**2.4.2 Use, complications and treatment of arteriovenous fistula/graft**

#### **2.4.2.1 Arteriovenous fistula**

Use of AVF is recommended as it is superior in enabling sufficient blood flow in hemodialysis patient group and has fewer complications. NKF DOQI targets the percentage of AVF usage in hemodialysis units to be 65% (NKF KDOQI,2006). AVFs are more commonly preferred to AVGs. The reason for AVFs to be preferred more than grafts is that they have longer access life because there are fewer incidences of thrombosis or infection and fewer procedures requiring punctures, and the cost is less. It was shown in various studies that access-related complications were 3 to 7 times more in AVGs than in fistulae (Di Iorio et al., 2004; Enzler et al.,1996; Gibson et al., 2001a; Gibson et al., 2001b). The access potency was found in a study to be 85% in negative AVF while it was 40% in grafts (Hodges et al., 1997).

Besides its advantages, AVFs also involve some complications. While a maturation defect in AVFs lead to venous stenosis and thrombosis, low dialysis blood flow and inefficiency in dialysis, the high flow rate in fistulae may cause a high-output heart failure. Besides these, access-related infections, steal syndrome and aneurism are other complications associated with AVFs. Arteriovenous fistulae are required to mature in 6 weeks on the average. The factors influencing development of a maturation defect include age, DM, obesity and female gender (Allon et al., 2000; Enzler et al.,1996; Lin et al., 1998). A fistulography may be attempted in cases involving immature fistulae (NKF KDOQI,2006). A cause-oriented treatment may be employed.

AVF thrombosis is the major cause of access failure. An average of 0.5 to 0.8 fistula thrombosis is observed per patient in a year (Fan & Schwab, 1992). The cause in 85% of the cases is venous stenosis resulting from neointimal hyperplasia (Bent et al., 2011). The other reasons that create a tendency to fistula thrombosis are excessive compression on the fistula after dialysis, hypotension, hypovolemia, susceptibility to hypercoagulation, arterial

Acute Complications of Hemodialysis 265

of fistula trill and murmur during a physical examination, an increase in swelling, redness and heat in the arm carrying the fistula, and not being able to stop bleeding for a long time after pulling out the fistula needle. Direct flow measurement and dublex USG are preferred diagnostic methods in these cases. A fistulagraphy may also be carried out as an advanced

The use of grafts as vascular access in hemodialysis patient group varies from country to country. It is most common in the USA, but quite uncommon in the European countries (Hirth et al., 1996). Studies demonstrated that its primary and secondary potency is less as compared to native AVF and it involved more complications than native AVFs. Since it may involve more mortality and morbidity for this reason, the use of grafts as vascular access is only recommended for the patients who are problematic in making native AVFs (Coburn&Carney,1994; Di Iorio et al.,2004; Enzler et al.,1996; Gibson et al., 2001a; Gibson et al., 2001b). AVG may be used as an access in elderly patients, those with comorbid diseases, those whose vascular structures are impaired or those who require an early access. Grafts

All the complications seen in native AVFs may also bee seen in AVGs. However, frequency of such complications is more in grafts (Coburn&Carney,1994; Di Iorio et al.,2004; Enzler et

There are some points to pay attention to in grafts that differ from the treatments of native AVF complications. These include spontaneous bleeding, suspecting graft rapture in the case of a fast increase in the diameter of pseudoaneurysm and a severe degenerative change in the graft material and considering an urgent surgery in this situation, the initial treatment of a graft infection needing to cover gram negatives and positives, then selection of a suitable antibiotherapy according to culture result, incision and drainage also possibly being useful, and replacing the graft material in prolonged infections. Furthermore, when an edema lasts more than 2 weeks in patients with AVGs, a fistulography should be made and if any stenosis is found, it should be treated via either

Prevalence of cardiovascular diseases in dialysis patients increased as compared to the normal population. The most important reason of this increase is the increased number of incidences of diabetes mellitus (DM) and hypertension in this patient group. Cardiovascular diseases accounts for approximately 45% of the causes of mortality in dialysis patients (Shastri&Sarnak,2010). Besides the patient-related factors, the hemodialysis therapy itself

The frequency of intradialytic hypotension (IDH) in patients receiving hemodialysis therapy has been assessed in various studies. For example, in a study made by Andrulli et al on 123 hemodialysis patients, IDH was considered to prevail if there was a decrease of 30 mmHg or more in Systolic blood pressure (SBP) or if IDH appeared symptomatically and the prevalence of IDH in the group that has a tendency to hypotension was found to be 44% (Andrulli et al., 2002). In another study made by Emily S et al, IDH was found in 608 (24%) of 2559 dialysis

diagnostic test (NKF KDOQI,2006; Tordoir et al.,2007).

usually become ready for hemodialysis approximately in 3 weeks.

al.,1996; Gibson et al., 2001a; Gibson et al., 2001b).

