Low haemolysis pulsatile impeller pump: design concepts and experimental results

A pulsatile fully implantable impeller pump with low haemolysis has been produced by developing a pulsatile impeller for a nonpulsatile pump also developed in this laboratory. The impeller was designed according to the 3-dimensional theory of fluid dynamics. The impeller shroud retains the same parabolic form and the vane has a form compacted by a radial logarithmic spiral and an axial helical spiral so that the absolute vibration velocity of the blood in a peripheral direction is a minimum as the impellar changes its speed periodically to generate a physiological pulsatile blood flow. Thus the Reynolds shear and the Newton shear are a minimum for the required pulse pressure. The mean volume and mean pressure are controlled by adjusting the voltage. The shape of the pressure pulse is determined by a square was of vollage and the systole/diastole ratio. In order to abolish regurgitation of the pump, a 40 per cent systole period and a 5 V voltage pulse are desirable for 40 mmHg pulse pressure (80–120 mmHg mean pressure). The pulse frequency has almost no effect on pump output. The pump can delivery 4 l/min mean volume and 100 mmHg mean pressure (40 mmHg pulse pressure), and these conditions result in an index of heamolysis (IH) for porcine blood of 0.020—only slighly more than the nonpulsatile pump (0.016). When the pulsatile impeller was used under nonpulsatile conditions its IH was almost doubled, but when the nonpulsatile impeller was used under pulsatile conditions the IH reached 0.13. The power consumption is approximately equal to that for the nonpulsatile pump: 3 W for 4 l/min and 100 mmHg output. The pump weights 240 g (including 190 g for the motor) and, because a commercial motor has been used, costs only a few hundred US dollars.     

心室辅助径流泵的设计方法

我们正在研制一种心室辅助径流泵,可在体外循环中代替血泵使用,也可作为心衰病人短期心脏辅助泵使用。此种无密封件的径流的泵的轴尖支承结构由一根据氧化铝陶瓷制成的叶轮轴和两只氧化锆陶瓷制成的轴尖轴承组成。叶轮的外径为７２毫米,进流处直径为２４毫米。位于叶轮上表面的六个叶片的进流侧高度为５．５毫米。出流侧高度为３毫米。     

Computational Fluid Dynamics (CFD) study of the 4th generation prototype of a continuous flow Ventricular Assist Device (VAD)

The continuous flow ventricular assist device (VAD) is a miniature centrifugal pump, fully suspended by magnetic bearings, which is being developed for implantation in humans. The CF4 model is the first actual prototype of the final design product. The overall performances of blood flow in CF4 have been simulated using computational fluid dynamics (CFD) software: CFX, which is commercially available from ANSYS Inc. The flow regions modeled in CF4 include the inlet elbow, the five-blade impeller, the clearance gap below the impeller, and the exit volute. According to different needs from patients, a wide range of flow rates and revolutions per minute (RPM) have been studied. The flow rate-pressure curves are given. The streamlines in the flow field are drawn to detect stagnation points and vortices that could lead to thrombosis. The stress is calculated in the fluid field to estimate potential hemolysis. The stress is elevated to the decreased size of the blood flow paths through the smaller pump, but is still within the safe range. The thermal study on the pump, the blood and the surrounding tissue shows the temperature rise due to magnetoelectric heat sources and thermal dissipation is insignificant. CFD simulation proved valuable to demonstrate and to improve the performance of fluid flow in the design of a small size pump.     

Haemodynamic approach to reducing thrombosis and haemolysis in an impeller pump

In the experimental and clinical support of the failing heart, the impeller-type centrifugal pumps continue to be of interest because of their inherent advantages; however, the blood compatibility of these pumps still remains to be improved. From the viewpoint of haemodynamics, thrombosis and haemolysis could be reduced by eliminating the stagnation and turbulence of blood flow within the pump, which frequently takes place near the blood contracting surfaces of the pump, when the impeller contours do not coincide with the stream surfaces of the blood. It is suggested that it could be advantageous to design impeller contours according to the stream surfaces, by solving the partial differential equations of continuity, motion and energy. An impeller shroud and vane based on this approach would be fully rinsed by non-turbulent flow and there would then be neither stagnation nor turbulence within the pump, with the result that thrombosis and haemolysis could be reduced. A new impeller pump, developed according to this method, was evaluated as a left ventricular device in four dogs. The bypass flow was controlled at 40–50% of the total flow, each test lasting 6 h. All of the haematological parameters, measured every 2 h, remained within normal range. There was no thrombosis, and coagulation in the pump was avoided by a small dose of heparin to maintain the activated coagulation time (ACT) under 200″ in the experiments.     

