G. WARWICK 482 Table 13.1.2 Guidelines for initiating renal replacement therapy Table 13.1.1 Symptoms and signs of uremia System Symptoms Signs Other criteria/ descriptors Source Year Indicative eGFR (mL/ min/1.73 m2) Weight loss Anorexia Nausea/vomiting Diarrhea Gastrointestinal 2006 <15 If evidence of characteristic complications of uremia. US NKF K/DOQI Breathlessness Edema Signs of volume overload Cardiorespiratory 2002 8 \200\22310 Dialysis may be started at any time if GFR <15 and symptoms or signs attributable to uremia ; in all patients dialysis should be started before GFR <6 irrespective of symptoms. European Best Practice Paresthesia Restless legs Insomnia Seizures Coma Peripheral neuropathy Neurological 2005 6 \200\22310 Commence dialysis if GFR <10 or if there is evidence of uremia or its complications such as malnutrition; if there is no evidence of uremia or its complications, commence dialysis wh en GFR falls to <6. CARI Impotence Menstrual irregularity Endocrine Tiredness, lethargy Bruising Increased bleeding Pallor Hematological Pruritus Dry skin Excoriation Dermatological 2002 <14 Where there is evidence of malnutrition; symptoms interfere with quality of life; or there is predictable decline in GFR. UK Renal Association Different treatments may be appropriate at different times in an individual \200\231s treat ment \200\230career \200\231. Equally it is important to give a realistic picture of life on RRT. Even those who do well are likely to have temporary peri- ods where they experience intercurrent illness or prob- lems related to dialysis treatment. K/DOQI, Kidney Disease Outcomes Quality Initiative; CARI, Caring for Australians with Renal Impairment. Choosing the time to start dialysis treatment There is no universal agreement on the optima l time for starting dialysis. Dialysis imposes considerable physical, social and eco- nomic costs for patients. These have to be balanced against the bene \201 ts of control of urem ia and salt and water bal- ance in terms of symptom improvement, quality of life and prolon gation of survival. Psychosocial aspects of predialysis care Many patients may feel well with no symptoms despi te sig- ni \201 cant reductions in GFR. In some societies and cultures, there may be dif \201 culties in accepting advice about preparation for a future illness. There may be compl ex psychological and social issues regarding acceptance/denial of the diagnosis and prognos is; adherence to treatment regimens; participation in predial- ysis counseling/ education. There are several other aspects which should be consid- ered in predialysis clinics: Absolute indications for starting dialysis These are all the consequences of advanced renal failure and are usually accompanied by a severe biochemical dis- turbance: \200 uncontrolled uremic symptoms (e.g. nausea, vomiting, itching, insomnia, neuropathy); salt a nd water overload; persistent hyperkalemia; progressive malnutrition; pericarditis; severe acidosis. Employment An important part of planning for RRT should be to mini- mize disruption for pat ients who are in employment. \200 \200 \200 \200 Social interactions Involvement of family, carers and often professional social workers is helpful to maintain normal social function and to assist with access to support at home and other bene \201 ts. Guidelines for commencement of dialysis Exactly when dialysis should be started for individ ual patients is not clear. Patients known to a nephrologist should be started on dialysis b efore the onset of life-threatening complica- tions. The inability to reliably predict when an individual patient will become symptomatic has led many experts and guide- lines to rec ommend starting dialysis electively based on measurements of GFR. Sexual health Advice is often sought about sexual activity. There is a high prevalence of e rectile dysfunction and low libido. Although pregnancy is rare in patients with advanced CK D, patients of childbearing age should be advised about contraception. Hepatitis B vaccination This should be performed using a high dose regimen as soon as it is clear that patients will progress to RRT; earlier vaccination leads to a greater rate of s eroconversion. CHAPTER 13.1 Dialysis strategies 483 Guidelines from different authorities regarding the level of renal function to start dialys is are shown in Table 13.1.2. However, all of these still leave room for clinical judgment. Hemodialysis Hemodialysis (HD) therapy is often the default for many patients, especially t hose presenting late as uremic emer- gencies without established vascular or peritoneal acc ess or after PD has failed. GFR at commencement of dialysis Over the last 20 years the level of renal function (as esti - mated by derived GFR) at which dialysis has started has tended to increase. Data from the United States Renal Data System (USRDS) show that the mean eGFR at start of