Vascular Access and Peritoneal Dialysis Catheter Placement in Children

Introduction

Renal transplantation is the most common renal replacement modality for prevalent children with end-stage renal disease (ESRD). However, hemodialysis (HD) continues to be the most common initial treatment. Of 1319 incident children with ESRD in 2017, 51.3% began treatment with HD. Because of their young age, children with ESRD will require decades of renal replacement therapy and will need HD at some point in their lives. Worldwide, most prevalent children on HD are dialyzed with a central venous catheter (CVC), whereas only about 25% are dialyzed with an arteriovenous fistula (AVF). This preference for CVC for long-term HD continues in spite of international efforts and guidelines emphasizing the clinical importance of creating a permanent vascular access, AVF or arteriovenous graft (AVG), for long-term HD in children.

CVCs offer the benefit of immediate and painless access and are best suited for acute HD. However, when used long-term, CVCs have a high risk of infection and malfunction and place the child at significant risk for central venous stenosis and thrombosis. Recurrent hospitalizations and procedures to replace CVCs not only increase health care costs but also increase missed school days in the life of a developing child, thereby impairing cognitive and social development. Expected short time to transplant in children is another reason CVCs are favored. However, most children on HD spend at least 1 year on dialysis before receiving a renal transplant.

Preparation

Vein preservation is of particular importance for future AVF creation. Upon diagnosis of CKD in a child, patients and families should be educated on the importance of protecting veins, especially in the nondominant arm. Venipunctures for blood draws and intravenous lines should be performed at distal sites of the dominant arm whenever possible. Educating the patient and family will empower them to best defend their “venous capital.”

Location

In general, “distal before proximal” and “autogenous before prosthetic” principles should be followed when planning an AVF. The nondominant arm is the preferred limb. If vessels on the nondominant arm are not adequate, the dominant arm is then preferred over the lower limb. A wrist AVF (radiocephalic) remains the first choice for chronic HD in children. The surgery involves the cephalic vein, which is anastomosed to the radial artery in an end-to-side fashion. This AVF allows for preservation of more proximal vessels for future access, and it has high long-term patency. The disadvantages include high primary failure rates when microsurgery is not used and a long maturation time in young children. The high primary failure rates in small children are attributed to small vessel size, vascular spasm, and poor venous outflow.

If a radiocephalic AVF is not possible, or primary failure occurs, the brachial artery can be used in the creation of a brachio-cephalic AVF in the elbow as the next preferred location. A brachio-basilic AVF is another option on the upper arm. Two-stage basilic vein transposition allows for maturation of small veins, which can offer a superior alternative in small children. The basilic vein, located deep in the upper arm, is usually protected from the repeated trauma of previous venipunctures and may be of particular use in children who have small vessels and are not good candidates for a more distal AVF. The arterialized vein, once it has reached a diameter of 6 mm, is moved up to a more superficial position in a second-stage procedure to allow for easier cannulation. This type of AVF has been reported to have high immediate and long-term patency rates. Another alternative is the use of the proximal radial artery. Construction of this AVF involves disruption of venous valves to achieve bidirectional AVF flow. The vein used depends on the patient’s anatomy and can include the median antebrachial, median cephalic, median cubital, or deep communicating vein. This type of AVF has a lower risk of steal phenomena than brachial artery fistulae and has been successfully used in children with high patency rates.

Following the “autogenous before prosthetic” principle, some centers create a thigh AVF in preference over an AVG. Sapheno-femoral or transposed femoral vein AVFs have been used in children. These are more likely to have primary failure compared to radial AVF.

Preoperative Planning

Children with CKD, who are expected to be on HD for at least 6 to 12 months, should be referred to a vascular surgeon when the GFR drops below 30 mL/min/1.73 m ² . Early referral is important in children, especially small children, because of long maturation times. The overarching goal should be avoidance of CVC. Dedicated CKD clinics are particularly successful at achieving this goal. Patients who present with ESRD and require an urgent start HD session will need a CVC placed; however, a CVC should be considered as a bridge to permanent access. Patients and parents should be educated about the benefits of an AVF and referred as soon as possible for evaluation of AVF placement if they plan to continue with HD.

Pertinent information in a child with ESRD or advanced CKD being evaluated for vascular access placement includes a history of prolonged hospitalizations and the location and complications of previous central lines. Symptoms of central vein stenosis could include swelling and discomfort of the extremity or face and presence of collateral veins. It is important to note the dominant arm. Physical examination should focus on the presence of scars from previous catheters, extremity edema, collateral veins, and the presence and quality of arterial pulses. The veins are typically examined with more detail, evaluating their length and determining their elasticity. Elasticity of the vein may be assessed with the use of a proximal tourniquet. Morbidly obese patients may present particular challenges in AVF creation with longer surgical and healing time and AVF use due to more difficult cannulation.