**3. Cardiovascular complications of hemodialysis** 

brings about a number of cardiovascular complications.

surgery or PTA (NKF KDOQI,2006).

**3.1 Hypotension** 

**2.4.2.2 AV graft** 

stenosis and the fistula being made subject to a prolonged compression for some reason. The thromboses observed especially in the first month after the implantation of a fistula relate to the fistula implantation technique used and the use of fistula before its maturation (Fan & Schwab, 1992). When treating a fistula thrombosis, a thrombectomy should be employed as soon as possible. The thrombectomy may be conducted using surgical or percutaneous interventional techniques (Bent et al., 2011).

AVF stenosis is the most common cause of a fistula failure. Since a fistula-related stenosis may result in susceptibility to thrombosis, dialysis failure and consequently loss of the fistula, its early diagnosis and treatment is very important (Chandra et al.,2010, Tessitore et al.,2004). The Doppler USG is a noninvasive and reliable technique for its diagnosis (Chandra et al.,2010; Sands et al.,1999). Various studies have been done to determine at what stage of the stenosis the treatment should start. While some of these studies produced results evidencing that an angioplasty or a surgical intervention at the early stenosis stage prolonged fistula survival (Schwabet al.,2001;Tessitore et al.,2003,), other studies defended that an early intervention was not advantageous (Turmel-Rodrigues et al.,2000). The commonly accepted approach today is that the fistula should be treated via PTA or surgically if the stenosis is more than 50% and shows clinical signs (NKF KDOQI,2006).

The ischemia that develops as a result of diversion of the arterial flow to the access site is referred to as the steal syndrome. Although a steal syndrome is seen rarely, it produces significant clinical results. The risk factors are female gender, diabetes mellitus, old age, a history of an operation in the extremity which previously had an AVF and the use of a brachial artery rather than a radial artery in making a fistula (Maliket al., 2008). A short time after making the AVF, patients may experience chilling, pain, numbness and paleness in the fingers of their extremity where the fistula is located and after a few months, necrosis or permanent nerve damages may occur in the fingers (Akoh, 2009). Diagnosis of steal syndrome involves hearing the history and carrying out a physical examination followed by an arteriogram to support the diagnosis and viewing the extremity via duplex Doppler ultrasound (DDU). Surgical methods such as access banding, ligation, angioplasty, bypass and sympathectomy may be used in treating it (Berman et al.,1997; Jean-Baptiste et al., 2004; Schanzer et al., 1992).

Native AVF infections are seen less frequently than in CVCs and AVGs (Inrig et al., 2006; Hoen et al.,1998). In the case of an infection, an antibiotherapy should be administered in periods up to 6 weeks due to the risk of developing an infective endocarditis (NKF KDOQI,2006; Tordoir et al.,2007).

In preventing arteriovenous fistula complications, it is recommended to brief, patients with a GFR under 30 ml/min. / 1.73 m2 about a permanent renal replacement therapy, to avoid any vascular puncture (for placing a catheter or taking blood) in the veins that are suitable for making an AVF and the large veins on that side in stage 4 and 5 patients, to make the AVF 6 months before the starting of hemodialysis when possible, to obtain patient histories and physically examine patients before making an AVF, to examine the upper extremity veins and arteries via a duplex USG and to view the central veins of those patients with a previous central vein catheterization history. The aseptic techniques should be adhered to in all vascular access cannulations. In order for an AVF to be ready, there must be a flow of more than 600 ml/min, and the fistula vein diameter must be at least 0.6 cm and its depth should not exceed 0.6 cm. It should be checked by an experienced physician or nurse at least once a month for any signs of dysfunction, which include any change in the characteristics of fistula trill and murmur during a physical examination, an increase in swelling, redness and heat in the arm carrying the fistula, and not being able to stop bleeding for a long time after pulling out the fistula needle. Direct flow measurement and dublex USG are preferred diagnostic methods in these cases. A fistulagraphy may also be carried out as an advanced diagnostic test (NKF KDOQI,2006; Tordoir et al.,2007).