Thermal instability of red blood cell membrane bilayers: Temperature dependence of hemolysis

Summary Rates of human red blood cell hemolysis were measured as a function of temperature. Three distinct temperature intervals for hemolysis were noted: a) At temperatures equal to or less than 37°C no hemolysis was observed for the duration of the incubation (30 hr). b) For temperatures exceeding 45°C hemolysis rates are rapid and are accompanied by gross changes in cellular morphology. The activation energy for hemolysis is 80 kcal/mole; this value is characteristic of protein denaturation and enzyme inactivation suggesting that these processes contribute to hemolysis at these high temperatures. c) Between 38 and 45°C the energy of activation is 29 kcal/mole, indicating that a fundamentally different process than protein inactivation is responsible for hemolysis at these relatively low temperatures. A mechanism based on the concept of the critical bilayer assembly temperature of cell membranes (N.L. Gershfeld,Biophys. J. 50:457–461, 1986) accounts for hemolysis at these relatively mild temperatures: The unilamellar state of the membrane is stable at 37°C, but is transformed to a multibilayer when the temperature is raised; hemolysis results because formation of the multibilayer requires exposing lipid-free areas of the erythrocyte surface. An analysis of the activation energy for hemolysis is presented that is consistent with the proposed unilamellar-multibilayer transformation.     

PIV measurements of flow in a centrifugal blood pump: steady flow

Magnetically suspended left ventricular assist devices have only one moving part, the impeller. The impeller has absolutely no contact with any of the fixed parts, thus greatly reducing the regions of stagnant or high shear stress that surround a mechanical or fluid bearing. Measurements of the mean flow patterns as well as viscous and turbulent stresses were made in a shaft-driven prototype of a magnetically suspended centrifugal blood pump at several constant flow rates (3-9 L/min) using particle image velocimetry (PIV). The chosen range of flow rates is representative of the range over which the pump may operate while implanted. Measurements on a three-dimensional measurement grid within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser are reported. The measurements are used to identify regions of potential blood damage due to high shear stress and/or stagnation of the blood, both of which have been associated with blood damage within artificial heart valves and diaphragm-type pumps. Levels of turbulence intensity and Reynolds stresses that are comparable to those in artificial heart valves are reported. At the design flow rate (6 L/min), the flow is generally well behaved (no recirculation or stagnant flow) and stress levels are below levels that would be expected to contribute to hemolysis or thrombosis. The flow at both high (9 L/min) and low (3 L/min) flow rates introduces anomalies into the flow, such as recirculation, stagnation, and high stress regions. Levels of viscous and Reynolds shear stresses everywhere within the pump are below reported threshold values for damage to red cells over the entire range of flow rates investigated; however, at both high and low flow rate conditions, the flow field may promote activation of the clotting cascade due to regions of elevated shear stress adjacent to separated or stagnant flow.     

Trauma to erythrocytes induced by long term in vitro pumping using a roller pump

The objective of this study is to investigate the impact of trauma on erythrocyte caused by long term in vitro pumping using roller pump. Ten bags of human blood (400 ml each) were provided by a local blood bank and they were divided into two groups with five bags in each group. Each blood bag was subject to pumping in a closed circuit, which was composed of silica gel tubes and a roller pump. Polystan and COBE pumps were used for the two groups, respectively. The blood was pumped for 16 h in vitro. Free hemoglobin (FHb), platelets (PLT), erythrocyte fragility (EF), and morphological analysis of erythrocytes observed under scanning electron microscope were measured to evaluate the impact of trauma on erythrocytes. A small amount of blood was collected for analysis before pumping, at the end of the 4th hour and then every 2 h till the end of the 16th hour. Some blood samples were also collected for electron microscope scanning before pumping and every 4 h during pumping. It was found that FHb and PLT linearly increased with the pumping time. There was a significant correlation between the two parameters (r=0.7745, p<0.001). The hemolysis indexes of the two groups were 0.296 and 0.3993 mg/L/h, respectively, with no significant difference. During the pumping process, EF changed slightly. The observation of scanning electron microscopy showed various deformed erythrocytes after pumping, including the distortion of cell membrane and the appearance of echinocytes, which increased with pumping time. This study demonstrated that long term pumping using roller pump not only caused the immediate rupture of red blood cells, i.e. the immediate hemolysis, but also caused sub-trauma to a large number of erythrocytes, which led to the delayed hemolysis. The change of erythrocyte morphology was the basis of the delayed hemolysis.     

