Partial Bowls Using the Haemonetics Cell Saver 5: Does It Produce a Quality Product?

Controversy still exists on the validity of processing a partial bowl during the collection of shed blood lost through surgery during cell salvaging. The purpose of this study was to assess the quality of red blood cells produced from a partial bowl of autologous suctioned blood using the Haemonetics Cell Saver 5. Suctioned blood was collected from 17 patients undergoing cardiac surgery. A partially filled cell saver bowl was washed with 1500 mL of NaCl. Reservoir and processed blood samples were examined for potassium, leukocytes, hematocrit, platelets, and plasma-free hemoglobin and then compared with 22 previously studied full bowls. Results are summarized in the table below: In conclusion, the Haemonetics Cell Saver 5 can produce a quality product from washing a partial bowl with a better washout of white blood cells compared with a full bowl. However, there is a reduction in red blood cell recovery.     

Effect of partial-filling autotransfusion bowls on the quality of reinfused product

Intraoperative autotransfusion is used in a variety of surgical procedures with the quantity of blood loss dependent upon numerous factors. These procedures may or may not produce a full autotransfusion bowl. The inadequate removal of contaminants has been correlated to the incomplete filling of bowls, resulting in a condition called "Salvaged Blood Syndrome." The purpose of this study was to assess the quality of aspirated whole blood after processing with an autotransfusion system using various fill volumes and two wash volumes. An in vitro circuit was designed to mimic the mechanical effects of extracorporeal flow on blood. Twenty-four Baylor-style bowls were filled at 400 mL min(-1) and washed at 300 mL min(-1). Two wash volumes, 1000 and 2000 mL, and three bowl volumes: low, mid, and full, were used in this study. The bowl volumes were determined by using red cell quantities of 60, 100, and 135 mL for the low-fill, mid-fill, and full bowls, respectively. Samples were drawn pre-autotransfusion and post-autotransfusion and analyzed for plasma-free hemoglobin, IL-8, white blood cell count, platelet count, albumin, and total protein. All data were analyzed using one-way analysis of variance (ANOVA) with significance accepted at p > or = .05. Plasma-free hemoglobin levels and hematocrit were concentrated significantly (p < .05) as bowl volume increased. A significant difference in IL-8 levels was found in the wash volumes in the low-fill bowls (p < .02). Platelet count was significantly decreased between the full bowl with 1000 mL wash and the full bowl with 2000 mL wash (p < .0004). Total protein reduction was significantly less in the low-fill bowl with 1000 mL wash as compared to the other bowl treatments (p < .05). In conclusion, the quality of the washed product did not vary significantly between fill or wash volumes, with the exception of the low-fill bowl with 1000 mL wash.     

Quality of processed blood for autotransfusion

Centrifugal red blood cell washers for intraoperative autotransfusion process shed blood during surgery. In this study, the quality of processed fresh, human bank blood was assessed in a standardized laboratory setting during standard, medium, and high flow processing. Red cell recovery rates and plasma washout efficiencies were compared using three different devices. The accurate parameters measuring effectiveness and product quality were red cell mass (RCM) flow rate and the plasma washout efficiency. Cobe BRAT 2, a system with discontinuous flow (DF) and a cylindrical centrifuge bowl, permitted processing in standard and medium flow of 26 and 35 mL RCM/min, respectively, with washout of residual plasma albumin of 93.2 and 91.2%. The Medtronic Sequestra 1000, a DF system with a conical centrifuge bowl processed blood at 15 and 23 mL RCM/min and eliminated plasma albumin with 98.4 and 96.8% washout during standard and medium flow, respectively, with significant red cell loss occurring during medium flow. The respective speeds of high-flow programs with BRAT 2 and Sequestra 1000 were 15 and 22 mL RCM/min, related to a hematocrit in the holding bag, less than that of the incoming blood from the reservoir. Washout was 58.2 and 58.3%, respectively. Fresenius CATS, a continuous flow (CF) device, produced flow rates of 19, 24, and 43 mL RCM/min and plasma albumin elimination of 97.8, 94.4, and 93.3% in standard, medium, and high-flow, respectively. Holding bag hematocrits with CF exceeded that of DF. Standard, medium, and high-flow programs of CATS may be used without restriction.     

