**7. References**

210 Progress in Hemodialysis – From Emergent Biotechnology to Clinical Practice

of utilizing photometry to detect and measure endotoxin in patient plasma samples (Nakazawa et al., 2010), which would have direct impact on research clinics and for septic patients. PCR techniques have also been utilized for their application to dialysis research, by analyzing total flora in dialysis water via the 16s rDNA. As this technique guarantees a high degree of detection, it does not specify whether bacteria or live or dead, or what species are

Studies involving endotoxin in hemodialysis have been going on for quite some time – covering how to prevent and remove biofilm from water distribution systems, how endotoxin interacts with the body, and how to increase removal efficiencies. Going forward, future work may involve identifying new bacterial contaminants that cause adverse patient reactions, but may not be identified by the LAL assay (Glorieux et al., 2009). There are a number of smaller bacterial components released during cell lysis, with bacterial DNA fragments recently receiving considerable attention in research studies (Handelman et al., 2009; Schindler et al., 2004). Some of these studies have shown a correlation between bDNA fragments present in patient blood, and higher levels of CRP and IL-6 (Bossola et al., 2009). Current limitations in endotoxin quantitative methodology, which influence how bacterial contaminant results and target values are interpreted (Ledebo, 2007b) will hopefully be

improved upon and expanded to cover additional areas of focus in ESRD treatment.

The future of any therapy used to treat patients with ESRD needs to focus on the associated mortality and morbidity influencing factors. Whether ESRD therapy will focus on smaller, wearable devices (Gura et al., 2008; Ronco & Fecondini, 2007), strive for increases in home treatment (Moran, 2009), or devices utilizing living cells (Humes et al., 2006), the effect of endotoxin must be taken into account for each application – and to address the specific actions necessary to remove endotoxin thus ensuring patient safety. Future progress in endotoxin research will hopefully alleviate inflammation-related complications, and

In conclusion, endotoxin contamination of fluid for dialysis therapy is an important aspect of patient safety and well-being. Regardless of the microbiological quality of the water coming into the hemodialysis machine, the dialysis membrane is the final barrier between potentially contaminated dialysis fluid, and the blood of the patient. We have examined how manipulation of specific fiber membrane parameters (geometric properties, materials, coatings, chemical modifications) can be utilized to improve the endotoxin retentive properties to limit trans-membrane flux, whether they contribute to adsorptive improvements, sieving improvements, or both. Membrane structure, surface chemistry, material, and surface coatings all have an impact on how endotoxin is filtered and adsorbed from solution. In addition to better understanding endotoxin-membrane interactions, studies of endotoxin removal by membrane modifications will result in better approaches to manufacture dialysis membranes that remove endotoxin from solution quickly and with

As future hemodialysis membranes are designed to further improve upon convective removal of larger middle molecular solutes such as B2M, the opportunity for pyrogenic

prevalent within the sample (Nystrand, 2006).

improve patient outcomes for all aspects of ESRD.

**4. Future work** 

**5. Conclusion** 

improved efficiency.


Dialysis Membrane Manipulation for Endotoxin Removal 213

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**11** 

*USA* 

Stephan Thijssen *Renal Research Institute* 

**Citrate Anticoagulation in Hemodialysis** 

In hemodialysis, the patient's blood is flown through an extracorporeal circuit containing a hemodialyzer. This process stimulates coagulation for several reasons, most notably the blood's contact with the artificial surfaces of the tubing and dialyzer membrane and with air in the venous bubble trap, turbulent and stagnant blood flow, shear stress and hemoconcentration during the treatment [1]. Technological advances, e.g., the development of air-free blood circuits and more biocompatible materials for both tubing and dialyzer membranes, may eventually help reduce thrombogenicity of the extracorporeal circuit but are unlikely to eliminate this problem anytime soon. As a result, anticoagulation is (and will be, for the years to come) generally required for hemodialysis in the vast majority of patients. In most cases in the United States, unfractionated heparin is the agent of choice to provide dialysis anticoagulation. While this is usually well-tolerated and relatively safe, there are significant drawbacks. The most obvious of these is that the anticoagulation is systemic in nature, which translates into an increased bleeding risk. This is certainly undesirable in endstage renal disease patients, who are already afflicted with uremic thrombocytopathy, and it is particularly dangerous for patients with additionally increased bleeding risk, e.g., patients after surgery or trauma, and patients with active (e.g., gastro-intestinal) bleeding. Another possible complication related to heparin use, albeit rare in dialysis patients, is heparininduced thrombocytopenia (HIT) type II [2], a potentially life-threatening condition associated with a mortality rate of 8 to 20 percent. Other possible side-effects of heparin use include osteoporosis, hair loss, and hyperlipidemia. Starting in late 2007, a series of severe anaphylactoid reactions had caused serious injuries and deaths. These reactions were later

linked to heparin contaminated with oversulfated chondroitin sulfate [3, 4].

Several alternatives to heparin anticoagulation are potentially available, each of them accompanied by specific disadvantages. Intermittent saline flushes, i.e., flushing of the extracorporeal circuit with 25 to 50 mL of 0.9% sodium chloride solution every 15 to 30 minutes, is often used during acute dialysis in patients with increased bleeding risk or in patients with HIT type II. Since the procedure, surprisingly, is not automated, it is very laborious. Furthermore, its capacity to prevent clotting is rather limited, with partial clotting occurring in approximately 20 percent, and complete clotting of the extracorporeal circuit in about 7 percent of treatments [1]. Clotting of the extracorporeal system, of course, is associated with blood loss to the patient, and even with partial clotting, solute clearances will be impaired. Other agents used for systemic anticoagulation in hemodialysis are fondaparinux, danaparoid, and direct thrombin inhibitors. These have other downsides,

**1. Introduction** 

endotoxin adsorber column improves hemodynamics and reduces oxidative stress: results of a feasibility study. *Blood Purificaiton*, Vol.26, No.1, pp.333-339.