dialysis has i ncreased progressively since 1995 and was 9.8 mL/min/1.73 m2 in 2004. In the UK the mean eG FR of patients starting RRT was: \200 \200 Home HD Home HD is a successful treatment with excellent out- comes in terms of survival an d quality of life. This form of treatment was pioneered in the late 1960s when chronic dial ysis started and is still the treatment of choice in some centers around the world. Home HD was endorsed by the UK National Institute for Clinical Excellence in 2002 although this wa s not a surprise to experienced nephrologists. Over the years, both the percentage and abso lute numbers of patients carrying out HD at home has declined. This re \202 ects the aging dialysis population and the increased availability of center or satellite unit based dialy sis nearer patients \200\231 homes. Nevertheless, it is important to identify suitable cand idates for home HD in the predialysis phase based on local facili- ties/resources, patient preference and the availability of a suitable helper and home premises. These patients can then be fast-tracked to an independent treatment at home. 6.0 mL/min/1.73 m2 in 1997; 7.9 mL/min/1.73 m2 in 2005. The starting eGFR seems to be stable over more recent years. Predicting rate of decline in GFR Even with the use of eGFR-vs-time plots to extrapolate wh en a certain eGFR value (e.g. 10 mL/min/1.73 m2) will be reached, many patients develop sym ptoms earlier than anticipated or conversely kidney function may stabilize for many years. Commencing dialysis with a higher GFR: \200\230early start \200\231 Some experts have sugg ested that starting dialysis earlier will lead to improved survival. However, there are no con- trolled studies proving this and there are con \202 icting data from observational an d cohort studies. An important confounding factor is adjustment for lead time bias. Surviva l must be counted from the point where dialysis may have been started and therefore will in clude a period of nondialysis treatment for patients starting later. A randomized study to investigate this is dif \201 cult due to issues with funding earlier dialysis treatment an d patient consent/recruitment. Despite these problems, one such trial is underway in Austra lia and New Zealand (The IDEAL study: Initiation of Dialysis Early and Late) in which patie nts are being randomized to start RRT at esti- mated GFRs of 5 \200\2237 versus 10 \200\223 14 mL/min/1.73 m2 (Cockcroft \200\223Gault formula). The study is due to report in 2010 and potentially will give important information on this dif \201 cult question. Unit-based HD Many patients choose HD at a main center or satellite unit when offered choic e. In the UK, the percentage of patients starting HD (versus PD or pre-emptive transplantat ion) as initial therapy has increased from 58% in 1998 to 76% in 2005. Some of this re \202 ects the previous overreliance on PD due to a lack of HD facilities. Contraindications for HD Patients with extremely poor peripheral veins or severe cardiac di sease which might cause hemodynamic instability are often considered to do badly on HD. How ever, neither of these are absolute contraindications. Vascular access can nearly always be obtained in the short term using a tunneled dialysis catheter and the hemody- namic respon se to dialysis is quite variable. Recent studies have shown better outcomes from HD for pat ients with impaired cardiac function compared to PD. Choosing an initial mode of renal replacement therapy The choice of initial treatment for p atients with progressive renal failure is in \202 uenced by a whole range of factors \200 \223 medical, social and psychological. Absolute and relative contraindications to both PD and HD are listed in Table 13.1.3. Although many centers claim to offer a free choice of tr eatments, this is in \202 uenced by the views and opinions of health professionals and oft en by the availability and local experience of different forms of therapy. The initial mode of RRT varies considerably between cent- ers and countries, probably re \202 ecting avail able facilities, geography and physician opinion/prejudice: \200 \200 Vascular access planning Planning for vascular access is an essential and important part of the predialysis process. Patients should be advised to preserve the forearm veins in their nondominant arm by restricting venepuncture and avoiding the use of intravenous lines. For patients planned to have HD, an arteriovenous \201 stula (AVF) should be constructed >6 months before the pre- dicted time when dialysis will be required. This gives time for the \201 stula to develop adequately. Once formed, the AVF should be carefully monitored and assessed. When adequate vessel enlargement does not develop, revision by surgery or percuta neous angioplasty may be required or a second \201 stula may be created. Although it may be argued that all patients should