Fluid Mechanics and Clinical Success of Central Venous Catheters for Dialysis-Answers to Simple but Persisting Problems

Variables Leading to Usage of Alteplase Versus Heparin Lock in Patients With Tunneled Catheters in Hemodialysis Care Project Centers, Saudi Arabia

INTRODUCTION

A hemodialysis tunneled catheter is one option for vascular access used with hemodialysis patients; however, catheter complications such as thrombosis are still inevitable. To prevent thrombosis formation, a catheter-locking solution is instilled between dialysis sessions. Heparin is used as a default locking solution in our Hemodialysis Care Project centers, while a recombinant tissue plasminogen activator (rt-PA) such as alteplase is used to treat suspected catheter thrombosis. This study aimed to identify the clinical factors, catheter brands, and hemodialysis variables that influence the choice of use for alteplase versus heparin, for those patients with tunneled catheters, and reduce overprescribing of high-alert medication alteplase.

METHODS

A retrospective medical chart review study was conducted involving 230 patients with tunneled catheters; the first group of 133 patients used alteplase regularly three times a week, while the second group of 97 patients completed at least one year using the same catheter access with heparin lock only.

RESULTS

Multivariate logistic regression and logistic regression analysis showed a significant association (p < 0.05) between different variables. Results suggest that overweight and hyperlipidemia patients are more likely to use alteplase. Patients using brand-name catheters such as Hemostar/Vas-cath (BD, Franklin Lakes, NJ) are less likely to use heparin than those using Medcomp catheters (Medcomp, Yuma, AZ). In addition, patients having a history of angioplasty would be less likely to have heparin than no angioplasty. Moreover, if the patient's fluid removal were equal to or less than 2 kg, they would be more likely to use heparin and vice versa.

CONCLUSION

The study postulates that identified variables affect whether alteplase or heparin is used in hemodialysis tunneled catheters, and may be useful to increase awareness, improve practices, or judiciously control the use of alteplase within Saudi Arabia and globally.

Safety and durable patency of tunneled hemodialysis catheter inserted without fluoroscopy

BACKGROUND

A tunneled hemodialysis (HD) catheter is preferred due to its lower incidence of infection and malfunction than non-tunneled ones. For safer insertion, fluoroscopic guidance is desirable. However, if the patient is unstable, transfer to the fluoroscopy may be impossible or inappropriate.

METHODS

From June 2019 to September 2022, 81 tunneled HD catheter insertion cases performed under ultrasound guidance without fluoroscopy and 474 cases with fluoroscopy in our institutional HD catheter cohort were retrospectively compared.

RESULTS

Immediate complications, later catheter-associated problems, including infections and catheter dysfunction, were comparable between the two groups (p = 0.20 and p = 0.37, respectively). The patency of tunneled catheters inserted without fluoroscopy was comparable to the patency of tunneled catheters inserted with fluoroscopic guidance (p = 0.90).

CONCLUSION

Tunneled HD catheter insertion without fluoroscopy can be performed safely and has durable patency compared to the insertion with fluoroscopy. Therefore, this method can be considered for the selected unstable patients (e.g., ventilator care) in the intensive care unit.

Development of in-vitro pulsatile flow generator for evaluating the performance of hemodialysis catheters

Hemodialysis (HD) using an HD catheter is performed widely on renal failure patients. The catheter was evaluated using the recirculation ratio in pre-clinical status, which is a crucial index indicating its performance. However, pre-clinical in-vivo experiments have limitations: high cost, and ethical issues. Hence, computational and in-vitro methods have been developed as alternatives. However, computational methods require fluid dynamic knowledge, whereas in-vitro experiments are complicated and expensive. In this study, we developed a pulsatile flow generator to mimic blood flow achieving cost effectiveness and user convenience. The device used iterative learning control, achieving blood flow in the superior and inferior vena cava within a 3.3% error. Furthermore, the recirculation ratios were measured based on two insertion directions and two different external pipe materials to evaluate the catheter regarding patients' posture and blood vessel stiffness. The results provide a better understanding of cardiovascular device performance without complicated and costly pre-clinical tests.

