الفهرس 
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Abstract
Kidney damage refers to a broad range of abnormalities
observed clinical assessment , which may be in sensitive and nonspecific
for the cause of disease but may precede elevation in kidney
function. Excretory, endocrine and metabolic functions decline together
in most chronic kidney diseases. GFR is generally accepted as the best
over all index of kidney function. We refer to a GFR<60 ml/min/1.73m2
as decreased GFR and a GFR <15 ml/min 1.73m2 as kidney failure. AKI
may occur in patients with CKD and hasten the progression to kidney
failure (Hsu CY et al ., 2008).
Vascular access to obtain a functional portal to a patient’s
circulatory system is vital to delivering adequate hemodialysis therapy.
The ideal hemodialysis access would fulfill three criteria. It would have a
long use-life, provide an adequate blood flow rate to achieve the dialysis
prescription, and have a low rate of associated complications .Currently
no form of hemodialysis access perfectly achieves all three criteria;
however , the native forearm arteriovenous fistula (AVF) comes closest,
with studies showing that this form of access provides the best 4–5-year
patency rates and requires the fewest interventions. Following the
forearm AVF, in order of preference, are the upper arm AVF, the
arteriovenous graft (AVG) and the cuffed central venous catheter
(K/DOQI ., 2000)
Summary
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The 2000 guidelines recommend that at least 50% of patients
electing to receive hemodialysis for renal replacement therapy should
have a native AVF placed, and that 40% of prevalent dialysis patients
should have a native AVF. Since the publication of this guideline,
numerous studies have shown a graded mortality risk dependent on
access type, with the highest risk associated with central venous dialysis
catheters, followed by AVGs and then AVFs (K/DOQI ., 2000).
Proper patient evaluation and dialysis access selection prior to
access placement are important to success. Factors such as the
characteristics of a patient’s arterial and venous systems cardiopulmonary
adequacy, and life expectancy can all influence which access type and
location are desirable for a given patient. A thorough physical
examination should be performed to help guide additional diagnostic
testing prior to access placement (Robbin ML et al., 2002).
Routine preoperative vascular mapping with doppler ultrasound to
dentify suitable vessels prior to AVF placement has been shown to
increase numbers of AVFs placed (as opposed to AVGs and central
venous catheters) and to improve access outcomes, especially for forearm
fistulas, in women and patients with diabetes .If the patient has physical
findings indicative of, or risk factors for, venous impairment in the target
extremity (such as edema, collateral vein development, differential
extremity sizes, a pace maker or previous catheter placement) then
venography should be considered , as doppler ultrasound is generally less
accurate for evaluation of central venous structures (Allon M et al.,
2001).
Summary
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Infectious complications of the vascular access are a major source
of morbidity and mortality among hemodialysis (HD) patients. Numerous
reports implicate the vascular access in up to 48 to 73% counted of all
bacteremia in HD patients. Mortality among the HD population accessrelated
infection is highest when central venous are employed. Native
arteriovenous fistulas carry lowest risk of infection. Unfortunately,
prosthetic arteriovenous grafts, which represent the most common type of
HD access in the United States, have been repeatedly shown to be a risk
factor for bacteremic and non bacteremic infections. Silent infection in
old nonfunctional clotted prosthetic arteriovenous grafts has recently
been recognized as a frequent cause of bacteremia and morbidity among
HD patients (GEORGE M et al., 2001).
Management of vascular access-related infection has two aspects:
The first relates choice, duration, and mode of administration of antibiotic
therapy. Empiric antibiotic therapy, guided by demographic and severity
of illness, should be employed when the causative organisms are
unknown. Prolonged administration of specific parenteral antibiotics is
Infection , especially in cases of staphylococcal bacteremia. The second
aspect relates to management of the vascular access (GEORGE M et al.,
2001).
All other things being equal, fistulas are preferred over grafts, and
grafts are preferred over catheters. Mature fistulas have better longevity
and require fewer interventions, as compared with mature grafts. The
major hurdle to increasing fistula use is the high rate of failure to mature
of newly created fistulas. There is a desperate need for enhanced
understanding of the mechanisms of failure to mature and the optimal
type and timing of interventions to promote maturity. Grafts are prone to
Summary
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frequent stenosis and thrombosis .Surveillance for graft stenosis with
preemptive angioplasty may reduce graft thrombosis, but recent
randomized clinical trials have questioned the efficacy of this approach.
Graft stenosis results from aggressive neointimal hyperplasia, and
pharmacological pproaches to slowing this process are being investigated
in clinical trials. Catheters are prone to frequent thrombosis and infection
(Allon ., 2007).
Fistulas have the longest patency and require the fewest
interventions after they are cannulated successfully for dialysis.
However, they have the greatest primary failure rate and require the
longest time for maturation (6 to 12 weeks). Grafts have a lower primary
failure rate than fistulas and can be cannulated fairly quickly (within 2 to
3 weeks). However, they are prone to recurrent stenosis and thrombosis
and have a greater frequency of salvage procedures (angioplasty,
thrombectomy , and surgical revision) to maintain their long-term patency
for dialysis. Finally, catheters are easily placed and can be used for
dialysis immediately (Ivan D. Maya et al ., 2008).