have an AVF formed even if their initial mode of therapy will be PD worldwide, 90% of patients starting dialysis start on HD. In the UK in 2005, 23.7% of all i ncident patients were on some form of PD at 90 days from start of RRT. This \201 gure var ied from 4.6 to 58.3% among units offering PD. G. WARWICK 484 The timing of catheter insertion for PD is crucial. Ideally the catheter should be inserted at least 2 weeks before required to allow wound healing and to reduce the risk of leaks al ong the catheter track. This requires careful planning which may be easier if there is easy access to day- case insertion by nephrologists. An interesting development over recent yea rs has been the early insertion of PD catheters with subcutaneous placement of the external part of the catheter. This can then be quickly exteriorized when required to permit dialys is to start. (due to the limited longevity of this form of treatment), studies have shown that only a sm all proportion of such AVFs are ever used for HD. Peritoneal dialysis Peritoneal dialysis (PD) was \201 rst described as a chronic form of treatment for renal failure in 1976. Its potential was not fully accepted initially but, in the 1980s, PD programs expanded rapidly in certain countries, notably the UK and Mexico. T his re \202 ected inadequate investment in HD facilities at a time when dialysis programs were expanding rapidly. Patients who are informed about the options for RRT may choose PD b ecause of: \200 \200 \200 \200 Supportive nondialysis treatment Over 40 years of RRT the average age of patients starting dialysis has gradually increased. Many patients with comor- bid conditions which would prev iously have excluded them from treatment are now accepted onto dialysis pro- grammes and th ere is general agreement that age by itself is not a contraindication to treatment. Previou s policies restricting access to dialysis on the basis of age were often driven by resource issues or physician prejudice. However, increasingly the bene \201 t in terms of long-ter m sur- vival and quality of life in frail elderly patients with multiple comorbidities has been questioned. Many physicians believe that for some patients in this category, a conserv ative and supportive approach is justi \201 ed. This approach focuses on dealing with medi cal problems which can be treated with- out dialysis (e.g. anemia, \202 uid overload, aci dosis, disturbances of bone mineral metabolism) and careful attention to symp- tom control. In addition, patients \200\231 psychological and social needs are addressed and, as patien ts become more sympto- matic, a clear plan for end-of-life care including symptom control a nd place of death can be agreed by the patient, their family and carers and the multidiscip linary team. There is evidence from observational studies that elderly patients with multip le comorbid conditions and poor func- tional status treated in this way have similar or eve n improved survival compared to those starting dialysis pro- grams. However, this has not b een tested in a randomized trial and probably never will be. Thus nephrologists and multidi sciplinary teams have to discuss with such patients and their families the advantages and d isadvantages of dialysis and promote supportive care as a valid choice for many patients. W here there is uncertainty about the bene \201 ts of RRT, one option is to initiate a time- limited trial of dialysis. A speci \201 c date can be set, often 30 \200\22360 days after starting dialysis, to review with patients and their families whether quality of life has i mproved suf \201 ciently to justify continuing treat- ment. its relative simplicity and ease of learning; desire for independence; geography (distance from a HD unit); home circumstances. Overnight automated PD has made this a more attractive option for those with responsibiliti es during the day (e.g. work, childcare). There are few absolute contraindications to PD (T able 13.1.3). However, there are many relative contraindications but even major disabilitie s such as blindness and severe arthritis of the hands can be overcome by use of a variety o f ingenious devices to permit patients to carry out exchanges. During the predialysis phase it is important to clarify that PD is unlikely to be a long-term option. As residual renal function declines, patients may not obtain adequate control of solute balance or salt and water overload, necessitating transfer to HD. Table 13.1.3 Contraindications to different forms of dialysis Modality Absolute Relative Severe cardiac disease Extensive vascular disease (e.g. absent pulses in arms) Poor venous access Geographical isolation Body image (concern regarding appearance of arteriovenous \201 stula) Needle phobia Hemodialysis Gastrointestinal or urinary stoma Known peri- toneal sclerosis Diaphragmatic \202 uid lea k Multiple abdominal operations Peritoneal