21毫米人造心脏瓣膜泵的设计及研制

为了研究能够长期置入主动脉瓣环的左心室辅助装置,研制出直径21毫米重27克可植入的主动脉瓣膜泵.装置包括一个转子和一个定子.转子由驱动磁钢和叶轮组成;定子装有带铁心的电机线圈和出口导叶.装置被置於主动脉瓣位置,所以不占用额外的解剖空间.血泵能像自然心脏一样直接将血液由心室输送到主动脉,不需要连接管道和旁路,因此对自然生理循环的干扰可以减到最低.血泵流量由最大到零周期变化.血液动力学测试表明,当血泵转速为17500转/分钟时,可以产生流量5升/分钟、压力增益50毫米汞柱的血流;同一转速下,当流量为零时,血泵能保持主动脉舒张压为80毫米汞柱.     

Initial hydrodynamic study on a new intraaortic axial flow pump: Dynamic aortic valve

Rotary blood pumps have been researched as implantable ventricular assist devices for years. To further reduce the complex of implanted axial pumps, the authors proposed a new concept of intraaortic axial pump, termed previously as "dynamic aortic valve (DAV)". Instead of being driven by an intraaortic micro-electric motor, it was powered by a magnetic field from outside of body. To ensure the perfusion of coronary artery, the axial flow pump is to be implanted in the position of aortic valve. It could serve as either a blood pump or a mechanical valve depending on the power input. This research tested the feasibility of the new concept in model study. A column, made from permanent magnet, is jointed to an impeller in a concentric way to form a "rotor-impeller". Supported by a hanging shaft cantilevered in the center of a rigid cage, the rotor-impeller can be turned by the magnetic field in the surrounding space. In the present prototype, the rotor is 8 mm in diameter and 15 mm in length, the impeller ha     

Numerical simulation of cardiovascular dynamics with different types of VAD assistance

A variety of methods by which mechanical circulatory support (MCS) can be provided have been described. However, the haemodynamic benefits of the different methods have not been adequately quantified. The aim of this paper is to compare the haemodynamic effects of six forms of MCS by numerical simulation. Three types of ventricular assist device (VAD) are studied: positive displacement; impeller and a novel reciprocating-valve design. Similarly, three pumping modes are modelled: constant flow; counterpulsation and copulsation. The cardiovascular system is modelled using an approach developed previously, using the concentrated parameter method by considering flow resistance, vessel elasticity and inertial effects of blood in individual conduit segments. The dynamic modelling of displacement and impeller pumps is represented by VAD inlet/outlet flow-rate changes. The dynamics of the reciprocating-valve pump is modelled with a specified displacement profile. Results show that in each simulation, the physiological variables of mean arterial pressure and systemic flow are adequately maintained. Modulation of the impeller pump flow profile produces a small (5 mmHg) oscillatory component to arterial pressure, whereas the displacement and reciprocating-valve pumps generate substantial arterial pressure and flow pulsatility. The impeller pump requires the least power input, the reciprocating valve pump slightly more, and the displacement pump the most. The in parallel configuration of the impeller and displacement pump designs with respect to the left ventricle provides near complete unloading and can cause the aortic valve to remain closed throughout the entire cardiac cycle with the attendant risk of aortic valve leaflet fusion following prolonged support. The in series configuration of the reciprocating-valve pump avoids this shortcoming but activation must be carefully synchronized to the cardiac cycle to allow adequate coronary perfusion. The reciprocating-valve pump is associated with haemodynamic advantages and a favourable power consumption.     