Transfusion medicine and surgical practice

When contemplating the transfusion of blood products (that is, red cells, platelets, and plasma proteins), the surgeon must always analyze the patient's clinical condition and not be influenced solely by laboratory tests. Risks associated with allogeneic blood products must be weighed, and alternatives such as autologous blood products and crystalloid and colloid solutions should be considered. Autologous blood can be collected weeks or months prior to elective surgery, immediately prior to surgery, intraoperatively, or postoperatively. The important things to remember about transfusion therapy are that: (a) the patient's clinical condition should dictate what blood product to transfuse and in what quantity; (b) temperature is a very important factor in transfusion therapy; and (c) washed filtered shed blood is safer than nonwashed filtered shed blood, although nonwashed filtered shed blood can be reinfused safely but in a smaller quantity.     

Survival, function, and hemolysis of shed red blood cells processed as nonwashed blood and washed red blood cells.

BACKGROUND: Shed nonwashed blood and shed washed red blood cells (RBC) are being used as alternatives to allogeneic liquid-preserved RBC for patients during thoracic and cardiovascular surgical procedures. METHODS: Mongrel dogs were bled a volume of blood into the abdominal cavity and the shed blood was reinfused as nonwashed blood or washed RBC. The 51Cr RBC volumes were measured before, immediately after, and 24 hours after the exchange transfusion to assess the recovery of the shed RBC and the 24-hour posttransfusion survival. Compatible dogs were given allogeneic transfusions of 51Cr-labeled nonwashed blood and washed RBC, and 24-hour posttransfusion survival and half-life were measured. RESULTS: Immediately after the 100% exchange transfusion, the recovery value was 62% for the nonwashed shed blood and 82% for the washed RBC. Both the nonwashed blood and the washed RBC had 24-hour posttransfusion survival values of 90% and normal oxygen transport function after the exchange transfusion. Compatible allogeneic 51Cr-labeled nonwashed blood and washed RBC had normal 24-hour posttranfusion survival and 51Cr half-life values. CONCLUSIONS: The survival, function, and hemolysis of shed nonwashed blood and shed washed RBC were similar to fresh blood in the dog that underwent a 100% exchange transfusion.     

Quality of red blood cells using the Dideco Electa autotransfusion device

The purpose of this study was to evaluate the quality of washed, concentrated red blood cells (RBCs) produced by the new Electa autotransfusion device from Cobe Cardiovascular (Dideco). Blood was collected intraoperatively in 16 patients undergoing cardiac surgery for whom routine cell savage was being used and then washed using the Electa. According to the manufacture's protocol. 125-mL bowls were used in the standard wash program. Reservoir and washed RBCs were analyzed for platelets (PLTs), leukocytes (WBCs), potassium (K+), and plasma-free hemoglobin (PFH) removal, as well as, hematocrit (Hct) and RBC recovery. The Electa cell saver produced a product with an average Hct of 58+/-5% and a RBC recovery rate of 87+/-10%. Its removal of waste products resulted in the washout of 54+/-18% WBCs, 87+/-6% PLTs, 91+/-4% K+, and 77+/-17% PFH. The Electa produces a good-quality washed RBC product that is comparable with other autotransfusion devices on the market.     

Enhancing the safety of intraoperative RBC salvage

Devices for intraoperative blood salvage remove plasma and, in theory, all of the cellular elements of blood except for rbcs. We have previously shown that complete white cell and platelet removal does not always occur and that the retained platelet-leukocyte deposit is potentially harmful (2). In this study we investigated the hydraulic conditions in the centrifuge bowl that allow activated platelets and leukocytes to adhere, the histology of the resulting cellular deposit, and the effects of reinfusing a saline extract of the deposit. Earlier work had suggested that the addition of calcium, of partially clotted blood, and of excessive saline should be avoided during intraoperative rbc salvage (2). The present observations explain, in part, why such measures would be expected to be beneficial.     

