Hemodialysis access in the pediatric patient population

Hemodialysis Access in the Pediatric Patient Population Alan B. Lumsden, MB, ChB, M. Julia MacDonald, RN, Robert C. Allen, MD, Thomas F. Dodson, MD, Atlanta, Georgia

BACKGROUND: E a c h year, t h r e e to five children r~cr million develop chronic renal failure. O f ;~lese, 7 0 % will r e q u i r e dialysis for short peri• ds, and 2 3 % will r e q u i r e p r o l o n g e d hemodialyis support. It is in the latter g r o u p that difficulty e n c o u n t e r e d in establishing dialysis access. VlETHODS: F r o m 1 9 8 5 to 1 9 9 2 , we p r o v i d e d ,emodialysis access f o r a g r o u p o f 2 4 children. ,'here w e r e 16 boys and 8 girls, with a m e a n .ge o f 1 1 . 1 ± 4 years (range 3 to 17). All chil'.ten w e r e significantly below the 5 0 t h perentile weight f o r t h e i r age and sex. Seven h i l d r e n e n t e r e d hemodialysis following failed ,eritoneal dialysis after an average o f 2 1 ± [ 0 . 5 months. S e v e n t e e n patients r e c e i v e d a •enal transplant. Seven o f these children h a v e •esumed hemodialysis. RESULTS: T h e technique for establishing h e m o lialysis was varied: 15 arteriovenous fistulae, 3 7 ,xpanded polytetrafluoroethylene ( e P T F E ) bridge ;,rafts, 9 bovine arteriovenous bridge grafts, and ~9 chronic central venous catheters. T h e overall nean functional patency o f the fistulae was 6.2 ± 10.2 months. One third o f these fistulae failed to mature sufficiently to p e r m i t their use for dialysis purposes. Twenty-one u p p e r extremity e P T F E ~ a f t s were implanted, with a m e a n functional pa~ency o f 11 ± 11.1 months. Sixteen groin loop gTafts were utilized, with a p r i m a r y patency o f only 4.1 ± 5 months. T h r o m b e c t o m y was pert'ormed in 2 5 cases (patch o r interposition in 8 cases), with a s e c o n d a r y patency in these grafts of 1 0 . 5 ± 17 months. An inability to achieve access in 2 children resulted in the creation o f unusual types o f access: an aorto-caval fistula and an axillo-femoral fistula and a combination o f single-needle p u n c t u r e o f an i m m a t u r e fistula with one l u m e n o f a P e r m C a t h . T h e r e were eight e P T F E graft infections, with graft loss o c c u r r i n g in seven cases. S u p e r i o r vena caval occlusion o c c u r r e d in two patients, "ihferior vena caval thrombosis in one patient, and axillo-subclavian venous occlusion in two patients. D e v e l o p m e n t o f central venous occlu-

sions significantly increased the difficulty in establishing dialysis access. T h e total dialysis period provided by the 9 0 prim a r y p r o c e d u r e s p e r f o r m e d in thi~ study was 6 5 8 months. Each p r o c e d u r e , therefore, provided access for a m e a n duration of only 7.3 months. CONCLUSION: Providin~ dialysis access in the pediatric population is a time-cousunfing and frustrating challenge. We believe that all patients with renal dysfunction should have their conditions managed as potential long-term dialysis candidates. T h e r e f o r e , o u r philosophy is to achieve maximal use f r o m each access site. Although the p r i m a r y patency o f u p p e r - a r m e P T F E grafts was g r e a t e r than that for the f o r e a r m fistulae in this study, failure o f the u p p e r - a r m graft can result in loss o f that limb for the purposes o f future dialysis access. Consequently, we strongly advocate the "distal b e f o r e p r o x i m a l " and "autogenous bef o r e prosthetic" dogma in providing pediatric hemodialysis access. "odem hemodialysis became feasible when Scribner . introduced the external arteriovenous shunt in 1960. M Recurrent thromboses, infections, and occasional major

