Hemodialysis catheter tip design: observations on fluid flow and recirculation.

PURPOSE: To observe fluid flow patterns and measure recirculation rates of tunneled hemodialysis catheters using a mechanical model that simulates hemodialysis treatment. MATERIALS AND METHODS: Nine tunneled hemodialysis catheters were evaluated using a mechanical model that simulated catheter conditions during a routine hemodialysis treatment. Objective and subjective determinants of catheter performance were measured and compared. Catheters were evaluated with blood lines connected in standard and reversed configurations using a fluid flow rate of 425 ml/min. RESULTS: With blood lines in standard configuration the Split Cath® was the only catheter to exhibit an atypical fluid flow pattern and significant tip movement. When the blood lines were reversed, three split-tip catheters had significant tip movement. The three step-tip catheters and two symmetric tip catheters had stable fluid flow patterns and no significant tip movement with blood lines connected in standard and reverse configurations.The nine catheters had no recirculation when connected in standard configuration. When the blood lines were reversed the percentage of recirculating fluid for symmetric tip, step-tip, and split-tip catheters was 0%, 15% to 20%, and 20% to 30%, respectively. The Equistream®, Palindrome™, and Symetrex catheters had no recirculation with blood lines connected in standard or reversed configurations. CONCLUSIONS: Eight of the nine catheters evaluated in this study performed well with blood lines connected in standard configuration. When blood lines were reversed, symmetric tip and step-tip designs had more stable fluid flow patterns, less tip movement and lower recirculation rates when compared to split-tip designs.

GAVeCeLT* consensus statement on the correct use of totally implantable venous access devices for diagnostic radiology procedures.

The use of totally implantable venous access devices in radiology may be associated with complications such as occlusion of the system (because of the high density of some contrast), infection (if the port is not handled in aseptic conditions, using proper barrier protections), and mechanical complications due to the high-pressure administration of contrast by automatic injectors (so-called power injector), including extravasation of contrast media into the soft tissues, subintimal venous or myocardial injection, or serious damage to the device itself (breakage of the external connections, dislocation of the non-coring needle, or breakage of the catheter). The last problem - i.e., the damage of the device from a power injection - is not an unjustified fear, but a reality. A warning by the US Food and Drug Administration of July 2004 reports around 250 complications of this kind, referring to both port and central venous catheters and peripherally inserted central catheter systems, which occurred over a period of several years; in all cases, the damage occurred during the injection of contrast material by means of power injectors for computed tomography or magnetic resonance imaging procedures. Though the risk associated with the use of ports in radiodiagnostics is thus clear, it has been suggested that administration of the contrast material via the port may have some advantage in terms of image quality, increased comfort for the patient, and maybe more accurate reproducibility of the patient's own follow-up exams. This contention needs to be supported by evidence. Also, since many cancer patients who need frequent computed tomography studies already have totally implantable systems, it would seem reasonable to try to define how and when such systems may safely be used. The purpose of this consensus statement is to define recommendations based on the best available evidence, for the safe use of implantable ports in radiodiagnostics.

Guidelines for venous access in patients with chronic kidney disease. A Position Statement from the American Society of Diagnostic and Interventional Nephrology, Clinical Practice Committee and the Association for Vascular Access.

At the time of hemodialysis vascular access evaluation, many chronic kidney disease patients already have iatrogenic injury to their veins which impedes the surgical construction of an arteriovenous fistula (AVF). Achieving the important goal of a greater prevalence of arteriovenous fistulae in the US hemodialysis population will require identification of those patients prior to reaching end-stage renal disease and an educational and procedural system for preserving their veins.

Use of stents and stent grafts to salvage angioplasty failures in patients with hemodialysis grafts.

To determine the efficacy of using stents and stent grafts for treatment of hemodialysis graft-related stenoses which have failed angioplasty. This retrospective study was composed of 51 patients with polytetrafluoroethylene hemodialysis grafts who underwent angioplasty of a graft-related stenosis but subsequently required insertion of a stent or stent graft. The study group included 40 patients with >30% residual stenosis and 11 patients with angioplasty-induced venous ruptures. The patient's medical records and radiology reports were reviewed. Patient demographics, indication for stent placement, and the type of stent were recorded. Stent patency was determined using Kaplan-Meier analysis. A total of 70 stents were used; most (57.7%) were deployed across the venous anastomosis. A variety of different types of stents and stent grafts were used including 26 SMART, 18 Viabahn, 13 aSpire, and 13 other stents. The technical success rate for insertion of the device was 100%. Following insertion of the device the primary patency of the vascular access was 81%, 70%, and 54% at 1, 3, and 6 months, respectively. The secondary patency of the vascular access was 89%, 82%, and 74% at 3, 6, and 12 months, respectively. The primary patency of the stent or stent graft was 96%, 93%, 87%, and 47% at 1, 3, 6, and 12 months, respectively. Stents and stent grafts are useful for salvaging failed angioplasty procedures and thereby maintaining patency of the hemodialysis graft. By inserting a stent, the resultant patency rates are similar to those following a successful angioplasty procedure. Importantly, the primary patency of the stent was substantially better than the primary patency of the entire vascular access.

