Prevention and Treatment of Thrombosis Associated With Long-Term Hemodialysis Catheters

Soft, cuffed, central vein hemodialysis catheters are used in about 20% of chronic hemodialysis patients in the United States, because long-term arteriovenous blood access cannot be maintained in an aging patient population with a large proportion of diabetics. The most frequent complication of these catheters is thrombosis. The treatment of catheter-related thrombosis is difficult and expensive; thus the emphasis should be on prevention. The preferred material for a long-term catheter is silicone rubber, since it is the least thombogenic. Anticoagulation should be more vigorous during “catheter dialysis” than during “fistula dialysis.” Heparin is the least expensive and most convenient anticoagulant, suitable for over 99% of chronic dialysis patients. The dose of heparin for sufficient anticoagulation depends on many factors, varies widely, and should be established for each patient based on activated clotting time (ACT). ACT should be kept over 270 sec throughout dialysis. Recently we introduced a method of locking catheter lumina with a predetermined amount of heparin; this heparin is not discarded before the next dialysis, but serves as a loading dose. This saves a number of connections/ disconnections and decreases dialysis-associated blood losses. To prevent catheter thrombosis, over 60% of patients require warfarin in sufficient doses to keep the international normalized ratio (INR) between 1.5 and 2.5. The most common catheter-related thrombus is a periluminal fibrin sleeve. Locking the catheter with urokinase to dissolve the clot is of little value, because the bulk of the thrombus is outside the catheter. We have found a high-dose (250 000 U or more) intradialytic urokinase infusion through the venous chamber to be a very efficient and convenient method for dissolving clots. Cumulative success of up to three infusions is over 99%. This obviates the need of catheter stripping or replacement, which is more cumbersome and expensive.     

Successful Long-Term Central Venous Access

Daily home hemodialysis (DHHD) requires simple, vascular access to minimize patients' discomfort but also to guarantee tolerance and long-term efficiency. The arteriovenous fistula is not ideal for DHHD because of the double puncture required every day; in addition, the rate of dysfunction is probably greater because of the more frequent use. Central venous catheters may be a good alternative to the arteriovenous fistula as long-term vascular access for DHHD. In this study we report our experience with the internal jugular vein two-catheter access for long-term dialysis and evaluate its possible use for DHHD. Since 1988, Tesio's twin catheters have been positioned in 908 patients with exhausted peripheral vascular bed. In all patients hemodialysis could be performed a few minutes after the surgical procedure. The survival rate of catheters, in a selected group of 46 patients, at 1, 2, and 5 years was, respectively, 92%, 87%, and 82%. The mean blood flow was 282±29 mL/min at 1 month, 286±36 mL/min at 1 year, and 274±37 mL/min at 5 years. Venous pressure in the inlet side was 102±31 mm Hg at 1 month, 126±36 mm Hg at 1 year, and 132±58 mm Hg at 5 years. Catheter clotting was treated either with thrombolytic agents or with catheter (one or both) replacement. Sepsis was treated with systemic antibiotic therapy or catheter removal. Data support the potential role of the internal jugular vein two-catheter system for DHHD.     

Efficacy of Tissue Plasminogen Activator for Thrombolysis in Central Venous Dialysis Catheters

Background:  Low blood flow is a frequent complication of central‐vein (CV) dialysis catheters. Since thrombotic occlusion accounts for many cases of reduced blood flow, it is common practice to administer empiric thrombolytic therapy in an attempt to restore catheter patency and improve function.
Methods:  We prepared tissue plasminogen activator (tPA) from 50 mg lyophilized powder, which was diluted (1 mg/mL) in sterile water for injection. A volume of 1 mL was frozen in 3 cc polystyrene syringes at −20 °C and thawed at room temperature when needed. tPA was then administered into the arterial and venous ports of the central venous catheter in a volume equal to the manufacturer's stated luminal volume and was allowed to dwell for 30 minutes.
Results:  tPA was administered 62 times in 25 patients with 30 catheters (11 Tesio, 17 PermCath, 2 Shiley) for treatment of low blood flow (pump speed < 250 mL/min). Complete restoration of patency was achieved in 23 episodes (mean blood flow pre‐tPA 130 mL/min; post‐tPA 320 mL/min); partial restoration of patency was achieved in 20 episodes (mean blood flow pre‐tPA 69 mL/min; post‐tPA 233 mL/min). tPA was just as likely to be effective in patients with complete catheter occlusion (i.e., no blood flow) as it was when some initial blood flow was present. Nineteen episodes failed to respond to tPA. These episodes occurred in 13 catheters, 12 of which ultimately underwent radiologic evaluation; an extraluminal cause for low blood flow was found in all 12 catheters (6 malpositioned, 6 fibrin sheaths).
Conclusions:  tPA at a dose of 1 mg/mL is effective for restoring patency in CV dialysis catheters. Failure to respond to tPA strongly suggests an extraluminal cause of catheter malfunction.     