bleeding episodes, however, prompted development of the subcutaneous arteriovenous fistula by Brescia et al2 in 1966. This procedure remains the gold standard in dialysis access. The expanded polytetrafiuoroethylene (ePTFE) graft was first used as a bridge conduit in 19763 and is currently the most popular method of establishing hemodialysis access. These techniques have been increasingly applied to the pediatric patient who has end-stage renal disease; however, because of the smaller diameter and lower flow rates in the arteries of children, this group presents a much more stringent test both of the surgeon's ability to establish reliable access and of biomaterials used as conduits. Each year three to five children per million develop chronic renal failure.4 The ultimate goal for renal replacement therapy is transplantation, but 70% will require dialysis for short periods while awaiting transplantation, and 23% will require long-term dialysis following failed transplantation or determination of ineligibility for transplantation. Despite the small number of children requiring longterm maintenance dialysis, they represent a major commitment in resources, costs, and time invested by both Fromthe Divisionof VascularSurgery,Departmentof Surgery,Emory the patient and dialysis staff to establish and preserve the UmversitySchoolof Medicine,Atlanta,Georgia. mode of dialysis access. Requests for reprints should be addressedto Alan B. Lurnsden,MD, It has been noted that dialysis access is the "Achilles' 1364ChftonRoad, NE, Box M-I 1, Atlanta,Georgia30322. Presented at the 22nd Annual Meeting of the Society for Clinical heel" of care for the adult patient with chronic renal failVascularSurgery,Tucson,Arizona,March 2-6, 1994. ure. This is particularly true for the pediatric population. THE AMERICANJOURNALOF SURGERY* VOLUME168 AUGUST1994 197

HEMODIALYSIS ACCESS IN THE PEDIATRIC PATIENT/LUMSDEN ET AL

TABLE Etiology of Chronic Renal Failure Idiopathic Renal aplasla/hypoplasta Glomerulonephntls Medullary cystic disease Renal vein thrombosts Vasculibs Posterior urethral valves Hemolytic uremic syndrome Alport's syndrome Neurogenic bladder

5 3 5 1 1 3 4 1 1 1

P A T I E N T S AND M E T H O D S From January 1985 to December 1992, a total of 24 pediatric patients were evaluated by a single group of vascular surgeons at Egleston Children's Hospital at Emory University for placement of permanent hemodialysis access. Information was obtained by reviewing the hospital records and the personal operative logs of the participating surgeons. There were 16 boys and 8 girls, with an average age of 11.1 +_4 years at the start of dialysis and 14.2 _+ 3.4 years at the end of the study. The youngest child for whom hemodialysis access was provided was age 3. The average weight of these children at the end of the study was 32 _.+6.5 kg (range 12 to 41). This is approximately 18 kg under the 50th-percentile weight for a child of 14.2 years. The etiology of the renal failure is delineated in the Table. Peritoneal dialysis (PD) had been selected as the initial mode of renal replacement therapy in eight children, and had failed in each case due to development of multiple episodes of peritonitis. Satisfactory dialysis had been achieved with PD in these children for an average of 21 _+10.5 months (range 5 to 36). Seventeen patients received a kidney transplant including 1 who received 4 cadaveric grafts. The average time on hemodialysis pretransplant in these patients was 10.9 _+9.4 months. Of the 17 patients who underwent renal transplantation, 10 have not subsequently required hemodialysis, while 7 have resumed dialysis. The remaining 7 patients were ineligible for renal transplantation. It is in the subgroup of patients who fail or are ineligible for transplantation in which severe access problems develop; indeed, greater than 10 procedures had been performed in each of 5 patients. Numerous forms of access were utilized: 15 arteriovenous fistulae, 37 ePTFE bridge grafts, 9 bovine arteriovenous bridge grafts, 29 chronic central venous catheters (PermCath [Quinton Instruments Co., Harleysville, Pennsylvania] or Soft Cell [Vas-Cath, Inc., Missauga, Ontario, Canada]), and 25 acute venous catheters. The 15 primary arteriovenous fistulae consisted of I0 radiocephalic fistulae, 3 brachiocephalic fistulae, 1 saphenofemoral fistula, and 1 saphenopopliteal fistula. Overall, there was a mean functional patency of 6.2 _+ 10.2 months. Five fistulae, although remaining patent, failed to mature sufficiently to permit dialysis to be established despite observation for up to 9 months. In 2 cases, however, the fistulae resulted in a significant increase in both the size of the radial artery and antecubital veins, permitting a successful forearm ePTFE graft to be established. 198

