Bacterial Contamination of Hemodialysis Center Water and Dialysate: Are Current Assays Adequate?

Many dialysis centers depend on clinical laboratories or a commercially available dip culture to determine the contamination levels in water and dialysate. To determine whether these standard clinical culture procedures adequately quantitate bacterial contamination in hemodialysis center water and dialysate, test results of two routine clinical media was compared, trypticase soy agar (TSA) and plate count agar (PCA), with those of nutrient-poor R2A medium. Dialysate samples demonstrated significant differences in media, the temperature of incubation, and plating techniques (pour plate versus spread plates). Purified water for dialysis demonstrated significant differences only for media; however, temperature was an important variable. Selective growth on R2A agar of some water- and dialysate-contaminating species was studied by velvet disk and loop transfer of colonies. A strong selectivity for water-borne bacteria was demonstrated by R2A agar; the bacteria that did not grow on TSA and PCA have been identified.     

Bacterial contamination of saline used for epidural procedures in an obstetric setting: a randomised comparison of two drawing-up techniques

BackgroundThere is little evidence to inform practice regarding the optimum aseptic technique of drawing up saline for epidural insertion. Our regional practice is to draw up saline from a non-sterile packaged plastic ampoule, therefore introducing the risk of bacterial contamination. Usually, the anaesthetist draws up saline directly from the vial held by an assistant using a needle (needle technique). Alternatively, the saline vial is emptied onto a sterile tray by an assistant and then drawn up by the anaesthetist (tray technique). We hypothesised that the latter will lead to an increase in the number of contaminated saline samples as they are exposed to the environment.MethodsIn labour rooms and before epidural catheter insertion, 110 samples of saline 20 mL were randomly drawn up using our hospital’s recommended epidural aseptic precautions, using either the needle or the tray technique. Equal amounts of saline were inoculated into aerobic and anaerobic blood culture bottles.ResultsEleven percent of samples in the needle arm and 24% of samples in the tray arm grew commensal micro-organisms including coagulase-negative Staphylococcus, Micrococcus luteus and Streptococcus viridans. A two-sided Fisher’s exact test for categorical unpaired data showed no statistical difference between the two arms of the trial (P=0.13).ConclusionThe difference in the saline contamination rate between the two techniques did not reach statistical significance. As bacterial contamination occurred with both techniques, we recommend using sterile saline pre-packaged in the epidural tray or individually wrapped sterile glass saline ampoules.     

溶血性葡萄珠菌前列腺炎细菌鉴定及药敏试验

目的：给溶血性葡萄球菌引起的慢性细菌性前列腺炎患者治疗提供病原学诊断及用药依据。方法：采用MicroScan自动微生物鉴定／药敏测定系统及Pos Combo Panel Type9板型,对36例溶血性葡萄球菌前列腺炎患者进行了细菌鉴定和药敏试验。结果：溶血性葡萄球菌对氨苄青霉素、环丙氟哌酸、红霉素、 青霉素、呋喃坦啶、氟哌酸及氟嗪酸呈完全 耐药,对万古霉素呈高度敏感,对利福平、氯林克霉素、复方新诺明、庆大霉素呈多数或大多数敏感。结论：在选用抗生素时,应以药敏测定结果为依据。     

