**3.2.2 Arteriovenous graft**

AVGs (Figure 10-12) were the most commonly used type of dialysis access in the U.S. [62]. However, they do not last as long as AVFs and they have higher rates of infection and thrombosis [52]. Grafts present a second choice of VA when AVF is not able to be performed because of vascular problems. They can be placed in the forearm, the upper arm, and the thigh, and can have a straight, curved or loop configuration. They may offer a large surface area for cannulation. AVGs can be cannulated about 2-3 weeks after placement, although there are studies suggesting that immediate assessment after placement for PTFE AVGs is possible [63, 64]. This interval is needed in order to allow the surrounding tissue to adhere to the PTFE conduit, to reduce the postsurgical oedema and the risk for local complications such as perigraft hematoma and seroma [65].

Fig. 10. Upper arm AVG

Fig. 11. Looped Forearm AVG

Fig. 12. Straight femoral AVG

Vascular Access for Hemodialysis 53

be well tolerated, and as the child becomes larger in size, a larger volume access can be placed [78]. Vascular access should be able to provide sufficient blood flow and adequate dialysis with a Kt/V greater than 1.2. A recommended flow rate of 3 to 5 mL/kg/min is acceptable in most patients due to the fact that flow rates in paediatrics vary by the size of

Studies have shown a mortality risk dependent on access type, with the highest risk associated with central venous dialysis catheters, followed by AVGs and then AVFs [80, 81]. Additionally, patients who had a catheter as first VA, had more complications and higher mortality [82]. Same results have been presented by Ng LJ et al who examined hospitalization burden related to VA type among 2635 incident patients [83]. The CHOICE study examined mortality based on access type in 616 hemodialysis patients for up to 3 years of follow-up. Central venous catheters and AVGs were associated with approximately 50% and 26% increased mortality respectively, compared with AVFs with prevalence in men and elderly patients [84, 85]. Despite these findings and the KDOQI recommendations, dialysis access data from 2002–2003 showed that only 33% of prevalent hemodialysis patients in the US were being dialyzed via AVFs. On the contrary in Europe and Canada, the majority of the patients (74% and 53% respectively) were being dialyzed

Vascular access admissions continue to fall, with more procedures now performed in an outpatient setting, and are 45% below than in 1993. Among African American patients, the relative risk of an all-cause hospitalization or one related to infection is almost equal to that of Caucasians; the risk of a vascular access hospitalization, however, is 24 percent higher [87]. Thrombotic occlusion remains a major event, leading to permanent failure in 10% of AVFs and 20% of grafts each year. Interventional (percutaneous transluminal angioplasty and/or stent implantation) or surgical revision of thrombosed accesses has similar outcomes with a high rate of reinterventions. The elderly diabetic population with peripheral arteriosclerotic obstructive disease is in particularly prone to angio-access induced hand ischemia. [88]. It has been shown that patients with AVGs and TCs have higher levels of chronic inflammation than those with AVFs, and increased requirements in epoetin [89]. In our previous work with 149 hemodialysis patients who had undergone 202 vascular access procedures (177 Cimino-Brescia fistulae and 25 PTFE grafts) we found that the Cimino-Brescia fistula was used as the first choice of vascular access in all patients, except one in the elderly group. PTFE grafts were the second or third choice in 7 patients younger than 65 and 15 in the elderly group (p: NS). The only reason for technique failure was vascular thrombosis in both groups (p: NS). Other complications were: aneurysms (10/48 and 14/101, p: NS), infections (0/48 and 2/101 p: NS) and oedema (0/48 and 6/101, p: NS). (Table 1) Five-year technique survival of the first AV fistula in the two groups was 35% and 45% respectively (log-rank test, p: NS). (Figure 13) Our findings suggested that there was no difference in vascular access complications across age groups and the survival of the first AV fistula was independent of age [8]. Similar reports have been published by Swindlehurst N et all according to which the creation of permanent hemodialysis access in the elderly with AVF is not only possible but also proved to have a short hospital stay, high patency rates, and an acceptable rate of

catheter depending on the size of the patient, [79].

via AVFs [86].

further intervention [90].

**5. Vascular access complications and survival** 

#### **3.2.3 Tunnelled hemodialysis catheter**

TCs (Figure 2,3) are used when AVFs or AVGs are not possible to be created for several reasons such as multiple vascular surgeries, which lead to vascular thrombosis, or when patients have severe peripheral vascular disease or very low cardiac output. This is more frequently encountered in paediatric and very old patients.

Unfortunately, these are associated with the highest infection rate and they are not a very long-term access option. Studies have revealed that central venous catheters are colonized within 10 days of placement; however, colonization of the catheter biofilm does not correspond to positive blood cultures or clinical signs of bacteremia [66]. It seems that outcome of the infection treatment does not differ if, in addition to antibiotic therapy, the catheter will be guidewire changed or completely removed [67]. Recently Power A. et al published their experience with 759 TCs. The survival rate at 1, 2 and 5 years was 85%, 72% and 48% respectively. The infection rate was 0.34 per 1000 catheter days showing that with careful and appropriate use of TCs, they can provide effective and adequate long-term hemodialysis and rates of access related infection almost similar to AVGs' [68].

