sophisticated techniques are needed to investigate multiple rounds of division and these include the addition of a nucleotide analog such as bromodeoyurdine (BrdU) which can follow cells through 1-2 rounds of cell division; the BrdU-Hoechst quenching technique which can follow 3-4 rounds of cell division or the use of a dye dilution technique using protein binding dyes such as CFSE or the CellTrace dyes or lipid-binding dyes such as the PKH dyes. We recently developed a method to study cell cycle analysis in multiple rounds of division using a combination of CellTrace Violet for round of division, propidium iodide for DNA content and staining for phoshpoH3 to identify mitotic cells [1]. This enables us to follow cells through up to 6 rounds of cell division. By adding drugs that interfere with the cell cycle either by inhibiting DNA synthesis (etoposide) or that inhibit mitosis (Nocodazol) we are able to look at the effect in cells at a known point in division history without the need for blocking the cells beforehand. This gives a true sense of how individual cells relate to one another. In addition, by using imaging flow cytometry we are able to sub-divide the individual phases of mitosis which can give further information on the action of cell-cycle inhibiting drugs and may allow this method to be used to give mechanistic information of the action of candidate anti-cancer drugs.

Amniotic fluid volume in normal singleton pregnancies: modeling with quantile regression

To develop uniform and reliable reference ranges for amniotic fluid volume (AFV) across gestation in normal singleton pregnancies using quantile regression (QR). An analysis of true AFVs determined by dye-dilution techniques or by direct measurement at cesarean delivery in normal singleton pregnancies. AFV centiles were established by QR, a flexible semi-parametric approach of estimating rates of change across the entire distribution of AFV rather than just in the mean as is observed with standard linear regression. The study evaluated 379 women with normal singleton pregnancies between 16 and 41 weeks gestation. QR was used to determine the association between AFV and gestational age (GA). A second-order quantile regression model indicated a nonlinear relationship between AFV and gestational age at the upper centile range (≥80th percentile). This study defines normative centile charts for true AFVs between 16 and 41 weeks gestation in normal singleton pregnancies using QR. This statistical approach more appropriately reflects true AFV across gestation at each centile of interest (e.g. 5th, 50th, 95th, etc.) as compared to standard linear regression.

Liquid–liquid mixing using micro-fluidised beds

This study experimentally investigates the application of a solid–liquid micro-fluidised bed as a micro-mixing device. The experiments were performed in a borosilicate capillary tube with an internal diameter of 1.2mm (i.e. near the upper-limit dimension of a micro-fluidic system) using borosilicate particles with a mean diameter of 98μm. Refractive index matching technique using sodium iodide solution was employed to achieve a transparent fluidised bed. Mixing performance of the micro-fluidised bed in terms of mixing time was investigated using a dye dilution technique. Experiments were carried out in the creeping flow regime at Reynolds numbers ranging between 0.27 and 0.72. It was demonstrated that the micro-fluidised bed mixing time sharply decreases as the Reynolds number increases. That is because at relatively high Reynolds numbers, the particle oscillation is stronger creating larger disturbances in the flow. The energy dissipation rate in micro fluidised bed was estimated to be four orders of magnitude less than other passive micro mixers which operate in the turbulent regime. It was also demonstrated that the ratio of mixing time and the energy dissipation rate for fluidised bed micro-mixer was comparable to K-M, Tangential IMTEK, and interdigital micro-mixers. However, the fluidised bed micro-mixer was found to operate at much lower Reynolds numbers compared to other passive mixers, with a mixing time of the order of few seconds.

Do We Need to Monitor Cardiac Output during Major Surgery?

Do We Need to Monitor Cardiac Output during Major Surgery?

Model-independent dynamic constraint to improve the optical reconstruction of regional kinetic parameters

Optical dye-dilution techniques can quantify kinetic parameters in a region of tissue, but currently rely on a two-step process-spatial reconstruction of the dye concentration, repeated at every time-point, and subsequent kinetic analysis of the time-dependent change in dye concentration. Inaccuracies, in this approach, are due mainly to the ill-posed nature of the spatial reconstruction problem, which propagates into kinetic analysis and result in errors in extracted dynamic parameters. We present a hybrid kinetic deconvolution optical reconstruction algorithm, effectively combining optical reconstruction and model-independent kinetic analysis into a single inverse problem that is better posed. Kinetic parameters of multiple tissue regions can be quantified simultaneously. As proof of principle, we provide numerical experiments in reflectance-based and fluorescence molecular tomography scenarios.