Role of stents and stent grafts in management of hemodialysis access complications.

Different types of complications may occur during a percutaneous vascular access procedure and the majority of these complications are caused by balloon angioplasty. These balloon angioplasty-induced complications include venous rupture, venous dissection, and the development of an acute pseudoaneurysm. Balloon tamponade is the traditional percutaneous technique for management of these complications. However, insertion of a stent or stent graft has become an increasingly popular method to quickly and effectively repair a venous injury. A stent or stent graft may provide a more effective and durable method to treat balloon angioplasty-induced complications. Unfortunately, there are few, if any, clinical studies to substantiate the advantages and cost-effectiveness of these devices and so their use remains controversial.

A position statement from the American Society of Diagnostic and Interventional Nephrology.

A procedure-related complication is an unanticipated adverse event that requires therapy. In order to analyze frequency and severity of complications in the process of quality assurance, it is useful to have a classification of complications, indicating the type and severity. The Clinical Practice Committee of American Society of Diagnostic and Interventional Nephrology has developed a Classification of Complications relating to Hemodialysis Vascular Access Procedures, based on the system first proposed by Beathard in 2006. In this system, the "type" refers to the procedure being performed or vessel entered, and the "grade" is based on the intensity of medical care needed to address the complication. This publication describes 10 Types and 4 Grades of complications.

Günther Tulip filter retrievability multicenter study including CT follow-up: final report.

PURPOSE: To evaluate the safety and effectiveness of retrieval of the Günther Tulip inferior vena cava (IVC) filter. MATERIALS AND METHODS: This was a nonrandomized, single-armed, multicenter prospective investigation. Patients at temporary high risk for pulmonary embolism (PE) or deep vein thrombosis (DVT) who did not require a permanent filter were eligible. Forty-one patients received 42 Günther Tulip filters: 22 men and 19 women with a mean age of 47.7 years. Indications for filter placement included prophylaxis, PE, and DVT. Three months after filter retrieval, contrast agent-enhanced computed tomography of the abdomen, jugular vein ultrasonography, and clinical follow-up were performed. RESULTS: The filter retrieval rate was 57% (23 of 41). Günther Tulip filters were removed at a mean of 11.1 days (range, 2-14 d). The technical and clinical success rates for filter retrieval were both 100%. One placement complication and two protocol deviations occurred. These patients were excluded in terms of retrieval-related outcomes. One case of PE occurred with a filter in place, and one filter migrated to the heart. There were no acute complications caused by filter retrieval. At 3-month follow-up, there was no recurrent PE, DVT, jugular vein occlusion, or IVC stenosis or occlusion. CONCLUSION: In this multicenter study, retrieval of the Günther Tulip filter was safe and without recurrent thromboembolic events or evidence of IVC or jugular vein damage at 3-month follow-up.

Angioplasty balloon inflation pressures during treatment of hemodialysis graft-related stenoses.

PURPOSE: This two-part prospective investigation was designed to determine the balloon inflation pressures required to dilate stenoses associated with hemodialysis grafts and evaluate the burst pressures of five different angioplasty balloons. MATERIALS AND METHODS: Eighty-nine patients with dysfunctional hemodialysis grafts were enrolled and underwent fistulography. The diagnostic studies revealed 104 stenoses, which were treated with balloon angioplasty. The characteristics of these stenoses and the balloon inflation pressures required to dilate the lesions were recorded. In part two of this investigation, the burst pressures of five different angioplasty balloons were evaluated immediately after their use during angioplasty procedures. Twenty-five balloons of each type were inflated until the balloon burst or 30 atm of pressure was achieved. Several different statistical tests were used to analyze the data set. RESULTS: The mean balloon inflation pressure required to dilate all 104 stenoses was 17.2 atm. Subgroup analysis revealed that the mean balloon inflation pressure required to dilate 75 venous anastomotic stenoses was 17.9 atm and that a mean pressure of 15.6 atm was required to dilate 29 stenoses located within the native outflow veins. The angioplasty balloon burst pressure experiments revealed that the majority of the tested balloons can be inflated to pressures 5-6 atm greater than the manufacturers' rated burst pressures. However, the margin of safety for overinflation was variable among the balloons tested, and angioplasty balloons experience fatigue with repeated inflations. CONCLUSION: The majority of stenoses associated with hemodialysis grafts can be successfully dilated with use of available high-pressure angioplasty balloons.