dialysis Ascites Pre-emptive transplantation Where patients with CKD are known to have progres- sively decli ning renal function, pre-emptive (i.e. before dialysis is required) transplantation is an a ttractive option. Many studies have shown that patients transplanted pre- emptively have be tter outcomes in terms of transplant and patient survival. Pre-emptive transplants may be c arried out by: \200 \200 Morbid obesity/large muscle bulk Hernia Severe organomegaly (e.g. massive polycystic kidneys) Severe respiratory disease Ong oing nephrotic syndrome Suppurative or broken abdominal skin wound Severe back pain Lack of manual dexterity Unsuitable home environment Body image Cognitive problems living related or living unrelated transplantation; cadaveric transplantation with a kidney obtained through a national or regional waiting list. In recent years, living related and living unrelated trans- plantation has increased in man y countries. Where this CHAPTER 13.1 Dialysis strategies 485 service is available, every effort should be made to identify a living donor as part of the predialysis education process. This allows a programmed, elective transplant to be per- fo rmed when the recipient \200\231s condition is stable. Different rules and regulations gove rn the placement of predialysis patients on cadaveric kidney transplant lists. In the UK, p atients may be added to the national cadaveric transplant list if it is estimated that they will need dialysis within 6 months \200\223 although as discussed elsewhere in this chapt er this is notoriously hard to predict. One group of patients who may particularly bene \201 t from the pre-emptive approach is those with type I diabetes mel- litus and advanced CKD who may be worked up for simul- taneous pancreas and kidney (SPK) transplantation from a cadaveric donor. These patients have a predictable decline in renal function and often ha ve unstable diabetes mellitus and bene \201 t doubly from successful SPK transplants. these patients may be predetermined to have poorer out- comes as a result of comorbid condi tions which may have delayed their referral in the \201 rst place. Reasons for late referral The reasons why patients are referred late is not clear. Studies have shown that up to 50% of patients were already known to have renal impairment and oppor tunities to refer were missed by both primary and secondary care physicians. This may be be cause the severity or progression of the renal disease is missed or because the patient is not considered to be a candidate for RRT until the last moment. Outcomes of different modes of RRT An important question for patients starting RRT is which modality will improve survival. There is unequivocal evidence that renal transplantation p rovides the best chance of survival and improves quality of life. Earlier studies which com pared survival post transplant with patients on dialysis were \202 awed by the selection bias of those who had been transplanted. However, studies comparing outcomes only with pati ents listed for transplantation clearly show the survival benefit of transplantation over t hose who remain on the waiting list even in higher risk patients with diabetes mellitus or older age. Controversy exists about the survival advantage of PD ver- sus HD. Over the year s there have been con \202 icting reports favoring each modality. However, all the studies are retro- spective or observational and it is dif \201 cult to control for other factors , particularly comorbidity, which have a major in \202 uence on survival. There are no con trolled trials randomizing patients to these treatments. One such study was attempted in Th e Netherlands but recruitment was dif \201 cult and the study was abandoned. The best sour ce of comparative data is probably from large registries (Table 13.1.4 and Fig. 13.1.3). Late referral Many patients with CKD and diabetes mellitus, hyperten- sion and vascular dis ease are known to primary care or to general physicians. Despite this, late referral to nep hrolo- gists continues to handicap the care of patients who will require dialysis or transp lantation. These patients are sometimes referred to as \200\230crash-landers \200\231. The re is no universally agreed de \201 nition of late referral. Most studies have included pa tients referred within 3 or 4 months of the need to start dialysis. However, recent stud- i es in this area suggest that it may take up to a year to prepare a patient for dialysis or transplantation. Implications of late referral Numerous studies over the years have shown that patients refe rred for nephrology care late have poorer outcomes compared to patients known to nephrology services for longer. These include: \200 increased mortality; \200 reduced treatment c hoices with more patients receiving HD; reduced access to transplantation; increased morbid ity and hospitalization. \200 USRDS