When conventional venous accesses have been exhausted and peritoneal dialysis is impossible, it is mandatory to use alternative procedures for VA in order to continue HD. Translumbar inferior vena caval CVCs belong to this category and it seems that they can offer relatively safe and effective long-term HD access [69]. Another alternative is the transhepatic hemodialysis catheters; they seem to be a potentially viable option with low rates of morbidity due to placement, high rates catheter-related maintenance and possibility of long-term functionality [70].

#### **4. Hemodialysis vascular access in children**

The choice of replacement therapy in children is variable. The registry of the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) reports that of patients initiating renal replacement therapy in paediatric centres [71, 72]: one quarter of children underwent preemptive renal transplantation, one half were started on peritoneal dialysis and one quarter were started on hemodialysis. Kidney transplantation remains the preferred therapy for paediatric patients. Therefore, many of them receive maintenance HD through an indwelling catheter in perspective of short HD period [73]. In the United States, less than 800 paediatric patients receive maintenance HD therapy. The majority of smaller patients especially those less than 10kg or less than 2 years old, receive PD [74-76].

However, hemodialysis can be performed successfully in infants and very young children, as well [77]. Children who will undergo hemodialysis will need evaluation of their vasculature for placement of an arteriovenous (AV) fistula, arteriovenous graft, or cuffed double lumen catheter. The use of an AV fistula, which is the recommended type of vascular access in adults, is limited in children due to the size of their vessels. In the 2008 NAPRTCS annual report, vascular access for hemodialysis included external percutaneous catheter in 78% of patients, internal AV fistula in 12%, and internal and external AV shunt in 7.3 and 0.7 %, respectively [72]. K/DOQI has encouraged greater use of AV fistulas in larger children receiving hemodialysis who are not likely to receive a transplant within 12 months, with a goal of achieving more effective dialysis with fewer complications than the ones occuring with catheters. The choice of catheter size and configuration depends on the size of the patient. It is suggested that in children as small as 4 to 5 kg, a dual-lumen 8 Fr catheter can

TCs (Figure 2,3) are used when AVFs or AVGs are not possible to be created for several reasons such as multiple vascular surgeries, which lead to vascular thrombosis, or when patients have severe peripheral vascular disease or very low cardiac output. This is more

Unfortunately, these are associated with the highest infection rate and they are not a very long-term access option. Studies have revealed that central venous catheters are colonized within 10 days of placement; however, colonization of the catheter biofilm does not correspond to positive blood cultures or clinical signs of bacteremia [66]. It seems that outcome of the infection treatment does not differ if, in addition to antibiotic therapy, the catheter will be guidewire changed or completely removed [67]. Recently Power A. et al published their experience with 759 TCs. The survival rate at 1, 2 and 5 years was 85%, 72% and 48% respectively. The infection rate was 0.34 per 1000 catheter days showing that with careful and appropriate use of TCs, they can provide effective and adequate long-term

When conventional venous accesses have been exhausted and peritoneal dialysis is impossible, it is mandatory to use alternative procedures for VA in order to continue HD. Translumbar inferior vena caval CVCs belong to this category and it seems that they can offer relatively safe and effective long-term HD access [69]. Another alternative is the transhepatic hemodialysis catheters; they seem to be a potentially viable option with low rates of morbidity due to placement, high rates catheter-related maintenance and possibility

The choice of replacement therapy in children is variable. The registry of the North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) reports that of patients initiating renal replacement therapy in paediatric centres [71, 72]: one quarter of children underwent preemptive renal transplantation, one half were started on peritoneal dialysis and one quarter were started on hemodialysis. Kidney transplantation remains the preferred therapy for paediatric patients. Therefore, many of them receive maintenance HD through an indwelling catheter in perspective of short HD period [73]. In the United States, less than 800 paediatric patients receive maintenance HD therapy. The majority of smaller

However, hemodialysis can be performed successfully in infants and very young children, as well [77]. Children who will undergo hemodialysis will need evaluation of their vasculature for placement of an arteriovenous (AV) fistula, arteriovenous graft, or cuffed double lumen catheter. The use of an AV fistula, which is the recommended type of vascular access in adults, is limited in children due to the size of their vessels. In the 2008 NAPRTCS annual report, vascular access for hemodialysis included external percutaneous catheter in 78% of patients, internal AV fistula in 12%, and internal and external AV shunt in 7.3 and 0.7 %, respectively [72]. K/DOQI has encouraged greater use of AV fistulas in larger children receiving hemodialysis who are not likely to receive a transplant within 12 months, with a goal of achieving more effective dialysis with fewer complications than the ones occuring with catheters. The choice of catheter size and configuration depends on the size of the patient. It is suggested that in children as small as 4 to 5 kg, a dual-lumen 8 Fr catheter can

patients especially those less than 10kg or less than 2 years old, receive PD [74-76].

hemodialysis and rates of access related infection almost similar to AVGs' [68].