Pharmacokinetics of Certoparin During In Vitro and In Vivo Dialysis

The efficacy and safety of certoparin in the prophylaxis of clotting during hemodialysis have recently been proven. Different to other low‐molecular weight heparins (LMWHs), certoparin does not accumulate in maintenance dialysis patients for unknown reasons. The purpose of the present study was to examine the impact of the dialysis procedure on the removal of certoparin. In a subgroup of the MEMBRANE study consisting of 12 patients, the pharmacokinetics of certoparin during hemodialysis was determined by means of the anti‐Xa activity. In addition, the elimination of certoparin into continuously collected dialysate was assessed. Further, in vitro experiments with human blood‐simulating high‐flux hemodialysis and hemofiltration were performed to quantify the elimination and the sieving coefficients S_K of the two LMWHs certoparin and enoxaparin compared with unfractionated heparin (UFH). The surrogate marker middle molecules inulin and myoglobin served as reference solutes during the experiments. Finally, the adsorption of ¹²⁵iodine‐radiolabeled certoparin onto the synthetic dialysis membrane was quantified. The clinical study reconfirmed the absence of bioaccumulation of certoparin with anti‐Xa activities between <0.01 and 0.02 IU/mL after 24 h. A short plasma half‐life time of 2.0 ± 0.7 h was determined during hemodialysis. Of the total certoparin dose injected intravenously prior to hemodialysis, only 2.7% was eliminated into dialysate. The in vitro experiments further revealed only 6% of certoparin to be adsorbed onto the dialysis membrane. The anti‐Xa activities of certoparin and enoxaparin slowly declined during in vitro hemofiltration to 87.3 ± 5.5 and 82.5 ± 9.4% of baseline, respectively, while inulin and myoglobin concentrations rapidly decreased. The anti‐Xa activity of UFH remained unchanged. The S_K of both LMWH and UFH was very low in hemofiltration and particularly in hemodialysis with values ≤0.1. The elimination kinetics during hemodialysis suggests strong protein‐binding of certoparin. Different from LMWH significantly cleared by the kidneys, the relatively short half‐life time of certoparin of only 2 h during hemodialysis allows a more reliable control of the anti‐coagulatory effects and decreases the risk of bleeding complications. Dialytic removal does not significantly contribute to the clearance of certoparin in maintenance dialysis patients.     

Risk of bacterial infection in patients under intravenous iron therapy: dose versus length of treatment

Some studies have suggested that intravenous iron therapy may be associated with an increased risk of infection. We analyzed the incidence of bacterial infection in 111 hemodialysis patients. Group 1 (n = 39, transferrin saturation <20%) received 10 doses of 100 mg of intravenous iron saccharate, 3 doses per week (28 treatment days); Group 2 (n = 13, transferrin saturation <20%) received 20 doses, 3 doses per week (70 treatment days); and Group 3 (n = 59, transferrin saturation 20-50%) received 10 doses, 1 dose per week (70 treatment days). The follow-up was 150 days for all groups, and all infectious episodes were recorded. Pulmonary infection was the most frequent event observed in all of the groups. In an incidence-density analysis, Group 2, which received a total of 20 doses, presented a significantly higher incidence of infection than Group 3, which received only 10 doses over the same period (0.13 versus 0.06 infections per patient per month, p = 0.04). No difference was observed between Groups 1 and 2 suggesting that the risk of infection during iron therapy is dose dependent rather than time length dependent.     

The Implantable Fuzzy Controlled Helmholtz-Left Ventricular Assist Device: First In Vitro Testing

Abstract: To perform first experimental tests for validation of a new left ventricular assist device (LVAD) with a high efficiency energy converter, a new pump design and a novel type of perfusion control, a functional labtype, were manufactured. With a stroke volume of 65 ml, a total pump housing volume of 450 ml (including valves and connectors), and a weight of 430 g, it is one of the smallest and lightest implantable pulsatile electromechanical LVADs. Pulsatile operation is generated by a special reduction and displacement gear, which transforms a uniform rotational movement of a sensorless, electronically commutated DC motor into a translatory pusher plate movement. A prolonged duration for filling (60% of the cycle time) supports full-empty pumping and consequently high overall pump efficiency. Active adaptation of output flow to organ perfusion demand is achieved by changing the rotational speed of the motor by means of a sensorless fuzzy controller, which detects preload and afterload induced effects at the motor current input. First in vitro test results obtained within a circulatory mock loop that simulates physiological preloads and afterloads are presented. They comprise preload sensitivity and the function of the novel perfusion controller as well as preload and afterload related flow data. The results prove the feasability of the energy conversion with the novel gear and control concept for an implantable electromechanical pulsatile LVAD.     

