Pathophysiology of Wound Healing

Question 1

The would healing cascade involved various cellular and molecular components acting in synchrony. Wounds close by formation of new tissue or scar.

What are the 4 phases of wound healing?

Answer 1

1. Haemostasis
2. Inflammation
3. Proliferation
4. Remodelling

Question 2

What happens in phase 1 of wound healing?

Answer 2

• Haemostasis
• Immediate process → clot forms to limit blood loss
• Mediators result in vasoconstriction
• Mins to hours
• The close proximity of the wound edges allows for ease of clot formation and prevents infection by forming a scab

Question 3

What happens in phase 2 of wound healing?

Answer 3

• Inflammation
• Immediate to 2-5 days
• Sx → redness, swelling, pain, loss of fxn
• Inflammation opens the blood supply (from being constricted previously) and cleanses the wound
• Neutrophils engulf and destroy bacteria

Question 4

What is phase 3 of wound healing?

Answer 4

• Proliferation / Regeneration
• 5 days to 4 weeks following injury
• Fibroblasts proliferate, driven by cytokines
• Granulation: new collagen tissue laid down, new capillaries fill defect (angiogenesis)
• Contraction: wound edges pull together
• Epithelialisation: cells cross over the moist surface and travel about 3cm from point of origin

Question 5

What is phase 4 of wound healing?

Answer 5

• Remodelling
• Weeks to months/years from onset of injury
• Longest phase of healing process
• Type III collagen replaced by type I → increases tensile strength to wounds
• Scar tissue is only 80% as strong as original tissue
• Devascularisation of region occurs and fibroblasts undergo apoptosis

Question 6

There are several factors that affect the success of any wound healing. They can be divided into local factors and systemic factors.

What local factors affect wound healing?

Answer 6

• Type, size and location of wound
• Local blood supply
• De-innervation
• Infection
• Foreign material or contamination
• Trauma
• Radiation damage

Question 7

Which systemic factors affect wound healing?

Answer 7

• Increasing age
• Co-morbidities (CV disease, DM)
• Nutritional deficiencies (Vit C)
• Medications
• Smoking
• Obesity

Question 8

What is the reconstructive ladder?

Answer 8

• Various ways to get wounds to heal from simple to more complicated
• Use the easiest option(s) where possible
• Can be in any order
• “Reconstructive toolbox”

Question 9

Which drugs impair wound healing?

Answer 9

• NSAIDs
• Steroids
• Immunosupressive agents
• Anti neoplastic drugs

Question 10

What is healing primary intention?

Answer 10

• When wound edges are well opposed
• Clean, narrow wound
• Results in minimal scarring
• Healing by closing (sutures)

Question 11

What is healing by secondary intention?

Answer 11

• Wound edges poorly opposed (eg. pressure ulcer)
• Broader-based wound
• Results in wider, more visible scar
• Healing occurs from bottom of wound upwards
• Myofibroblasts are vital cells in secondary intention - contract wound and despoit collagen for scar healing

Question 12

What are the differences between primary intention and secondary closure?

Answer 12

Question 13

Surgical site infections (SSI) occur when any infection gains entry to the body via a surgical environment. They represent around 15% of all healthcare-associated infections. Wound contamination increases the risk of infection.

What are the four classes of wound contamination?

Answer 13

Question 14

What is meant by surgical wound healing?

Answer 14

• Any wound made by scalpel will heal by primary intention
• Surgeons aid healing by ensuring adequate opposition of wound edges, through use of surgical glue, sutures or staples
• Ensuring correct tensions of sutures is essential:
  
  • too loose → wound edges will be poorly opposed, limiting the primary intention healing and reducing wound strength
  • too tight → blood supply to region may become compromised + lead to tissue necrosis and wound breakdown

Question 15

What are five important aspects of wound cleaning?

Answer 15

• Disinfect skin around wound
• Decontaminate by manually removing foreign bodies
• Debride any devitalised tissue
• Irrigate with saline, low pressure if no obvious contamination, but high-pressure if clearly contaminated
• Antibiotics for high-risk wounds or signs of infection
  
  • RFs = foreign body present, heavily soiled, bites (incl human), puncture wounds, open fractures

Question 16

What analgesia can be administered for wound care?

Answer 16

• Local anaesthetic + systemic analgesia (paracetamol) adjunct
• LA eg. lidocaine, max dose 3mg/kg + adrenaline
• Don’t use adrenaline with local if adminsitering in/near appendages (eg. finger)

Question 17

To aid wound healing, the edges of a wound can be manually opposed. How can this be done?

Answer 17

• Skin adhesive strips (steri-strips) if no risk factors for infection present
• Tissue adhesive glue for small lacerations w/ easily opposable edges
• Sutures for lacertions >5cm, deep dermal wounds or in locations prone to flexion, tension or wetting
• Staples can be used for some scalp wounds

Question 18

What constitutes dressing the wound & follow-up?

Answer 18

• Non-infected → non-adherent first layer (eg. saline-soaked gauze), followed by absorbent material to attract any wound exudate + finally soft gauze tape to secure dressing in place
• Tetanus prophylaxis → if not up to date or unsure
• Advise pts to seek medical attention for any signs of infection
• Take simple analgesia (eg. paracetamol)
• Keep wound dry as much as possible, even if wearing a waterproof dressing
• Sutures/strips removed 10-14days after initial closure (or 3-5days if on head)
• Tissue adhesive glue will slough off after 1-2 weeks
• Remove dressings at the same time as sutures or adhesive strips