**3.2.3 Tunnelled hemodialysis catheter** 

of long-term functionality [70].

**4. Hemodialysis vascular access in children** 

frequently encountered in paediatric and very old patients.

be well tolerated, and as the child becomes larger in size, a larger volume access can be placed [78]. Vascular access should be able to provide sufficient blood flow and adequate dialysis with a Kt/V greater than 1.2. A recommended flow rate of 3 to 5 mL/kg/min is acceptable in most patients due to the fact that flow rates in paediatrics vary by the size of catheter depending on the size of the patient, [79].

#### **5. Vascular access complications and survival**

Studies have shown a mortality risk dependent on access type, with the highest risk associated with central venous dialysis catheters, followed by AVGs and then AVFs [80, 81]. Additionally, patients who had a catheter as first VA, had more complications and higher mortality [82]. Same results have been presented by Ng LJ et al who examined hospitalization burden related to VA type among 2635 incident patients [83]. The CHOICE study examined mortality based on access type in 616 hemodialysis patients for up to 3 years of follow-up. Central venous catheters and AVGs were associated with approximately 50% and 26% increased mortality respectively, compared with AVFs with prevalence in men and elderly patients [84, 85]. Despite these findings and the KDOQI recommendations, dialysis access data from 2002–2003 showed that only 33% of prevalent hemodialysis patients in the US were being dialyzed via AVFs. On the contrary in Europe and Canada, the majority of the patients (74% and 53% respectively) were being dialyzed via AVFs [86].

Vascular access admissions continue to fall, with more procedures now performed in an outpatient setting, and are 45% below than in 1993. Among African American patients, the relative risk of an all-cause hospitalization or one related to infection is almost equal to that of Caucasians; the risk of a vascular access hospitalization, however, is 24 percent higher [87]. Thrombotic occlusion remains a major event, leading to permanent failure in 10% of AVFs and 20% of grafts each year. Interventional (percutaneous transluminal angioplasty and/or stent implantation) or surgical revision of thrombosed accesses has similar outcomes with a high rate of reinterventions. The elderly diabetic population with peripheral arteriosclerotic obstructive disease is in particularly prone to angio-access induced hand ischemia. [88]. It has been shown that patients with AVGs and TCs have higher levels of chronic inflammation than those with AVFs, and increased requirements in epoetin [89]. In our previous work with 149 hemodialysis patients who had undergone 202 vascular access procedures (177 Cimino-Brescia fistulae and 25 PTFE grafts) we found that the Cimino-Brescia fistula was used as the first choice of vascular access in all patients, except one in the elderly group. PTFE grafts were the second or third choice in 7 patients younger than 65 and 15 in the elderly group (p: NS). The only reason for technique failure was vascular thrombosis in both groups (p: NS). Other complications were: aneurysms (10/48 and 14/101, p: NS), infections (0/48 and 2/101 p: NS) and oedema (0/48 and 6/101, p: NS). (Table 1) Five-year technique survival of the first AV fistula in the two groups was 35% and 45% respectively (log-rank test, p: NS). (Figure 13) Our findings suggested that there was no difference in vascular access complications across age groups and the survival of the first AV fistula was independent of age [8]. Similar reports have been published by Swindlehurst N et all according to which the creation of permanent hemodialysis access in the elderly with AVF is not only possible but also proved to have a short hospital stay, high patency rates, and an acceptable rate of further intervention [90].

Vascular Access for Hemodialysis 55

increased risk of pneumothorax and atrial perforation which can be presented with acute hemopericardium upon initiation of dialysis. Internal jugular vein is the preferred site of insertion because of subclavian stenosis and loss of the ipsilateral arm for future hemodialysis access. This complication appears to occur more often with subclavian (40 to 50 %) than with internal jugular insertions (up to 10 %) [96, 97]. At internal jugular insertions a carotid artery penetration may occur, but there is also a lower risk of

Prevention and treatment of catheter thrombosis are important clinical issues. To prevent formation of thrombus, both lumens of the double lumen catheter are instilled with heparin following hemodialysis [41]. Lytic agents such as urokinase and alteplase are effective in treatment of catheter thrombosis. Alteplase has effectiveness rates in thrombosis treatment comparable to the ones observed with urokinase [98]. Central vein catheters are associated with the development of central vein stenosis [99]. The K/DOQI guidelines therefore recommend avoiding placement in the subclavian vein, unless no other options are available. If central venous thrombosis is detected early, it responds well to directly applied thrombolytic therapy [99] or to percutaneous transluminal angioplasty when the fibrotic stenosis can be crossed with a guidewire [100]. The infection risks associated with temporary double lumen catheters include local exit site infection and systemic bacteremia, both of which require prompt removal of the catheter and appropriate intravenous antibiotic therapy [45, 101, 102]. Bacteremia generally results from either contamination of the catheter lumen or migration of bacteria from the skin through the entry site, down the hemodialysis catheter into the blood stream [103-105]. Skin flora, Staphylococcus and