In Vitro and In Vivo Testing of an Implantable Motor-Driven Left Ventricular Assist Device

Abstract: A totally implantable motor-driven left ventricular assist device (LVAD) has been developed and tested. The performance of this LVAD was tested in a mock circulatory system. This pump provided 8 L/min of output against a mean afterload of 120 mm Hg with a filling pressure of 20 mm Hg when the pump was operated in the fill/empty mode. The right and left pumps were tested in a mock loop. The right pump afterload was kept in the range from 23–32 mm Hg. With increase in the left pump afterload, the pump power output varied from 1.64 to 2.37 W. The instantaneous motor power input varied from 22.6 to 30.6 W with the total system efficiency ranging from 6.7 to 9.4%. To date, 4 in vivo studies have been conducted for up to 12 h. Two animals survived 12 and 10 h, respectively. Termination was due to bleeding in 1 animal, vent tube obstruction in 1, and respiratory failure in 2. All animals died of technical failure. Another experiment is to be undertaken, and a newly designed cannula is now being manufactured.     

In Vitro Testing of Artificial Heart Valves: Comparison Between Newtonian and Non-Newtonian Fluids

Abstract: The in vitro testing of artificial heart valves is often performed with simple fluids like glycerol solutions. Blood, however, is a non-Newtonian fluid with a complex viscoelastic behavior, and different flow fields in comparable geometries may result. Therefore, we used different polymer solutions (Polyacrylamid, Xanthan gum) with blood-like rheological properties as well as various Newtonian fluids (water, glycerol solutions) in our heart valve test device. Hydrodynamic parameters of Björk-Shiley heart valves with a tissue annulus diameter (TAD) of 21–29 mm were investigated under aortic flow conditions. Major results can be summarized as follows. The mean systolic pressure differences depend on the model fluids tested. Closing time and closing volume are not influenced by the rheological behavior of fluids. These parameters depend on TAD and the pressure differences across the valve. In contrast, rheological behavior has a pronounced influence upon leakage flow and leakage volume, respectively. Results show furthermore that the apparent viscosity data as a function of shear rate are not sufficient to characterize the rheological fluid behavior relevant to hydrodynamic parameters of the heart valves investigated. Therefore, similarity in the yield curves of non-Newtonian test fluids mimicing blood is only a prerequisite for a suitable test fluid. More information about the viscous and elastic component of the fluid viscosity is required, especially in geometries where a complex flow field exists as in the case of leakage flow.     

In Vitro Hematological Testing of Rotary Blood Pumps: Remarks on Standardization and Data Interpretation

Abstract: Pump test procedures using blood will have to meet several standards not only to obtain reliable results in vitro but also to allow comparison of results of different investigators. This article reviews some of the issues that should be considered in pump testing, especially referring to the discussions held at the International Workshops on Rotary Blood Pumps in 1988 and 1991. The test loop itself should meet some requirements such as constant physiological temperature, standardized circulating volume, control of pressure and flow, and exact definition of the blood-contacting surface. Specifications have to be made concerning the test fluid blood, including sampling technique, anticoagulation, blood gases, pH, and glucose level. Only fresh blood should be used. Heparin is recommended for anticoagulation because it will be used also in vivo. Different procedures for cleaning and rinsing of plastic materials for reuse are mentioned. Bacterial overgrowth, which can lead to extreme oxygen consumption and acidosis, may be avoided through addition of antibiotics (e.g., gentamicin). To be able to compare data of the different working groups, a new modified index of hemolysis (MIH) has been defined.     

Subcutaneous Transposition of the Superficial Femoral Artery for Arterioarterial Hemodialysis: Technique and Results

We report the use of subcutaneous transposition of the femoral artery (STFA) for placement of both inflow and outflow needles in 14 hemodialysis (HD) adult patients with difficult access. Follow‐up time was 318 months during which a total of 3215 arterioarterial HD sessions were done. Kt/V values ranged between 0.71 and 1.59. Elevated access recirculation and dialysis outflow pressures were common findings to all patients. Complications were: (i) two episodes of bleeding secondary to puncture‐related arterial wall laceration, repaired by stitching; (ii) three episodes of thrombosis in two patients, all successfully declotted; (iii) three puncture‐related complications needing placement of a vein interposition graft, namely, aneurysm, pseudoaneurysm, and arterial stenosis; and (iv) one case of arterial ligation because of suppurative puncture site infection, without subsequent distal ischemia signs or claudication. The use of STFA should only be reserved for patients in urgent need for vascular access with no remaining options.     

