Chapter 65 - Biologic grafts

Question 1

Cryoprotectants

what are they and examples

Answer 1

Protect cell viability and improve stability during freezing process

Dimethylsulfoxide
Glycerol

Question 2

Mechanism of cryoprotectants

Answer 2

Enter cellular cytoplasm and decrease vapor pressure gradient between intracellular and extracellular components

Question 3

Rapid freezing rate and storage temperature for cryopreserved grafts

Answer 3

5C/sec

-102 to -196C

Question 4

Cryopreserved vein vs fresh vein differences in histological response

Answer 4

Endothelial loss
Minimal re-endothelilization
accumulate low-density lipoprotein cholesterol at a faster rate

diminished endothelial vasodilation function

Question 5

Structurally modified biologic grafts

Answer 5

1) bovine carotid artery
2) bovine mesenteric veins
3) human umbilical vein

Question 6

Thawing allograft

Answer 6

Submersion in warm water bath 37-42C for 20 minutes

Question 7

Human umbilical vein graft key points

Answer 7

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

Question 8

Cryo GSV for lower leg bypass patency

Answer 8

30-37% 1 year

very poor

Question 9

Cryo GSV for LE bypass aneurysm rate

Answer 9

25-44% in 2 years

Question 10

Concern for using cryo FV in dialysis access

Answer 10

1) good for preventing infection
2) higher risk of pseudoaneurysm
3) allosensitization so do not use in kidney transplant candidates

Question 11

Use of cryopreserved arterial allografts in lower extremity

Answer 11

Low patency
high pseudoaneurysm
too short need more segments
no advantage over cryo vein

Question 12

Infected aortic replacement with cryograft

morbidity
delayed mortality
aneurysm

Answer 12

18-55% morbidity

2-14% delayed mortality in 4 years with rupture

aneurysm 8%

Question 13

Human umbilical vein graft results

aneurysms
patency to popliteal/tibial

Answer 13

Aneurysm: 0-57%
Popliteal 49-57%
Tibial 19-61%

Question 14

Complication with umbilical vein grafts

Answer 14

1) infection
2) stenosis
3) thrombosis
4) dissection
5) pseudoaneurysm

Question 15

Bovine carotid arteries key points

Answer 15

harder to excise due to increased fibrosis

expensive

Question 16

bovine mesenteric vein xenografts key points

Answer 16

poor primary patency and high occlusion rate

not used for infrainguinal bypass

Question 17

Benefit of tissue-engineered vascular grafts

Answer 17

1) eliminate immunogenicity

2) against infection

Question 18

tissue engineered vascular graft manufacture

Answer 18

1) living fibroblast from human biopsy samples
2) wrapped in stainless steel mandrel
3) fuse for 10 weeks to mature
4) autologous endothelial cells used to seed and precondition the conduit 7 days prior to surgery