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Surgery and wound healing (MOD) > Principles of wound healing > Flashcards

Principles of wound healing Flashcards

1
Q

What is the aim with wound healing?

A

Restore normal physical form, structure and function

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2
Q

What are some consequences of bad wound technique and management?

A

Delayed healing
Prolonged discomfort
Extra cost

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3
Q

What are the 5 layers of the epidermis?

A 
Stratum basale
Stratum spinous 
Stratum granulosum 
Stratum lucidum 
Stratum corneum
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4
Q

What are the 2 layers of the dermis?

A

Superficial papillary layer

Deep reticular layer

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5
Q

Tension lines of skin are normal. What are they due to?

A

Elastic fibres in the dermis

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6
Q

What is the name of the tension lines in the skin

A

Langer’s lines of tension

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7
Q

What happens if you make an incision along the Langer’s lines of tension?

A

Skin edges retract

Make incision parallel

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8
Q

What are the 3 phases of wound healing?

A

Inflammatory (lag) phase
Proliferative (repair) phase
Remodelling phase

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9
Q

What cells are involved with wound healing?

A 
(Platelets)
Neutrophils, monocytes, macrophages
Endothelial cells
Fibroblasts/myofibroblasts
Keratinocytes
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10
Q

What are the 2 cellular mediators for wound healing?

A

Growth factors

Cytokines/chemokines

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11
Q

What are growth factors and what do they do?

A

Proteins that bind to cell surface receptors

Activate cellular proliferation and differentiation

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12
Q

What are cytokines?

A

Small signalling proteins secreted by cells - cause growth differentiation and activation
Chemokine = type of cytokine with chemotactic function

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13
Q

After injury, tissue strength reaches what % of the original tissue strength?

A

80%
Even after years
(20% at 3 wks, 50% at 3 months)

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14
Q

What are the 3 main processes of the inflammatory phase

A

Haemostasis
Protection against infection
Substrate/cellular signals for next stages

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15
Q

What happens to the blood vessels (in terms of blood flow) after they are injured?

A

Transient vasoconstriction - occludes vessels

Vasodilation minutes after (heat, redness, swelling)

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16
Q

Platelets aggregate at the site of injury in the inflammatory phase. What do platelets release? What is the result of this?

A

Chemoattractants, growth factors, proteases

Attracts other cells whilst providing temporary scaffold

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17
Q

How long does the inflammatory phase tend to last?

A

4 days

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18
Q

After stimulation by factors, how long does it take neutrophils to arrive to the site of injury?

A

24-48 hrs

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19
Q

Neutrophils kill bacteria and are recruited during the inflammatory phase. What pp of O2 do they need? How long do they last?

A

Require high pp of O2

Short lived

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20
Q

Monocytes mature to macrophages in tissue. What are they essential for secreting?

A

Signalling molecules

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21
Q

How many days after injury does it take for the primary WBCs to arrive?

A

2-3 days

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22
Q

What are the main features of the proliferative phase of wound healing?

A

Angiogenesis
Fibroplasia and granulation tissue formation
Epithelialisation
Contraction

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23
Q

When does the proliferative phase tend to occur?

A

4-12 days post injury

24
Q

The duration of the proliferative phase of wound healing depends on what factors?

A

Wound size
Location
Age and health

25
Q

Within the proliferative phase, what do fibroblasts secrete?

A

Collagen (type III)
Glycosaminogylcans
Fibronectin

26
Q

Fibroblasts are transformed to myofibroblasts within the proliferative phase. What do myofibroblasts do?

A

Cause wound contraction

27
Q

What is the proliferative phase of wound healing characterised by?

A

Development of granulation tissue

28
Q

Epithelial cells move to the site of injury during what phase? What do they do?

A

Proliferative phase

Minimise fluid loss and bacterial invasion

29
Q

What are the main characteristics of the remodelling phase?