In Vitro Testing of Femoral Impaction Grafting With Porous Titanium Particles: A Pilot Study

The disadvantages of allografts to restore femoral bone defects during revision hip surgery have led to the search for alternative materials. We investigated the feasibility of using porous titanium particles and posed the following questions: (1) Is it possible to create a high-quality femoral graft of porous titanium particles in terms of graft thickness, cement thickness, and cement penetration? (2) Does this titanium particle graft layer provide initial stability when a femoral cemented stem is implanted in it? (3) What sizes of particles are released from the porous titanium particles during impaction and subsequent cyclic loading of the reconstruction? We simulated cemented revision reconstructions with titanium particles in seven composite femurs loaded for 300,000 cycles and measured stem subsidence. Particle release from the titanium particle grafts was analyzed during impaction and loading. Impacted titanium particles formed a highly interlocked graft layer. We observed limited cement penetration into the titanium particle graft. A total mean subsidence of 1.04 mm was observed after 300,000 cycles. Most particles released during impaction were in the phagocytable range (< 10 μm). There was no detectable particle release during loading. Based on the data, we believe titanium particles are a promising alternative for allografts. However, animal testing is warranted to investigate the biologic effect of small-particle release.     

人工颈椎间盘假体体外功能试验方法及评价策略

人工颈椎间盘置换术保留了相邻椎体节段的运动功能,减少了相邻节段的应力水平,有利于防止术后邻近节段发生退变。目前,国内应用的人工颈椎间盘假体主要是进口产品,国产同类产品大多处于研发生产过程中。本文通过介绍人工颈椎间盘假体的体外功能评价方法,包括假体沉陷、蠕变、推出、半脱位试验,以及动静态压缩、剪切试验和磨损试验等,结合人体颈椎的生物力学数据,以评价产品临床使用的安全性和有效性;基于FDA关于人工颈椎间盘假体的公开数据,对5种不同设计的人工颈椎间盘假体体外功能性试验结果进行分析比较,探讨人工椎间盘假体体外评价试验的可接受依据,为国产同类产品的研发提供参考。     

In Vitro Comparative Assessment of Mechanical Blood Damage Induced by Different Hemodialysis Treatments

Gradual deterioration of red blood cells (RBCs) due to mechanical stress (chronic hemolysis) is unavoidable during treatments that involve extracorporeal blood circulation, such as hemodialysis (HD). This effect is generally undetectable and does not generate any acute symptoms, but it leads to an increase in plasma free hemoglobin (fHb). There are no absolute safety levels for fHb increase, indicating the need for an empirical evaluation using comparative testing. The increase in fHb levels was investigated in vitro by applying double‐needle double‐pump HD (HD‐DNDP), a new modality in which arterial and venous pumps both run continuously. fHb was measured during typical and worst‐case simulated dialysis treatments (double‐needle single‐pump HD [HD‐DNSP], hemodiafiltration [HDF‐DN], single‐needle double‐pump HD [HD‐SNDP], and HD‐DNDP) performed in vitro using bovine blood for 4 h. Hemolysis‐related indices (fHb%; index of hemolysis, IH; and normalized IH) were calculated and used for comparison. The increase in fHb during either HDF‐DN or HD‐SNDP with Artis and AK200 dialysis machines was similar, while the fHb at the maximum real blood flow rate (Qb_real) at the completion of the HD‐DNDP treatment on Artis was higher than that for HD‐DNSP using a Phoenix dialysis machine (fHb% = 1.24 ± 0.13 and 0.92 ± 0.12 for the Artis machine with HD‐DNDP at Qb_real = 450 mL/min and Phoenix with HD‐DNSP at Qb_real = 500 mL/min, respectively). However, the fHb levels increased linearly, and no steep changes were observed. The increases observed during HD‐DNDP were the same order of magnitude as those for widely used bloodlines and treatment modes for delivering dialysis treatments. The observed results matched literature findings, and thus the measured fHb trends are not predicted to have clinical side effects. HD‐DNDP treatment with Artis does not merit any additional concern regarding mechanical stress to RBCs compared with that observed for routinely used dialysis treatments, bloodlines and machines. Although the in vitro measurement of the fHb increase in bovine blood does not allow a prediction of the absolute level of blood mechanical damage or the possible effects in humans, such measurements are valuable for assessing hemolytic harm by performing tests comparing the proposed treatment with existing devices.     