 There is conflicting evidence concerning the risk of infection based upon the site of insertion. In a large prospective randomized study (750 patients), the risk of infection was not reduced with jugular versus femoral venous catheterization [106]. But other prospective nonrandomized studies suggest, that the infection risk appears to sequentially increase for hemodialysis catheters inserted into the subclavian, internal jugular, and femoral veins, respectively [101, 107]. Coagulase-negative staphylococci, Staphylococcus aureus, aerobic gram-negative bacilli, and Candida albicans most commonly cause catheter-related bloodstream infection. In most cases of non-tunneled CVC-related bacteremia and fungemia, the CVC should be removed. The decision should be based on the severity of the patient's illness, documentation that the vascular-access device is infected, assessment of the specific pathogen involved, and presence of complications, such as endocarditis, septic

Overall, compared with the subclavian vein, the internal jugular vein remains the preferred access site in ambulatory patients. In the Intensive Care Unit, either femoral or internal jugular vein placement is satisfactory, with the use of ultrasound making internal jugular

The best solution is to prevent the infection by proper placement technique, optimal exit site

Early causes include inflow problems due to small or atherosclerotic arteries, or juxtaanastomotic stenosis, so a pre-operative evaluation for suitable access sites has to been

Streptococcus species, are responsible for the majority of infections.

thrombosis, tunnel infection, or metastatic seeding [108].

**5.2 Arteriovenous fistulas complications** 

care and management of the catheter within the HD facility [41, 109].

Complications of AVFs can be divided into early and late causes.

vein placement safer.

performed [110].

pneumothorax (0.1 percent).


Table 1. Complications of vascular acces (Reference 8)

Fig. 13. Cumulative survival of first VA accord1ing to the patients' age(Reference 8)

In 2010 USRDS Annual Data Report, hospitalization in 2008 increased again, to a point 46% above their 1993 level. In 2007–2008, women treated with hemodialysis were 16 % more likely to be hospitalized, overall, than men. They also had a greater risk than men of cardiovascular, infectious and vascular access hospitalizations 11%, 14%, and 29% greater, respectively. Recently unpublished, our data are different than those we published in 1998. Our findings showed that among 189 patients, the female ones had had more possibility to start HD with double lumen catheter than the male ones, and also patients with heart failure independent of gender. Female patients had PTFE grafts as first vascular access (p=0,023) and the elderly patients had more complications and more vascular access procedures (p=0.026).

#### **5.1 Non-tunnelled double lumen catheters complications**

The non-tunnelled double lumen catheters' complications concern the early ones during the insertion and the late ones such as infection and thrombosis of the vessels.

The severity of acute complications varies with the site of insertion. The lowest rate is in the femoral position. A significant complication is perforation of the femoral artery. Bleeding usually resolves within minutes of direct compression and large femoral or retroperitoneal hematomas occur occasionally [91]. Subclavian insertion complications are more serious. Over-insertion of guide-wire can occasionally lead to atrial or ventricular arrhythmias but they are frequently transient [92]. Penetration or cannulation of the subclavian artery can lead to hemothorax, which may require a thoracotomy tube. The incidence of pneumothorax varies from less than 1 percent to more than 10 percent of insertions, depending on the skill and experience of the physician. Pericardial rupture and tamponade also have been described [93, 94]. There is less likelihood of arterial puncture or pneumothorax in ultrasound-guided catheter insertion [95]. Subclavian insertion from the left has an

Thrombosis 14/48 39/101 N.S. Aneurysm 10/48 14/101 N.S. Oedema 0/48 6/101 N.S. Infection 0/48 2/101 N.S.

Fig. 13. Cumulative survival of first VA accord1ing to the patients' age(Reference 8)

**5.1 Non-tunnelled double lumen catheters complications** 

insertion and the late ones such as infection and thrombosis of the vessels.

In 2010 USRDS Annual Data Report, hospitalization in 2008 increased again, to a point 46% above their 1993 level. In 2007–2008, women treated with hemodialysis were 16 % more likely to be hospitalized, overall, than men. They also had a greater risk than men of cardiovascular, infectious and vascular access hospitalizations 11%, 14%, and 29% greater, respectively. Recently unpublished, our data are different than those we published in 1998. Our findings showed that among 189 patients, the female ones had had more possibility to start HD with double lumen catheter than the male ones, and also patients with heart failure independent of gender. Female patients had PTFE grafts as first vascular access (p=0,023) and the elderly patients had more complications and more vascular access procedures (p=0.026).