Staphylococcus aureus accumulation at the tip of hemodialysis catheters with or without tip side holes in catheter related bloodstream infection in a large animal

BACKGROUND

Eighty percent of hemodialysis patients start their dialysis with a tunneled hemodialysis catheter. Catheter related bacteremia is the second most common cause of death in these patients. Side holes near the tips of the tunneled cuffed central venous catheters are associated with accumulation of thrombus, which can lead to catheter dysfunction and, possibly, also to catheter-related infection. To assess the hypothesis that a catheter without side holes would be associated with less bacterial growth, this study compared the susceptibility of a side-hole-free catheter to accumulation of pathogenic bacteria at the catheter tip with that of two catheters which have side holes.

METHODS

Eight tunneled cuffed double-lumen central venous catheters were inserted into both jugular veins of four sheep; one side-hole-free and one control catheter with side holes at the tip in each animal. Staphylococcus aureus bacteria were then infused intravenously to cause bacteremia. Six hours later, the catheters were removed, the clots that accumulated in their tips were collected and cultured, and the bacterial colonies were counted after additional 12 h of incubation.

RESULTS

Bacteria grew on culture plates seeded with the clot homogenate obtained from the tips of all catheters. The colony counts from the catheters with side holes at the tip exceeded the colony counts of bacteria accumulated in the tips of the side-hole-free hemodialysis catheters by one or more orders of magnitude, with a difference of at least two orders of magnitude observed in three of the four intra-animal comparisons.

CONCLUSIONS

In paired intra-animal post-inoculation comparison made in this limited study, fewer colony forming units of pathogenic bacteria accumulated at the tip of the side-hole-free catheters than at the tips of the catheters which have side holes. This may translate to a decreased rate of catheter-related blood stream infections in the side-hole-free catheters.

Hemodynamic Analysis of the Geometric Features of Side Holes Based on GDK Catheter

Hemodialysis is an important means to maintain life in patients with end-stage renal disease (ESRD). Approximately 76.8% of patients who begin hemodialysis do so through catheters, which play vital roles in the delivery of hemodialysis to patients. During the past decade, the materials, structures, and surface-coating technologies of catheters have constantly been evolving to ameliorate catheter-related problems, such as recirculation, thrombosis, catheter-related infections, and malfunction. In this study, based on the commercial GDK catheter, six catheter models (GDK, GDK1, GDK2, GDK3, GDK4, and GDK5) with different lumen diameters and different geometric features of side holes were established, and computational flow dynamics (CFD) were used to measure flow rate, shear stress, residence time (RT), and platelet lysis index (PLI). These six catheters were then printed with polycarbonate PC using 3D printing technology to verify recirculation rates. The results indicated that: (1) the catheter with a 5.5 mm outer diameter had the smallest average shear stress in the arterial lumen and the smallest proportion of areas with shear stress > 10 pa. With increasing catheter diameter, the shear stress in the tip volume became lower, the average RT increased, and the PLI decreased due to larger changes in shear stress; (2) the catheters with oval-shaped side holes had smaller shear stress levels than those with circular-shaped holes, indicating that the oval design was more effective; (3) the catheter with parallel dual side holes had uniformly distributed flow around side holes and exhibited lower recirculation rates in both forward and reverse connections, while linear multi-side holes had higher shear stress levels due to the large differences in flow around side holes. The selection of the material and the optimization of the side holes of catheters have significant impacts on hemodynamic performances and reduce the probability of thrombosis, thus improving the efficiency of dialysis. This study would provide some guidance for optimizing catheter structures and help toward the commercialization of more efficient HD catheters.

