How do we manage vascular access complications?
- Use of angioplasty insignificant stenosis of AV Fistula or AV graft. If this is not possible then revision is done.
- In AV a fistula aneurysm intervene only of the overlying skin is compromised or the aneurysm is expanding or there are limited puncture sites.
- AV graft surgery is done if the graft has degenerated or pseudo-aneurysm is present.
- Correct the thrombosis of the AV graft with thrombolysis or surgical thrombectomy.
- The commonest site of stenosis or thrombosis is near the AV anastomosis
- After correction, the parameters should return to within normal limits of patency.
When do we call it reasonable patency?
The goals of reasonable patency in the absence of thrombosis are:
- After Angioplasty – 50% unassisted patency at 6 months. No more than 30% residual stenosis after the procedure and resolution of physical indicators of stenosis.
- After surgical revision: 50% unassisted patency at 1 year.
- If angioplasty is needed more than 2 times in 3 months then surgical revision is considered.
- Stents are useful in selected cases when angioplasty fails:
Central venous stenosis
Limited residual access sites
Surgical inaccessible lesion
Contraindication to surgery
- Thrombosis should be corrected within 24 hours and the venous access then evaluated for stenosis by doing a fistulogram. Outflow venous stenosis is present in > 85% of the thrombosis in AV grafts. Angioplasty or surgical correction is performed.
Are there any problems after thrombolysis?
- Thrombolysis followed by angioplasty – 40% unassisted patency at 3 months
- Surgical thrombectomy and revision – 50% unassisted patency at 6 months and 40% at 1 year.
- Immediate patency 85% in both techniques
- The use of aspirin or warfarin in graft and fistula thrombosis has not been very encouraging.
- Treat hand ischemia due to arterial steal with distal revascularisation along with internal ligation procedure. If not possible then ligation of AV graft or AV fistula.
- Treat central vein thrombosis with angioplasty and stenting if necessary.
- Thrombosed hemodialysis catheters are treated with tPA.
How is steal syndrome treated?
Significant hand ischemia occurs in 2-8% after AV access Risk factors are:
- Female sex
- >60 years
- Use of the brachial artery as a donor site
Treatment is by ligating the artery distal to the fistula site and a short bypass from proximal to the inflow of AV access till just distal to the ligation. Immediate relief of the symptoms occur and 1-year patency was 70%
Central vein stenosis may cause marked limb swelling with AV access on the same side. Percutaneous angioplasty is helpful and if this repeatedly occurs when a stent is placed.
What are dysfunctional hemodialysis catheters?
This is a failure to perform hemodialysis based on catheter-related thrombotic or mechanical factors. It could be due to the formation of a fibrin sheath within the catheter which acts as a nidus for thrombosis. tPA can restore the patency. 2 mg of tPA in each lumen for 24 hours makes them patent in 80%. If there is a contraindication to the use of tPA then the catheter needs to be changed over a guide wire or the fibrin sheath stripped.
What is the role fo antibiotics in infected venous access?
- Treat extensive infection of the AV Graft with parenteral antibiotics and graft excision.
- Treat infections of the primary AV fistulas as subacute endocarditis with 6 weeks antibiotics.
- Treat Central venous catheters related bacteria with systemic antibiotics and catheter exchange over a guide wire.
- Treat central tunnel infection without bacteremia with systemic antibiotics appropriate local measures. Remove catheter if it fails to resolve in 2 weeks of therapy
- Central venous catheters are associated with a significantly higher risk of bacteremia compared to AV Fistulas. With AV Grafts the risk is moderate. The grafts must be removed under systemic antibiotic cover.
- If there is bacteria in any of these venous accesses start with broad-spectrum antibiotics like cefazolin along with gentamycin after the drawing of blood cultures. If the patient is allergic to cefazolin then substitute vancomycin.
- The sensitive antibiotics are given for 2-4 weeks
- Central venous catheters should be removed rather than exchanged over a guidewire if the patient is unstable or symptomatic for over 36 hours.
- The new catheter should not be placed until the blood culture taken 48 hours after the cessation of antibiotics has been negative.
- If the catheter exit site shows redness, crusting or exudate but no systemic symptoms and negative blood cultures just care for the local site and perhaps oral antibiotics. The catheter need not be removed.
- If infection fails to come under control within 2 weeks despite therapy replace the catheter and place another one at a different site.
What is the quality of care standards in venous access?
- 60% of the venous access would be AV fistulas
- A rate of Graft thrombosis should be less than 0.5 thrombotic episodes per patient-year at risk.
- After the first 2 months, the rate of thrombosis should be < 0.25 episodes per patient-year at risk.
- The rate of infection should be below 0.01 episode per patient-year at risk for primary AV Fistulas and 0.1 episodes per patient-year at risk for AV Grafts.
- For tunneled cuffed grafts the target rate of systemic infection is < 0.5 episodes per patient-year at risk.
- The primary failure rates for AV Grafts in the forearm straight grafts should be < 15%, < 10% in forearm loop grafts and < 5% in the upper arm grafts.
- The cumulative patency rates for all AV Grafts should be > 70% at one year, > 60% at 2 years and > 50% at 3 years.