Massive catheter‐related thrombosis of vena cava superior protruding into the right atrium in a hemodialysis patient

A 36‐year‐old man with chronic renal insufficiency secondary to type 1 diabetes mellitus was on hemodialysis via central venous catheter (CVC), newly placed into the right subclavian vein after his arteriovenous fistula became dysfunctional. Seven days after CVC insertion, the patient developed fever and on day 11 echocardiography showed a large nearly occluding thrombus in the superior vena cava (SVC) extending into the right atrium (RA). Emergency surgical thrombectomy was successfully performed and an 11 cm long thrombus extending from the RA cranially into the SVC occupying majority of the vein's lumen was removed. Cultures from the thrombus and CVC were negative, but polymerase chain reaction was positive for Staphylococcus aureus. This particular case was interesting for a marked discrepancy between large SVC occluding thrombosis and a relatively mild clinical presentation with fever, and it highlights the importance of correct timing of echocardiography exam which might prevent potentially fatal consequences such as pulmonary embolism.     

Successful Long-Term Central Venous Access; Daily Home Hemodialysis Blood Access

Successful long-term central venous access is a complex subject. The concept of “long term” implies that continued surveillance will be required. This also requires the catheter to be placed, initially, in its best configuration. To achieve long-term performance and durability, a thorough understanding of all aspects related to the catheter, catheter placement, and catheter maintenance is essential.     

Hemodialysis Central Venous Catheter-Related Bacteremia: Time to Onset

Bacteremia (B) is a well-known complication of an indwelling central venous catheter (CVC). Although prophylactic measures such as topical and catheter lock antibiotics have been demonstrated to decrease the risk of B in hemodialysis (HD) in patients with a CVC, there are concerns about the development of resistance to these agents when used for long periods of time.
Objective:  We wondered if we could limit the use of these agents by identifying the period when B was most common after CVC placement.
Method: We prospectively noted all patients with a CVC who developed B in any of our 3 units in CT, U.S.A.; 62 episodes of B occurred between 1/1/03 and 9/18/03. 35% of all of the HD patients had a CVC for access during the study period.
Results: Staphylococcus aureus accounted for 22 (35.5%) episodes; Gram-negative organisms for 21 (33.8%) and other staphylococcal species for 14 (22.6%). The other 3 episodes were other Gram-positive organisms and 6 patients developed B with more than 1 organism. 3 (4.8%) patients expired while being treated for the B. The average time to onset of B was 96 ± 98 CVC days with a range of 1–365 days. There was no difference in time to onset based on organism. 43.5% of the episodes of B occurred less than 60 days after the CVC was inserted, but 27.4% occurred greater than 100 days after CVC insertion.
Conclusion:  The time to onset of CVC-related B was variable among the patients developing B in this study. Preventative strategies aimed at reducing the risk of B in patients with a CVC must be used for the life of the CVC.     

Nephrotic syndrome complicated with femoral vein catheter‐related phlegmasia cerulea dolens: A case report

Nephrotic syndrome is a well‐known risk factor of deep vein thrombosis (DVT). Catheter‐related DVT under the setting of nephrotic syndrome may be presented as a more fulminant form, phlegmasia cerulea dolens. Phlegmasia cerulea dolens may lead to severe obstruction of venous drainage of the extremities and presents with compartment syndrome that impairs arterial perfusion. Aggressive management with thrombolysis and/or thrombectomy are considered with simultaneous anticoagulant treatment.     