The Evaluation of Leukocytes in Response to the In Vitro Testing of Ventricular Assist Devices

Infection is a clinically relevant adverse event in patients with ventricular assist device (VAD) support. The risk of infection could be linked to a reduced immune response resulting from damage to leukocytes during VAD support. The purpose of this study was to develop an understanding of leukocyte responses during the in vitro testing of VADs by analyzing the changes to their morphology and biochemistry. The VentrAssist implantable rotary blood pump (IRBP) and RotaFlow centrifugal pump (CP) were tested in vitro under constant hemodynamic conditions. Automated hematology analysis of samples collected regularly over 25‐h tests was undertaken. A new flow cytometric assay was employed to measure biochemical alteration, necrosis (7‐AAD) and morphological alteration (CD45 expression) of the circulating leukocytes during the pumping process. The results of hematology analysis show the total leukocyte number and subset counts decreased over the period of in vitro tests dependent on different blood pumps. The percentage of leukocytes damaged during 6‐h tests was 40.8 ± 5.7% for the VentrAssist IRBP, 17.6 ± 5.4% for the RotaFlow CP, and 2.7 ± 1.8% for the static control (all n = 5). Flow cytometric monitoring of CD45 expression and forward/side scatter characteristics revealed leukocytes that were fragmented into smaller pieces (microparticles). Scanning electron microscopy and imaging flow cytometry were used to confirm this. Device developers could use these robust cellular assays to gain a better understanding of leukocyte‐specific VAD performance.     

Evaluation of Phase Stability in Zirconia Femoral Heads From Different Manufacturers After In Vitro Testing or In Vivo Retrieval

Yttria-stabilized zirconia femoral heads from 3 different manufacturers were tested in vitro with respect to their phase stability and compared with retrieved zirconia heads. The monoclinic content on the surface of unused heads was analyzed by confocal Raman spectroscopy after exposure for increasing times to moist atmosphere. The increase in monoclinic content was then plotted as a function of geometric location on the head surface of the head and compared with that measured at similar locations after in vivo exposure. Profiles of residual stress associated to polymorphic transformation were also measured from the collected Raman spectra. A striking finding was that, in some samples, polymorphic transformation occurred since the very early stage of the environmental exposure even if those samples belonged to new-generation products.     

Concept, Realization, and First In Vitro Testing of an Intraarterial Microaxial Blood Pump

Abstract: Intravascular operating microaxial pumps have been clinically introduced (Hemopump 21; Hemopump 14) and have proven to be useful tools for cardiac assist. Due to device-related complications that are associated with the drive concept of an extracorporeal motor and a flexible drive shaft cable, a new pump concept is presented and has been refined in the development process. The cable is replaced by a proximally attached drive unit and an extracorporeal power supply. In addition to ongoing hydrodynamic studies of the flow inside the pump and improvements of the overall hydraulic performance, a microelectric motor was realized and integrated. In vitro tests revealed the feasibility of such a concept.     

In Vitro Maintenance of Terminal-Differentiated State in Hepatocytes Entrapped Within Calcium Alginate

In cultured hepatocytes entrapped within Ca-alginate, liver-specific functions such as induction of tyrosine aminotransferase and serine dehydratase were stimulated by increasing the cell density. In contrast, a growth-related function such as induction of glucose-6-phosphate dehydrogenase was strongly stimulated by decreasing the cell density. This reciprocal regulation was mimicked by the addition of plasma membranes purified from adult rat liver to entrapment cultures at low cell density. Also, gluconeogenesis from lactate was stimulated by the addition of epinephrine (alpha,beta-agonist) with propranolol (beta-blocker). These results suggest that entrapped hepatocytes maintain not only terminal-differentiated state but also alpha-adrenergic response as shown in vivo.     