Pathology of catheter-related complications: what we need to know and what should be discovered

Despite the considerable efforts made to increase the prevalence of autogenous fistula in patients on hemodialysis, tunneled cuffed catheters are still an important access modality and used in a high percentage of the hemodialysis population. However, because of the conundrum posed by tunneled cuffed catheters, patients can develop a multitude of complications, including thrombosis, infections, formation of a fibrin sheath, and central vein stenosis, resulting in increased morbidity and mortality as well as placing a heavy burden on the healthcare system. However, with an increasing number of studies now focusing on how to manage these catheter-related complications, there has been less translational research on the pathology of these complications. This review of the most recent literature provides an update on the pathological aspects of catheter-related complications, highlighting what we need to know and what is yet to be discovered. The future research strategies and innovations needed to prevent these complications are also addressed.

The Ash Split Cath(TM) : The best inventions are simple

Dual-lumen "acute" central venous catheters (CVC) for dialysis were developed in the 1970s and tunneled "chronic" CVC in the 1980s. Fibrous sheathing of these catheters diminished the patency after weeks to months of use. Double catheters like Canaud/Tesio worked better and longer than single body catheters but were tedious to place. I decided that the optimal CVC design would be a single body that split into two tips within the vena cava. The "Ash Split Cath^(TM) " was developed in cooperation with a company focused on dialysis access catheters, and quickly became widely used around the world. However, the patent did not prevent other companies from marketing split-tip catheters. A disagreement on the terms of a royalty agreement further weakened the relationship between the marketing company and our R&D company.

Development of New Hemodialysis Catheter Using Numerical Analysis and Experiments

A hemodialysis (HD) catheter, especially one with a symmetric tip design, plays an important role in the long-term treatment of patients with renal failure. It is well known that the design of the HD catheter has a considerable effect on blood recirculation and thrombus formation around it, which may cause inefficiencies or malfunctions during HD. However, hemodynamic analyses through parametric studies of its designs have been rarely performed; moreover, only comparisons between the existing models have been reported. In this study, we numerically analyzed the design of the HD catheter's side hole and distal tip for evaluating their effects on hemodynamic factors such as recirculation rate (RR), shear stress, and blood damage index (BDI). The results indicated that a larger side hole and a nozzle-shaped distal tip can significantly reduce the RR and shear stress around the HD catheter. Furthermore, based on these hemodynamic insights, we proposed three new HD catheter designs and compared their performances with existing catheters using numerical and in vitro methods. These new designs exhibited lower RRs and BDI values, thus providing better performance than the existing models. These results can help toward commercialization of more efficient HD catheters.

Clot accumulation at the tip of hemodialysis catheters in a large animal model

Background:

The issue of side holes in the tips of the tunneled cuffed central venous catheters is complex and has been subject to longstanding debate. This study sought to compare the clotting potential of the side-hole-free Pristine hemodialysis catheter with that of a symmetric catheter with side holes.

Methods:

Both jugular veins of five goats were catheterized with the two different catheters. The catheters were left in place for 4 weeks and were flushed and locked with heparin thrice weekly. The aspirated intraluminal clot length was assessed visually prior to each flushing. In addition, the size and weight of the clot were recorded upon catheter extraction at the end of the 4-week follow-up

Results:

The mean intraluminal clot length observed during the entire study follow-up measured up to a mean of 0.66 cm in the GlidePath (95% CI, 0.14–1.18) and 0.19 cm in the Pristine hemodialysis catheter (95% CI, −0.33 to 0.71), the difference being statistically significant (p = 0.026). On average, 0.01 g and 0.07 g of intraluminal clot were retrieved from the Pristine and GlidePath catheters, respectively (p = 0.052).

Conclusion:

The Pristine hemodialysis catheter was largely superior to a standard side hole catheter in impeding clot formation, and, contrary to the side hole catheter, allowed for complete aspiration of the intraluminal clot.

Long-term outcome of posterior approach insertion of tunneled cuffed catheter: A single clinic retrospective analysis

BACKGROUND AND OBJECTIVES

For patients who rely on a tunneled cuffed catheter, the internal jugular vein is the preferred site of insertion. A few studies have suggested that the posterior approach for central lines is equivalent or better in comparison to the conventional central approach. However, there have been fewer studies examining tunneled cuffed catheter insertion using the posterior approach. We have performed many posterior insertions of tunneled cuffed catheters in our practice, and because the technique has not yet been comprehensively studied for long-term use, we performed a retrospective study to evaluate the safety and efficacy of posterior approach for tunneled cuffed catheter in maintained hemodialysis patients.