Twenty-one upper-extremity ePTFE arteriovenous graft., were placed (17 brachial artery to axillary vein, 2 radial artery to median basilic vein, and 2 forearm loop grafts) Collectively, these grafts had a mean patency of 11.0 _~ 11. i months. Groin loop ePTFE grafts (n = 16), in contrast, had a mean patency of only 4.1 _+5 months. Thenwere 8 graft infections (5 upper-extremity and 3 lowerextremity), all of which resulted in graft loss, with th~ exception of a single femoral loop graft in which a segmental resection with rerouting of the graft producer, graft salvage. Thrombectomy of an ePTFE graft was performed on 2: occasions, with patch angioplasty of outflow stenoses in ,~ cases and placement of a new outflow segment in 5 cases Grafts that had undergone thrombectomy alone, or revision, had a secondary patency of 10.5 _+ 17 months. A total of 29 chronic, indwelling venous dialysis catheter: (11.5-Fr [Soft Cell]; 11.5-Fr or 8-Fr hemodialysis cathetei [PermCath]) were placed during the study period. The mean duration of dialysis provided by these catheters wa,' 8.1 _+ 6.9 weeks. Catheter dislodgment occurred in eigh~, cases; there were eight catheter infections. Five catheter,, were removed because of thrombosis which was unre. sponsive to lytic therapy. One catheter failed due to development of a crack adjacent to the hub, and another catheter although patent, would not sustain adequate flow. Lack of available access sites became a major problem in four children, resulting in the creation of unusual forms of arteriovenous conduits (axillary to femoral, loop aortocaval fistula, use of an immature fistula, dialysis via a single functioning lumen of a PermCath). Adjunctive percutaneous radiologic procedures were employed, including urokinase administration and angioplasty of an extemal iliac vein stenosis (which recurred within 1 month). In another case, angioplasty and stenring of an external iliac vein stenosis resulted in acute thrombosis. Superior vena caval obstruction developed in 2 patients. Lyric therapy was attempted, but was unsuccessful in each case. This is a serious complication which, although often asymptomatic, significantly compromises the ability to provide long-term dialysis access. One of these patients also developed occlusion of the inferior vena cava. Hemodialysis access was provided by an ePTFE fistula from the aorta to the suprarenal inferior vena cava. This patient has had multiple graft occlusions due to inferior vena caval stenosis. These occlusions were successfully treated by surgical thrombectomy (5 occasions) and subsequently by lyric therapy, angioplasty, and stenting of the inferior vena cava (3 occasions). Recently, an infected portion of the subcutaneous abdominal loop required excision, replacement with a new graft, and rotation of a myocutaneous flap to provide soft tissue coverage. In addition, 8 major venous occlusions were identified in 6 other patients, including 2 stenoses of the external lilac vein, 2 superior vena cava thromboses, 2 subclavian/axillary vein thromboses, 1 inferior vena cava thrombosis, and 1 inferior vena cava stenosis. The total dialysis period covered by these procedures was 658 months, during which 90 primary procedures were performed (arteriovenous fistulae, arteriovenous grafts, and PermCaths). Each procedure, therefore, provided a mean dialysis period of only 7.3 months.

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HEMODIALYSIS ACCESS IN THE PEDIATRIC PATW.IX~/LUMSDF~,E~ ~I.

End Stage Renal Disease

Nonsupport,ve Environment

Supportive h o m e Env,ronment

~er~'oneal D,alysis vKa Tenckhoff Catheter

a) Child < 2030 kg b) Fear of needle puncture c) Family support adequate to care for catheter

1

Central Venous Catheter

:OMMENTS The approach to pediatric hemodialysis access differs in ,1any respects from that taken with the adult population. ;uccessful renal transplantation is clearly the principal oal. 5 Transplantation is cheaper, provides a better qualy of life, and avoids the psychologic problems encoun"red with regular dialysis. 6-14However, hemodialysis may ,e required for prolonged periods, and multiple occlusions ,f access sites are common. While dialysis-dependent, the hildren in one large series were hospitalized for a mean )f 32.3 days per year.6 This was prompted primarily by hrombosis or infection at the access site. Frequency of ~ospital admission and time spent in dialysis centers are najor factors in the poor psychosocial adaptation that is =revalent in dialysis-dependent children. 7 Nevertheless, ~emodialysis is an important component of renal replacenent therapy in these children either pretransplant, folowing failed transplantation, or in those ineligible for ransplantation. Consequently, several strategic principles .hould be observed during the establishment of pediatric lialysis access: • Aim for maximal use of each access site. • Do not provide short-term access with procedures which viii have limited durability and compromise long-term ~,enous patency. • Minimize the risk of central venous thrombosis. • Consider the home environment when selecting exterlal devices. • Do not compromise the possibility of subsequent transplantation; specifically, prevent bilateral iliac stenoses by avoiding use of both groins. Although these criteria should guide procedure selection, success of a procedure in specific cases is determined largely by the size of the child, length of time on dialysis, and prior use of access sites.