Clinical implications of procoagulant and leukoattractant formation during intraoperative blood salvage

Experiments using 21 dogs and red cell salvage equipment (Haemonetics Cell Saver, Haemonetics Corp, Braintree, Mass) were employed to study the formation and potency of procoagulant and leukoattractant material during experimental autologous blood salvage. Washed red cell suspensions were found to include toxic degradation products that had been released from a deposit of platelets and white cells adherent to the centrifuge bowl wall. When reinfused, these toxic products resulted in a "salvaged blood syndrome" of intravascular clotting and pulmonary damage. The pulmonary arterioles showed leukocyte margination and tangled fibrin skeins with occlusive thrombi. Intra-alveolar and perivascular hemorrhages, along with extensive pulmonary edema, were also observed. The formation of procoagulant and leukoattractant material could be markedly decreased when the red cell salvage technique incorporated the following precautions: (1) minimal dilution with saline (normal plasma protein levels), (2) a low calcium level, and (3) minimal platelet activation (avoidance of the aspiration of clotted blood just before processing).     

On-line autotransfusion waste calculator

Cell concentrating and washing techniques are widely accepted and believed to be beneficial to cardiac surgery patients. During cell processing, platelets, proteins, and clotting factors are wasted as the plasma is washed away by saline. Beneficial and costly plasma constituents are sacrificed for the sake of removing potentially harmful drugs, debris, and naturally activated cells and chemical mediators. An interactive Microsoft Excel spreadsheet was designed to input patient and autotransfusion system (ATS) reservoir blood values, processed centrifugal bowl data, and hospital allogeneic blood product concentration and cost information. The spreadsheet calculates the number of wasted platelets, grams of protein, and milligrams of fibrinogen. The calculator further estimates the number of units and cost of allogeneic blood products needed to replace the wasted blood components. The simulation allows for variable levels of platelet activation and protein removal during centrifugal cell processing. Specific case scenarios may be simulated with the calculator. If a known volume of residual extracorporeal circuit blood with a known hematocrit, platelet count, and protein concentration is diverted to the ATS reservoir to be processed and washed after bypass, the number of units of fresh frozen plasma, platelet packs, and albumin concentrate needed to replace the wasted proteins and platelets may be calculated. When typical end-bypass patient and blood bank product values are input, the cost to replace the wasted blood components in 1550 mL of residual circuit blood with allogeneic blood products is about US $2097. There are risks and costs associated with replacing the platelets, proteins, and clotting factors wasted during cell washing compared with other techniques such as whole blood ultrafiltration.     

Computational Fluid Dynamic Analyses to Establish Design Process of Centrifugal Blood Pumps

Abstract To establish quantitative, efficient design theories for centrifugal blood pumps, computational fluid dynamics (CFD) analyses were compared to the results of flow visualization tests and hemolysis tests, mainly on the Nikkiso centrifugal blood pump. The results turned out to coincide in the velocity vector plots. CFD analysis revealed that the smaller the gap is, the greater the shear stress becomes. This tendency becomes even greater with a radial gap change. Hemolysis study also indicated that the smaller the gap is, the greater the hemolysis. CFD analysis in comparison with hemolysis tests could be a useful index for developing blood pumps in the future.     

