Hemodialysis & Fistulas Flashcards
What is hemodialysis?
The removal of certain elements from the blood through a semi-permeable membrane while being circulated outside the body.
When is hemodialysis needed?
End stage renal disease (ESRD)
What does hemodialysis require? (2)
- High flow
2. Easily accessed vessel that can tolerate multiple punctures with catheters
How is the high flow situation created for dialysis? (2)
- AV fistula surgically created by connecting an artery to a vein (high pressure flow from artery to vein)
- AVG (graft) surgically inserted to connect artery and vein
What are the two methods of AVG?
- Prosthetic graft
2. Using a vein as a conduit
What has a high prevalence with dialysis graft patients?
Subclavian vein thrombus
What are the different types of grafts?
- Loop
2. Straight
What are the methods for hemodialysis with fistula evaluation and what is the preferred method?
- Duplex ultrasound (preferred)
- Arteriography (x-ray)
- Fistulography (x-ray)
What are the indications for a hemodialysis/fistula exam? (13)
- Abnormal measurements during dialysis session
- Extremity symptoms
- UE swelling
- Decrease in bruit/thrill in conduit
- Evaluation of AVF maturity
- Pulsatile mass
- Thromboses conduit/access
- Peri-graft mass
- Decreased thrill/pulse
- Suspected steal
- Infection
- Bleeding
- Post revision follow-up
What are AVG’s evaluated for on Duplex exams? (6)
- Stenosis
- Thrombosis
- Aneurysms
- Pseudoaneurysms
- Hematomas
- Arterial steal from hand
What is the most common cause of failure in the 1st month of AVG’s?
Thrombosis of graft
What transducer is preferred for graft analysis?
10-12 MHz
What is the patient position for AVG duplex exam?
Supine
What is the sample gate opened for in the duplex exam?
Volume flow calculation
What is the volume flow calculation?
Volume flow (Q) ml/min = TAV(time average velocity) x area x 60
Where should PSV be recorded in a AVG duplex exam? (5)
- native artery prox
- arterial anastomosis
- graft
- venous anastomosis
- venous outflow
What is important to sample with an AV fistula?
2-3 sites distal to the arterial anastomosis
What does reversal in the ulnar or radial artery indicate?
That the graft is stealing blood from the hand due to a lower pressure upstream (stenosis) from the wrist
Why may a steal from the hand arteries (ulnar or radial) be common in a graft?
Due to the pressure diff between the artery and vein and the narrowing (stenosis) of a graft, high flow is directed into the graft towards the low pressure vein from the distal arteries (reversal).
What is more frequently used to determine the severity of stenosis than PSV’s?
Peak Systolic Velocity Ratio’s (V2/V1)
What do normal hemodialysis waveforms display? (3)
- High-flow states
- Low resistance
- Increased PSV and EDV
What depth is required for successful access for dialysis?
Less than 5 mm from skins surface
What PSV is considered normal for both fistulas and grafts?
PSV < 400 cm/s
What is the normal PSV and EDV for dialysis grafts?
PSV: 100-400 cm/s
EDV: 60-200 cm/s
