wound healing for undergraduate medical students

1. WOUND HEALING
Prof . Dr . Mahmoud Ameen
Plastic and Maxillofacial Surgery

2. • Surgery
It is often said that it is “controlled trauma”
Carried out in a sterile environment Under
aseptic conditions

3. • Many protocols are put in place to prevent
infections in surgical wounds
o Hand washing
o Gowns and gloves
o Painting and draping
o Drains
o Antibiotics
o Laminar flow theatres
o Sterile instruments
o Sterile dressing

4. • But wound infections can occur despite
these measures causing:
• Death
• Morbidity
• Longer hospital stays
• Cosmetically displeasing wounds

5. Wound Infection

7. Wound Dehiscence

8. Healthy Wound

9. Anatomy of Skin
• Epidermis:
– composed of several thin layers:
stratum basale, stratum spinosum, stratum
granulosum, stratum lucidum, stratum corneum
– the several thin layers of the epidermis contain the
following:
a) melanocytes, which produce melanin, a pigment
that
gives skin its color and protects it from the damaging
effects of ultraviolet radiation.
b) keratinocytes, which produce keratin, a water
Repellent protein that gives the epidermis its tough,
Protective quality.

10. Anatomy of Skin
• Dermis:
– composed of a thick layer of skin that contains collagen
and elastic fibers, nerve fibers, blood vessels, sweat
and sebaceous glands, and hair follicles.
• Subcutaneous Tissue:
– composed of a fatty layer of skin that contains blood
vessels, nerves, lymph, and loose connective tissue
filled with fat cells

12. Function of Integument
• Protection:
– intact skin prevents invasion of the body by bacteria
• Thermoregulation:
• intact skin facilitates heat loss and cools the
body when necessary through the following
processes:
– production of perspiration which assists in cooling the
body through evaporation
– production of vasodilatation which assists in facilitating
heat loss from the body through radiation and
conduction
– production of vasoconstriction which assists in
preventing heat loss from the body through radiation
and conduction

13. Function of Integument
• Fluid and Electrolyte Balance:
– intact skin prevents the escape of water and
electrolytes from the body
• Vitamin D Synthesis
• Sensation
• Psychosocial

14. • The risk of a wound infection depends on
the operation
For that reason, operations are classified
into distinct types
o Clean
o Clean-Contaminated
o Contaminated
o Dirty

15. Classification of Wounds
• 1) Clean Wound:
– Operative incisional wounds that follow nonpenetrating
(blunt) trauma.
• 2) Clean/Contaminated Wound:
– uninfected wounds in which no inflammation is
encountered but the respiratory, gastrointestinal,
genital, and/or urinary tract have been entered.
• 3) Contaminated Wound:
– open, traumatic wounds or surgical wounds involving a
major break in sterile technique that show evidence of
inflammation.
• 4) Infected Wound:
– old, traumatic wounds containing dead tissue and
wounds with evidence of a clinical infection (e.g.,
purulent drainage).

16. Class I :Clean wounds
• Elective operations (non emergency)
Non traumatic injury
Good surgical technique
Respiratory, gastrointestinal, biliary and
genitourinary tracts not breached
Risk of infection < 2%
Eg: mastectomy, hernia repair

17. Class II: Clean - Contaminated
Urgent or emergency case that is
otherwise clean
GI, GU or respiratory tracts entered
electively, no spillage or unusual contamination
Minor break in sterile technique occurre
Endogenous flora involved
Risk of infection: <10 %
Eg: appendictomy, bowel resection

18. Class III: Contaminated
• Non-purulent inflammation
Gross spillage from GIT, entry into GU
or
biliary tract in the presence of infected
bile/urine.
Major break in technique
Penetrating trauma < 4hrs old
Chronic open wounds
Risk of infection: 20%
Eg: GSW, rectal surgery

19. Class IV : Dirty
• Purulent inflammation (abscess)
Pre-operative perforation of GI, GU,
biliary
or respiratory tract
Penetrating trauma > 4 hrs
Existing acute bacterial infection or a
perforated viscera is encountered (clean
tissue is transected to gain access to pus).
Risk of infection: 40%

20. Signs of Infection
• Patient may be systemically unwell
↑ Temp
Tachycardic
Hypotension
Wound breakdown
Wound discharge
Warm peripheries
Septic shock

21. Prevention
• Aseptic technique
Good technique
Prophylactic antibiotics where appropriate
Clean operating theatre
Elective surgery
Good post op care

22. Primary wound healing
• Also known as “healing by primary
intention”
Think of a typical surgical wound: the
wound edges are approximated
Minimal number of cellular constituents
die
Results in a small line of scar tissue
Minimizes the need for granulation
tissue
so scarring is minimized