-a) Child > 20-30 kg b) Adequate ve=n

Artenovenous F=stula (order of selechon) 1) Rad,ocephalic 2) Brach,ocephalic 3) Brechiobosihc 4) Saphenotemoral

Figure.

Suggested algorithm for establishing inCial access for dialysis In pediatric patients.

Our philosophy for providing chronic renal replacement therapy is depicted in the algorithm in the Figure. Peritoneal dialysis via a Tenckhoff catheter is the primary dialysis modality. 15 However, successful peritoneal dialysis depends on the availability of a family support group whose members can learn sterile technique, are willing to conduct the dialysis sessions, and can be trained to recognize problems such as dehydration or symptoms of peritonitis. Peritoneal dialysis has been used particularly in children less than 10 kg in weight and in those who live far from a dialysis center. '6 In patients who fail peritoneal dialysis, or in whom it is deemed inappropriate, hemodialysis is necessary. For children under 20 kg, central venous dialysis via a tunneled catheter would be our first choice. This may be placed via a cutdown on the internal or external jugular vein or via percutaneous puncture of the subclavian vein in older children. Regardless of site, the catheter should be tunneled into the lower pectoral area to ensure that the exit site is concealed by the child's clothing. Likewise, for those patients in whom transplantation is likely within 6 to 12 months, dialysis via a central venous catheter should be the primary access method. In the older child, or in those greater than 30 kg, a radiocephalic, brachiocephalic, or brachiobasilic fistula should be attempted. Several options have been described for establishing hemodialysis access in children. The external Scribner shunt and central venous catheters are the predominantly used method for acute dialysis. When chronic hemodialysis is anticipated, the autogenous fistula or the ePTFE arteriovenous graft have been the principal techniques employed, but chronic indwelling venous catheters are being increasingly utilized. As mentioned, Scribner shunts have been widely used for acute dialysis/They are most frequently placed between the radial artery and cephalic vein, but have been inserted

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HEMODIALYSIS ACCESS IN THE PEDIATRIC PATIENT/LUMSDEN El' AL

at various sites: profunda femoris artery to saphenous vein, superficial femoral artery to saphenous vein, superficial femoral artery to superficial femoral vein, posterior tibial artery to saphenous vein, and brachial artery to cephalic vein.17 They have the advantage of immediate and painless access, as well as ease of insertion and removal. Multiple shunts may be serially inserted along the length of a single artery. However, the average shunt life is only 8 weeks,/8 and thrombosis or infection occurs in up to 50%19; 31% require multiple revisions. Hemorrhage, when it occurs, may be life-threatening, and curtailment of physical activity is necessary. Limb-threatening ischemia may occur, but is uncommon. 17For these reasons, we rarely use this type of access procedure and, given the ready availability of central venous dialysis catheters, believe that Scribner shunts currently have little role. Thomas shunts 19 consist of Silastic tubes with a Dacron skirt which is anastomosed end-to-side to the brachial artery and vein. The arterial and venous lines are then connected with a Teflon tube. The authors have no experience with this type of shunt. Central venous catheters have been extensively used for dialysis purposes. The Soft Cell chronic dual-lumen catheter and the PermCath hemodialysis catheter are both 11.5Fr devices with a 12-cm insertion length for pediatric use. These catheters are straight or have a preformed 180 ° curve to minimize the risk of kinking. Initially, central venous devices were single-lumen, with dialysis being performed with a single-needle system and unipuncture clamp. 2° Double-lumen devices can be inserted by percutaneous puncture or via a cutdown on either the internal or external jugular vein and provide more rapid dialysis. The problems which develop with this form of access include catheter kinking, causing inadequate flow rates for dialysis in up to 29% of patients, 2~ and infection in up to 30%. 2~ Thrombosis of the catheter lumen can occur, but is usually easily corrected by instillation of intraluminal urokinase. Our experience in the current study is similar to that reported by others. A more important complication, and one for which the incidence is undefined in children, is the risk of central venous thrombosis secondary to placement of the catheter or to purse-string sutures placed in the internal jugular vein at the time of catheter insertion. It is imperative not to ligate major venous conduits during catheter placement. Ultimately, successful creation of new access sites will be determined by continued patency of the central veins. Arteriovenous fistulae are the method of choice in larger children (>30 kg). When an adequate cephalic vein is available at the wrist, then a Brescia-Cimino fistula should be constructed. We would define an adequate vein as greater than 1.5 mm in diameter with a sphygmometer inflated to greater than 40 mm Hg pressure. Other major centers have used radiocephalic fistulae in children weighing greater than 20 kg, 4 and Bell 22 has argued that any visible cephalic vein should prompt creation of a fistula. In smaller children, fistula construction is more technically demanding, but, with modem magnification (x 3.5 loupe), can be readily constructed with good patency rates. Interrupted sutures should be used around the toe of the graft to permit growth with time. 23 Brachial artery to cephalic vein fistulae may be satisfactorily constructed in 200