Colonic sterilization for natural orifice translumenal endoscopic surgery (NOTES) procedures: a comparison of two decontamination protocols

Background  This study aimed to evaluate the effect of two different sterilization protocols on the bacterial counts in the swine colon as preparation for natural orifice translumenal endoscopic surgery (NOTES) surgery. Methods  In this study, 16 swine were randomized to two different colonic sterilization protocols: low colonic irrigation using 300 ml of a 1:1 dilution of 10% povidone–iodine (Betadine) with sterile saline, followed by 1 g of cefoxitin dissolved in 300 ml of saline or two consecutive 300-ml irrigations using a quaternary ammonium antimicrobial agent (Onamer M). Colonic cultures were taken before colonic cleansing after a decontamination protocol and after completion of the NOTES procedure. The Invitrogen live/dead bacterial viability kit was used to assess for change in the bacterial load. A qualitative culture of peritoneal fluid was obtained at the end of the NOTES procedure. Colon mucosal biopsies obtained immediately after the sterilization procedure and at the 2-week necropsy point were evaluated for mucosal changes. Results  Protocol 1 resulted in an average 93% decrease in live colonic bacteria versus 90% with protocol 2 (nonsignificant difference). After a NOTES procedure, group 1 had a 62% increase in live bacteria and group 2 had a 31% increase (nonsignificant difference). Peritoneal cultures also were obtained. Bacteria were isolated from the peritoneal fluid of all the animals, and two or more species were isolated from 75% of the animals. There was no evidence of peritoneal infection at necropsy. Reactive epithelial changes and mild inflammation were the only pathologic abnormalities. No changes were noted at histologic evaluation of colonic mucosa after 2 weeks, demonstrating that these were temporary changes. Conclusion  Colonic irrigation with Betadine and antibiotics are as effective for bacterial decontamination of the swine colon as a quaternary ammonium compound. The results of this study support the use of either protocol. Despite thorough decontamination, peritoneal contamination occurs. The significance of this for humans is unknown. Presented at the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) 2008.     

Efficacy of GM-CSF as an Adjuvant to Hepatitis B Vaccination in Patients with Chronic Renal Failure—Results of a Prospective,Randomized Trial

Background.?Chronic renal failure patients on hemodialysis are at an increased risk of acquiring hepatitis B infection. Hence vaccination against hepatitis B assumes great importance in these patients. However, the response to hepatitis B vaccination is poor, even when 4 double doses (40 µg) of the vaccine are given. This study was conducted to determine the efficacy of GM-CSF as an adjuvant to hepatitis B vaccine in CRF patients. Methods.?CRF patients including both hemodialysis (HD) and non-dialysis (ND) patients were randomized to receive either placebo or a single injection of GM-CSF (in varying doses of 50 µg, 100 µg, 150 µg) a day prior to the 1st dose of recombinant hepatitis B vaccine (40 µg). Three more doses of the vaccine were given at 1, 2, and 6 months. The anti-HBs antibody titres were measured by ELISA at 3 and 7 months. Patients having antibody titres less than 10 IU/L were considered non-responders. The response rate and mean antibody titers were compared between the control (I) and GM-CSF (II) groups. Results.?In group I, 31 and 27 patients were available for evaluation at 3 and 7 months respectively. In group II, 33 and 28 patients could be evaluated at the same time points. Within the control group (group I), the response rate in hemodialysis patients (63.6%) was lower as compared to non-dialysis patients (81.2%). The response rate in group II was higher than that in group I at both 3 months as well as 7 months (78.1% vs. 62.3% and 89.3% vs. 74.1%, p = ns). The best response rates in group II were observed when GM-CSF was used in a dose of 150 µg (90.9% at 3 months and 100% at 7 months). The mean antibody titers were also found to be higher in the group II as compared to group I (409.6 vs. 243.9 IU/L, p = 0.01). Conclusion.?The results of this randomized, prospective study suggest that: 1. Patients with chronic renal failure should be vaccinated for hepatitis B as chronic renal insufficiency is established. 2. GM-CSF is an effective adjuvant to hepatitis B vaccine in these patients especially when a priming dose of 150 µg is used prior to 1st dose of hepatitis B vaccination.