L06: Wound Healing "Flesh and Bood" (Case)

Question 1

skin functions

Answer 1

• maintain hydration and thermoregulation
• defense against pathogens and chemicals
• vitamin D synthesis
• sensory (e.g. mechanoreceptors)
• storage (H2O, electrolytes, fat, proteins)
• insulation

Question 2

chars. of Epidermis

Answer 2

• superficial
• cuboidal/stratified epithelium
• avascular (completely reliant on underlying blood supply)
• variable thickness depending on location

Question 3

chars. of Dermis

Answer 3

• below epidermis
• collagen/elasticity
• vascular plexus, lymphatics, nerves
• hair follicles, glands
• vessels susceptible to collapse under too much tension

Question 4

chars. of Hypodermis

Answer 4

• assoc. with dermis
• mostly fat/CT
• contains panniculus
• contains subdermal plexus and direct cutaneous artery and vein, which runs PARALLEL in dogs/cats**

Question 5

5 stages of wound healing and length of time for each**

Answer 5

Coagulation (<5 min)
Inflammation (0-24hrs) 
Debridement (2-5d)
Proliferation (Repair) (4-21d)
Maturation (21d-2 years)

Question 6

main players of primary coag. (formation of platelet plug)

Answer 6

platelets
vWF
subendothelial collagen

Question 7

Describe process of inflammation

Answer 7

• vasodilation (redness, heat)
• egress of leukocytes and serum (swelling)
• fibrin cross-links through platelet plug
• neuts come first to engulf bacteria, release proteases, and prepare wound for macs (24-48hrs)
• macs engulf dead neut debris and clean up wound (2-5d)
• platelets&raquo_space;cytokines

Question 8

1st and 2nd phases of wound healing

Answer 8

1st: inflammatory
2nd: proliferative

Question 9

Describe process of debridement

Answer 9

• removal of necrotic tissue and debris by macs

- aka lag phase

Question 10

lag phase

Answer 10

critical period when wound is becoming weaker and you must rely solely on suture technique to hold it together
-duration dependent on: amt. of necrotic tissue, tissue type (presence of collagenase, metalloproteinase? what pH?)

Question 11

Describe process of proliferation

Answer 11

• influx of fibroblasts (max @ 7-10d) signaled by mac after adequate debridement has occurs
• random, rapid deposition of type 1 collagen
• rapid gain in tensile strength “log phase”
• angiogenesis
• granulation tissue formation
• cytokine dependent
• pink, glistening
• epithelialization as myofibroblasts contract edges of wound

Question 12

describe process of maturation

Answer 12

• collagen remodeling
• “second lag phase”
• linearization
• cross-linking
• continues for weeks to years

Question 13

at how many days is tensile strength of tissue relatively equal to strength of tissue?

Answer 13

7-14 days

Question 14

intrinsic wound factors

Answer 14

hypoproteinemia
anemia
malnutrition
uremia
DM
hyperadrenocorticism
infection

Question 15

Extrinsic wound factors

Answer 15

mechanism (shear, crush, laceration, etc.)
foreign material
irradiation
antiseptics

Question 16

T?F:steroids will delay collagen formation and wound healing

Answer 16

T

Question 17

3 classes of wounds based on TIME and CONTAMINATION***

Answer 17

1) class 1: 0-6hrs, minimal contamination, 1ary closure common
2) 6-12 hrs, moderatie contamination, may use 1ary closure in some cicumstances
3) >12 hours, gross contamination, never use primary closre

Question 18

What is a “clean” wound?

Answer 18

wound created by surgery, not entering GI or respiratory tract. No contamination or break in asepsis. (ie spay/neuter; SSI 5%)

Question 19

irradiation and steroid effect on wound healing

Answer 19

delay wound healing

Question 20

What is a “clean-contaminated” wound?

Answer 20

GI or resp. tract entered, minor break in asepsis.

ie. enterotomy or lung lobectomy; SSI = 10%

Question 21

What is a “contaminated” wound?

Answer 21

> GI with gross contamination, inflammation, major break in aspepsis (ie enterotomy with spillage; SSI = 30%)

Question 22

What is a “dirty” wound?

Answer 22

devitalized or necrotic tissue, gross debris, pus. (ie. infected bite wound)

Question 23

Abx use in Class 1 and clean wounds

Answer 23

rarely necessary, unless systemically unhealthy.

-exceptions: time, foreign material

Question 24

Abx use in Class 2-3 and clean-contaminated, contaminated, dirty

Answer 24

Should use broad spec penicillin or cephalosporin.

• takes 3-5days to do culture and sensitivity testing
• monitor well if wound based

Question 25

what to use for debridement and lavage

Answer 25

sterile saline 0.9%, liberal volume. (betadine can kill fibroblasts if too high conc.)

Question 26

wet to dry bandage

Answer 26

use physiologic/hypertonic saline and gauze as primary layer to suck moisture out of wound
-honey, sugar, antiseptics unnecessary

Question 27

negative pressure bandage

Answer 27

• use porous sponge with subatmospheric pressure
• continuous removal of bacteria, exudate and edema fluid
• improves perfusion and granulation tissue

Question 28

nonadherent dry to dry bandage

Answer 28

-indicated following debridement, to protect wound, encourage moist healing and epithelialization

Question 29

semiocclusive nonadherent dry to dry bandage

Answer 29

• has evaporative fluid loss
• doesn’t harm wound bed
• ie. telfa and Ca alginate

Question 30

types of drains

Answer 30

Active (preferred, creates vacuum in wound to remove exudative fluid and eliminate dead space; Jackson-Pratt)
Passive (relies on gravity and appropriate use to work; Penrose)
drains are always temporary - 3-5d max because presence of tube keeps debridement phase active, even though it is allowing drainage

Question 31

Types of wound closure

Answer 31

Primary (immediate, 6hrs but before granulation 2d)
Second intention (no sx closure, dependent on wound healing)