Cold-induced hemolysis in a hypertonic milieu

Summary Suspension of human erythrocytes at 37° C in an environment made hypertonic by increasing concentrations of sodium chloride and sucrose was followed by hemolysis when the temperature was lowered to 0° C. Two distinct stages were involved in this hemolytic phenomenon, the first being incubation with hypertonic solute at some temperature above 20° C with an increasing effect up to 45° C, and the second stage consisting of lowering the temperature below 15° C with increasing hemolysis down to 0° C. The rate of cooling was not an important factor, but the presence of ions reduced the extent of cold-induced hemolysis in hypertonic sucrose. No significant release of membrane phospholipid and cholesterol accompanied this hemolysis. The solubilization of membrane protein components was investigated, with some differences appearing on sodium dodecyl sulfate polyacrylamide gel electrophoresis between hypertonic and isotonic supernatants. Spectrin could not be identified in solubilized form. Correlation of the temperatures of note in these studies with results from the literature on other biological effects of temperature-induced phase transitions in membrane lipids strongly points to the conclusion that such transitions are involved in the mechanism of cold-induced hypertonic hemolysis. It is postulated that the hypertonic milieu has resulted in membrane-protein alteration damage which prevents normal adaption to the new physical state of the membrane lipids during cooling.     

Factors controlling the resealing of the membrane of human erythrocyte ghosts after hypotonic hemolysis

Summary In accordance with former observations of Hoffman (1962a), ghost populations obtained by hypotonic hemolysis and subsequent restoration of isotonicity by the addition of alkali salts, were found to be composed of 3 types of ghosts. For our purposes it was useful to distinguish between: (1) ghosts which reseal immediately after hemolysis (type I); these ghosts are incapable of incorporating alkali ions which are added after hemolysis; (2) ghosts which reseal after the addition of alkali ions (type II); salt added to the hemolysate becomes trapped inside these ghosts in the course of the resealing process at temperatures above 0°C; and (3) ghosts which remain leaky regardless of the experimental condition (type III). The discrimination between the various types of ghosts was partly achieved by a kinetic method first devised by Hoffman (1962a), and partly by sucrose density gradient centrifugation.The relative sizes of the 3 fractions depend on the temperature at which hemolysis took place and on the time interval which elapsed between hemolysis and the addition of salt. At 37°C the resealing process is fast. Many of the ghosts reseal before salt can be added to the hemolysate. Hence, the fraction of type I ghosts is high after hemolysis at that temperature. At 0°C resealing is extremely slow. Hence, salt which has been added to the hemolysate at that temperature will enter the ghosts and become trapped during subsequent incubation at 37°C. There are no ghosts of type I and many ghosts of type II (about 60%). Regardless of the temperature at hemolysis, there are always ghosts which do not reseal even after prolonged incubation at 37°C. A method has been designed which permits the preparation of homogeneous populations of type II ghosts.Complexing agents (ATP, EDTA, 2,3-DPG) may prevent the resealing of the ghost membrane. However, they exert this effect only at elevated temperatures and when present in the medium at the instant of hemolysis. At 0°C, the presence of complexing agents in the medium at the instant of hemolysis has no effect on the subsequent resealing at 37°C. The recovery of the ghost membrane takes place in spite of the continued presence of the agents and eventually leads to trapping of these agents inside the resealed ghosts.The experiments support the contention that the complexing agents interact with a membrane constituent which is neither accessible from the inner nor from the outer surface of the cell membrane but becomes exposed during the hemolytic event when the complexing agents penetrate across the membrane. Apparently, at low tempertrures membrane ligands are more successful in competing with the added complexing agents for this constituent than at higher temperatures.Extending former observations of Hoffman, we found that not only Mg⁺⁺ but also Ca⁺⁺ facilitates the resealing process. Perhaps one or the other of the two alkaline earth ions is the membrane constituent which normally participates in the maintenance of the integrity of the red blood cell membrane.     