survival data The 5 year survival adjusted for age, gender, race and pri- mary renal diagnosis is: \200 \200 This reflects the complexity of the process regarding choice of RRT. Late-referred patients have to cope with the implications of the diagnosis, undergo educational programs and quic kly make a decision about modality of dialysis and transplanta- tion. Local facilities and resources may dictate the speed with which vascular or peritoneal access can be established . For many patients, late referral restricts choice and patients are often established on H D via a tunneled HD catheter. Peritoneal dialysis is less likely to be the initial mode of therapy and the opportunity to perform pre-emptive transplantation is lost. More importantl y, for elderly and frail patients and their families, the opportunity to have information a nd a careful consideration of the bene \201 ts of dialysis compared to sup- portive treatm ent is lost. Some patients may start dialysis inappropriately when they present as uremic e mergencies. There is an association between late referral and poorer outcomes but this may not be causal. Although late referral may be associated with increased complications associ ated with acute hospitalization and temporary vascular access, 34.1% for PD; 34.7% for HD. European registry data Data for survival on PD and HD are shown in Fig. 13.1.3 and again th ere is no difference although there is improved Table 13.1.4 United States Renal Data Systems survival of incident patients by modality of \201 rst RRT adjusted for age, gender, race and primary renal diagnosis % survival unadjusted % survival adjusted Year of incident cohort Dialysis modality No. of years survival 3 2000 59.3 55.7 Peritoneal dialysis 5 1998 37.0 34.1 10 1993 12.2 11.1 3 2000 50.2 53.2 Hemodialysis 5 1998 31.4 34.7 10 1993 9.7 11.9 G. WARWICK 486 Hemodialysis Peritoneal dialysis 1.0 1.0 0.9 0.9 0.8 0.8 0.7 0.7 y t i l i y t i l i 0.6 0.6 b a b o r p b a b o r p 0.5 0.5 l a v v r u l a v v r u i i 0.4S 0.4S Diabetes Diabetes 0.3 0.3 Hypertension / renal vascular disease Hypertension / renal vascular disease 0.2 0.2 Glomerulonephritis Glomerulonephritis Other cause Other cause 0.1 0.1 All All 0.0 0.0 4 5 0 1 2 3 4 5 0 1 2 3 Years Years Fig. 13.1.3 Adjusted survival from day 91 for incident patients 1995 \200\2231999 from Euro pean Renal Registry by primary diagnosis. survival compared to USRDS data. This is a consistent \201 nd- ing comparing USRDS data t o European and Japanese data. Within the limitations of these data, there appears to be no clear survival advantage of one form of dialysis treatment. clearance may be inadequate especially for larger patients. This is a major cause of techni que failure and transfer to HD. Withdrawal of dialysis The increasing age and comorbidity of the prevalent dialy- sis popul ation means that patients and nephrologists are frequently faced with choices about continu ing dialysis treatment. Data from North America suggest that stopping dialysis accounts for 20% of all deaths of patients on RRT. This outcome is less often reported in Europe. Deat h usually follows within 7 \200\22314 days of stopping RRT although some patients may survi ve much longer especially if they retain some residual renal function. Withdrawal of dialys is occurs more frequently in associa- tion with: \200 \200 \200 \200 \200 \200 \200 The importance of residual renal function Replacement of renal function by dialysis, althou gh life-sus- taining, is a very crude, empiric and inadequate therapy. Peritoneal dialysis will deliver an average clearance of small molecules of 5-8 mL/min and although the ef \201 ciency of HD is much greater the time-averaged value will be similar for conventional thrice weekly sessions. Therefore, when a patient starts dialysis with an eGFR of 5 \200 \22310 mL/min/1.73 m2, solute clearance will often be greater through native kidney functio n than by dialysis. Those patients who retain this residual renal function often remain hea lthier on dialysis with better appetite, improved solute and phosphate control, better BP a nd salt and water balance and less anemia. Unfortunately, over time for many kidney disease s, the GFR continues to decline once dialysis is started. Most studies suggest that this ha ppens more quickly on HD but this is not a universal \201 nding. Some have advocated the continued use of renin \200\223angi- otensin blockage once dialysis has started to preserve residual function but the evidence for this strategy is weak. Diuretic therapy has not bee n shown to preserve GFR. The loss of residual renal function is particularly important for patients on PD where the scope for increasing dialysis dose is limited. When residual renal function declines, total increasing age; diabetes mellitus; widespread vascular disease; race (Caucasians > Blacks i n USA); female sex; greater educational