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Adv. Vas. Son.

Test 2 Hemodialysys Fistulas and Grafts

QuestionAnswer
Graft and Fistula facts: Created to sustain PTs W/ end-stage renal failure
What does hemodialysis do? Removes waste products from blood
How many Pts in the USA are dialysis dependent and that number continues to increase? 300,000-400,000
Want to create a fistula where? As far distally as possible in nondominant arm, Preserves Prox vessels for potential future access
Why are upper extremities preferred with fistulas? Lower infection rate and easier access
What are signs of possible access failure? Pre-op assessment for vein/artery suitability, Difficult cannulation or thrombus aspiration, Elevated venous pressure during dialysis, Poor dialysis
More signs of possible access failure? Unexplained area reduction ratio <60%, Shunt collapse, Distal limb ischemia, Abcene of fistula palpable "thrill", Per-graft fluids or mass
Where is a central venous catheter places of access? IJV or subclavian vein insertion, Temporary- short term solution
Where is an Arteriovenous Fistula (AVF)? Usually in non-dominate arm
What is a Brescia-Cimino Fistula? Rad A to Ceph V (most common), Autogenous, Known for long term patency, Low complication rate, Ulnar A to Basilic V may also be created but uncommon
AVF has to do what before it can be used? Mature- or adequate flow volume may not occur
How long should Fistula Maturity take? 8-12 weeks
What does a fistula look like once it has become mature? Sausage like from increased pressure
Why is TD contact sometimes difficult? Superficial location (lots gel and little pressure
What are other fistula sites? Brach A to Ceph V. Brach A to Basilic V, Brach A to Brach V
Approx how many PTs are not candidates for AVF? 50%
Grafts are favored in the USA but there is a strong trend towards? Fistula creation
The Polyurethane, Vectra graft (Thoralon)facts: Can be used immediately, no maturation time, Self-sealing, IMPENETRABLE BY ULTRASOUND
If an Access graft is straight then it courses which way? From Distal A to more Prox superficial V
What is good about the Forearm Loop Graft? Provides more length and more puncture locations for dialysis
Other access graft locations? Brach A to Basilic V, Subclacian A to Jugular V, Superficial fem A to GSV
Grafts have shorter what than fistulas? Shorter patency rates
Abroad about 80% of hemodialysis PTs have native fistulas, whole 20% have grafts. The % are ______ in the US? Reversed, but there is a strong trend towards increasing the number of fistulas
What is the % of Early failures with No Mapping, and Mapping? No Mapping= 36%, and Mapping =8%
What is the % of 1-Yr Patency with No Mapping and Mapping? No Mapping= 48%, and Mapping= 83%
What should you look for post-op? Graft thrombosis/stenosis, Flow volume, Arterial steal, Venous outflow, Peri-graft mass
What is the suitable radial arterial diameter? ≥2.0 mm
What is the suitable PSV? ≥ 50 cm/s
What is the required venous luminal diameter (W/ or W/out arm tourniquet)? ≥2.5 mm for Fistula. ≥4.0 mm for Graft
Why are brachial veins rarely used for hemodialysis access? They are TINY
What are Graft/Fistula complications? Thrombosis/Occlusion, Stenosis, Arterial Steal(digit ischemia), Distal venous HTN, Aneurysms/Pseudoaneurysms, Elevated right sided heart pressure due to excessive graft flow, Infection(mostly synthetic grafts)
Where do you measure stenosis? @ Prox and Distal anastomosis, W/in graft, and in venous outflow tract- due to initmal hyperplasia or thrombus
Hoe long do grafts and fistulas mature for 4-6 weeks
Grafts (PTFE) are the most common? Procedure
NO BLOOD PRESSURE where? OVER A GRAFT
In a Fistula/Graft flow should be high/low resistance, (high/low diastolic flow) LOW resistance, HIGH diastolic flow
If there is retrograde arterial flow what does that mean? Steal
Flow may be higher resistance Distal/Proximal? Distal
Where do you measure and record PSV & EDV? Prox, Mid, & Distal, @ any region of suspected stenosis, and @ anastomotic sites
What should Doppler waveforms demonstrate just proximal to the graft or fistula? Low resistance (High diastolic flow)
High resistance in the brachial or radialartery flow prox to a graft of AVF is a sign of? Graft/Fistula occlusion or severe stenosis
Vein stenosis is more likely to occur where? In a a graft than a fistula
When is it common to have flow reversal back down into the limb? Under high arterial pressure
Increased venous pressure in itself may cause what type of symptoms? Edema in the hand
What are the Flow Volume (ml/min) calcs? Q=Area x TAV x 60 sec Q=Areax Avg Max Vel x 60 sec
What is TAV? Average velocity over time, so mean systolic velocity, mean diastolic velocity and mean velocity through a cardiac cycle are calculated
Assess Per-graft/fistula tissue for: Hematomas, & Pseudoaneurysms
Pseudoaneurysms are common and result from? Dialysis puncture
If Pseudoaneurysm is < 5mm they? Remain stable
If pseudoaneurysm > 5mm they? Should be carefully followed or surgically repaired
Steal facts: May be ASX or cause digit ischemia, If SX get PVR or PPG WFs from ipsilateral digits, Obtain pressure from the most symptomatic digit
Digit pressures <69 mmHg are associated with what? Ischemia
Infection Etiology: Operative contamination Puncture, Wound infection, Appears as peri-graft fluid collection, Can resemble a seroma, Confirmation usually requires analysis of aspirated fluid
What is a seroma? Serous fluid collection adjacent to graft, Appear as peri-graft fluid collection, result from serum filtering thorough the graft wall, Usually benign condition as long as there is no extrinsic compression on the graft
Other complications: Venous HTN, Outflow stenosis, Arterial flow decrease
What do NORMAL grafts and fistulas have? Very HIGH systolic and diastolic velocities, Flow is v "low-res", continuous forward, High vel flow
What is the PSV in Normal grafts and fistulas? PSV between 150 and 300 cm/s
What is the EDV in Normal grafts and fistulas? EDV between 60 and 300 cm/s
Inflow artery should have LOW res flow with increased? Increased PSV (30 - 100 cm/s)
Normal Volume Flow? >800 mL/min
Dialysis Graft Stenosis: >50% diameter stenosis what is the peak systole? what is the velocity ratio? Peak Systole >400 cm/s, Velocity Ratio 2:1 or 3:1 (some reports)
Criteria for > 50% Fistula Stenosis: Radial artery to Cephalic vein (end to side): facts: PSV> 400 cm/s, Ratio 2:1 or 3:1 (Anastomotic stenosis PSV/ Radial Artery PSV)
For outflow cephalic vein stenosis what is the ratio? ≥ 3:1
Graft flow Volumes (mL/min) for access grafts: <350- poor dialysis, pending graft failure. <5000 increased risk of failure >800- normal flow >1500- possible CHF
Fistula Flow Volumes (ml/min): Fistulas can survive at lower flow volumes <300 poor dialysis 300-500 borderline >500 (w/ 4 mm outflow vein) acceptable >800= NORMAL
Where do you obtain flow volume? From feeding artery (brachial, radial, or ulnar)
Created by: EmilyGriffin
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