Initial hydrodynamic study on a new intraaortic axial flow pump: Dynamic aortic valve

Rotary blood pumps have been researched as implantable ventricular assist devices for years. To further reduce the complex of implanted axial pumps, the authors proposed a new concept of intraaortic axial pump, termed previously as “dynamic aortic valve (DAV)”. Instead of being driven by an intraaortic micro-electric motor, it was powered by a magnetic field from outside of body. To ensure the perfusion of coronary artery, the axial flow pump is to be implanted in the position of aortic valve. It could serve as either a blood pump or a mechanical valve depending on the power input. This research tested the feasibility of the new concept in model study. A column, made from permanent magnet, is jointed to an impeller in a concentric way to form a “rotor-impeller”. Supported by a hanging shaft cantilevered in the center of a rigid cage, the rotor-impeller can be turned by the magnetic field in the surrounding space. In the present prototype, the rotor is 8 mm in diameter and 15 mm in length, the impeller has 3 vanes with an outer diameter of 18 mm. The supporting cage is 22 mm in outer diameter and 20 mm in length. When tested, the DAV prototype is inserted into the tube of a mock circuit. The alternative magnetic field is produced by a rotating magnet placed side by side with the rotor-impeller at a distance of 30 mm. Once the alternative magnetic field is presented in the surrounding space, the DAV starts to turn, leading to a pressure difference and liquid flow in the tube. The flow rate or pressure difference is proportioned to rotary speed. At the maximal output of hydraulic power, the flow rate reached 5 L/min against an afterload of 100 mmHg. The maximal pressure difference generated by DAV at a rotation rate of 12600 r/min was 147 mmHg. The preliminary results demonstrated the feasibility of “DAV”, further research on this concept is justifiable.     

Trehalose loading into red blood cells is accompanied with hemoglobin oxidation and membrane lipid peroxidation

One of the recent approaches to enhance desiccation tolerance in red blood cells (RBCs) is by loading trehalose. This process has been shown to increase the recovery of lyophilized RBCs; conversely, it results in cellular damage including hemoglobin oxidation and loss of membrane integrity. The purpose of this study was to further investigate the extent of oxidative injury during the loading of trehalose into RBCs.RBCs were incubated in the absence (control) or presence of trehalose (0.8 mol/l) at 4 °C or 37 °C for different time scales. Oxidative damage was monitored by flow cytometry using dichlorofluorescin for reactive oxygen species formation, Annexin V-FITC for phosphatidylserine translocation and fluorescein-DHPE for lipid peroxidation. Percent methemoglobin, percent hemolysis and thiobarbituric acid reactive substances were measured by spectrophotometry. The extent of oxidative damage during trehalose loading is affected by the incubation temperature, incubation time and the presence of trehalose. Incubation at 4 °C was relatively innocuous; however, oxidative injury was evident at 37 °C in both RBC groups. The addition of trehalose is correlated with high osmotic pressure, which had minor effects during incubation at 4 °C, but seemed to have exacerbated the severity of cellular injury at 37 °C, as measured by higher levels of hemolysis, methemoglobin and lipid peroxidation.The process of trehalose-loading is problematic due to its requirement for prolonged incubations at 37 °C. These conditions are correlated with oxidative injury, even in the absence of trehalose. While trehalose is believed to be crucial for stabilizing biomembranes, the consequences of its introduction into the cells require further investigation.     

Technical-Induced Hemolysis in Patients with Respiratory Failure Supported with Veno-Venous ECMO – Prevalence and Risk Factors

The aim of the study was to explore the prevalence and risk factors for technical-induced hemolysis in adults supported with veno-venous extracorporeal membrane oxygenation (vvECMO) and to analyze the effect of hemolytic episodes on outcome. This was a retrospective, single-center study that included 318 adult patients (Regensburg ECMO Registry, 2009–2014) with acute respiratory failure treated with different modern miniaturized ECMO systems. Free plasma hemoglobin (fHb) was used as indicator for hemolysis. Throughout a cumulative support duration of 4,142 days on ECMO only 1.7% of the fHb levels were above a critical value of 500 mg/l. A grave rise in fHb indicated pumphead thrombosis (n = 8), while acute oxygenator thrombosis (n = 15) did not affect fHb. Replacement of the pumphead normalized fHb within two days. Neither pump or cannula type nor duration on the first system was associated with hemolysis. Multiple trauma, need for kidney replacement therapy, increased daily red blood cell transfusion requirements, and high blood flow (3.0–4.5 L/min) through small-sized cannulas significantly resulted in augmented blood cell trauma. Survivors were characterized by lower peak levels of fHb [90 (60, 142) mg/l] in comparison to non-survivors [148 (91, 256) mg/l, p≤0.001]. In conclusion, marked hemolysis is not common in vvECMO with modern devices. Clinically obvious hemolysis often is caused by pumphead thrombosis. High flow velocity through small cannulas may also cause technical-induced hemolysis. In patients who developed lung failure due to trauma, fHb was elevated independantly of ECMO. In our cohort, the occurance of hemolysis was associated with increased mortality.     