The non-tunnelled double lumen catheters' complications concern the early ones during the

The severity of acute complications varies with the site of insertion. The lowest rate is in the femoral position. A significant complication is perforation of the femoral artery. Bleeding usually resolves within minutes of direct compression and large femoral or retroperitoneal hematomas occur occasionally [91]. Subclavian insertion complications are more serious. Over-insertion of guide-wire can occasionally lead to atrial or ventricular arrhythmias but they are frequently transient [92]. Penetration or cannulation of the subclavian artery can lead to hemothorax, which may require a thoracotomy tube. The incidence of pneumothorax varies from less than 1 percent to more than 10 percent of insertions, depending on the skill and experience of the physician. Pericardial rupture and tamponade also have been described [93, 94]. There is less likelihood of arterial puncture or pneumothorax in ultrasound-guided catheter insertion [95]. Subclavian insertion from the left has an

Table 1. Complications of vascular acces (Reference 8)

Group A (age>60) Group B(age<60) P

increased risk of pneumothorax and atrial perforation which can be presented with acute hemopericardium upon initiation of dialysis. Internal jugular vein is the preferred site of insertion because of subclavian stenosis and loss of the ipsilateral arm for future hemodialysis access. This complication appears to occur more often with subclavian (40 to 50 %) than with internal jugular insertions (up to 10 %) [96, 97]. At internal jugular insertions a carotid artery penetration may occur, but there is also a lower risk of pneumothorax (0.1 percent).

Prevention and treatment of catheter thrombosis are important clinical issues. To prevent formation of thrombus, both lumens of the double lumen catheter are instilled with heparin following hemodialysis [41]. Lytic agents such as urokinase and alteplase are effective in treatment of catheter thrombosis. Alteplase has effectiveness rates in thrombosis treatment comparable to the ones observed with urokinase [98]. Central vein catheters are associated with the development of central vein stenosis [99]. The K/DOQI guidelines therefore recommend avoiding placement in the subclavian vein, unless no other options are available. If central venous thrombosis is detected early, it responds well to directly applied thrombolytic therapy [99] or to percutaneous transluminal angioplasty when the fibrotic stenosis can be crossed with a guidewire [100]. The infection risks associated with temporary double lumen catheters include local exit site infection and systemic bacteremia, both of which require prompt removal of the catheter and appropriate intravenous antibiotic therapy [45, 101, 102]. Bacteremia generally results from either contamination of the catheter lumen or migration of bacteria from the skin through the entry site, down the hemodialysis catheter into the blood stream [103-105]. Skin flora, Staphylococcus and Streptococcus species, are responsible for the majority of infections.

 There is conflicting evidence concerning the risk of infection based upon the site of insertion. In a large prospective randomized study (750 patients), the risk of infection was not reduced with jugular versus femoral venous catheterization [106]. But other prospective nonrandomized studies suggest, that the infection risk appears to sequentially increase for hemodialysis catheters inserted into the subclavian, internal jugular, and femoral veins, respectively [101, 107]. Coagulase-negative staphylococci, Staphylococcus aureus, aerobic gram-negative bacilli, and Candida albicans most commonly cause catheter-related bloodstream infection. In most cases of non-tunneled CVC-related bacteremia and fungemia, the CVC should be removed. The decision should be based on the severity of the patient's illness, documentation that the vascular-access device is infected, assessment of the specific pathogen involved, and presence of complications, such as endocarditis, septic thrombosis, tunnel infection, or metastatic seeding [108].

Overall, compared with the subclavian vein, the internal jugular vein remains the preferred access site in ambulatory patients. In the Intensive Care Unit, either femoral or internal jugular vein placement is satisfactory, with the use of ultrasound making internal jugular vein placement safer.

The best solution is to prevent the infection by proper placement technique, optimal exit site care and management of the catheter within the HD facility [41, 109].

#### **5.2 Arteriovenous fistulas complications**

Complications of AVFs can be divided into early and late causes.

Early causes include inflow problems due to small or atherosclerotic arteries, or juxtaanastomotic stenosis, so a pre-operative evaluation for suitable access sites has to been performed [110].

Vascular Access for Hemodialysis 57

leads to decreased blood flow and thrombosis, at a rate of 1–1.5 times/patient/ year [52]. In most cases, thrombosis is associated with anatomical stenosis, which is mostly located in the venous anastomosis (60%), followed by the peripheral vein (37%), and within the graft (38%) [125]. Percutaneous angioplasty is safe and effective in treating venous stenosis [126] with a success rate from 80%–94%, and primary patency around 60% at 6 months and 40% at 1 year. Placement of self-expanding nitinol endovascular stents, appears to prolong patency in cases where focal lesions are resistant to repeated angioplasty [127]. Central stenosis is technically more difficult to treat, and stenotic

Thrombosis of an AVG is usually the result of multiple factors; such as the stenosis, hypotension, and the excessive compression for haemostasis. Haemodialysis' nurses have to be careful in order to avoid these factors. The risk for thrombosis increases with decreasing blood flow (BF). May RE et al found a 19% risk of thrombosis in 3-month period for an AVG with BF between 1010 and 1395 mL/min. This risk increased continuously with decreased BF; 1.67-fold at a BF of 650 mL/min, and 2.39-fold at a BF of 300 mL/min [128]. Graft thrombosis can be treated in outpatients by endovascular therapy. Angiographic search for a venous stenosis is always appropriate, and angioplasty is often indicated. Timely pharmacological thrombolysis or mechanical removal of the thrombus with a Fogarty catheter, and thrombo -aspiration or thrombectomy with a mechanical device [129] can