Computational modeling of the Food and Drug Administration’s benchmark centrifugal blood pump

In order to simulate hemodynamics within centrifugal blood pumps and to predict pump hemolysis, CFD simulations must be thoroughly validated against experimental data. They must also account for and accurately model the specific working fluid in the pump, whether that is a blood-analog solution to match an experimental PIV study or animal blood in a hemolysis experiment. Therefore, the Food and Drug Administration (FDA) benchmark centrifugal blood pump and its database of experimental PIV and hemolysis data were used to thoroughly validate CFD simulations of the same blood pump. A Newtonian blood model was first used to compare to the PIV data with a blood analog fluid while hemolysis data were compared using a power-law hemolysis model fit to porcine blood data. A viscoelastic blood model was then incorporated into the CFD solver to investigate the importance of modeling blood’s viscoelasticity in centrifugal pumps. The established computational framework, including a dynamic rotating mesh, animal blood-specific fluid properties and hemolysis modeling, and a k-ω SST turbulence model, was shown to more accurately predict pump pressure heads, velocity fields, and hemolysis compared to previously published CFD studies of the FDA centrifugal pump. The CFD simulations were able to match the FDA pressure and hemolysis data for multiple pump operating conditions, with the CFD results being within the standard deviations of the experimental results. While CFD radial velocity profiles between the impeller blades also compared well to the PIV velocity results, more work is still needed to address the large variability among both experimental and computational predictions of velocity in the diffuser outlet jet. Small differences were observed between the Newtonian and viscoelastic blood models in pressure head and hemolysis at the higher flow rate cases (FDA Conditions 4 and 5) but were more significant at lower flow rate and pump impeller speeds (FDA Condition 1). These results suggest that the importance of accounting for blood’s viscoelasticity may be dependent on the specific blood pump operating conditions. This detailed computational framework with improved modeling techniques and an extensive validation procedure will be used in future CFD studies of centrifugal blood pumps to aid in device design and predictions of their biological responses.     

Computational Fluid Dynamics Analysis to Establish the Design Process of a Centrifugal Blood Pump: Second Report

To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the radial gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.     

A large-scale automated method for hepatocyte isolation: effects on proliferation in culture

Large-scale sterile methods for isolating hepatocytes are desirable for the development of bioartificial liver support systems. In this study the traditional centrifuge method was compared with the use of a Baylor Rapid Autologous Transfusion (BRAT) machine for isolating large quantities of porcine hepatocytes. After isolating hepatocytes, the methods were evaluated in terms of cell viability and yield per liver, proliferation over 7 days, and the effects on the cell cycle using the trypan blue exclusion test, conventional phase-contrast light microscopy, the lactate to pyruvate ratio, the leakage of lactate dehydrogenase (LD) and aspartate aminotransferase (AST), lidocaine clearance, albumin production, and flow cytometry. With the centrifuge method the mean cell viability was 92.5%, while with the BRAT method the viability was 95.9%. The minimal cell yields with the BRAT procedure were 7.3 x 10(9) for 250-ml centrifuge bowls and 2.8 x 10(9) for 165-ml bowls, which compares well with that found by other authors. Because the same initial procedures were employed in both methods the total hepatocyte yield per liver was comparable. Flow cytometry confirmed that the proliferation of hepatocytes was facilitated by oxygenation during the isolation procedure. The recovery of hepatocytes in culture following isolation was similar after either method. Daily microscopic investigation indicated that cytoplasmic vacuolization and granularities were present after either procedure and these disappeared following 3-4 days of culturing. Flow cytometry indicated that the hepatocyte cell cycle was similar after either method; at 7 days the profile indicated that the cells were still proliferating. Trends in the lactate to pyruvate ratio and the leakage of LD and AST indicated that the functional polarity of hepatocytes was regained after approximately 3 days. Lidocaine clearance at 4 days indicated that the cytochrome P450 system was active, while significant albumin production was apparent at day 5. The benefit of using BRAT technology in hepatocyte isolation lies in guaranteed sterility, convenience, speed, and the ability to oxygenate media and cell suspensions during the procedure.     