Inability to start hemodialysis after a smooth temporary hemodialysis catheter insertion procedure

Cannulation of the central vein for placement of the temporary dual-lumen catheter for hemodialysis can usually be safely and reliably performed under ultrasonographic guidance. Here, we report a case of aberrant catheter entry into the internal thoracic vein during an apparently smooth procedure. The value of sonographic guidance, together with fluoroscopy with or without venography, will be discussed.     

Late onset of clinically apparent central vein stenosis due to previous central venous catheter in a patient with inherited thrombophilia

We describe a case of a patient with a functional kidney transplant who was admitted to our department with clinically evident central vein stenosis (CVS) 7 years after the removal of a central venous catheter (CVC) from the right internal jugular vein. The catheter was used as a hemodialysis access for a 2‐month period. In the interval before his last admission, the patient suffered two episodes of deep vein thrombosis. Investigation revealed heterozygosity for factor V Leiden, the most common inherited thrombophilia encountered in 5% of Caucasians, and anticoagulation treatment was started. Magnetic resonance angiography showed stenosis just after the convergence of the right subclavian vein with the internal jugular vein to the innominate vein. Transluminal angioplasty restored venous patency and right upper arm edema resolved. Coexistence of CVS, accompanied by hemodynamic changes and endothelial dysfunction, with thrombophilia fulfill all the elements of the Virchow's triad. Therefore, the patient was at great risk for central vein thrombosis, from which he was possibly protected by the early administration of anticoagulant treatment. This case indicates that CVS can be asymptomatic for several years after CVC removal and also raises the question if thrombophilia workup and investigation for CVS may be beneficial in every patient with CVC placement in order to avoid any harmful outcomes.     

地铁集中供冷的几个问题

本文结合理论计算和广州地铁二号线集中冷站系统的工程实例,对地铁车站冷负荷、区间内冷冻水管尺寸限制、管网承压进行了分析,为地铁集中实施集中供冷提供了参考.     

Evaluating safety of tunneled small bore central venous catheters in chronic kidney disease population: A quality improvement initiative

Introduction: Peripherally inserted central venous catheters (PICCs) may adversely impact future successful arteriovenous fistulae (AVF). As part of a quality improvement project, the performance of tunneled small bore tunneled central venous catheters (TSB‐CVCs), as alternatives to PICCs, was evaluated. Methods: A retrospective observational study, involving individuals ≥18 years of age who underwent TSB‐CVC placement by Interventional Radiology at Mayo Clinic, Rochester, MN between 1/1/2010 and 8/30/2013. Findings: The study cohort included 92 patients with a median age of 55 (46–67) years, who underwent 108 TSB‐CVC placements. Baseline renal disease was present in 71% (77/108). Most TSB‐CVCs were placed in hospitalized patients (94%; 102/108); five French in diameter (61%; 66/108) and located in an internal jugular vein (84%; 91/108). Median catheter indwelling time was 20 (11–43) days (n = 84). TSB‐CVC‐related bloodstream infection, deep venous thrombosis (DVT), and superficial venous thrombosis (SpVT) rates per line were 0.009 (1/108), 0.018 (2/108), and 0.009 (1/108), respectively. Venous outcomes in a subgroup of 54 patients, who had documented PICC placements (n = 161) in addition to TSB‐CVC (n = 58) were compared. TSB‐CVC‐DVT rate was lower than the PICC‐DVT rate (0.017 [1/58] vs. 0.106 per line [17/161]; P = 0.04). The TSB‐CVC‐SpVT rate was not different from the PICC‐SpVT rate (0 [0/58] vs. 0.037 [6/161] per line; P = 0.14). Discussion: TSB‐CVCs demonstrated an excellent safety profile in our study. These catheters should be preferentially utilized for arm vein preservation in advanced kidney disease. Their impact on future AVF success needs further evaluation.     