AVG infections are serious complications and are the second leading cause of dialysis access loss. The incidence of hemodialysis-related bacteremia is more than 10-fold higher in AVGs than AVFs: 2.5 episodes per 1000 dialysis procedures versus 0.2 [130]. Patient have to be more careful for their hygiene because it seems to be the most important modifiable risk

Pseudoaneurysms should be referred to a surgeon for resection when they are >2 times wider than the graft, rapidly increasing in size, or the overlying skin appears under duress

Ischemia, as a result of access placement is more common for AVGs than AVFs: vascular steal syndrome and ischemic monomelic neuropathy are two important clinical entities to

Physiologic steal occurs in 73% of AVFs and 90% of AVGs, .Thus, in a radiocephalic fistula, arterial blood from the palmar arch may also deliver blood into the fistula. Unless there is the capacity for collateralization, this can lead to ischemia in the hand, ranging from complaints about cold hands to necrotic fingertips. Most of these complaints improve over time, but 1% of AVFs and up to 4% of AVGs require surgical revision [133]. Ischemic monomelic neuropathy is characterized by warm hands with a good pulse, but the hands are tender and swollen, usually immediately after surgery, and there is muscle weakness [134]. The cause is likely ischemia of the nerves and rapid surgical re-evaluation is needed. Nevertheless, there is evidence that the only differences between patients with PTFE older than 65 years old and younger ones are minor. Wound and skin complications and greater incidence of thromposis of VA associated with recombinant human erythropoietin have

Early or late catheter dysfunctions are the functional complications of TCs. Kinking and unsuitable positioning of the catheter tip may be the cause of early dysfunction and can be

lesions often recur within 6 months [54].

prevent placement of a dialysis catheter.

(thin, bleeding, blanching) [132].

been reported (rHuEPO) [135].

**5.4 Tunneled catheter complications** 

factor [131].

distinguish.

The aetiology of this acquired lesion is not entirely clear, but may be related to manipulating the free end of the vein, torsion, poor angulation, or loss of the vasa vasorum during anatomic dissection. More often than not, this lesion can be adequately treated with angioplasty [111, 112] or by surgical revision [113]. Outflow problems may include accessory veins that divert blood flow from the intended superficial vessel to deeper conduits, or central venous stenosis in patients with prior central venous catheters. Vessels, smaller than one-fourth of the fistula diameter, are usually not hemodynamically relevant. Juxta-anastomotic stenosis and accessory veins are the most common causes for early failure AVFs when pre-operative evaluations for suitable access sites have been performed [110].

Late causes for failure of AVFs include venous stenosis, thrombosis, and acquired arterial lesions such as aneurysms or stenoses. Venous stenosis may become apparent as flow decreases over time, worsening weekly Kt/V ([dialyzer clearance

\_ time]/body volume) or increasing recirculation. Native fistulas will not typically thrombose until flow is severely diminished. Thrombectomy of fistulas, although technically more challenging than in AVGs, is often successful and if flow is re-established, primary patency is longer than in grafts [114]. Aneurysms may form over the course of years as the fistula increases with increased flow and, unless associated with stenotic lesions, are more a cosmetic than functional concern. If the skin overlying the aneurysm is blanching or atrophic, or if there are signs of ulceration or bleeding, surgical evaluation should be obtained urgently [115]. Rupture of such aneurysms in high-flow fistulas can lead to exsanguination and death. (Figure 14)

Fig. 14. Aneurysm in forearm AVF

#### **5.3 Arteriovenous graft complications**

Functional survival of AVGs is much sorter than AVFs. The natural course of AVGs is thrombosis due to venous stenosis caused by neointimal hyperplasia. The increased production of smooth muscle cells, myofibroblasts, and vascularisation within the neointima is the main cause of thrombosis. There is also angiogenesis and numerous macrophages in the tissue around the graft.[116, 117] Within the neointimal lesion, growth factors (GF) such as PDGF (platelet derived), VEGF (vascular endothelial), and basic FGF (fibroblast) are present.[117] Vascular endothelium is regulated by the presence of shear stress, [118, 119] and that flow within AVGs is likely to be different from native veins. Understanding the pathophysiology of neointimal hyperplasia would allow targeted therapy. Current studies are evaluating the role of radiation,[120] decoy peptides against transcription factors [121, 122] and local delivery of drugs with cell-cycle inhibitory effects (e.g., paclitaxel [123] and sirolimus). Cell-based strategies seek to take advantage of endothelial progenitor cells that release endogenous inhibitors of proliferation and thrombosis, such as nitric oxide (NO) and prostacyclin.[124] Venous stenosis in AVGs