METHODS

A retrospective review was conducted of 200 hemodialysis patients who were treated with tunneled cuffed catheters over a period of 3 years. There were 104 patients in the study group, as well as a 96-patient control group, who underwent catheter insertion by central approach. The clinical follow-up data were collected and analyzed.

RESULTS

All catheters were successfully placed. The mean primary patency days per catheter were 712 catheter days for the study group and 585 catheter days for the control group. The episode of catheter infection was similar in both groups (p = 0.874), but the case of total catheter dysfunction was significantly lower in the study group compared to the control group (p = 0.006). The cumulative patency of catheters was higher in the study group than that in the control group (p = 0.02), while patient survival was the same in the two groups (p = 0.325).

CONCLUSION

The posterior approach is safe, and similar infection rates were observed with lower dysfunction rates compared to tunneled catheter insertion by the conventional central approach.

Solutions to stuck tunneled cuffed catheters in patients undergoing maintenance hemodialysis

OBJECTIVE

To study and discuss treatments for stuck tunneled cuffed catheter in patients undergoing maintenance hemodialysis.

METHOD

Retrospectively analyzing clinical data of 13 patients with stuck tunneled cuffed catheter in the Kidney Disease Center of the First Affiliated Hospital, College of Medicine, Zhejiang University in the period between September 2012 and October 2018. All patients failed to remove hemodialysis catheters by regular technique. The stuck catheters were treated by thoracotomy, endoluminal percutaneous transluminal angioplasty with blunt dissection or embedded and left in situ.

RESULTS

In 13 patients, one was successfully treated by thoracotomy, one failed to remove the catheter by regular technique and blunt dissection, and the stump of the catheter was clamped and buried in the subcutaneous fascia of the neck, and the other 11 were treated by endoluminal percutaneous transluminal angioplasty with blunt dissection. The average time of catheter removal procedure is 25 min, the overall success rate is 92.3%, and the success rate of percutaneous transluminal angioplasty is 100%.

CONCLUSION

Thoracotomy is an efficient way to treat stuck catheter but is limited by its high risk and complications. Leaving part of catheter in situ may increase the risk of central vein stenosis. Comparing to the former two, endoluminal percutaneous transluminal angioplasty is a safe, efficient, and practical way for stuck catheters and should be recommended as the first choice.

New Directions in Ensuring Catheter Safety

Tunneled dialysis catheters remain the most common vascular access used to initiate hemodialysis. Unfortunately, their use is associated with higher morbidity and mortality when compared with arteriovenous fistulae or grafts. Different types of catheters with different designs and material properties function differently. Additional devices and medications can be used to decrease the rates of infection and thrombosis. The current available tunneled dialysis catheters remain far from the desired goal and innovation in the field of dialysis vascular access remains in dire need.

Dialysis catheters in the ICU: selection, insertion and maintenance

PURPOSE OF REVIEW

Choosing the best catheter for renal replacement therapy (RRT) is not an easy task. Beyond catheter length, many of its properties can influence effectiveness of the RRT session. Maintenance between sessions, particularly the locking solution, also impacts catheter lifespan and infection rates.

RECENT FINDINGS

Many innovations in dialysis catheters have been proposed by the industry over the past decade, including the material used, the shape of the lumens and the position of the inflow and outflow holes. Impregnated catheters have also been developed to prevent catheter-related infections. Many locking solutions are available, either for maintaining catheter patency or for preventing infections.

SUMMARY

Although studies conducted in the specific context of the ICU are still scarce, some conclusions can be drawn. Catheter length must be adapted to the insertion site to reach an area of high blood flow. Kidney-shape lumens appear to be less thrombogenic and seem to prevent catheter dysfunction. Catheter tip and lumen holes also affect catheter function. For catheter locking, 4% citrate appears nowadays as one of the best options, but taurolidine-based solutions are also interesting.