Maintenance of blood flow rate on dialysis with self‐centering CentrosFLO catheter: A multicenter prospective study

Introduction Chronic central venous catheters (CVC) for dialysis lose patency and deliver lower blood flow over time, often due to fibrous sheathing that covers the lumen tips. The CentrosFLO central venous catheter has a shape that directs the arterial and venous tips away from the walls of the vena cava and right atrium, making sheathing of the tips less likely. Methods A prospective, multicenter, single arm, non‐controlled, observational study was conducted at eight sites in the United States. All consenting dialysis patients receiving CentrosFLO catheters through the right or left internal jugular veins were accepted in the study, as long as the catheter was expected to be used for 45 days and was not an over‐the‐wire replacement for a previous CVC. Data were automatically collected on initial and average dialysis blood flow rate and initial arterial and venous pressures, for up to 26 weeks of dialysis therapy. Findings 75 patients were enrolled. Kaplan‐Meier analysis indicated that 87% of patients maintained blood flow rate over 300 mL/min throughout 26 weeks of follow‐up. There was no decline in average dialysis blood flow rate and no significant change in hydraulic resistance of the arterial or venous lumens of the catheters during the study. Discussion The CentrosFLO catheter demonstrates long term patency with good flow rates on dialysis, which, by comparison with previous studies, shows a clinically significant improvement in blood flow rate vs. other catheters. Stable hydraulic resistance of the catheter lumens showed no evidence of tip encroachment by fibrous sheaths.     

Air-Bubble Method of Locking Central-Vein Catheters for Prevention of Hub Colonization: A Pilot Study

Background: The major source of catheter‐associated bacteremia is contamination of the catheter hub during connection–disconnection procedures. A new method of catheter locking has been developed wherein anticoagulant is injected first, followed by a 0.1‐mL air bubble and 0.9 mL of bactericidal solution. The anticoagulant is then located at the catheter tip and the bactericidal solution is located at the catheter hub. The air bubble prevents mixing of the two solutions. The bactericidal solution was acidified concentrated saline (ACS). The 27% saline solution has a pH of 2.0. ACS was chosen because it is theoretically harmless if injected in the amount used to lock the catheter lumens. The goals of this pilot study were to determine whether the new method of catheter locking is easy to perform with available syringes and whether eventual injection of the experimental solution is well tolerated. Methods: Ten patients were randomly assigned, either to heparin lock (5 patients, 62 treatments) or air‐bubble method (5 patients, 56 treatments). In the control group, the catheters were locked with heparin, 5000 U/mL. In the experimental group, the catheters were locked with heparin, air bubble, and ACS. Altogether, the lumens were overfilled by 0.2 mL. Results: Compared to the routine method, the experimental method required a 1‐ to 2‐min‐longer procedure time. There were no errors in proper sequence of injections into the lumina. There were no episodes of bacteremia related to hub contamination in either group. In the air‐bubble group, there was one case of bacteremia associated with purulent drainage from the exit and the same organism in both cultures. In three instances in each group, the locking solution could not be aspirated and was injected without any subjective symptoms or objective signs. Conclusion: We conclude that the air‐bubble method of locking central‐vein catheters is easy to perform. In three instances of air‐bubble and ACS injection, there were no adverse effects. A full‐scale prospective randomized study is feasible and warranted.     

