Blog from the Guest Lecture Series at East Carolina University – Brody School of Medicine
Lecturer: Tushar Vachharajani, MD
Blogger: Tejas Desai, MD
Dr. V started out with a background of the Fistula First initiative. K/DOQI first indicated that an AVF is the first choice of dialysis access since 2003. The current goal is to have 66% of all accesses AVF by the end of December 2010 – we are currently at 57.5%.
One of the biggest misconceptions is that every ESRD patient should have an AVF. In reality, Dr. V feels that every patient should be evaluated for an AVF, but not all patients should obtain one. AVF’s are optimal because they provide better dialysis, last longer, and have less complications (infections, sepsis, and need for interventions).
Dr. V indicated that AVF’s are the best access but only when they work. There is a lot of primary AVF failures. 23-60% of AVF’s undergo primary failure (an access that never matures enough to provide dialysis). Dr. V showed a graph that highlights the probability of having a catheter as your first access: those patients that are not followed by a nephrologist have > 90% chance of having a catheter as their first access. This probability drops to 70% if you have seen at least 2 nephrologists during your CKD phase. Catheters have the highest infectious rates within the first 6 months.
Is an AVF always better than an AVG? Dr. V suggests looking at the data. When one compares the patency of AVF versus AVG (in the context of excluding all primary failure AVF’s), the patency of AVF’s is greater than AVG’s. However, when one includes all AVF’s (w/o any exclusion parameters), the long-term patency rates are practically the same as AVG’s. So which is a better access?
Mature AVF’s are certainly the best access. However, AVF’s that require multiple interventions lead to prolonged catheter use. Dr. V was suggesting that such AVF’s should be abandoned and a graft should be pursued in order to avoid prolonged catheter exposure.
The most important criteria for AVF success is an experienced vascular surgeon. Second, patient education leads to timely AVF creation. Third, individualized evaluation to determine if your particular patient will succeed with an AVF.
Dr. V then presented a case and wanted to know if age, gender, and body habitus had any influence in a nephrologist’s opinion of the most suitable access.
AVF and the Elderly
First, how do we define elderly? The WHO defines elderly as > 65 in the developed world, > 50 in the underdeveloped world. Dr. V also questioned whether functional status in the “elderly” is being assessed accurately because this characteristic seems to play a role in the success of AVF’s. This is important to study because the fastest growing age group developing ESRD are > 65 years of age.
In 2008, the primary patency of the radiocephalic AVF’s was not dependent on patient age. A number of other studies have not shown a difference in AVF success/patency and patient age.
The vessel size has an impact in successful AVF creation, but does not seem to be correlated with patient age, provided that a minimum vessel diameter is present.
Once created, do AVF’s behave differently in the elderly? Dr. V presented data from the University of Alabama – Birmingham that did not show a difference between the elderly and young once the AVF was created. However, another study showed a failure to maturation almost 2 times higher in the elderly than the young. The number of interventions required has been similar in both age groups. Data from Dr. V’s group looked at 39 octagenarian patients over 4 years and their functional status once starting dialysis. They defined poor functional status as those patients who went to a nursing home after initiating chronic hemodialysis. Of the patients that had a poor functional status, 70% of them had an AVF that was never used because they did not live long enough to have it used.
A Canadian group performed a study to determine the key risk factors for AVF maturation failure:
- age > 65
- presence of peripheral vascular disease or coronary artery disease
- non-White race
This group also came up with a scoring system to help nephrologists determine if placement of an AVF would have a high probability of maturation failure. The authors developed an algorithm to help nephrologists determine if an AVG should be pursued over an AVF [click here].
AVF and Gender
Dr. V went through a lot of data from a number of studies in this section. The basic point is that despite having a smaller vessel sizes, the primary patency rates of AVF’s in females are not different than in males.
Once created, do AVF’s in females behave differently? Some studies have shown an increase in the number of required interventions in females. Dr. V did not know why there is an increase in interventions in females because the vessel sizes don’t seem to influence AVF maturation rates.
AVF and the Obese
Dr. V pointed out a number of studies that looked at the success of AVF creation in patients of different BMI’s. In one study in 2007, patients with a BMI > 30 had a 30% AVF successful placement rate. Primary patency had no relation to BMI, but secondary patency was significantly lower in the obese population.
Placing an AVF in an obese patient is not difficult, but to keep them functioning (secondary patency) is difficult. He did not have an explanation for why this occurs.
In summary: Patient first, Catheter last, and Fistula Best.
Question and Answer Session
Question: if you have an elderly patient with good functional status with a very good surgeon, do you ask your surgeons to place a graft or allow them to place a fistula?
Answer: Fistula would still be the first option in such a patient unless the vessel diameter did not meet the minimum caliber.
Question: With adequate vessel size, would you ever tell a surgeon to place a graft?
Question: What’s your perspective on button-holes?
Answer: this is a double-edged sword. The ideal situation is a patient cannulating his/her own fistula or a consistent, experienced cannulator.
Question: it seems that button-holes are falling out of favor for in-center patients. What is your take?
Answer: I agree that in-center patients don’t receive adequate cannulation through the button hole. The issue has to deal with the inconsistency of cannulators, inexperience, and the use of sharp needles in the button-hole tract.
Question: What’s your take on antibiotic cream?
Answer: Not needed. In patients who have a scab, the scab should be removed just prior to cannulation, and the underlying skin cleaned only with soap and water. It is the scab that allows bacterial to grow on the underlying skin.
Question: What’s your perspective on the HeRO catheter?
Answer: Dr. V is really not in favor of the HeRO. Many are not placed correctly (they kink quite a bit) and patency is certainly an issue (primarily at the titanium connector). He would prefer a tunneled catheter over the HeRO. In fact, Dr. V looks at the future of the HeRO as that of the LifeSite portacaths – dismal survival rates within one year.
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