Vascular access patency

The assessment of patency of an implanted vascular graft or operation technique is a special modality of a clinical study. Valid comparisons on vascular access patency rates can be made only if patency is defined in a way that can be universally used by all specialties in a consistent manner [10]. Kaplan-Meier analysis is the most commonly used life table method in medical practice. It adequately copes with the issues such as patients for whom the event has not yet occurred and for those lost to follow-up. The data required by the method include the time of commencement of the treatment and the time the measured event occurred (e.g. thrombosis, infection). Patients who dropped out of treat-... 

S.K. Kakkos, R. Haddad, G.K. Haddad, D.J. Reddy, T.J. Nypaver, J.C. Lin, A.D. Shepard, Results of aggressive graft surveillance and endovascular treatment on secondary patency rates of Vectra Vascular Access Grafts, J. Vase. Surg. 45 (2007) 974-980. 

The first aspect of lead assessment is vascular access, that is, the venous route used. Identification of the venous route used is not critical, but there are two clinical reasons for attempting to identify the venous route. First, different stresses on the lead system exist at different venous sites. Second, if lead revision is planned, the options for new lead placement should be clear. Adjunctive dye studies may be helpful in determining vein patency or accessibility. Figure 18.7 demonstrates peripheral dye injection to determine the patency of the vein. 

The complication and patency rates of PTFE and PU grafts implanted for hemodialysis vascular access were compared by Kiyama et al. " by a long-term follow up of 53 patients who received 58 arteriovenous grafts between 1997 and 2000. Both problem-free (primary) and functional (secondary) patency rates for PU and PTFE grafts were similar at 1 year and 2 years. 

One issue with the use of blood gases as an endpoint in a safety pharmacology study is the technical challenge to collect them. For proper evaluation of respiratory effects, the blood sample must be collected from an artery which is difficult to locate in small species such as rats and difficult to obtain safely from any species without some form of physical or chemical restraint. As a modification for access, an arterial vascular access port (VAP) can be placed surgically, prior to study activities, but then requires subsequent careful maintenance to ensure patency. 

Considerable morbidity exists when dealing with vascular access (VA) creation. Native arteriovenous fistulae (AVF) are the desired VA for patients on dialysis due to their comparably low morbidity and fairly good long-term patency. However, they are also at risk for nonmaturation, stenosis, thrombosis, infection, aneurysm formation, and steal syndrome [ 1 ]. Fistula success is dependent on the center of access creation. Hence, the vascular surgeon s skills and decisions are key [2]. Furthermore, success is also determined by preoperative, technical, and postoperative factors that will be discussed in this chapter (fig. 1). 

Prolongation of access patency begins with developing and implementing a strategy to provide vascular access (VA) for the entire end-stage renal disease life by a VA specialist and constant reinforcement by a multidisciplinary dialysis care team along with active patient participation. 

Saran R, Elder SJ, Goodkin DA, Akiba T, Ethier J, Rayner HC, Saito A, Young EW, Gillespie BW, Merion RM, Pisoni RL Enhanced training in vascular access creation predicts arteriovenous fistula placement and patency in hemodialysis patients results from the Dialysis Outcomes and Practice Patterns Study. Ann Surg 2008 247 885-891. 

Catheter-related bacteraemia (CRB) and catheter dysfxmction are major sources of morbidity and mortality when central venous catheters (CVCs) are used as long-term vascular access devices in haemodialysis patients. Attempts have been made to minimise these complications by the prophylactic use of catheter locking solutions. The current study aims to describe the recent advances in the field of lock solutions and discusses the benefits and risks associated with the routine use of antimicrobial and/or antithrombotic lock solutions [ll J. These solutions may improve patency and CRB, but at the same time, these may be cost-prohibitive. 

Self-expanding stents with a higher radial force (e.g., WingSpan, Boston Scientific Corp.) will probably play a key role in acute stroke cases related to intracranial atherosclerotic disease. Antegrade flow is essential for the maintenance of vascular patency, as particularly evident in patients with severe proximal stenoses who commonly develop rethrombosis after vessel recanalization. Furthermore, stenting of the proximal vessels may be required in order to gain access to the intracranial thrombus with other mechanical devices or catheters. In a recent series, 23 of 25 patients (92%) with acute n = 15) or subacute n = 10) ICA occlusions were successfully revascularized with this technique. " ... 

Williams, S.K., D.G. Rose, and B.E. Jarrell, Microvascular endothelial ceU sodding of ePTFE vascular grafts Improved patency and stabihty of the cellular lining. / Btomed Mater Res, 1994.28(2) 203-12. Schmidt, S.P. et al.. Evaluation of expanded polytetrafluoroethylene arteriovenous access grafts onto which microvessel-derived cells were transplanted to improve graft performance Preliminary results. Ann Vase Surg, 1998.12(5) 405-11. 

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