Amniotic Fluid and the Clinical Relevance of the Sonographically Estimated Amniotic Fluid Volume

The amniotic fluid volume (AFV) is regulated by several systems, including the in-tramembranous pathway, fetal production (fetal urine and lung fluid) and uptake (fetal swallowing), and the balance of fluid movement via osmotic gradients. The normal AFV across gestation has not been clearly defined; consequently, abnormal volumes are also poorly defined. Actual AFVs can be measured by dye dilution techniques and directly measured at cesarean delivery; however, these techniques are time-consuming, are invasive, and require laboratory support, and direct measurement can only be done at cesarean delivery. As a result of these limitations, the AFV is estimated by the amniotic fluid index (AFI), the single deepest pocket, and subjective assessment of the AFV. Unfortunately, sonographic estimates of the AFV correlate poorly with dye-determined or directly measured amniotic fluid. The recent use of color Doppler sonography has not improved the diagnostic accuracy of sonographic estimates of the AFV but instead has led to overdiagnosis of oligohydramnios. The relationship between the fixed cutoffs of an AFI of 5 cm or less and a single deepest pocket of 2 cm or less for identifying adverse pregnancy outcomes is uncertain. The use of the single deepest pocket compared to the AFI to identify oligohydramnios in at-risk pregnancies seems to be a better choice because the use of the AFI leads to an increase in the diagnosis of oligohydramnios, resulting in more labor inductions and cesarean deliveries without any improvement in peripartum outcomes.

Oligohydramnios, Small for Gestational Age and Pregnancy Outcomes: An Analysis Using Precise Measures

Background/Aim: Marginal or decreased amniotic fluid volume by ultrasound estimate and fetal growth restriction have been shown to be significantly associated with perinatal mortality. The association of fetal growth restriction and precisely measured amniotic fluid volume is unknown. The purpose of this study was to determine if adverse pregnancy outcomes are more likely in pregnancies complicated by small-for-gestational-age (SGA) neonates and dye-determined oligohydramnios. Methods: Admissions to neonatal intensive care unit (NICU) and other pregnancy outcomes were analyzed in parturients with known amniotic fluid volume, calculated by the dye-dilution technique. The pregnancy outcomes of those with oligohydramnios and SGA were compared with pregnancies complicated by just one of these two conditions and pregnancies with normal fluid and birth weight. Results: Of 202 patients, oligohydramnios was present in 26% (53), SGA in 15% (30) and both conditions in (5%) (11). Logistic regression, controlling for gestational age, demonstrated that the combination of oligohydramnios and SGA, compared to normal growth and fluid strongly predicted NICU admission (OR 11.1; 95% CI 2.1–59.2) but not other complications. (OR 4.8; 95% CI 0.3–62.9). Conclu sions: SGA with oligohydramnios significantly increases the likelihood of a NICU admission, but not other morbidity.

Estabilidad a la congelación descongelación de emulsiones o/w preparadas con aislados de soja nativos y desnaturalizados con diferente solubilidad

The aim of this work was to evaluate the freeze-thaw stability of model o/w emulsions prepared with four soy isolates: two native (NSI-1 and NSI-2, with similar composition but different protein solubility, &gt;90% and 75%, respectively), and two denatured (DSI-1 and DSI-2), resulting from heating the respective native ones (90 °C, 5 min). Emulsions prepared with NSI or DSI aqueous dispersions (2% w/v) and refined sunflower oil (Φ = 0.25) were frozen at -20 °C for 24 h and subsequently thawed at 20 °C. Freeze-thaw stability was evaluated by particle size distribution (laser diffraction) and free oil (FO, dye-dilution technique) measurements. Emulsions prepared with NSI-2 and DSI-2 were highly destabilized after freeze-thawing process, as was demonstrated by the increase of particle size and FO&gt;25%. More stable emulsions were obtained with the high soluble sample NSI-1, and a noticeable increase in stability was observed with denaturation of their proteins (DSI-1). The coalescence and oiling off was almost completely inhibited in DSI-1 emulsions. In summary, solubility and denaturation degree of soy protein isolates have a decisive influence on freeze-thaw stability of protein-stabilized emulsions.