The aetiology of this acquired lesion is not entirely clear, but may be related to manipulating the free end of the vein, torsion, poor angulation, or loss of the vasa vasorum during anatomic dissection. More often than not, this lesion can be adequately treated with angioplasty [111, 112] or by surgical revision [113]. Outflow problems may include accessory veins that divert blood flow from the intended superficial vessel to deeper conduits, or central venous stenosis in patients with prior central venous catheters. Vessels, smaller than one-fourth of the fistula diameter, are usually not hemodynamically relevant. Juxta-anastomotic stenosis and accessory veins are the most common causes for early failure AVFs when pre-operative evaluations for suitable access sites have been performed [110]. Late causes for failure of AVFs include venous stenosis, thrombosis, and acquired arterial lesions such as aneurysms or stenoses. Venous stenosis may become apparent as flow

\_ time]/body volume) or increasing recirculation. Native fistulas will not typically thrombose until flow is severely diminished. Thrombectomy of fistulas, although technically more challenging than in AVGs, is often successful and if flow is re-established, primary patency is longer than in grafts [114]. Aneurysms may form over the course of years as the fistula increases with increased flow and, unless associated with stenotic lesions, are more a cosmetic than functional concern. If the skin overlying the aneurysm is blanching or atrophic, or if there are signs of ulceration or bleeding, surgical evaluation should be obtained urgently [115]. Rupture of such aneurysms in high-flow fistulas can lead to

Functional survival of AVGs is much sorter than AVFs. The natural course of AVGs is thrombosis due to venous stenosis caused by neointimal hyperplasia. The increased production of smooth muscle cells, myofibroblasts, and vascularisation within the neointima is the main cause of thrombosis. There is also angiogenesis and numerous macrophages in the tissue around the graft.[116, 117] Within the neointimal lesion, growth factors (GF) such as PDGF (platelet derived), VEGF (vascular endothelial), and basic FGF (fibroblast) are present.[117] Vascular endothelium is regulated by the presence of shear stress, [118, 119] and that flow within AVGs is likely to be different from native veins. Understanding the pathophysiology of neointimal hyperplasia would allow targeted therapy. Current studies are evaluating the role of radiation,[120] decoy peptides against transcription factors [121, 122] and local delivery of drugs with cell-cycle inhibitory effects (e.g., paclitaxel [123] and sirolimus). Cell-based strategies seek to take advantage of endothelial progenitor cells that release endogenous inhibitors of proliferation and thrombosis, such as nitric oxide (NO) and prostacyclin.[124] Venous stenosis in AVGs

decreases over time, worsening weekly Kt/V ([dialyzer clearance

exsanguination and death. (Figure 14)

Fig. 14. Aneurysm in forearm AVF

**5.3 Arteriovenous graft complications** 

leads to decreased blood flow and thrombosis, at a rate of 1–1.5 times/patient/ year [52]. In most cases, thrombosis is associated with anatomical stenosis, which is mostly located in the venous anastomosis (60%), followed by the peripheral vein (37%), and within the graft (38%) [125]. Percutaneous angioplasty is safe and effective in treating venous stenosis [126] with a success rate from 80%–94%, and primary patency around 60% at 6 months and 40% at 1 year. Placement of self-expanding nitinol endovascular stents, appears to prolong patency in cases where focal lesions are resistant to repeated angioplasty [127]. Central stenosis is technically more difficult to treat, and stenotic lesions often recur within 6 months [54].

Thrombosis of an AVG is usually the result of multiple factors; such as the stenosis, hypotension, and the excessive compression for haemostasis. Haemodialysis' nurses have to be careful in order to avoid these factors. The risk for thrombosis increases with decreasing blood flow (BF). May RE et al found a 19% risk of thrombosis in 3-month period for an AVG with BF between 1010 and 1395 mL/min. This risk increased continuously with decreased BF; 1.67-fold at a BF of 650 mL/min, and 2.39-fold at a BF of 300 mL/min [128]. Graft thrombosis can be treated in outpatients by endovascular therapy. Angiographic search for a venous stenosis is always appropriate, and angioplasty is often indicated. Timely pharmacological thrombolysis or mechanical removal of the thrombus with a Fogarty catheter, and thrombo -aspiration or thrombectomy with a mechanical device [129] can prevent placement of a dialysis catheter.

AVG infections are serious complications and are the second leading cause of dialysis access loss. The incidence of hemodialysis-related bacteremia is more than 10-fold higher in AVGs than AVFs: 2.5 episodes per 1000 dialysis procedures versus 0.2 [130]. Patient have to be more careful for their hygiene because it seems to be the most important modifiable risk factor [131].

Pseudoaneurysms should be referred to a surgeon for resection when they are >2 times wider than the graft, rapidly increasing in size, or the overlying skin appears under duress (thin, bleeding, blanching) [132].

Ischemia, as a result of access placement is more common for AVGs than AVFs: vascular steal syndrome and ischemic monomelic neuropathy are two important clinical entities to distinguish.