Effects of pre-freeze incubation of human red blood cells with various sugars on postthaw recovery when using a dextran-rapid cooling protocol

Polymer has been used as substitute to replace glycerol for cryopreservation of red blood cells (RBCs). But polymer can not penetrate cell membrane, it can not efficiently protect the inner membrane. In this study, RBCs were incubated with glucose, fructose, galactose or trehalose and frozen in liquid nitrogen for 24 h using dextran as the extracellular protectant. The postthaw quality was assessed by RBC hemolysis, RBC morphology, PS distribution, osmotic fragility, and the 4 °C stability. The results indicated the loading efficiency of monosaccharide was significantly higher than that of trehalose. Adding trehalose and 40% dextran caused more serious hemolysis before freezing. The percent hemolysis of RBCs loaded with high concentration of trehalose was approximately 16% and significantly more than that of RBCs loaded with glucose (approximately 5%, P < 0.05). Intracellular trehalose can not increase the postthaw recovery of RBCs compared with cells frozen without sugar. However, low concentration of intracellular glucose or galactose can reduce the percent hemolysis to less than 5% and significantly less than that of RBCs frozen without sugar (P < 0.05). Finally, the ability of galactose or fructose to maintain the 4 °C stability was significantly more than that of glucose. In conclusion, the injuries caused by trehalose loading may directly lead to postthaw hemolysis and poor quality of RBCs. However, monosaccharide can enhance the recovery of frozen RBCs. The cryoprotective effect of galactose may be better than that of glucose or fructose. In the future, we will continue to look for a safe and efficient trehalose loading process and try to decrease the osmotic fragility of RBCs frozen with polymers and sugars.     

Addition of oligosaccharide decreases the freezing lesions on human red blood cell membrane in the presence of dextran and glucose

Although incubation with glucose before freezing can increase the recovery of human red blood cells frozen with polymer, this method can also result in membrane lesions. This study will evaluate whether addition of oligosaccharide (trehalose, sucrose, maltose, or raffinose) can improve the quality of red blood cell membrane after freezing in the presence of glucose and dextran. Following incubation with glucose or the combinations of glucose and oligosaccharides for 3 h in a 37 °C water bath, red blood cells were frozen in liquid nitrogen for 24 h using 40% dextran (W/V) as the extracellular protective solution. The postthaw quality was assessed by percent hemolysis, osmotic fragility, mean corpuscle volume (MCV), distribution of phosphatidylserine, the postthaw 4 °C stability, and the integrity of membrane. The results indicated the loading efficiency of glucose or oligosaccharide was dependent on their concentrations. Moreover, addition of trehalose or sucrose could efficiently decrease osmotic fragility of red blood cells caused by incubation with glucose before freezing. The percentage of damaged cell following incubation with glucose was 38.04 ± 21.68% and significantly more than that of the unfrozen cells (0.95 ± 0.28%, P < 0.01). However, with the increase of the concentrations of trehalose, the percentages of damaged cells were decreased steadily. When the concentration of trehalose was 400 mM, the percentage of damaged cells was 1.97 ± 0.73% and similar to that of the unfrozen cells (P > 0.05). Moreover, similar to trehalose, raffinose can also efficiently prevent the osmotic injury caused by incubation with glucose. The microscopy results also indicated addition of trehalose could efficiently decrease the formation of ghosts caused by incubation with glucose. In addition, the gradient hemolysis study showed addition of oligosaccharide could significantly decrease the osmotic fragility of red blood cells caused by incubation with glucose. After freezing and thawing, when both glucose and trehalose, sucrose, or maltose were on the both sides of membrane, with increase of the concentrations of sugar, the percent hemolysis of frozen red blood cells was firstly decreased and then increased. When the total concentration of sugars was 400 mM, the percent hemolysis was significantly less than that of cells frozen in the presence of dextran and in the absence of glucose and various oligosaccharides (P < 0.01). However, when both glucose and trehalose were only on the outer side of membrane, with increase of the concentrations of sugars, the percent hemolysis was increased steadily. Furthermore, addition of oligosaccharides can efficiently decrease the osmotic fragility and exposure of phosphatidylserine of red blood cells frozen with glucose and dextran. In addition, trehalose or raffinose can also efficiently mitigate the malignant effect of glucose on the postthaw 4 °C stability of red blood cells frozen in the presence of dextran. Finally, addition of trehalose can efficiently protect the integrity of red blood cell membrane following freezing with dextran and glucose. In conclusion, addition of oligosaccharide can efficiently reduce lesions of freezing on red blood cell membrane in the presence of glucose and dextran.     

