Chapter 65 - Biologic grafts Flashcards
Cryoprotectants
what are they and examples
Protect cell viability and improve stability during freezing process
Dimethylsulfoxide
Glycerol
Mechanism of cryoprotectants
Enter cellular cytoplasm and decrease vapor pressure gradient between intracellular and extracellular components
Rapid freezing rate and storage temperature for cryopreserved grafts
5C/sec
-102 to -196C
Cryopreserved vein vs fresh vein differences in histological response
Endothelial loss
Minimal re-endothelilization
accumulate low-density lipoprotein cholesterol at a faster rate
diminished endothelial vasodilation function
Structurally modified biologic grafts
1) bovine carotid artery
2) bovine mesenteric veins
3) human umbilical vein
Thawing allograft
Submersion in warm water bath 37-42C for 20 minutes
Human umbilical vein graft key points
1) shipped in 50% ethanol
2) does not tolerate traction or clamp
3) vein and dacron mesh both need to be sewn into the anastomosis
4) low molecular weight dextra to prevent thrombosis
Cryo GSV for lower leg bypass patency
30-37% 1 year
very poor
Cryo GSV for LE bypass aneurysm rate
25-44% in 2 years
Concern for using cryo FV in dialysis access
1) good for preventing infection
2) higher risk of pseudoaneurysm
3) allosensitization so do not use in kidney transplant candidates
Use of cryopreserved arterial allografts in lower extremity
Low patency
high pseudoaneurysm
too short need more segments
no advantage over cryo vein
Infected aortic replacement with cryograft
morbidity
delayed mortality
aneurysm
18-55% morbidity
2-14% delayed mortality in 4 years with rupture
aneurysm 8%
Human umbilical vein graft results
aneurysms
patency to popliteal/tibial
Aneurysm: 0-57%
Popliteal 49-57%
Tibial 19-61%
Complication with umbilical vein grafts
1) infection
2) stenosis
3) thrombosis
4) dissection
5) pseudoaneurysm
Bovine carotid arteries key points
harder to excise due to increased fibrosis
expensive