Physiologic steal occurs in 73% of AVFs and 90% of AVGs, .Thus, in a radiocephalic fistula, arterial blood from the palmar arch may also deliver blood into the fistula. Unless there is the capacity for collateralization, this can lead to ischemia in the hand, ranging from complaints about cold hands to necrotic fingertips. Most of these complaints improve over time, but 1% of AVFs and up to 4% of AVGs require surgical revision [133]. Ischemic monomelic neuropathy is characterized by warm hands with a good pulse, but the hands are tender and swollen, usually immediately after surgery, and there is muscle weakness [134]. The cause is likely ischemia of the nerves and rapid surgical re-evaluation is needed. Nevertheless, there is evidence that the only differences between patients with PTFE older than 65 years old and younger ones are minor. Wound and skin complications and greater incidence of thromposis of VA associated with recombinant human erythropoietin have been reported (rHuEPO) [135].

#### **5.4 Tunneled catheter complications**

Early or late catheter dysfunctions are the functional complications of TCs. Kinking and unsuitable positioning of the catheter tip may be the cause of early dysfunction and can be

Vascular Access for Hemodialysis 59

Korsheed et al report that AVF formation resulted in a sustained reduction in arterial stiffness and BP as well as an increase in LVEF. These data state that the lower mortality of these patients with AVF, may be due to factors beyond VA associated infections and

However, data from 1996 to 2006 collected from DOPPS indicate a growing use of catheters in many countries [153]. Also, our data in 2011 shows increased patency for TCs in female gender patients. Rayener et al report growing use of catheter according to DOPPS data. They also indicate that in facilities with the practice of early cannulation of AVF (within 4 weeks from their creation) and promptly performed VA surgeries with success in creating VA in older, diabetic women greatly enhance the odds of their patients for using a permanent access rather than TC [153]. In new dialysis patients, early referral to a nephrologist and early patient education strongly predict a successful functioning permanent VA at dialysis initiation and it also seems that the patients have better metabolic and clinical situation at the beginning of HD, lower long-term morbidity and higher survival for the first two years [154-158]. AV fistula is better when used for the first haemodialysis treatment compared to starting haemodialysis with a catheter [55, 159, 160]. Graft is, however, a better alternative than catheter for patients, where the creation of an

In conclusion, as far as literature and our experience are concerned, arteriovenous fistula has to be the first choice in vascular access when suitable vessels are available. Arteriovenous grafts and Central Venous Catheters may be also a good alternative as fist choice when suitable vessels are not available or as a second choice when there is AVF failure. Female gender and old patients are more likely to start hemodialysis with a TC. Finally, a well matured vascular access is important for long access survival and early referral to nephrologists is mandatory.

Acknowledgements to Ioannis T. Papadakis Director of Nephrology Department Hippokration General Hospital and to the patients of Renal Unit who gave us the permission to add their pictures in our chapter. Also acknowledgements must be given to

[1] Eggers, P.W., *Has the incidence of end-stage renal disease in the USA and other countries* 

[2] Lee, H., et al., *Cost analysis of ongoing care of patients with end-stage renal disease: the impact of dialysis modality and dialysis access.* Am J Kidney Dis, 2002. 40(3): p. 611-22.

[4] Allon, M., *Implementing a vascular access programm: improved outcomes with multidisciplinary* 

[5] System, U.S.R.D., *2002 Annual Data Report.* Bethesda, National Institutes of Health,

[6] Feldman, H.I., S. Kobrin, and A. Wasserstein, *Hemodialysis vascular access morbidity*. J Am

*approaches, in Dialysis Access: A Multidisciplinary Approach,* S. Gray Richard J., Jeffrey

[3] Santoro, A., et al., *Vascular access for hemodialysis.* J Nephrol, 2006. 19(3): p. 259-64.

J., Editor. 2002, Lippincott Williams & Wilkins: Philadelphia. p. 6-9.

National Institute of Diabetes and Digestive Diseases, 2002.

attempted AVF failed or could not be created for different reasons [161].

*stabilized?* Curr Opin Nephrol Hypertens, 2011.

Soc Nephrol, 1996. 7(4): p. 523-35.

dysfunctions [152].

**7. Acknowledgements** 

**8. References** 

Mrs Sofia Andrikou for her designs of VA.

addressed under fluoroscopic guidance. Among late causes of failure, are fibrin sheaths and thrombi around or at the catheter tip. Fibrinous sheaths can be disrupted by balloon angioplasty with improved flow through a new catheter in the same location. Symptomatic occlusions of the central veins usually require the removal of the catheter and system anticoagulation and must be weighed in the context of a continued need for dialysis and other available access options. Catheter use is linked to higher rates of infection and could compromise dialysis adequacy [136, 137]. Catheter related infections (CRI) are associated with increased all cause mortality and morbidity. 8-10% of MRSA bacteraemia in the UK occurs in patients receiving long term haemodialysis. It recently seems that the appropriately chosen antimicrobial lock solutions (ALS) reduce frequency of infections in HD patients [138]. Prophylaxis with gentamicin of the catheter lumens reduces bacterial infection morbidity and mortality related bacteremia of catheter without obvious bacterial resistance, making such use advisable [139]. Del Pozo et al in their prospective study showed that evaluation of tunnelled catheters with intra-catheter leukocyte culture helps in early HD catheters colonization, giving the possibility to eradicate biofilm without the removal of catheter [140].