A

Remodelling and strengthening of collagen

Increase stiffness of tissue and matrix more rigid

30
Q

How long does it take for most of collagen synthesis to be complete after an injury (remodelling phase)?

A

4-5 weeks

Maturation continues for 12-18 months

31
Q

Phases of wound healing are similar in all tissues, but there are significant difference between skin and which tissues?

A

GI tract
Fascia
Bladder
Bone

32
Q

What is the difference between ponies and horses in terms of wound healing?

A

Ponies better at healing

Horses prone to XS granulation - ‘proud flesh’

33
Q

What is the difference between cats and dogs in terms of wound healing?

A

Cats have slower healing of subcutis layer

34
Q

What local factors influence wound healing?

A 
Wound perfusion 
Tissue viability 
Fluid accumultion 
Foreign bodies
Infection 
Mechanical factors (movement)
35
Q

What systemic factors influence wound healing?

A

Immune status
Drugs (prednisolone weakens immune system)
Systemic condiitons (obesity, diabetes, malnutrition)

36
Q

Abrasions and erosions affect which levels of the skin?

A

Superficial loss of surface epithelium

No exposure of dermis and submucosa

37
Q

What type of cell division is the primary healing mechanism of abrasions/erosions?

A

Mitosis

Epithelial cells fill the defect without needing inflammatory cells/capillaries etc

38
Q

What is ulceration?

A

Complete loss of surface epithelium

With exposure and damage to underlying tissue

39
Q

Burns can be thermal, chemical, electrical or radiation burns. How are they classified?

A

Depth - 1st-4th degree

Extent - % of body surface area

40
Q

What rule of thumb is used to estimate extent of burn wounds?

A

Rule of 9s

Each limb 9%, head 4.5%, back/belly 18%

41
Q

What history should be asked when assessing wounds?

A

When and how the injury occured

Concurrent disease, medication

42
Q

What should be done first when assessing wounds?

A 
Initial first aid:
Control haemorrhage (E.g. pressure)
Check CV system
Look for other injuries 
(May need to sedate, particularly in LA)
43
Q

How should a wound be cleaned?

A

Clip area to fully assess
Apply sterile gel (hair can be stuck in wound) then gently remove
Lavage with sterile saline

44
Q

What is the ‘golden period’ - the time taken for bacteria to inoculate a wound?

A

3-5 hrs

45
Q

What is tetanus?

A

Muscle spasms

Due to Clostridium tetani bacteria entering a wound

46
Q

Tetanus can affect all species. Which species in particular is affected? How is this reduced?

A

Horses

Vaccination against Clostridium tetani

47
Q

If a horse is not vaccinated against tetanus, what should you do?

A

Give tetanus antitoxin and tetanus toxoid vaccination

48
Q

What is the characteristic sign of tetanus in horses?

A

Protruding 3rd eyelid

49
Q

What is the prognosis of tetanus?

A

Fatal if left untreated

Preventable - antitoxin

50
Q

What aftercare should be given for a wound?

A 
Antibiotics (only if contaminated or infection likely)
NSAIDs
Devices to prevent self-trauma 
Rest
Removal of suture
51
Q

When should sutures be removed?

A

10-14 days post surgery

52
Q

What are the 3 types of wound healing?

A 
First intention 
Secondary intention 
Third intention (AKA delayed primary closure)
53
Q

What is healing by first intention?

A

Primary closure
Wound closed immediately and completely with strict asepsis
(No bacterial contamination, removal of dead tissues, FBs, blood clots, dead space, fluid, ischaemia)

54
Q

What is healing by second intention?

A

When wound cannot heal by first intention due to infection or severe tissue damage

55
Q

How does second intention differ to first intention healing in terms of wound care?

A

First intention = little/no care

Second intention = regular wound care (dressings, bandaging, debridement)

56
Q

What is healing by third intention?

A

Delayed primary closure
Wound treated initially as open wound (tissue debridement and lavage)
Wound then close and heals by primary intention

Surgery and wound healing (MOD) (4 decks)

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