Clinical and Regulatory Considerations for Central Venous Catheters for Hemodialysis

Central venous catheters remain a vital option for access for patients receiving maintenance hemodialysis. There are many important and evolving clinical and regulatory considerations for all stakeholders for these devices. Innovation and transparent and comprehensive regulatory review of these devices is essential to stimulate innovation to help promote better outcomes for patients receiving maintenance hemodialysis. A workgroup that included representatives from academia, industry, and the US Food and Drug Administration was convened to identify the major design considerations and clinical and regulatory challenges of central venous catheters for hemodialysis. Our intent is to foster improved understanding of these devices and provide the foundation for strategies to foster innovation of these devices.

Spanish Clinical Guidelines on Vascular Access for Haemodialysis

Vascular access for haemodialysis is key in renal patients both due to its associated morbidity and mortality and due to its impact on quality of life. The process, from the creation and maintenance of vascular access to the treatment of its complications, represents a challenge when it comes to decision-making, due to the complexity of the existing disease and the diversity of the specialities involved. With a view to finding a common approach, the Spanish Multidisciplinary Group on Vascular Access (GEMAV), which includes experts from the five scientific societies involved (nephrology [S.E.N.], vascular surgery [SEACV], vascular and interventional radiology [SERAM-SERVEI], infectious diseases [SEIMC] and nephrology nursing [SEDEN]), along with the methodological support of the Cochrane Center, has updated the Guidelines on Vascular Access for Haemodialysis, published in 2005. These guidelines maintain a similar structure, in that they review the evidence without compromising the educational aspects. However, on one hand, they provide an update to methodology development following the guidelines of the GRADE system in order to translate this systematic review of evidence into recommendations that facilitate decision-making in routine clinical practice, and, on the other hand, the guidelines establish quality indicators which make it possible to monitor the quality of healthcare.

Urea-based recirculation validation of the symmetrical palindrome catheter

BACKGROUND

High blood flow and low recirculation rates are central for adequate haemodialysis. A new symmetrical tip has been invented promising efficient haemodialysis even if the ports are reversed.

OBJECTIVE

To evaluate access recirculation of the 'palindrome' catheter and to report initial experiences in a clinical setting.

MATERIAL AND METHODS

After implantation of the new catheter in 20 patients (male: 14; female: 6; mean age 72 ± 12.2), access recirculation was evaluated using the urea-based recirculation test. After 30 minutes of haemodialysis, ultrafiltration was stopped and arterial and venous samples were taken. Afterwards, the blood flow rate was reduced to 120 ml/min. Another systemic arterial blood sample was taken 10 seconds after the blood pump was switched off.

RESULTS

All 20 interventions were performed successfully without complications. The average recirculation rate was 8.1% with a median of 2.5% ranging from 0 to 85.8%. Recirculation rates under 5% were measured in 13 patients and more than 10% recirculation were found in two patients. The median of days between catheter implantation and recirculation assessment was the day following implantation.

CONCLUSION

The new symmetrical catheter presented low recirculation rates in a clinical setting. Since there is just a single tip, fluoroscopic placement in the right atrium is facilitated.

A prospective comparison of the performance and survival of two different tunnelled haemodialysis catheters: SplitCath® versus DuraMax®

BACKGROUND

Despite their well-recognised shortcomings, haemodialysis catheters (HDCs) remain an important form of haemodialysis access for many patients. There are several HDCs commercially available, each differing considerably in design, which is known to significantly influence performance and survival. We sought to determine which of two tunnelled HDCs, DuraMax® (Angiodynamics, NY, USA) or SplitCath® (MedComp, PA, USA) delivers the best performance, safety and reliability for dialysis patients.

METHODS

Eighty-six patients were prospectively randomised to receive either DuraMax® (DM) or SplitCath® (SC). Outcomes included: (i) mean flow rates (mL/min) averaged over the first 10 weeks of dialysis, and urea reduction ratio (URR); and (ii) long-term catheter survival with appraisal of any events leading to catheter dysfunction and early removal.

