Hemodialsysi Access Grafts (13)

what are the risk facots for renal disease?

age

hypertension

race

diabetes

kidney disease

smoking

hyperlipidemia

obesity

cad

Qs what are the superficial veins in UE?

basilic

cephalic

median antecubital

what are the deep veins in UE?

internal jugular vein

subclavian vein

axillary vein

brachial veins

ulnar veins

radial veins

what are the arteries of the UE?

brachiocephalic artery

subclavian artery

axillary artery

brachial artery

ulnar artery

radial artery

deep palmar arch is formed by

radial art and branch of ulnar

superficial palmar arch is formed by

ulnar art and branch of radial art

what is hemodialysis?

method used to remove waste products such as creatinine and urea from blood

• blood cleansed by diffusion across a semipermeable membrane - dialyzer

• for patients with end stage renal disease

accesses centeral circulation via AVF, graft or central venous dialysis catheter

how do we create high flow situations for hemodialysis?

creating arteriovenous fistulas

• connects artery and vein together

in hemodialysis

distal needle →

prox needle →

distal needle → artery → to hemodialysis machine

prox needle → venous flow → from hemodialysis machine

best site for hemodialysis?

forearm

• then upper arm graft

• then thigh graft

Qs what is venous mapping?

mapping of both superficial venous system and arterial system in the upper and lower extremities before access placement

Qs which veins are mapped in UE?

basilic

• upper arm : prox, mid, distal

• forearm : prox mid distal

• wrist

cephalic

• upper arm : prox mid dist

• forearm : prox mid dist

• wrist

Qs how are the increments evaluated in UE mapping

compressibility (coaptation)

diameter (AP measurement in trv)

continuity (grayscale)

AP measurement (sag)

color dopp (sag)

PSV (sag)

which veins are mapped in LE?

great and/or small saphenous veins are mapped

• high mid distal thigh

• knee and below knee

• prox, mid, distal calf

• ankle

the increments for LE mapping are evaluated for

compressibility (coaptation of vessel walls)

diameter (AP measurement in trv)

continuity

*also look for wall thickening and mural classifications

adequate diameters for AVF placement

what is the optimal patient positioning for LE mapping?

hip externally rotated and knee slightly flexed

Qs after the first rib the subclavian v becomes the

axillary vein

Qs how central circulation for hemodialysis is accessed?

central venous catheter is inserted into large central vein that leads to heart

• usually basilic because it is large

• can be through AVF (surgical connection between artery and vein)

• can be through AVG (tube that connects artery and vein)

Qs what is the most desirable site for hemodialysis access?

forearm

Qs what is the minimum diameter criteria for AVF? graft? artery?

AVF : .25

graft : .4

artery : .2

what are the types of grafts?

prosthetic

• biological (bovine, heterografts,cryopreserved)

• synthetic
  

autogenous

• in situ vein (using native veins as a conduit)

  • basilic

  • cephalic

  • great saphenous

  • femoral

what are the common connections of AVF/AVG?

brescia cimino (A)

• radial artery to cephalic vein

radial artery-basilic vein

• forearm transposition

brachial artery to cephalic vein (B)

• antecubital area

• upper arm

snuffbox fisutal

• branch radial artery - cephalic vein

brachial artery to upper arm basilic vein transposition (C)

great saphenous, common fem or femoral vein

common femoral artery or superficial femo artery

axillary artery - axillary vien

axillary artery - ipsilateral or contralateral jugular vein

subclavian artery - contralateral subclavian vein

• “necklace graft”

in forearm and upper arm grafts are usually -

in thigh grafts -

forearm and upper arm : loop or straight

thigh grafts : loop

shows what

forearm loop graft

shows what

upper arm straight graft

what does this show?

axillary loop graft

what does this show

thigh graft

what are the inflow sites?

ALL ARTERIES

radial artery at wrist

brachial artery at antecubital fossa

prox brachial artery

axillary artery

common fem artery

superficial fem artery

subclavian artery

what are the outflow sites?

cephalic vein

median antecubital vein

basilic vein

great saphenous vein

femoral vein

subclavian vein

what are the access anastomoses?

end to side

end to end

side to side

Qs what is an AV fistula?

when native artery is connected to native vein

how long does it take for an AV fisutal to mature?

up to 24 months after surgery

• more blood flow into the vein causing it to grow larger and stronger

• if fails to grow twice → AV graft

which fistula is most commonly performed?

brescia cimino

• radial artery to cephalic vein

• end to side vein to artery anastomosis

Qs why is AVF preferred over AVG for vascular access in hemodialysis?

• provides adequate blood flow

• lasts longer than other types of access (can function up to 20 years)

• lower complication rate

• less likely to be infected/cause blood clots

review

what is this?

side to end AVF

what is this?

side to side AVF

what is this?

end to end AVF

Qs an AVF is mature when

venous diamter is >/= 4mm

flow volume is >/= 500 ml/min

*blood flow measured at midportion

stenosis in AVF is present when

PSV ratio is >/= 2

• >/= 50% diameter reduction

• sample gate encompasses the entire vessel width

how do you obtain volume in AVF?

• use straight, non tapering segment

• activate time averae maximum

• measure diameter of segment

• at same location ^ open doppler gate - entire width of vessel

• measure at least one cycle (PSV to PSV or EDV to EDV)

• obtain volume

Qs what is an AV graft?

synthetic connection between artery and vein

• looped plastic tube that essentially becomes an artificial vein

• no need to develop (can be used 2 weeks after placement)

• used when small veins do not mature into fistula

what are the indications for exam?

decreased bruit or thrill in access conduit

evaluate AVF maturity

pulsatile mass

pain

swelling

occlusion

edema

trauma

stenosis

collections/perigraft mass

low urea reduction rate less than 60%

access collapse → poor arterial inflow

infection

cold hands/fingers

what is the normal criteria for arteries and veins in AVF?

arterial

• PSV 150-300cm/s

• EDV 60-200 cm/s

venous

• PSV 30-100 cm/s

what is the most common cause of graft thrombosis?

stenosis at venous anastomosis

• arterial anastomosis is uncommon

high grade stenoses produce velocity ratio

>2

what is the normal flow volume in AVG?

normal flow volume : >800ml/min

severe stenosis L : <500 ml/min

review

in AVF prox arterial flow has

greatly increased diastolic flow

in AVF distal arterial flow has

normal triphasic pattern

what is flow like through AVF?

turbulent

in AVF venous outflow has

pulsatile quality

review

Qs how many anastomoses does an AVF have?

1

Qs how many anastomoses does an AV graft have?

two

Qs what is normal diagnostic criteria of an AVF?

arterial velocity : 150-300

venous velocity : 30-100

Qs what is abnormal diagnostic criteria?

velocity ratio >2

focal velocity increase by 100% compared to more prox segment

• indicates flow reducing stenosis

Qs what flow pattern does venous outflow usually take?

pulsatile

Qs what complications are associated with hemodialysis?

stenosis

thrombus

PSA

Qs what is most likely to lead to hemodialysis access failure?

stenosis

increase in venous pressure during dialysis indicates

outflow problems

high resistance pulsatile waveform within graft indicates

outflow stenosis

low resistance within graft indicates

arterial inflow problems