Dialysis Flashcards
Higher 1yr patency rates:
Brachiocephalic or radio-cephalic?
Brachiocephalic arteriovenous fistulas offer several advantages over radiocephalic arteriovenous fistulas, including a higher maturation rate, decreased time to maturity, and higher primary patency and functional primary patency. Despite these benefits, radiocephalic fistulas are generally preferred if there is adequate conduit available to prolong sites for future access placement, as many patients are on long-term dialysis and need all access options preserved.
Access is patients with AICDs?
Arteriovenous accesses created ipsilateral to an AICD have a higher primary failure rate compared with the contralateral arm and should be avoided as much as possible. If adequate vein is unavailable in the contralateral arm, it would be appropriate to consider a venogram to assess patency of the central veins, although that is controversial.
Regional anesthesia in upper extremity fistulas
Regional anesthesia has been associated with longer operative time. Perioperative flow in the access has been shown to be higher and association with vasospasm has been shown to be lower. This translates to an improved short-term patency. Regional anesthesia has not been shown to affect major morbidity, including perioperative myocardial infarction and mortality.
Prolonged bleeding after hemodialysis?
Patients often have prolonged bleeding after dialysis due to an underlying venous outflow stenosis with relative venous hypertension. This patient needs a fistulogram and possible intervention.
Lower extremity dialysis access
Of lower extremity access studies have demonstrated the best outcomes for femoral vein transpositions. Patients undergoing femoral vein transpositions should have minimal to no peripheral arterial disease or ischemic symptoms of the lower leg can develop after the fistula is created. Saphenous vein transpositions are another option and have superior patency to synthetic grafts. The major concern with synthetic grafts is infection, which has been reported to be as high as 22% in one series. Overall long-term patency rates for lower extremity grafts is poor with approximately half patent at 6 months.
Differences between 1 and 2 stage brachiobasilic fistulas?
A recent systematic review and meta-analysis included data from 2 randomized controlled trials and 9 case control studies to evaluate the difference between one- and two-stage brachial-basilic arteriovenous fistula creation. It showed no difference in failure rates, primary or secondary 1-year patency, or secondary 2-year patency. There was no difference in infection rates, steal syndrome, hematoma, pseudoaneurysms, or stenosis. There was a significant improvement in 2-year primary patency in the two-stage group (relative risk, 2.50; 95% confidence interval, 1.66-3.74; p < .00001) and a trend toward increased postoperative thrombosis in the one-stage procedure, although that did not reach statistical significance.
Absolute contraindications to hybrid catheter-graft access
Addition to pic:
Graft patency is significantly compromised in patients with a low systolic blood pressure (< 100 mm Hg) or severely depressed ejection fraction (<20%).
Optimal timeing of fistula creation? AVG?
Ideal timing for autogenous arteriovenous access is 6 months prior to dialysis initiation, while prosthetic access should be delayed until about 3 to 6 weeks prior to dialysis initiation. Early autogenous access is associated with reduced sepsis and death risk compared to late access.
Risk of gadolinium contrast in those with CKD?
MRI should not be used due to the risk of nephrogenic systemic fibrosis with gadolinium administration in patients with a glomerular filtration rate less than 30-45 mL/min.
What is recirculation?
Venous outflow stenosis is the most common reason for arteriovenous graft failure. A low flow rate that fails to exceed the dialysis pump rate results in recirculation during the dialysis session.
What is significant arterial stemosis?
Greater than 50% stenosis of the inflow artery associated with a non-functioning AVF is considered significant and should be treated
Tapered vs non-tapered grafts
Tapered grafts are often used with the intent of decreasing the incidence of ischemic steal. Recent studies have demonstrated that tapered grafts for upper extremity access do not affect primary patency, development of steal, or complication rates. There was also no difference in the number of endovascular interventions performed in comparison to non-tapered grafts. Graft choice should be based on operator comfort and familiarity.
Most common cause of AVG thrombosis
Intimal hyperplasia and stenosis can lead to arteriovenous graft thrombosis. In prosthetic access, this most commonly occurs at the venous anastomosis. Central venous stenosis can also lead to graft thrombosis, particularly in patients with arm swelling and a previous history of central venous access.
Signs of brachial shetah hematoma?
Clinical presentation
* The symptoms start with progressive pain, numbness and weakness. Then, the patient feels tingling of the thumb, index, middle, and half of the ring finger.
* Loss of sensation in the area where it is supplied by the median nerve in the hand (figure 1).
Source: Southern and Sloan, 2010
Figure 1. The area in the hand where its supplied by the median nerve sensory part.
* Loss or reduce the ability to move the thumb away from other fingers due to paralysis of the thumb muscles and inability to do a pinch grip (figure 2). Patient can not do things that required forearm, or wrist repetitive movements.