RESULTS

Median flow rates (interquartile range) in the DM and SC groups were 321 (309-343) and 309 (294-322) mL/min, respectively (p = 0.002). URR values for the DM and SC groups were 71 (65-76) and 74 (70-78), respectively, (p = 0.094). There was no significant difference in long-term survival or frequency of incidents that required early HDC removal (9/43 in the DM group, 5/43 patients SC). A slightly higher incidence of HDC dislodgement was noted in the DM group, although this study was not statistically powered to determine its significance.

CONCLUSIONS

We conclude that DM yields slightly higher flow rates in the first 10 weeks of dialysis, and a similar low incidence of complications and long-term survival for both DM and SC HDCs.

Imaging in Vascular Access

This review examines four imaging modalities; ultrasound (US), digital subtraction angiography (DSA), magnetic resonance imaging (MRI) and computed tomography (CT), that have common or potential applications in vascular access (VA). The four modalities are reviewed under their primary uses, techniques, advantages and disadvantages, and future directions that are specific to VA. Currently, US is the most commonly used modality in VA because it is cheaper (relative to other modalities), accessible, non-ionising, and does not require the use of contrast agents. DSA is predominantly only performed when an intervention is indicated. MRI is limited by its cost and the time required for image acquisition that mainly confines it to the realm of research where high resolution is required. CT’s short acquisition times and high resolution make it useful as a problem-solving tool in complex cases, although accessibility can be an issue. All four imaging modalities have advantages and disadvantages that limit their use in this particular patient cohort. Current imaging in VA comprises an integrated approach with each modality providing particular uses dependent on their capabilities. MRI and CT, which currently have limited use, may have increasingly important future roles in complex cases where detailed analysis is required.

Thrombotic complications and tip position of transjugular chronic dialysis catheter scheduled into superior vena cava: Findings on HR-MRCP and HR-T2WI

BACKGROUND

Catheter-related thrombotic complications(TCs) can occur during the long term use of a chronic dialysis catheter (CDC), including fibrin sheath (FS), mural thrombosis (MT), venous thrombosis (VT), and intraluminal clots (IC), which has not been reported with MRI. The aim of our study was to evaluate the determination of catheter tip position (TP) and resolution of TCs in patients with transjugular CDC scheduled into the superior vena cava using high resolution magnetic resonance cholangiopancreatography (HR-MRCP) and T2-weighted imaging (HR-T2WI).

METHODS

The study protocol was approved by the local Research Ethics Committee. Informed consent was obtained from all patients. In total, 41 consecutively enrolled transjugular CDC patients with suspected catheter dysfunction were scanned with HRMRCP and HR-T2WI. The distance from the top to the tip of the catheter and the presence and nature of catheter TCs were assessed by 2 experienced radiologists. Chest x-ray was taken within 1 to 2 days and CDC was withdrawn within 3 to 10 days from those patients with TCs identified by HR-MRI.

RESULTS

A total of 38 subjects successfully underwent HR-MRI, including 13 normal and 25 with TCs (fibrin sheath [FS]: n = 21, mural thrombosis [MT]: n = 7, venous thrombosis [VT]: n = 3, intraluminal clots [IC]: n = 4). There was no significant difference between HR-MRCP and chest x-ray in catheter TP determination (P = .124). Normal catheter appeared as "double eyes" on HR-T2WI and "double tracks" on HR-MRCP. TCs appeared as follows: FS displayed as a "thin ring" (<1mm) around the catheter, MT as patchy hyperintensity and VT as a "thick ring" (>5mm) on HR-T2WI. Unilateral IC appeared as a "single eye" on HR-T2WI and a "single track" on HR-MRCP (n = 3). Bilateral IC appeared as neither "eye" nor "track" (n = 1). Catheter withdrawal confirmed FS (n = 16), MT (n = 6), VT (n = 1), and IC (n = 4).

CONCLUSION

HR-MRCP and HR-T2WI are promising methods for visualizing TP and TCs in CDC patients, and are helpful in adjusting the treatment plan and avoiding the risk of pulmonary embolism.