attainment; poor functional and physical status. This decision may be initiated by the patient, family/carer or nephrologist. Often the deci sion is made after a progressive decline in physical and mental capacity due to comorbid il lness or sometimes after a severe acute illness. Some patients judge that their quality of life has declined to the point where the dif \201 culties associated with dialysis are no longer acceptable. CHAPTER 13.1 Dialysis strategies 487 Most societies accept the autonomy of the competent patient to make this decision. Dif \201 culties may arise where the patient is no longer competent and differences of opin- io n arise between the family and the physician. In the USA, the Renal Physicians Association and the American Society of Nephrology have produced useful clinical practice guidelines on these issues (see \200\230Further reading \200\231). Increasingly patients may draw up an advanced directive about their treatment should their mental capacity change. When patient s choose to stop dialysis, it is important to control symptoms including pain, vomiting and pruritus and to prevent pulmonary edema by judicious \202 uid man- agement and use of op iate drugs. Walser M, Thorpe B. 12-Step treatment program to help you avoid dialysis. Hoboken, NJ: Wiley; 2004. Internet resources The Renal Association: http://www.renal.org/ The Renal Registry: http://www.renalreg.org National Kidney Federation Dialysis Outcomes Quality Initiative: http://www.kidney.org/professionals/kdoqi/ UK National Kidney Federation: http://www.kidney.org.uk/ Care for Australians with Renal Impairment: Further reading Ansell D, Feest TG, Tomson C, et al. UK Renal Registry Report. http://www.cari.org.au/ European Best Practice Guidelines: Bristol: UK Renal Registry; 2006. Galla JH. Clinical practice guideline on shared decision-making in the appropriate initiati on of and withdrawal from dialysis. Am Soc Nephrol 2000; 11: 1340 \200\2231342. http://www.ndt-educational.org/guidelines.asp See also Clinical assessment of renal function, p. 12 Selection and preparation of recipien ts, p. 544 Vascular access, p. 488 Hemodialysis, hemofiltration, and hemodiafiltration, p. 494 Peritoneal dialysis, p. 506 Horl WH, Koch KM, Lindsay RM, Ronco C, Winchester JF (eds), Replacement of renal function b y dialysis. Dordrecht: Kluwer; 2004. UK Department of Health. The National Service Framework for Renal Services Part One: Dialys is and Transplantation, January 2004. US Renal Data System. USRDS 2006 Annual Data Report: Atlas of End-Stage Renal Disease in th e United States. Bethesda, MD: NIH, NIDDKD; 2006. Sources of information for patients and carers Stein A, Wild J. Kidney failure explained. L ondon: Class Health; 2006. A. BAKRAN 488 Vascular access Introduction Vascular access is currently the rate-limiting component for hemodialysis. Des pite major advances in dialysis tech- nology, without satisfactory access to the circulatio n, dialy- sis adequacy will remain poor. Blood needs to be taken from the patient, pumped t hrough the dialysis machine and returned back to the patient. The conduit from which blood is taken and through which it is returned is de \201 ned as the vascular access. It is the commonest vascular access \201 stula. Distal ulnar-basilic or radio-basilic This involves mobilizing the forearm basilic vein and either directly anastomosing to the ulnar artery or transposing to join the radial artery at the wrist. Brachio-cephalic The median cephalic vein is joined to the brachial artery in the antecubit al fossa. It is the second commonest form of \201 stula in Europe. Types of vascular access Autogenous arteriovenous \201 stula (AVF). Prosthetic graft \201 stula. Biological graft \201 stula. Central venous catheter. Brachio-basilic transposition The basilic vein is anastomosed to the brachial artery after being transposed super \201 cially and laterally from its deep lying medial position. Saph enous vein transposition to the arm Requirement for dialysis Blood \202 ow should be suf \201 cient to enable adequate hemo- dialysis. Generally blood \202 ows of >400 mL/min through \201 stulas are preferable a lthough \202 ows less than this are usual for dialy- sis central venous catheters. Autoge nous \201 stula blood \202 ow can range from <250 mL to several litres per minute, the former being inadequate and the latter excessive with risk of cardiac failure. Graft \201 stula blood \202 ow needs to be >600 mL/min to avoid thrombosis but again can reach seve ral litres per minute. Acceptable \201 stula blood \202 ow rates range between 500 mL/ min and 1.5 L/min. Lower limb \201 stulae Saphenous vein thigh loop This involves mobilizing the saphenous v ein and tunneling it in a U-shape bend to join the femoral artery. Super \201 cial femoral vein transposition This is a rare \201 stula which mobilizes the super \201 cial femoral vein and transposes it