#### **2.4.2.2 AV graft**

264 Technical Problems in Patients on Hemodialysis

stenosis and the fistula being made subject to a prolonged compression for some reason. The thromboses observed especially in the first month after the implantation of a fistula relate to the fistula implantation technique used and the use of fistula before its maturation (Fan & Schwab, 1992). When treating a fistula thrombosis, a thrombectomy should be employed as soon as possible. The thrombectomy may be conducted using surgical or percutaneous

AVF stenosis is the most common cause of a fistula failure. Since a fistula-related stenosis may result in susceptibility to thrombosis, dialysis failure and consequently loss of the fistula, its early diagnosis and treatment is very important (Chandra et al.,2010, Tessitore et al.,2004). The Doppler USG is a noninvasive and reliable technique for its diagnosis (Chandra et al.,2010; Sands et al.,1999). Various studies have been done to determine at what stage of the stenosis the treatment should start. While some of these studies produced results evidencing that an angioplasty or a surgical intervention at the early stenosis stage prolonged fistula survival (Schwabet al.,2001;Tessitore et al.,2003,), other studies defended that an early intervention was not advantageous (Turmel-Rodrigues et al.,2000). The commonly accepted approach today is that the fistula should be treated via PTA or surgically if the stenosis is more than 50% and shows clinical signs (NKF KDOQI,2006). The ischemia that develops as a result of diversion of the arterial flow to the access site is referred to as the steal syndrome. Although a steal syndrome is seen rarely, it produces significant clinical results. The risk factors are female gender, diabetes mellitus, old age, a history of an operation in the extremity which previously had an AVF and the use of a brachial artery rather than a radial artery in making a fistula (Maliket al., 2008). A short time after making the AVF, patients may experience chilling, pain, numbness and paleness in the fingers of their extremity where the fistula is located and after a few months, necrosis or permanent nerve damages may occur in the fingers (Akoh, 2009). Diagnosis of steal syndrome involves hearing the history and carrying out a physical examination followed by an arteriogram to support the diagnosis and viewing the extremity via duplex Doppler ultrasound (DDU). Surgical methods such as access banding, ligation, angioplasty, bypass and sympathectomy may be used in treating it (Berman et al.,1997; Jean-Baptiste et al., 2004;

Native AVF infections are seen less frequently than in CVCs and AVGs (Inrig et al., 2006; Hoen et al.,1998). In the case of an infection, an antibiotherapy should be administered in periods up to 6 weeks due to the risk of developing an infective endocarditis (NKF

In preventing arteriovenous fistula complications, it is recommended to brief, patients with a GFR under 30 ml/min. / 1.73 m2 about a permanent renal replacement therapy, to avoid any vascular puncture (for placing a catheter or taking blood) in the veins that are suitable for making an AVF and the large veins on that side in stage 4 and 5 patients, to make the AVF 6 months before the starting of hemodialysis when possible, to obtain patient histories and physically examine patients before making an AVF, to examine the upper extremity veins and arteries via a duplex USG and to view the central veins of those patients with a previous central vein catheterization history. The aseptic techniques should be adhered to in all vascular access cannulations. In order for an AVF to be ready, there must be a flow of more than 600 ml/min, and the fistula vein diameter must be at least 0.6 cm and its depth should not exceed 0.6 cm. It should be checked by an experienced physician or nurse at least once a month for any signs of dysfunction, which include any change in the characteristics

interventional techniques (Bent et al., 2011).

Schanzer et al., 1992).

KDOQI,2006; Tordoir et al.,2007).

The use of grafts as vascular access in hemodialysis patient group varies from country to country. It is most common in the USA, but quite uncommon in the European countries (Hirth et al., 1996). Studies demonstrated that its primary and secondary potency is less as compared to native AVF and it involved more complications than native AVFs. Since it may involve more mortality and morbidity for this reason, the use of grafts as vascular access is only recommended for the patients who are problematic in making native AVFs (Coburn&Carney,1994; Di Iorio et al.,2004; Enzler et al.,1996; Gibson et al., 2001a; Gibson et al., 2001b). AVG may be used as an access in elderly patients, those with comorbid diseases, those whose vascular structures are impaired or those who require an early access. Grafts usually become ready for hemodialysis approximately in 3 weeks.

All the complications seen in native AVFs may also bee seen in AVGs. However, frequency of such complications is more in grafts (Coburn&Carney,1994; Di Iorio et al.,2004; Enzler et al.,1996; Gibson et al., 2001a; Gibson et al., 2001b).

There are some points to pay attention to in grafts that differ from the treatments of native AVF complications. These include spontaneous bleeding, suspecting graft rapture in the case of a fast increase in the diameter of pseudoaneurysm and a severe degenerative change in the graft material and considering an urgent surgery in this situation, the initial treatment of a graft infection needing to cover gram negatives and positives, then selection of a suitable antibiotherapy according to culture result, incision and drainage also possibly being useful, and replacing the graft material in prolonged infections. Furthermore, when an edema lasts more than 2 weeks in patients with AVGs, a fistulography should be made and if any stenosis is found, it should be treated via either surgery or PTA (NKF KDOQI,2006).