Haemodialysis catheters in the intensive care unit

Ten to 15% of critically ill patients need renal replacement therapy (RRT) for severe acute kidney injury. The dialysis catheter is critical for RRT quality and efficiency. Catheters have several properties that must be optimized to promote RRT success. The distal tip has to be located in a high blood flow location, which means central venous territory. Therefore, catheters are mostly inserted into the right internal jugular vein or in femoral veins. External diameter should vary from 12 to 16 Fr in order to ensure adequate blood flow inside the catheter. Lumen shapes are theoretically designed to limit thrombotic risk with low turbulences and frictional forces against the internal wall. With low aspiration pressure, distal tip shape has to deliver sufficient blood flow, while limiting recirculation rate. Catheter material should be biocompatible. Despite in vitro data, no strong evidence supports the use of coated catheters in the ICU in order to reduce infectious risk. Antibiotic "lock" solutions are not routinely recommended. Ultrasound guidance for catheterization significantly decreases mechanical complications. Clinicians should select the optimal catheter according to patient body habitus, catheter intrinsic properties and RRT modality to be used.

Update on Insertion and Complications of Central Venous Catheters for Hemodialysis

Central venous catheters are a popular choice for the initiation of hemodialysis or for bridging between different types of access. Despite this, they have many drawbacks including a high morbidity from thrombosis and infection. Advances in technology have allowed placement of these lines relatively safely, and national guidelines have been established to help prevent complications. There is an established algorithm for location and technique for placement that minimizes harm to the patient; however, there are significant short- and long-term complications that proceduralists who place catheters should be able to recognize and manage. This review covers insertion and complications of central venous catheters for hemodialysis, and the social and economic impact of the use of catheters for initiating dialysis is reviewed.

Dialysis Central Venous Catheter Types and Performance

The choice of both short-term (nontunneled) and long-term (tunneled) central venous catheters (CVCs) for hemodialysis is a difficult one, due to the large number of available catheters, with very different characteristics and cost.

CVC-related complications (in particular infections, thrombosis and inefficient dialysis) can determine ominous consequences and death, with extremely elevated costs due to prolonged hospitalization and expensive procedures. Thus, the correct balance between cost and quality of CVC is required when deciding which kind of CVC should be adopted.

In this regard, the design of CVCs has become a very active area of industrial and clinical research, with the ultimate goal of improving the long-term function of the catheter and of reducing complication rates, because even small improvements in the complication or reintervention rates have a positive impact on individual patient care and cost to society. In this article we review the general features of CVCs, including differences between tunneled and nontunneled CVCs, materials and their compatibility with lock solutions, the implications of straight versus precurved design in nontunneled CVCs, lumen and tip features with their clinical implications, catheter coatings and their effect on infection and thrombosis.

Imaging and management of complications of central venous catheters

Central venous catheters (CVCs) provide valuable vascular access. Complications associated with the insertion and maintenance of CVCs includes pneumothorax, arterial puncture, arrhythmias, line fracture, malposition, migration, infection, thrombosis, and fibrin sheath formation. Image-guided CVC placement is now standard practice and reduces the risk of complications compared to the blind landmark insertion technique. This review demonstrates the imaging of a range of complications associated with CVCs and discusses their management with catheter salvage techniques.

ECMO cannula review

This paper reviews the basic fluid dynamics underlying extracorporeal membrane oxygenation (ECMO) cannula design. General cannula features and their effect on flow are discussed and the specific requirements of different ECMO circuits are explained. The current commercially available cannula options for veno-arterial and veno-venous circuits are reviewed and the main characteristics presented.

Time to move away from damage control strategy in hemodialysis vascular access management: a view from Saudi Arabia

For the last 40 years, most of the research and publications on hemodialysis access, has focused on the management of its complications e.g. thrombosis, infection, aneurysms. In other words, a damage control strategy. While this is undoubtedly an important part of access management, it is a deficient reactive strategy that does not enhance a better quality of life for patients or help reduce the burden on health care resources. To achieve these objectives, efforts should be directed at ways which provide a longer access life with fewer complications. Such an approach would save costs and reduce the suffering of the patient. In this paper we will focus on hemodialysis management in Saudi Arabia, describe the reasons for the current unsatisfactory situation, and highlight possible remedies.