super \201 cially and laterally, anastomo - sing it to the super \201 cial femoral artery Prosthetic and biological grafts These can be: \200 \200 \200 \200 \200 \200 Expanded polytetra \202 uoroethylene (ePTFE). Polyurethane. Dacron (rarely used). Bovine m esenteric vein. Bovine ureter. Bovine carotid artery. Guiding principles in vascular access surgery Use upper limb before lower limb (less risk o f infection). Use distal \201 stula sites (wrist) before proximal sites (allows proximal sites to be preserved for later use). Use autogenous vein before prosthetic graft (for reas ons given below). Use nondominant arm before dominant arm (allows the patient to use domina nt arm for eating, writing, etc., while on dialysis). Whilst creating the current \201 st ula, the surgeon needs to plan ahead to the next procedure. Prosthetic grafts ePTFE (the coating used in nonstick frying pans) has been used for the pa st 30 years. Despite lack of compliance, PTFE grafts are resilient due to hydrophobic prope rties making blood less likely to stick to it. The holes created by dialysis needles do not heal and are sealed by a pseudointimal lining and platelet plugs. The polyurethane graft d oes have self-sealing properties but has a greater risk of thrombosis. Assessment of patients for vascular access Clinical examination of the upper limbs with a t ourniquet in place in a warm room. Inspection of veins in both forearms and arms and checki ng the radial and brachial pulses. Duplex scan to map veins and \202 ow in arteries may b e undertaken routinely if available but is always required when there is clinical doubt, pa rticularly in a diabetic, eld- erly or complex patient. Venography or MR angiography is req uired when there is concern about central vein or arterial stenosis. Biological grafts The bovine biological grafts are essentially acellular colla- gen tubes. They are similar to vein, easier to implant but are more expensive than prosthetic grafts. Outcomes are similar to grafts. Types of graft \201 stula Upper limb Forearm straight graft Run from radial artery to ant ecubital vein. Types of autogenous AVF Upper limb \201 stulae Radio-cephalic This is eponymously known a s the Cimino \200\223Brescia AVF. The cephalic vein is joined to the radial artery at the w rist (Fig. 13.2.1). Forearm loop graft Run from brachial artery to antecubital vein in a U-shaped loop. CHAPTER 13.2 Vascular access 489 Disadvantages of autogenous AVF There is an early failure rate of up to 30% for radio-cepha lic AVFs, but less for others. Often suitable veins are not available due to prior usage fo r IV infusions. They need a maturation time of several weeks before usage. Fistula vein may need transposition to a super \201 cial position in obese patients. Cosmetically less sat isfactory, especially if they develop aneurysmal dilatation. Advantages of prosthetic or biological grafts Good quality grafts are easily available \200\230off the shelf \200\231 in appropriate lengths. They allow earlier needling for dia lysis, particularly the prosthetic grafts. In an emergency, the graft can be needled almost immediately although there is greater risk of infec- tion and bleeding at this early stage . Biological grafts are easy to handle and anastomose com- pared to prosthetic grafts. They are cosmetically more acceptable. Fig. 13.2.1 A mature radio-cephalic AVF used for hemodialysis. Arm graft Run from brachial artery to axillary vein. Lower limb Thigh loop graft Run from femoral artery to saphenous or femoral vein in the gro in. Disadvantages of prosthetic or biological grafts There is a lower long-term patency (Figs 1 3.2.3 and 13.2.4). The risk of thrombosis due to the development of neointi- mal hyperplasi a at the venous anastomosis is signi \201 cantly greater. There is a greater risk of infec tion requiring excision of the graft. Biological grafts are susceptible to aneurysm formati on. The cost is high. Thigh straight graft Run from the distal super \201 cial femoral artery to the saphe- nous or femoral vein in the groin. Advantages of autogenous AVF Biological tissues generally handle better than prosthetic. Th e long-term patency is better (Figs 13.1.3 and 13.1.4). There is resilience to thrombosis i n hemodynamically unstable patients. There are low rates of septic complications which gene r- ally respond to antibiotic therapy. There is ease of needling for dialysis except in obe se patients Low cost. Complications of \201 stulas Thrombosis This is the greatest risk, requiring radiological or surgical intervention to re-establish the \201 stula. Infection This is less with autogenous \201 stulas and usually responds to appropriate an tibiotic therapy but grafts frequently have to be removed when infection develops. Fig. 13.2.2 Complications of AVF formation: central venous occlusion following previous cen tral venous catheter insertion. Right arm swelling