Source; Mathiowetz et al., 1985
Figure 2. The pinch grip become poor with the patient with median nerve palsy due to paralysis of the thumb muscles.
* In addition, median nerve compression at the elbow level, result in hand of benediction due to loss of the innervation of the median nerve at the second and third digits (figure 3).
Endovascular AVF creation
An endovascular AVF (endoAVF) can be reliably created using a radiofrequency magnetic catheter-based system, without open surgery. This approach may reduce vessel trauma, leading to better fistula maturation, and potentially decreasing morbidity and improving patient acceptance. In the Novel Endovascular Access Trial (NEAT), the technical success rate of creating an EndoAVFs was 98%; 8% had a serious procedure-related adverse event (2% device related); and 87% were physiologically suitable for dialysis (mean brachial artery flow, 918 mL/min; endoAVF vein diameter, 5.2 mm [cephalic vein]). EndoAVF functional usability was 64% in participants who received dialysis with 12-month primary and cumulative patencies of 69% and 84%, respectively.
NSF
Nephrogenic systemic fibrosis can begin days to months, and even years, after exposure to an older gadolinium-based contrast agent (group 1). Some signs and symptoms of nephrogenic systemic fibrosis may include:
Swelling and tightening of the skin
Reddened or darkened patches on the skin
Thickening and hardening of the skin, typically on the arms and legs and sometimes on the body, but almost never on the face or head
Skin that may feel “woody” and develop an orange-peel appearance
Burning, itching or severe sharp pains in areas of involvement
Skin thickening that inhibits movement, resulting in loss of joint flexibility
Rarely, blisters or ulcers
In some people, involvement of muscles and body organs may cause:
Muscle weakness
Limitation of joint motion caused by muscle tightening (contractures) in arms, hands, legs and feet
Bone pain, particularly in the hip bones or ribs
Reduced internal organ function, including heart, lung, diaphragm, gastrointestinal tract or liver
Yellow plaques on the white surface (sclera) of the eyes
The condition is generally long term (chronic), but some people may improve. In a few people, it can cause severe disability, even death.
What AVFs have the best patency
Upper arm (brachial-basilic or brachial-cephalic)
What medical treatment improve patency?
CCB - Primery patency of AVG
Aspirin - Secondary patency of AVG
ARBs - improves AVG patency.
Ace-i - Primery Patency of AVF
ARBs + Antiplatlets - patency of AVF.
What medical treatment reduce patency?
Warfarin reduces AVG Primery Patency.
What 3 arterial factors improve AV success rate and patency?
No pressure differance between hands
Diameter of 2mm or above
Patent palmar arch
What venous factors improve AV success rate, matoration and patency?
Diameter of 2.5-3 is good of success and early maturation.
3mm is optimal.
What are the advantage of upper extremities shunt over lower extremities?
Lower infection rate.
Better and more comfortable access.
What are the main principals in planning and selecting shunt type and location?
Non dominant hand first.
Start as distal as possible.
Prefer autologous shunt
Prefer type of fistula by this order: Direct anastemosis, Venous transposition, Venous translocation, Prosthetic.
What is the preferred vein for fistula in the Forarm?
Chephalic
What is the order of seletction of arteries for anastomosis in the Forarm?
Posterior branch of Radial (Snuffbox)
Radial
Ulnar
Proximal Radial
Brachial
What is the chalange of using basilic vein in the the Arm and Forarm?
The vein is medial and always requieres transposition.
In case of no autologous vein in the Forarm, what is the next choice?
Translocation of Saphenous or femoral vein.
Prosthetic graft is the last choice as a bridge to AVF in the Arm.
What are the risk of too meny endovascular salvage treatments to AVF?
Can damage the venous outflow.
What is the preferred vein for fistula in the Forarm?
Chephalic
What is the order of seletction of arteries for anastomosis in the Arm?
Proximal Radial
Brachial
When would you prefer a two stage transposition access surgery over one stage surgery?
When the vein in less than 4mm
After how long can you use AFG?
2 weeks.
What is the avarge time to maturation of AVF?
12 weeks.
What is the disadvantage of Balloon assisted maturation (BAM)?
Patency equals prosthetic graft but more expensive.
What Graft-arterial ratio is abnormal?
>0.75
What Graft-venous ratio is abnormal?
<0.5
What is the 1 year primery and secondary partency of AVF?
Primery 85%
Secondary 90%
What is the 2 year primery and secondary partency of AVF?
Primery 69%
Secondary 75%
What is the 1 year primery and secondary partency of AVG?
Primery 54%
Secondary 65%
What is the 2 year primery and secondary partency of AVG?
Primery 30%
Secondary 60%
AVF - P vs. S - 1 vs 2 years
AVG - P vs. S - 1 vs 2 years
85, 90, 70, 75
55, 65, 30, 60
What is the most common way to measure fistula function?