Use of the peripheral cutting balloon to treat hemodialysis-related stenoses.

PURPOSE: To compare the effectiveness and safety of use of the peripheral cutting balloon (PCB) versus standard percutaneous transluminal angioplasty (PTA) for the treatment of hemodialysis-related stenoses. MATERIALS AND METHODS: This prospective, randomized multicenter clinical trial included 340 patients with stenotic or thrombosed hemodialysis grafts who were randomized to receive treatment with the PCB or PTA for venous outflow stenosis. One hundred seventy-three patients underwent treatment with the PCB, 101 with stenotic grafts and 72 with thrombosed grafts. PTA was used to treat 167 patients, 94 patients with stenotic grafts and 73 with thrombosed grafts. The follow-up period extended for 6 months. RESULTS: The procedural success rates were 80.8% and 75.4% for the PCB and PTA groups, respectively (P = .24). With use of the PCB, the primary patency rates of the target lesions were 84.3%, 65.8%, and 47.9% at 1 month, 3 months, and 6 months, respectively. With PTA, the primary patency rates of the target lesions were 77.7%, 63.4%, and 40.5% at 1 month, 3 months, and 6 months, respectively. The primary patency rates of the entire vascular access circuit were 82.6%, 61.0%, and 43.3% at 1 month, 3 months, and 6 months, respectively, with use of the PCB. For patients who were treated with PTA, the primary patency rates of the vascular access circuit were 75.9%, 61.0%, and 36.3% at 1 month, 3 months, and 6 months, respectively. When comparing the PCB and PTA, there was no difference in the 6-month primary patency rates in the target lesion (P = .373) or the entire vascular access circuit (P = .531). There were nine device-related complications in the PCB group (5.2%): five venous ruptures (2.9%), three venous dissections (1.7%), and one case of thrombosis (0.6%). There were no device-related complications in the PTA group. CONCLUSION: This prospective, randomized trial comparing use of the PCB versus standard PTA for treatment of hemodialysis-related venous stenoses demonstrated that the PCB provides equivalent 6-month patency to PTA for stenotic and thrombosed grafts.

Bench-top evaluation of air flow through a valved peelable introducer sheath.

PURPOSE: Air embolism is a rare but potentially fatal complication that may occur during the insertion of a central venous catheter. A valved peelable introducer sheath was developed to reduce the likelihood of an air embolus. This study was performed to determine the rate of air flow through this valved introducer sheath under different conditions that may be encountered in a clinical setting. MATERIALS AND METHODS: A 16-F-diameter valved peelable introducer sheath was used for all experiments. A bench-top testing system was constructed that consisted of a vacuum source, a mass flow meter, and a digital vacuum gauge. A coupling device with a pneumatic O-ring was used to seal and connect the distal end of the introducer sheath to the testing system. A vacuum of -5 mm Hg was applied to the sealed distal end of the sheath to simulate physiologic conditions. The rate of air flow through the valved sheath was measured under three different conditions; (i) valve open, (ii) valve closed, and (iii) valve open but with the sheath manually pinched. Thirty air flow measurements were performed for each of the three test conditions. RESULTS: When the valve was in the open position, the mean rate of air flow through the introducer sheath was 417.2 mL/sec (range, 415.5-419.7 mL/sec). When the valve was in the closed position, the mean rate of air flow was 0.004 mL/sec (range, 0.000-0.067 mL/sec). When the valve was open but the sheath was manually pinched, the mean rate of air flow through the sheath was 31.7 mL/sec (range, 23.0-38.8 mL/sec). During the 90 testing procedures, the mean vacuum was -5.10 mm Hg (range, -5.00 to -5.45 mm Hg). CONCLUSIONS: This bench-top study revealed that a massive amount of air flowed through the open 16-F introducer sheath when it was subjected to a vacuum of -5 mm Hg, a situation that may occur under normal physiologic conditions. The rate of air flow could be decreased by aggressively pinching the sheath but the rate of air flow was still substantial. This study demonstrated that the addition of a sophisticated valve mechanism can essentially eliminate air flow through a peelable introducer sheath.

Use of stent grafts to repair hemodialysis graft-related pseudoaneurysms.