Imaging tests are routinely done by some centers; others choose to perform them in select patients. An upper extremity Doppler ultrasound should be done if there are concerns on physical examination. For patients who have a history of previous CVCs and are suspected to have central venous stenosis, it is necessary to perform a venogram. The minimum acceptable vessel diameters for AVF creation are 2.5 mm for veins and 1.5 mm for arteries, although, with the use of microsurgery, successful fistulae have been created with vessels of smaller caliber. When patients are suspected to have central vein stenosis, central vessel imaging with venography or computed tomography venography may be helpful to avoid creating an AVF ipsilateral to a central vein occlusion. Of note, magnetic resonance venography requiring gadolinium administration should be avoided in advanced CKD or ESRD due to the risk of nephrogenic systemic fibrosis.

Surgical Considerations

Young patients need to be sedated or brought under general anesthesia for creation of an AVF. Cooperative adolescents could tolerate the procedure with local or regional anesthesia.

Microsurgery is used routinely for the creation of AVF in children in some European centers and selected cases in other centers. Its use increases success rates, particularly distal AVF in young children (< 10 years old) with small arteries. Bourquelot et al., Bagolan et al., Sanabia et al., and Gradman et al., who have reported large European series of children with AVF, achieved functioning radiocephalic AVF with very low failure rates and good long-term patency rates even in small patients (< 15 kg). These authors strongly advocate for the use of an intraoperative microscope to create distal AVF in children, as it allows for precise dissection and use of small sutures and avoids the need for dilation of the vessels and causing arterial spasm.

The use of an inflatable tourniquet on the upper arm when constructing a distal AVF is described by some authors to offer additional advantages such as “preventive hemostasis,” which results in avoidance of extensive arterial dissection, decreased use of clamps, and lower risk of damage to the intima.

Based on expert opinion, perioperative strategies to optimize early AVF function include starting low-dose daily aspirin at least 1 week prior to surgery, reducing antihypertensive medications in the immediate preoperative period, and directing intraoperative and postoperative fluid management by nephrology to keep blood pressures at or above the 90th percentile for age, height, and gender.

Postoperative Care and Maturation

Hand exercises have been shown to improve maturation in adults and should be encouraged after AVF creation in children old enough to cooperate. Low-dose aspirin is recommended to be continued at least for the first few months after AVF formation. Many pediatric dialysis centers reduce antihypertensive medication doses to allow “permissive” hypertension and carefully maintain adequate intravascular volume by reducing ultrafiltration to encourage maturation.

Maturation times vary widely in pediatric AVF and have been reported anywhere from 4 weeks to 6 months; however, the majority of AVFs in children mature between 8 and 10 weeks. Smaller children tend to have longer maturation times as well as children who have lower blood pressure.

The Kidney Disease Outcomes Quality Initiative (KDOQI) Clinical Practice Guideline For Vascular Access: 2019 Update suggests that an AVF is mature in adults when the flow is > 600 mL/min, the internal diameter of the draining vein is > 6 mm when measured by ultrasound, and the skin-to-vein distance is < 6 mm. Pediatric studies have found similar vessel diameter and flow rates indicative of maturation.

Communication between the nephrologist, vascular access surgeon, and HD nurse is imperative at this stage to determine the timing of the first AVF cannulation. Educating the patient and family on proper care of their AVF is of equal importance, especially regarding the need to avoid inadvertent compression of the involved extremity. Multidisciplinary vascular access clinics involving surgeons, nephrologists, dialysis nurses, and ultrasound technicians have shown great success in increasing the number of functioning AVFs long-term.

Cannulation

The first few treatments using a new AVF are usually performed with a 17G needle for cannulation in children. In some instances, single-needle cannulation of the AVF while using one port of the existing CVC can provide a first step strategy to enhance maturation of the AVF to facilitate transition away from the CVC. The pain and anxiety of needling an AVF may also be decreased using this approach in young children. Topical anesthetic creams, applied at home or a few minutes before the scheduled HD session, are useful and may be used routinely. The buttonhole and rope ladder techniques are both used in children; buttonhole cannulation has been associated with a higher incidence of Staphylococcus aureus infections in adult studies, so it is being used less frequently in adults. The area technique is no longer recommended as it is associated with higher risk of aneurysmal dilatation, longer bleeding times, and access failure.

Child life specialists may play an important role in cannulation, particularly in the initial cannulation. Although it is possible that children may experience significant pain during cannulation, only about 20% of children report great discomfort, and less than 10% of children report that they would prefer to return to a CVC.