Urea clearance > 1.2
What are the 3 craiteria for fistula maturation?
6 rule
6mm depth
6 mm diameter
> 600ml/min flow volume
What is recirculation?
Outflow blood contains inflow blood.
What is the flow volume requiered to avoid recirculation?
1000-2000ml/min
What is the influance of AVF/AVG on Cardiac Function?
Access creation increase Pulmonary hypertension and CO.
Hance patients with Pulmonary HTN or Heart faliure will have a diteriaration in their basic condition.
The High access flow (Qa) increase the preload and the extraction of flueids increase the CO.
If the heart can’t compensate and increase CO it will decline and also cause recirculation.
The danger zone (Q/CO >0.3) for developing CHF increase when CO decline.
What is considered abnormal Venous Pressure in dialysis?
50% above mean arterial pressure
Steal syndrome grading?
- Grade 0: No symptoms - “physiologic steal”
- Grade 1 Mild: Cool extremity, few symptoms, flow augmentation with access occlusion
- Grade 2 Moderate: Intermittent ischemia only during dialysis, claudication
- Grade 3 Severe: Ischemic pain at rest, tissue loss
Risk factors for Steal syndrome?
DM
PAD
Coronary Artery Disease
Brachial-based access (proximal)
Female
History of steal syndrome
mulltiple previous access procedures
What grade of steal syndrome need intervantion?
Grade 3 and somtimes 2.
What is Ischemic Monomelic Neuropathy?
Acute pain or anastesia developed hours after surgery.
Occur in 0.5% of cases.
Delayed recognition/intervention leads to irreversible neurologic deficits.
Treatment is ligation.
What is the 1-year mortality for patients on HD?
22%
mean life expectancy 5.8y
What are the SVS guidelines for starting HD?
For using AVF?
Cr clearance <25ml/min
autogenous should mature for 6 months (4-6weeks ok)
prosthetic 3-6weeks
would be constructed before initiation of HD
Why wait >4-6 months before initiation of HD?
lower risk of death and sepsis compared to <1 month
Does plavix help keep AVF open?
there is no evidence to support that
What are catheter options for dialysis?
short term
double lumen, non-tunneled, noncuffed, <6 months)
What bacteria are associated with catheter infection?
S.Aureus, CONS, enterococcus, pseudomonas
How do you clinically exam UE for AVF and important hx?
Neuro
derm
CHF, dominance, IV/central lines, trauma
pulses
edema
tourniquet to assess veins for continuity and size
tap
chest wall collaterals
What are ideal vessel sizes for UE AVF?
How does vein size affect maturation/patency?
artery 2mm
vein 3mm
if 2.5 maturation 90%, 80% 1 year patency
Why is cephalic better then basilica vein?
easier to access for HD puncture
minimal dissection
What is the order of forearm AVF?
Snuffbox/posterior radial branch-cephalic
radio-cephalic (Brescia-Cimino-Appel) (if PRB non palpable)
radio-cephalic transposition (if cephalic too far way)
ulnar-cepahlic (if radial not palpable)
Brachial-cephalic forearm looped transposition (if radial/ulnar pulse not palpable but brachial is)
autogenous radial-basilic forearm transposition OR
autogenous ulnar-basilic forearm transposition OR
autogenous brachial-basilic looped transposition (all if cephalic not adequate)
Once forearm options exhausted what are other options?
can consider prosthetic to exhausted forearm before moving to upper arm. can extend dialysis 1-3 years
6mm PTFE no rings
distal arterial inflow
radial-ac straight
brachial-ac forearm loop
What are upper arm AVF options?
brachial(or prox radial)-cephalic
autogenous brachial-cepahlic transposition (if cephalic too far away)
autogenous brachial-basilic transposition (if cephalic no good)
brachial-brahcial transposition OR GSV/femoral vein translocation if either vein no good)
What is femoral vein and SVG latency in UE AVF?
SVG not known, tends not to dilate
femoral vein 94% at 2 years
What is preferred vein and artery for LE AVF?
What size should anastomosis be?
GSV, femoral artery
4-6mm
Why are LE AVF bad?
high infection rates, higher likelihood of steal, higher rates of PVD
What are possible configurations for LE AVF?
autogenous femoral-GSV transposition (loop or straight)
autogenous tibial-GSV direct access
Femoral-femoral transposition
prosthetic femoral artery-femoral vein
What are possible configurations for body wall AVF?
venous outflow axillary, jugular, common femoral vein
prosthetic ax-ax chest
prosthetic ax-ax chest loop
prosthetic ax-common fem vein chest
How should grafts be surveilled post-op?
no clear benefit in surveillance
clinical monitoring by skilled personal is adequate
32% reduction in overall cost but mostly in prosthetic
seem more reasonable in prosthetic
What are clinical signs of distal graft stenosis for autogenous graft?
palpable pulse ar arterial end, failure to collapse with arm elevation, discontinuous bruit, complete access collapse proximally, persistent edema, venous collaterals on ipso chest wall, continued bleeding
What is static venous pressure?
turn dialysis pump off and equilibrate circuit. venous (efferent) needle pressured is measured. if >50% of MAP considered abnormal or if begins to increase over time
What three features make maturation more likely?
rule of 6
600ml.min flow
What flow rate is indicative of autogenous graft dysfunction?
