**4. Children's hemodialysis vascular access**

Renal replacement treatment in children varies. According to North American Pediatric Renal Trials and Collaborative Studies (NAPRTCS) registry of patients reaching ESRD in pediatric centers, 25% submitted preemptive renal transplantation, 50% joined in peritoneal dialysis, and 25% started hemodialysis [124, 125]. The preferable therapy is transplantation and in perspective of a rather short time on HD, children receive maintenance HD through an indwelling CVC [126]. In the USA, no more than 800 pediatric patients receive maintenance HD therapy, while the majority of smaller patients, less than 10 kg or 2 years old, receive peritoneal dialysis [127–129].

However, hemodialysis can be performed successfully in infants and very young children, as well [130]. An evaluation of the vasculature of children who will undergo hemodialysis will indicate the appropriate vascular access. Because of the size of their vessels, there is limited use of AVF in children, although there is an effort to make nephrology society to consider AVF as the best access in pediatric HD patients [131]. According to a 2008 pediatric registry (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 [125]. 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 occurring with catheters. Patient's size determines catheter size. An 8-F dual lumen catheter is well tolerated in 4- to 5-kg children, and as the child's size increases, a vascular access of larger volume can be placed [132]. Blood flow in pediatric patients varies due to the catheter size, which depends on the child's size. In most of the patients, a recommended blood flow of 3 to 5 ml/kg/min is acceptable [133], providing adequate dialysis with Kt/V equal or greater than 1.2. A recent study by Fadel et al. found a significant correlation between serum soluble vascular cell adhesion molecule 1 and ESA doses in thrombosed AVF, and this could have clinical significance after further investigation [134].