A tensor-based measure for estimating blood damage

Implantable ventricular assist devices give hope of a permanent clinical solution to heart failure. These devices, both pulsatile- and continuous-flow, are presently used as medium-term bridge to heart transplant or recovery. While long-term use of continuous-flow axial and centrifugal pumps is being explored, the excessive level of blood damage in these devices has emerged as a design challenge. Blood damage depends both on shear stress and exposure time, and device designers have relied traditionally on global space- and time-averaged estimates from experimental studies to make design decisions. Measuring distributions of shear stress levels and the blood cell's exposure to these conditions in complex rotary pump flow is difficult. On the other hand, computational fluid dynamics (CFD) is now being used as a tool for designing viable devices, offering more detailed information about the flow field. A tensor-based blood damage model for CFD analysis is proposed here. The model estimates the time- and space-dependent strain experienced by individual blood cells and correlates it to blood damage data from steady shear flow experiments. The blood cells are modeled as deforming droplets and their deformation is tracked along the pathlines of a computed flow. The model predicts that blood cells in a rapidly fluctuating shear flow can sustain high shear stress levels for very short exposure time without deforming considerably. In the context of mechanical modeling of the implantable Gyro blood pump being developed at Baylor College of Medicine, this suggests that blood cells traversing regions of highly fluctuating shear stress rapidly may not hemolyze significantly.     

Apparent coagulopathy caused by infusion of shed mediastinal blood and its prevention by washing of the infusate

We found that reinfusion of shed mediastinal blood (SMB) after a cardiac operation was associated with laboratory evidence of disseminated intravascular coagulation. In view of this, we compared the effect of infusing washed or unwashed SMB on the coagulation profiles and blood use of two serial groups of patients undergoing cardiopulmonary bypass. We found that the results of testing for fibrin degradation products converted from negative to positive in 17 of 20 patients who received unwashed SMB versus 1 of 14 patients who received washed SMB (p less than 0.0001). Other coagulation studies did not reveal disseminated intravascular coagulation in either group, nor were there differences in blood use between the two groups. The unwashed SMB contained high titers of fibrin degradation products (mean reciprocal titer = 354 +/- 161) compared with washed SMB (mean reciprocal titer = 34 +/- 18) (p less than 0.01). Based on the volume of SMB infused, the amount of fibrin degradation products in unwashed SMB was sufficient to account for the positive fibrin degradation product assays after infusion in this group. We conclude that infusion of unwashed SMB may confuse the interpretation of tests for disseminated intravascular coagulation or fibrinolysis. As this could lead to unnecessary blood component use and is preventable by washing before infusion, we recommend that the routine infusion of unwashed SMB no longer be employed.     

Computational Fluid Dynamics‐Based Design Optimization Method for Archimedes Screw Blood Pumps

An optimization method suitable for improving the performance of Archimedes screw axial rotary blood pumps is described in the present article. In order to achieve a more robust design and to save computational resources, this method combines the advantages of the established pump design theory with modern computer‐aided, computational fluid dynamics (CFD)‐based design optimization (CFD‐O) relying on evolutionary algorithms and computational fluid dynamics. The main purposes of this project are to: (i) integrate pump design theory within the already existing CFD‐based optimization; (ii) demonstrate that the resulting procedure is suitable for optimizing an Archimedes screw blood pump in terms of efficiency. Results obtained in this study demonstrate that the developed tool is able to meet both objectives. Finally, the resulting level of hemolysis can be numerically assessed for the optimal design, as hemolysis is an issue of overwhelming importance for blood pumps.     

Heparin washout in the pediatric Cell Saver bowl

The possibility of residual heparin in washed red cells transfused to neonatal or pediatric cardiac patients following bypass prompted a measurement of heparin concentrations. Samples were taken during 10 adult and 10 neonatal and pediatric bypass cases. Sample A was from the bypass circuit, Sample B from the Haemonetics Cell Saver bowl inlet before washing, Sample C from the Cell Saver bowl outlet after washing, and Sample D from the patient ten minutes after protamine. Heparin concentrations were measured by a chromogenic assay using activated Factor X. There was no significant difference between the adult and pediatric groups in the levels of heparin concentration on bypass, pre-washing and post-washing, and in the patients following protamine. In the pediatric group, only .002% of the pre-washed heparin remained after washing. This extremely low level of heparin (.0027 units/ml) is only 0.34 units in a 125 ml pediatric unit of Cell Saver blood. Based on post bypass patient samples, this has no clinical significance. Therefore, the Cell Saver can be used safely with neonates and pediatric patients without concern regarding residual heparin when properly processed.     