PURPOSE: To review the author's early experience with stent grafts to repair hemodialysis graft-related pseudoaneurysms. MATERIALS AND METHODS: Eleven patients had undergone insertion of a stent graft to repair a pseudoaneurysm arising from a PTFE hemodialysis graft. The study group consists of seven women and four men with a mean age of 50.7 years. The primary indications for stent graft placement were: rapid enlargement of a pseudoaneurysm in four patients, difficulty with cannulating the graft in two patients, high risk of acute rupture in three patients, persistent bleeding from the pseudoaneurysm in one patient, and one was incidentally discovered during diagnostic fistulography. In 10 of the 11 patients, the pseudoaneurysm arose from the arterial limb of a loop-configuration graft. A stent graft was successfully deployed in all patients. The radiological and surgical records were reviewed. RESULTS: The Viabahn endoprosthesis was successfully inserted and deployed in all 11 patients. Six patients underwent subsequent interventions, which ended primary patency at 39 days, 40 days, 63 days, 104 days, 120 days, and 327 days after insertion of the stent graft. However, no additional interventions have been performed in five patients and primary patency continues. In these five patients the interval of continuing primary patency is 55 days, 92 days, 103 days, 139 days, and 196 days. In this small group of patients the primary patency rate is 71% at 3 months and 20% at 6 months. DISCUSSION: Early experience has demonstrated that a stent graft can successfully exclude a pseudoaneurysm from a hemodialysis graft and may prevent further enlargement and decrease the likelihood of rupture. However, in two of these 11 patients, the large pseudoaneurysm remained problematic and required subsequent surgical repair.

Correlation of intragraft blood flow with characteristics of stenoses found during diagnostic fistulography.

PURPOSE: To determine if intragraft blood flow measurements correlate with the anatomical characteristics of stenoses found during diagnostic fistulography. MATERIALS AND METHODS: This investigation was a retrospective review of 40 patients with decreased intragraft blood flow (<600 mL/min) in patent polytetrafluoroethylene hemodialysis grafts who underwent diagnostic fistulography and angioplasty. Intragraft blood flow was measured with the ultrasonic dilution technique. The fistulogram images were reviewed and the anatomic characteristics of all stenoses were measured and recorded. These characteristics were correlated with the intragraft blood flow values. RESULTS: The mean intragraft blood flow was 476 mL/min (range, 270-600 mL/min). Fistulography revealed a total of 71 stenoses and all 40 patients had at least one lesion with > 50% stenosis. There was no correlation between the intragraft blood flow and the location, length, or number of stenoses. There was a moderate inverse correlation between the intragraft blood flow and the degree of stenosis (P =.08). Fifty-nine stenoses were treated with angioplasty. The mean postangioplasty blood flow was 796 mL/min (range, 470-1565 mL/min). The mean change in blood flow after angioplasty was 311 mL/min (range, 15-1154 mL/min) There was no association between the change in blood flow after angioplasty and the number, length, or degree of residual stenosis. CONCLUSION: Intragraft blood flow < 600 mL/min is an excellent predictor of the presence of at least one significant (>/=50%) stenosis. There was an inverse correlation between intragraft blood flow and the degree of stenosis. There was no association between the intragraft blood flow and the location, length, or number of stenosis.

Pharmacomechanical thrombolysis and early stent placement for iliofemoral deep vein thrombosis.

PURPOSE: To evaluate an approach to the treatment of iliofemoral deep vein thrombosis (DVT) that included pharmacomechanical catheter-directed thrombolysis with reteplase and the Helix mechanical thrombectomy device, followed by early stent placement. MATERIALS AND METHODS: During 3-year period, 23 symptomatic limbs in 18 patients with iliofemoral DVT were treated with reteplase catheter-directed thrombolysis. After an initial infusion of 8 to 16 hours, any residual acute thrombus over a long segment (> 10 cm) was treated by maceration with use of the Helix thrombectomy device. Residual short-segment (< 10 cm) iliac vein thrombus and/or stenosis were treated with stent placement. Technical success, clinical success, complications, thrombolytic infusion time, total thrombolytic agent dose, fibrinogen level changes, and late limb status were retrospectively analyzed. RESULTS: Technical success was achieved in 23 of 23 limbs (100%). Clinical success was achieved in 22 of 23 limbs (96%). Complete or partial thrombolysis was observed in 19 of 23 limbs (83%). Major bleeding was observed in one patient (6%) and necessitated blood transfusion. Mean per-limb thrombolytic infusion time and total dose were 19.6 hours +/- 8.1 and 13.8 U +/- 5.3 reteplase, respectively. Mean serum fibrinogen nadir and percentage drop in serum fibrinogen were 282 mg/dL +/- 167 and 47% +/- 24%, respectively. Late (mean, 19.8 +/- 11.6 months) modified Venous Disability Scores were 0 (none) for six limbs, 1 (mild) for 10 limbs, 2 (moderate) for two limbs, and 3 (severe) for no limbs. CONCLUSION: In a preliminary experience, pharmacomechanical catheter-directed iliofemoral DVT thrombolysis with early stent placement was safe and effective.