those children greater than 20 kg, and would be our sec ond choice if a Brescia-Cimino fistula were not feasible There are reports of satisfactory saphenofemoral fistula~ in children less than 9 kg in weight. 24,25 In a series of pa tients with a mean age of 25 months and 8 kg weigh1 Bourquelot et a126 reported successful dialysis in 9 of 2, patients in whom distal radiocephalic fistulae were ere ated using an operating microscope. In this group, th, mean interval between fistula creation and first needl, puncture was 4 months. Secondary procedures (transpt~ sition to subcutaneous site, revision of anastomosis, cor rection of proximal venous stenosis) were required in 40 ~, of these fistulae to permit initial access. The princip~ problems associated with these fistulae are the require ment for concurrent access availability (usually a centr~ venous catheter), and their failure to achieve adequate si2 to permit easy puncture and adequate dialysis. This w~" the outcome in five fistulae in the current series. Multipt attempts at puncture are often required, and are unsati: factory in children. However, the presence of a functior ing fistula did permit maturation of both the radial arter and forearm veins sufficient to support a forearm ePTF bridge fistula; consequently, despite inadequacy for dia. ysis, the access site was not lost. Perhaps most importaJ is the long-term access that can be provided by the "goo fistula." Although the mean functional patency rate of th forearm fistulae in our study (including the fistulae whic failed to mature) was disappointing, we nevertheless cor, tinue to advocate their use because the site is usually n( lost for subsequent access procedures. Applebaum et all6 reported the satisfactory use of ePTF bridge fistulae in children. Indeed, use of ePTFE bride grafts has been reported in children as small as 3.8 kg i weighty Nevertheless, there were complications in 9 c 25 grafts, with each graft supporting between 60 and 37 dialysis sessions. Long-term patency was reported to b 88%, although the definition of long-term patency was nc provided. A variety of ePTFE-based, nonconvention; conduits have been reported: femoral to popliteal subct, taneous arterial to arterial grafts, 27 free saphenous vei grafts interposed into the arterial circulation, 2s and 1oo aortocaval fistulae. 29 Such grafts, we believe, should b employed only when traditional routes of access hay been exhausted. Although we report a mean patency c 11 months, ePTFE bridge grafts functioned poorly in chil dren less than 30 kg in weight. Multiple revisions wer required in these children. It is notable that the patenc of femoral ePTFE grafts was less than that for the uppe extremity grafts. Decreased patency was attributed to combination of rapid development of outflow stenose~ early graft infection, and thrombosis (the latter in a par~ plegic, wheelchair-bound child). In summary, there remains no satisfactory method fc providing hemodialysis access in children. Each approac has significant limitations, particularly durability of th intervention. It is this lack of durability which shapes ot attitude toward pediatric dialysis access. We believe th~ the surgeon must regard all children as potentially r~ quiring long-term hemodialysis access. Fistulae, althoug much less satisfactory than in adults, can provide lone term access. Secondary procedures, such as a forean