Alteplase vs. urokinase for occluded hemodialysis catheter: A randomized trial

Introduction Thrombosis of tunneled central venous catheters (CVC) in hemodialysis (HD) patients is common and it can lead to the elimination of vascular sites. To compare the efficacy of alteplase vs. urokinase in reestablishing adequate blood flow through completely occluded vascular catheters. Methods In this randomized study, patients with completely occluded tunneled HD catheters received 40 minutes intracatheter dwell with alteplase (1 mg/mL) or urokinase (5000 IU/mL). Primary endpoint was the proportion of patients with occluded catheters achieving post‐thrombolytic blood flow of ≥250 mL/min. Safety endpoints included the incidence of hemorrhagic and infectious complications. Findings Eligible adult patients (n = 100) were treated with alteplase (n = 44) or urokinase (n = 56). The two groups were similar in gender (male: 51.8% vs. 56.8%, P = 0.35), age (60 ± 12 vs. 59 ± 13 years, P = 0.71), time on dialysis (678 ± 203 vs. 548 ± 189 days, P = 0.77), diabetes and cardiovascular disease (55.6% vs. 70.4%, P = 0.08 and 17.8% vs. 22.7%, P = 0.38, respectively), jugular vein as main vascular access (54.8% vs. 62.5%, P = 0.57), and time of CVC (278 ± 63 vs. 218 ± 59 days, P = 0.67). Primary success with alteplase and urokinase occurred in 42/44 (95%) vs. 46/56 (82%), P = 0.06. Success was not achieved after the second dose of alteplase and urokinase in 1 and 7 cases, respectively (2% vs. 12%, P = 0.075). Serious adverse effects were not observed in both groups. There was no difference between the two groups in infectious complications (P = 0.94). Discussion Alteplase and urokinase are effective thrombolytic agents for restoring HD catheter patency. Our study has revealed a likely slight superiority of alteplase over urokinase for unblocking central lines, but which has enrolled too few patients to be able to detect a difference of this size.     

中央空调系统水泵变频应用中存在的几个问题

本文分析了中央空调系统中水泵变频及其运行管理方面所存在的影响节能效果与运行管理质量的几个主要问题 ,提出了相应的解决办法 ,并对中央空调系统水泵变频决策与运行管理提出了几点建议。     

Use of an alteplase algorithm for the management of hemodialysis catheter dysfunction

Hemodialysis (HD) catheter dysfunction compromises HD adequacy and increases the cost of patient care. Repeated administration of alteplase in HD catheters typically produces only short-term benefits. The purpose of this study was to design, implement, and evaluate the efficacy of an experimental alteplase algorithm to manage HD catheter dysfunction. This was a two-part prospective nonrandomized study. Baseline data of alteplase use and catheter exchange were collected during part 1 of the study. Part 2 consisted of the alteplase algorithm implementation and repeat collection of catheter data. Rates of alteplase use and catheter exchange per 1000 catheter-days were the primary and secondary outcomes of the study. One hundred and seventy-two catheters in 131 patients were followed prospectively during the course of the study. The adjusted relative rate (RR) of alteplase use showed no significant difference between both parts of the study, adjusted RR: 1.10, 95% confidence interval (CI) (0.73-1.65). Similarly, catheter exchange rates were not significantly different over the duration of the study (1.12 vs. 1.03 per 1000 catheter-days). However, waiting time for catheter exchange increased from 20.36 ± 14 days in part 1 to 38.42 ± 28 days in part 2 (P < 0.05). The alteplase algorithm did not significantly reduce alteplase use. This may be partially explained by repeated use of alteplase in part 2, due to longer waiting times for catheter exchange procedures.     

深圳某中央空调教学设备系统设计及节能措施

中央空调教学设备系统是作为空调专业的辅助教学工具，其设计不同与一般中央空调的设计，本文就中央空调教学设备系统的设计过程及设计中的节能措施和几个具体问题处理做了具体说明。     

Challenges of long-term vascular access in pediatric hemodialysis: Recommendations for practitioners

Kidney transplantation is the preferred treatment of end-stage renal disease in children. However, time to transplant varies, making a well-functioning long-term vascular access essential for performing hemodialysis efficiently and without disruption until a kidney becomes available. However, establishing long-term vascular access in pediatric patients can present distinct challenges due to this population's unique characteristics, such as smaller body size and lower-diameter blood vessels. There are three main pediatric long-term vascular access options, which include central venous catheters (CVC), arteriovenous fistula (AVF), and arteriovenous graft (AVG). CVC are currently the most widely used modality, although various studies and guidelines recommend AVF or AVG as the preferred option. Although AVF should be used whenever possible, it is crucial that clinicians consider factors such as patient size, physical exam findings, comorbidities, predicted duration of treatment to decide on the most optimal long-term vascular access modality. This article reviews the three long-term vascular access methods in children and the benefits and complications of each.