following brachio-cephalic AVF formation due to a right subclavian vein occlusion following a previous right subclavian vein cathet er. Note the occluded subclavian stent previously inserted to open up the vein. The AVF had to be ligated eventually. A. BAKRAN 490 It may present even more dramatically as complete anesthe- sia of the \201 ngers, pain in the hand or forearm, loss of move- ment, and eventually with ulceration and gangrene. This presentation is a surgical emergency and is due to ischemia of the hand and forearm, with loss of sensory and motor nerve function. Unless the \201 stula is taken down or revised rapidly, it will lead to long-term loss of hand/fore- arm function. No patient should devel op pain in the hand after proximal \201 stula surgery and so the operating surgeon should be noti \201 ed to assess the possibility of a steal syndrome. Steal syndrome See below. Aneurysm formation The risk is greatest with biological and autogenous \201 stulas. High output cardiac failure This occurs when \201 stula blood \202 ow becomes excessive . One extraordinary case report revealed a blood \202 ow of >30 L/min before the surgeon banded the \201 stula down to a \202 ow of 600 mL/min. Venous hypertension This may develop in the \201 stula limb and be exacerbated by central vein stenoses from previous central venous cathe- ters (Fig. 13.2.2). If it fails to settl e as venous collaterals open, options include central vein angioplasty with or without sten t insertion or ligation of the AVF. Physiological changes after graft surgery Usually 6 mm PTFE grafts are implanted and the gr afts should not change in size with time. The principle problem with grafts is neointimal h yperplasia which causes a gradual narrowing of the venous anastomo- sis leading to \201 s tula thrombosis. Flow monitoring has been suggested as a means of detect- ing risk of graft thrombosis although evidence from the lit- erature is mixed. Percutaneous thrombectomy and angioplasty of the venous stenosis is the procedure of choice to re-establish patency with surgery as an alternative. Revision of the venous anastomosis may be required. Seroma This may occur with prosthetic \201 stulas. Physiological changes after \201 stula surgery Creation of an AVF or graft produces a new low pressure circuit through which blood \202 ows preferentially. The limb with a \201 stula attracts increased blood \202 ow com- pared to the other limb. The \201 stula ve in dilates rapidly over the \201 rst 2 \200\2233 weeks after surgery and then at a slower rate subsequently. The artery also remodels and dilates although less than the vein. Howev er, in some patients the artery can become huge over time. Major hemodynamic changes take p lace at the \201 stula anas- tomosis due to changes in \202 ow patterns. The normal lam inar blood \202 ow becomes turbulent with changes in wall shear stress, leading to variab le degrees of intimal hyperplasia and \201 stula vein stenosis. Percutaneous angioplasty or surgical revision of the \201 stula will be necessary in severe cases. Vascular access in special groups Diabetics Pose problems due to poor vessels. Often veins have already been used and arteries are calci \201 ed. Are more likely to need a proximal \201 stula hence greater risk of steal syndrome. Similar principles for vascular access p lanning apply in diabetics but there is a greater necessity for preoperative vessel imaging . Elderly patients Need to be evaluated more carefully before access per- formed. If survival prospects are poor then a long-term tunneled catheter may be appropriate, but if the progn osis is good then an AVF/graft should be considered. Failure of AVF maturation The radio-cephalic AVF has a high incidence of nonmatura- tion (u p to 30%) but when successful can survive >20 years without thrombosis. The causes of nonma turation can be related to: \200 \200 \200 Children PD is the preferred treatment but an AVF remains an option. small size and quality of vein or artery; raised blood viscosity; intimal hyperplasia in th e segment just distal to the anas- tomosis. When to needle a \201 stula AVFs can be needled mostly between 4 and 6 weeks (occa- siona lly earlier if well-developed). Needling is too often delayed in the UK compared to other E uropean countries. Grafts can be needled within 2 weeks after the pain of the tunneling has settled and a pseudointima allowed to develop. More proximal fistulas using the brachial artery as in \202 ow have less risk of failure a nd a higher blood \202 ow. However, there is a potential for development of a \200\230st eal syndrome \200\231. Steal syndrome A steal syndrome typically presents with: \200 \200 \200 \200 \200 Central venous catheters Types of catheters Catheters are generally made of polyurethane an d may be single lumen, double lumen or two separate single cathe- ters inserted for drawing and returning blood.