Blood compatible design of a pulsatile blood pump using computational fluid dynamics and computer-aided design and manufacturing technology

Thrombus formation is a critical issue when designing a long-term implantable left ventricular assist system (LVAS). Fluid dynamic characteristics of blood flow are one of the main factors that cause thrombus formation. In this study, we optimized the fluid dynamics of a sac blood pump in our LVAS to ensure minimization of shear-related blood damage that could lead to thrombus formation. A pump housing and a sac chamber were designed with computer-aided design (CAD) software, and fluid dynamics were estimated by computational fluid dynamic (CFD) analysis. We adopted distribution of CFD results for qualitative evaluation, and we also tried to estimate normalized index of hemolysis (NIH) from the results of CFD analysis as a quantitative index of optimization for geometry of the blood pump chamber. A prototype model of the optimized blood pump was made using a three-axis computer machine tool by whittling pieces of nonfoamed polyurethane. Shear stress and theoretical NIH in the redesigned model were lower than those in the first model. Area of flow stagnation that was observed in the first model was not seen in the redesigned model. The results demonstrate that application of CAD/CAM technology to design an artificial heart contributes to optimizing a blood pump chamber for the purpose of reducing thrombus formation.     

Retransfusion of thoracic drainage blood: qualitative analysis

In a prospective randomized study 10 patients received their shed mediastinal blood after elective coronary artery bypass surgery and were compared to 10 control patients without retransfusion. The quality assessment can be summarized as follows (mean +/- 1 SD): 1. Hemoglobin concentration of the shed blood was 9.6 +/- 1.45 g/dl. 2. The energy rich phosphate compounds of the shed blood erythrocytes were 2.6 +/- 0.8 mumol/gHb ATP (70% of the patients preoperative value) and 14.8 +/- 4.2 mumol/gHb 2.3-DPG (normal). 3. Proteins, immunoglobulins and especially albumin in the shed blood were not significantly different from the patients own values. 4. No electrolyte changes, safe for a slight increase in potassium (5.7 +/- 0.7 mmol/l). 5. The activated clotting time of the patient did not change during retransfusion. 7. Plasma free hemoglobin was elevated to 211.1 +/- 44.3 mg/dl in the shed blood; however, no significant increase could be noted in the retransfused patients and no hemoglobinuria occurred. Postoperative retransfusion of shed mediastinal blood is a simple and safe method of autologous transfusion early after cardiac surgery and should be combined with other methods of blood salvage. The qualitative advantages of blood retransfusion consist in the absence of storage damage and in the preservation of autologous proteins and immunoglobulins.     

The Haemonetics Cell Saver 5 washing properties: effect of different washing pump and centrifuge speeds

This study evaluated the effect of different washing and centrifuge rates of the Cell Saver 5 on the quality of processed autologous blood. Autologous blood was washed with 1000 ml of sterile normal saline at centrifuge speed of 5650 revolutions per minute (rpm) (group I) or 4350 rpm (group II) with different washing pump speeds--500, 800 and 1000 ml/min. Hemoglobin, free hemoglobin, hematocrit, erythrocytes, leukocytes, platelets, and protein were measured before and after processing. The highest values of hemoglobin, hematocrit and erythrocytes were achieved using 800 and 1000 ml/min pump speeds in group I and 500 ml/min speed in group II. Red blood cells concentration was higher in group I. There were no significant changes of free hemoglobin removal within group I. In group II the lowest free hemoglobin was achieved when 1000 ml/min rate was used. Platelets and protein did not depend on wash pump speeds in both groups. Platelet recovery in group I was higher than in group II at all washing pump speeds. Leukocytes were not adequately removed at all pump speeds. The Cell Saver 5 produces optimum results when the high wash pump speeds (800 and 1000 ml/min) and standard centrifuge speed are used.