Flow simulation-based particle swarm optimization for developing improved hemolysis models

The improvement and development of blood-contacting devices, such as mechanical circulatory support systems, is a life saving endeavor. These devices must be designed in such a way that they ensure the highest hemocompatibility. Therefore, in-silico trials (flow simulations) offer a quick and cost-effective way to analyze and optimize the hemocompatibility and performance of medical devices. In that regard, the prediction of blood trauma, such as hemolysis, is the key element to ensure the hemocompatibility of a device. But, despite decades of research related to numerical hemolysis models, their accuracy and reliability leaves much to be desired. This study proposes a novel optimization path, which is capable of improving existing models and aid in the development of future hemolysis models. First, flow simulations of three, turbulent blood flow test cases (capillary tube, FDA nozzle, FDA pump) were performed and hemolysis was numerically predicted by the widely-applied stress-based hemolysis models. Afterward, a multiple-objective particles swarm optimization (MOPSO) was performed to tie the physiological stresses of the simulated flow field to the measured hemolysis using an equivalent of over one million numerically determined hemolysis predictions. The results show that our optimization is capable of improving upon existing hemolysis models. However, it also unveils some deficiencies and limits of hemolysis prediction with stress-based models, which will need to be addressed in order to improve its reliability.

     

The recovery and hematological rehabilitation of chlorine stressed adult rainbow trout (Salmo gairdneri)

Synopsis The ability of adult rainbow trout (Salmo gairdneri) to recover from acute chlorine exposure was tested. Six separate tests were carried out in duplicate. Blood was collected from each duplicate group of fish at the beginning of the test, at the appearance of the chlorine-distress symptoms, and at 24 and 48 h after exposures. The total residual chlorine (TRC) concentrations used in these six tests were 1.67, 3.50, 1.10, 1.25, 1.02 and 0.0 mg 1^–1, at water temperatures of 13.5, 14.6, 17.2, 22.6, 23.0 and 26.0° C, respectively. The cumulative fish mortality for these six tests at 48 h after exposure were 11.5, 100, 0.0, 67.1, 36.1 and 100 percent. Blood of chlorine stressed fish exhibited signs of hemoconcentration and hemolysis. All blood parameters with the exception of hemolysis returned to control levels within 24 hours after exporsure. High TRC concentrations in the range of 3.5 mg 1^–1 at 14.0° C, and TRC of 1.25 and 1.02 mg 1^–1 TRC at 23° C, significantly diminished the rainbow trout recovery.     

PIV measurements of flow in a centrifugal blood pump: time-varying flow

Measurements of the time-varying flow in a centrifugal blood pump operating as a left ventricular assist device (LVAD) are presented. This includes changes in both the pump flow rate as a function of the left ventricle contraction and the interaction of the rotating impeller and fixed exit volute. When operating with a pulsing ventricle, the flow rate through the LVAD varies from 0-11 L/min during each cycle of the heartbeat. Phase-averaged measurements of mean velocity and some turbulence statistics within several regions of the pump, including the inlet, blade passage, exit volute, and diffuser, are reported at 20 phases of the cardiac cycle. The transient flow fields are compared to the constant flow rate condition that was reported previously in order to investigate the transient effects within the pump. It is shown that the quasi-steady assumption is a fair treatment of the time varying flow field in all regions of this representative pump, which greatly simplifies the comprehension and modeling of this flow field. The measurements are further interpreted to identify the effects that the transient nature of the flow field will have on blood damage. Although regions of recirculation and stagnant flow exist at some phases of the cardiac cycle, there is no location where flow is stagnant during the entire heartbeat.