Vascular access for extracorporeal renal replacement therapy in veterinary patients

Vascular access is the first and most basic requirement for successful extracorporeal renal replacement therapy (ERRT). Dual-lumen catheters are the most commonly used method of vascular access for ERRT in veterinary patients. An adequately functioning dialysis catheter allows for smooth and efficient patient management, whereas a poorly functioning catheter frustrates the technician, doctor, and patient. These catheters are fairly quick to place but require meticulous care for optimal function. The most common complications are thrombosis and infection. Monitoring catheter performance should be a routine part of dialysis patient care.

UVC fluencies for preventative treatment of Pseudomonas aeruginosa contaminated polymer tubes

Exposing Pseudomonas aeruginosa biofilm grown on the inner surface of Teflon and silicone tubes to UVC light (265 nm) from light emitting diodes (LED) has previously been shown to substantially reduce biofilm growth. Smaller UVC fluencies were required to disinfect Teflon tubes compared to silicone tubes. Light propagation enhancement in tubes can be obtained if the refractive index of the intra-luminal saline solution is higher than that of the polymer. This condition is achieved by using Teflon tubes with a low refractive index (1.34) instead of the polymers with a high refractive index (1.40-1.50) normally used for tubing in catheter production. Determining whether or not UVC light exposure can disinfect and maintain the intra-luminal number of colony forming units (CFUs) at an exceedingly low level and thus avoid the growth and establishment of biofilm is of interest. The use of UVC diodes is demonstrated to be a preventative disinfection treatment on tubes made of Teflon, which enhances the UVC light propagation, and on tubes made of a softer material, ethylene vinyl acetate (EVA), which is suitable for catheters but much less suitable for UVC light propagation. Simulating an aseptic breach (∼10(3)-10(4) CFU ml(-1)), the UVC disinfection set-up was demonstrated using tubes contaminated with planktonic P. aeruginosa. After the tubes (10-20 cm) were inoculated with the bacterial solution for 3 h, they were emptied and filled with saline solutions (0.9-20%). Next UVC fluencies (0-21 mJ cm(-2)) were applied to the tubes 3 h after inoculation. Colony counts were carried out on liquid samples drawn from the tubes the first day after UVC treatment and liquid and surface samples were collected and analyzed 3-4 days later. A fluence of approximately 1.0 mJ cm(-2) was noted as being sufficient for no growth for a period of 3-4 days for the Teflon tubes. Determining the fluence threshold for the EVA tubes was not possible. Almost all of the UVC-treated EVA tubes were disinfected simply by filling the tubes with a saline solution. Direct UVC treatment of the contaminated EVA tubes revealed, however, that a fluence of 21 mJ cm(-2) killed the bacteria present in the tubes and kept them disinfected for a period of 3-4 days.

Vascular access for dialysis: recent lessons and new insights

PURPOSE OF REVIEW

Vascular access complications are a major cause of excessive morbidity and mortality in the dialysis population. This review will focus on recent changes in vascular access practices and access management directly affecting patient outcomes.

RECENT FINDINGS

The proportion of patients dialyzing via arteriovenous fistulas continues to increase as a result of national initiatives. Maturation failure is now the main obstacle to successful use of fistulas. Arteriovenous grafts remain an important vascular access option for dialysis, and interventions to prevent progression of stenosis are being explored. Central venous catheter prevalence has increased and new interventions to address catheter-related complications such as thrombosis and infection are promising.

SUMMARY

Advances in understanding the factors related to fistula maturation failure will have a major beneficial effect on vascular access outcomes. New approaches to prevent graft and catheter-related complications should complement advances on fistula management. Optimal patient selection for specific access modalities and institution of timely access interventions tested in rigorous clinical trials should be the next step to improve access management.