< by 25%
What can cause failure of maturation? (4)
too deep (may need to retunnel)
non-ligated side branches
poor venous outflow
(distal stenosis, vein too small)
insuff arterial inflow
What can be done to accelerate maturation?
balloon access maturation (BAM)
2,46, weeks progressively larger balloons
What are AVF complications?
thrombosis
intimal hyperplasia
failure to mature
infection
seroma
pseudoaneurysm
aneurysm
steal
IMN
What is most common complication? how to deal with it?
thrombosis
early and late
prosthetic does better then autogenous
tpa 2-4mg
oen thrombectomy
How does intimal hyperplasia cause AVF complications? How to manage?
>90% graft failure
venous anastomosis stenosis
if >50% should be treated
patch, endovascular
what are RF associated with graft failure
age, DM, vein diameter <2mm, CHF, female
What are clinical features favouring use of a prosthetic?
imminent need of HD
short life expectancy
morbid obeisty
unfavorable vascular anatomy
What is the benefit or pre-op non-invasives studies?
no difference in primary patency but lowers initial failure rate and improved primary assisted patency
not SVS recommendation
Describe the two stage approach to the brachia-basilic AVF?
incision prox ac and anastomosis
once dilates to 6mm, skip or continuous incisions over course of the vein and dissect.
either elevate vein or disassemble anastomosis
simply elevating makes accessing difficult because courses medially
What nerves runs over basilic vein?
medial antecubital nerve so if elevate vein either transect nerve or transect anastomosis.
sensory medial cutaneous aspect of arm
what is the average life for autogenous and prosthetic?
infection rate?
3, 2 years
1-10%
What causes recirculation?
if dialysis flow exceeds AVF flow
venous outflow stenosis
arterial inflow stenosis
needles too close
What causes pseudoaneurysms? How to treat?
multiples punctures at same sites
tx reserved if enlarging
What causes autogenous access aneurysm? what is tx?
usually a result of outflow stenosis
can’t continue cannulation must fix
relocate more proximally
What are features of a seroma? how to manage?
not uncommon for prosthetic
usually resolve without intervention
usually near arterial anastomosis
may be associated with low grade infections
usually occur within first month
new tunnel usually best management
When does stew occur?
what is the cause?
usually immediately but can happen up to a year
prox or distal stenosis
What is the grading system for steal?
0: no steal
1: mild-cool extremity, flow aug with access occlusion
2: moderate-intermittent schema only during dialysis, claudication
3: severe-ischemic pain at rest, tissue loss
What are RF for steal?
hx of steal
elderly
multiple prior access
PVD
DM
prosthetic
brachial artery
What is treatment for steal?
DRIL procedure
banding
ligation
RUDI (revasc using distal inflow)
Proximalization of anastomosis
What is target DBI and pressure for banding ?
DBI 0.6 or pressure 50mmhg
What are three types of neuropathy patients with HD can get?
systemic disease neuropathy (ureic)
mononeuropathy from compression (carpel tunnel) HD patients get it more frequently
iscchemic monomelic neuropathy
What is IMN? What re the RF?
acute vascular compromise to the median, radial, ulnar nerves
DM, from brachial, older, PReexisting neuropathy
not seen distal to brachial
What are symptoms associated with IMN? tx?
pain, weakness, paralysis of muscles of forearm often with sensory loss within hours
hand is warm, palpable pulses, no muscle ischemia
surgical emergency with ligation or revasc
What is aetiology of IMN?
AC region is watershed for vasa vasorum of the three upper limb nerves
What are signs of outflow stenosis on dialysis?
High static venous pressure
Low flow rates
Urea clearance
What kind of balloons do you use for venous angioplasty?
High pressure
Usually stm 24-28
Sustained inflation
What stents are best used for venous stenting?
Covered stent
Hyperplasia can come through bare metal
Where does the DRIL proximal anastomosis need to be?
Proximal to the anastomosis by 5-7cm because otherwise there is a pressure drop just distal to the proximal bypass anastomosis
Why does proximalization of the anastomosis work for steal?
It lengthens the anastomosis so the resistance of the avf.
Same for RUDI
What is the cutoff for DBI for ischemia?
0.3-0.4