23. Primary wound healing

24. Delayed Primary healing
•  Occurs if wound egdes are not approximated
immediately
 May be desired in contaminated wounds
 By day 4: phagocytosis of contaminated
tissues has occurred
 Usually wound is closed surgically at this
stage
 If contamination is present still : chronic
inflammation ensues leading to prominent scar
eventually

26. Secondary Healing
Also called healing by secondary intention
A full thickness wound is allowed to heal
by itself: there is no approximation of
wound edges
Large amounts of granulation tissue
formed
Wound eventually very contracted
Takes much longer to heal

28. Normal Wound Healing
 There are 3 phases
II. Inflammatory phase: Days 0-4
III. Proliferative phase : Days 5-21
IV. Remodelling phase: Days 22-60

29. Wound Healing
 It can also be classified in 4 stages:
II. Haemostasis
III. Inflammation
IV. Granulation
V. Remodelling

30. Haemostasis
Injury causes local bleeding
Vasoconstriction is mediated by :
o Adrenaline
o Thrombaxane A2
o Prostaglandin 2α

31. Haemostasis
Platelets then adhere to damaged
endothelium and discharge ADP
o Which promotes thrombocyte clumping
and “dams” the wound
Inflammation is initiated by cytokine
release from platelets

32. Inflammatory Phase
• Capillary dilatation occurs due to:
• Histamine
• Bradykinin
• Prostaglandins
This dilatation allows inflammatory cells
to reach the wound site

33. Inflammatory Phase
These PMNs or leukocytes have several
functions:
• Scavenge for debris
• Debride the wound
• Help to kill bacteria

34. Proliferative Phase
• Angiogenesis
• Collagen deposition
• Granulation Tissue

35. Granulation Tissue
• Newly formed connective tissue, often
found at the edge or base of ulcers and
wounds made up of : capillaries,
fibroblasts, myofibroblasts, and
inflammatory cells embedded in a mucin
rich ground substance during healing

36. Granulation Tissue

38. Proliferative Phase
• Re-epithelialization occurs next:
By upward migration of epithelial cells if
BM is intact
Or from wound edges

39. Remodelling Phase
• Fibroblasts become myofibroblasts
And wound begins to contract

40. Abnormal Scars
Hypertrophic Scars
Keloid Scars

41. Hypertrophic Scars
Raised, red and thickened
Limited to boundaries of scar
Occurs shortly after injury
Common on anterior chest and deltoids
Regresses over time
Related to wound tension and prolonged
inflammatory phase of healing
Electron microscopy: flattened collagen
bundles parallel in orientation

44. Hypertrophic Scars
• Treatment:
Surgical excision
Intralesional steroid injection

45. Keloid Scars
 Raised, red and thickened scar
 Extends beyond original scar boundary
 Occurs months after injury
 Does not regress
 Commoner in darker skinned people
 Familial tendency
 ? Autoimmune phenomenon
 Worsened by surgery and in pregnancy
 Regresses post menopause

48. • Treatment:
Surgical excision : caveat- recurrence =
65%
Compression treatment
CO2 lasers
Cryotherapy

49. Factors influencing scarring
• These can be broken down into:
ii.Patient factors
iii.Surgical factors

50. Risk Factors for SWI
– Patient-related factors:
– Age > 60, sex (female), weight (obesity)
– Presence of remote infections
– Underlying disease states
– Diabetes, Congestive heart failure (CHF)
– Liver disease, renal failure
– Duration of preoperative stay hospitalization
– > 72 hours, ICU stay
– Immuno-suppression
– ASA (American Society of Anesthesiologists)
– physical status (3,4, or 5)

51. Risk Factors for SWI
Surgery-related factors:
– Type of procedure, site of surgery, emergent
surgery
– Duration of surgery (>60- 120 min)
– Previous surgery
– Timing of antibiotic administration
– Placement of foreign body
– Hip/knee replacement, heart valve insertion, shunt
insertion
– Hypotension, hypoxia, dehydration, hypothermia

52. Surgical factors
Atraumatic skin handling
Eversion of wound edges
Inversion places keratinised epidermis
between the healing surfaces = delayed
healing
Tension free closure
Clean and healthy wound edges

53. Everted Edges

54. Inverted Edges

55. Risk Factors for SWI
Surgery related factors:
– Patient preparation
– Shaving the operating site
– Preparation of operating site
– Draping the patient
– Surgeon preparation
– Hand washing
– Skin antiseptics
– Gloving

56. Risk Factors for SWI
Wound-related factors:
– Magnitude of tissue trauma and devitalization
– Blood loss, hematoma
– Wound classification
– Potential bacterial contamination
– Presence of drains, packs, drapes
– Ischemia
– Wound leakage

58. Questions?