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HEMODIALYSIS ACCESS IN THE PEDIATRIC PATIENT/LUMSDEN ET ~AL ePTFE graft, can be used following occlusion or failed maturation of a radiocephalic fistula, thereby providing maximal use of that site. A similar philosophy should be zlpplied to each access site. REFERENCES I Quinton WE, Dillard DH, Scribner BH. Cannulation of blood xessels for prolonged hemodiaiysis. Trans Amer Soc Artif Intern Organs. 1960;6:104-113. Brescia M J, Cimino JE, Appel K, Hurwich BJ. Chronic I;emodialysis using vempuncture and a surgically created arterio,cnous fistula. NEJM. 1966;275:1089-1092. ' Baker LD, Johnson JM, Goldfarb D. Expanded polytetrafluo,~thylene (ePTFE) subcutaneous arteriovenous conduit: an improved vascular access for chronic hemodlalysis. Trans Am Soc rtif lntern Organs. 1976;22:382-387. Pistor K, Olbing H, Sch~rer K. Children with chronic renal fail.re in the Federal Republic of Germany: I. Epidemiology, modes f treatment, survival. Arbeitsgemeinschaft ftir p~idlatrische Neph,~logie. Clin Nephrol. 1985;23:272--277. Fine RN. For children renal transplantation is the only realistic hoice. Kidney Int. 1985;28(suppl): 15-17. Offner G, Aschendorff C, Hoyer PF, et al. End stage renal failre. 14 years' experience of dialysis and renal transplantation. Arch ~is Child. 1988;63:120-126. Rosenkranz J, Bonzel KE, Bulla M, et al. Psychosocial adapta~on of children and adolescents with chronic renal failure. Pediatr ~:ephroL 1992;6:459---463. McEnery PT, Stablein DM, Arbus G, Tejani A. Renal transplantation in children--a report of the North American Pediatric renal Transplant Cooperative Study. NEJM. 1992;326:1727-1732. J Potter D, Feduska N, Melzer J, et al. Twenty years of renal trans,lantation in children. Pedzatrics. 1986;77:465-470. 0. Broyer M. Kidney transplantation in children: results of 383 rafts performed at Enfants Malades Hospital from 1973 to 1984. 'dv Nephrol Necker Hosp. 1987; 16:307-334. I. Potter D, Holliday M, Piel CF, et al. Treatment of end stage cnal disease in children: a 15 year experience. Kidney Int. 1980; 8:103-109. ,2. Trachtman H, Hackney P, Tejani A. Pediatric hemodialysis: a lecade's (1974-1984) perspective. Kidney Int. 1986;30:15-22. 3. Chantler C, Carter JE, Bewick M, et al. Ten years experience

with regular haemodialysis and renal transplantation. Arch l~is Child. 1980;55:435--445. 14. Kleinkneeht C, Broyer M, Gagnadoux MF, et ai. Growth in children treated with long-term dialysis. A study of 76 patients. Adv Nephrol Necker Hosp. 1980;9: i 33-163. 15. Fine RN, Salusky IB. CAPD/CCPD in children: four years' experience. Kidney Int. 1986;30:7-10. 16. Applebaum VL, Shashikumar LA, Somers H, et ai. Improved hemodiaiysis access in children. J Pediatr Surg. 1980; 15:764-769. 17. Beselmeier TJ, Santiago EA, Simmons RL, et ai. Arteriovenous shunts for pediatric hemodialysis. Surgery. 1971;70:638--646. 18. Franzone AJ, Tucker BL, Brennan LP, et al. Hemodialysis in children: experience with arteriovenous shunts. Arch Surg. 1971; 102:592-593. 19. Thomas GI. Large vessel applique arteriovenous shunt for hemodialysis: a new concept. Am J Surg. 1970;120:244-248. 20. Mahan JD, Mauer SM, Nevins TE. The Hickman catheter: a new haemodialysis access device for infants and small children. Kidney Int. 1983;24:694-697. 21. Gibson TC, Dyer DP, Postelthwatte ILl, Gough DCS. Vascular access for acute hemodialysis. Arch Dis Child. 1987;62:141-145. 22. Bell PRF. Haemodialysis in infants. Br J Hosp Med. 1984; 32:168-174. 23. Mansefield AO, Cooke TA. A microsurgical technique for the creation of arteriovenous fistulas. Br J Surg. 1978;65:406--409. 24. Idriss FS, Nikaidoh H, King LR, Swenson O. Arteriovenous shunts for hemodialysis in infants and children. J Pediatr Surg. 1971 ;6:639--644. 25. Hardy MA, Schneider Ki~, Levitt SB. An improved technique for the construction of internal arteriovenous fistulas in uremic patients. J Ped Surg. 1974;9:465--466. 26. Bourquelot P, Wolfeler L, Lamy L. Microsurgery for hemodialysis distal artefiovenous fistulae in children weighing less than 10 kg. Proc EDTA. 1981;18:537-541. 27. Robinson HB, Wenzl JE, Williams GR. Internal vascular access for hemodiaiysis access in children weighing less than 15 kg. Surgery. 1979;85:525-529. 28. Perez AJJ, Varagas RR, Gutierrez BR, et al. A new type of subcutaneous arteriovenous fistula for chronic hemodialysis in children. Surgery. 1970;67:355-359. 29. Dodson TF, Stewart MT, Martin LG. Polytetrafluoroethylene aorto-vena caval graft for hemodialysis: report of a case. J Vase Surg. 1993;17:759-761.

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