Wound healing

Question 1

4 stages of wound healing

Answer 1

1. Haemostasis (immediate)
   - reactive vasospasm/vasoconstriction
   - platelets bind to vWF at sites of exposed collagen –> aggregation and release of inflammatory mediators –> coagulation cascade –> thrombus
2. Inflammation (0-3 days)
   - vasodilation and capillary permeability –> inflammatory cell infiltration and swellimg
   - neutrophils and MOs release cytokines, GFs, collegenases, phagocytose and debride dead cells and debris
   - attracts fibroblasts
3. Proliferation (3 days - 3 weeks)
   - fibroblasts migrate to wound –> synthesise collagen
   - myofibroblasts cause wound contraction
   - hypoxia and cytokines stimulate angiogenesis
   - granulation tissue forms
4. Remodeling (3 weeks - 1yr)
   - reorientation and maturation of collagen fibres increases wound strength

Question 2

What are the mechanisms of wound healing

Answer 2

Healing by primary intention
Healing by delayed primary intention/tertiary intention
Healing by secondary intention

Question 3

What is healing by primary intention

Answer 3

Closure of recent wounds by approximation of the wound edges
- best for clean and recent wounds
- minimal inflammation and neat scar

Question 4

What is healing by secondary intention

Answer 4

Wounds are left open and allowed to heal by granulation, contraction and epithelialisation
- infected wounds/high risk of wound infection
- bite wounds
- wound too old for primary closure
- large wounds with irregular edges that cannot be approximated without tension
- inflammation and pronounced scarring

Question 5

What is healing by tertiary intention

Answer 5

Surgical closure of a wound after healing by secondary intention has already begun (i.e., wound edges are not opposed immediately)
- clean wounds with healthy edges but presenting too late for primary closure
- contaminated wounds left to heal by secondary intention and with no signs of infection after 3–5 days
- most pronounced scar

Question 6

Methods to prevent surgical wound infection

Answer 6

Avoid elective surgery in pts with active infection

Timely administration of prophylactic antibiotics

Proper skin preparation

Maintenance of sterile conditions
Good surgical technique → gentle traction, effective haemostasis, removal of devitalised tissues, obliteration of dead space, irrigation of tissues withsalineto avoid excessive drying, wound closure without tension, minimising duration of closed-suction drainage, and judicious use of electrosurgery to help reduce thermal damage to tissue (excessive use → areas of tissue necrosis that can serve as nidus for infection)

Consider prophylactic negative pressure wound therapy (NPWT; overlying closed incision) in certain high-risk surgeries and contaminated wounds
- evacuates accumulated wound drainage, minimises seroma formation and increases blood flow to wound edges to promote healing

Consider leaving wound open at primary operation for delayed primary closure in some cases

Wound protectors designed to protect wound edges from trauma and contamination, may be warranted for prevention of SSI in setting of clean-contaminated, contaminated, and dirty abdominal procedures

Question 7

Factors causing impaired wound healing

Answer 7

Impaired arterial supply or venous drainage (global or local)
- PAD, vasculitis, local
Age
Immunosuppression
Radiotherapy and chemotherapy
Metabolic: Diabetes, jaundice, uraemia

Site of wound
Tissue loss
Structure of wound
Sutures used
Contamination: infection/foreign body
Malignancy
Necrotic tissue
Distal obstruction
Tension/local distension

Malnutrition/nutrient deficiency
Smoking
Obesity
Excessive movement

Question 8

Discuss the process of obtaining consent for surgery

Answer 8