Wound Healing

The four phases

Healing is not one process. It is four, overlapping, and each one can stall independently — which is why "the wound isn't healing" is never a complete assessment.

Phase	Timing	What is happening	What you see
Haemostasis	Minutes	Vasoconstriction, platelet plug, clot	Bleeding stops
Inflammatory	Days 1–4	Neutrophils and macrophages clear debris	Redness, warmth, swelling, pain
Proliferative	Days 4–21	Granulation, angiogenesis, epithelialisation	Beefy red granulation tissue, wound edges drawing in
Maturation	21 days – 2 years	Collagen remodelling, tensile strength returns	Scar pales and flattens

Two things students get caught on. Inflammation is not infection — heat, redness and swelling in the first few days are the healing process working. And a healed scar never exceeds about 80% of original tensile strength, which is why a re-injured site tends to re-open at the same place.

Healing by intention

	Primary	Secondary	Tertiary
Wound edges	Approximated	Left open	Left open, then closed
Example	Surgical incision, sutured	Pressure injury, dehisced wound	Contaminated wound, closed after debridement
Granulation	Minimal	Extensive	Delayed
Scarring	Least	Most	Moderate

What stalls healing

• Poor perfusion or oxygenation — tissue cannot rebuild without oxygen. Peripheral vascular disease, smoking, anaemia, hypovolaemia.
• Diabetes — hyperglycaemia impairs neutrophil function and thickens capillary basement membranes. Blood glucose control is wound care.
• Protein and vitamin C deficiency — collagen is protein. A malnourished patient cannot build granulation tissue no matter what dressing you use.
• Corticosteroids — suppress the inflammatory phase the wound needs.
• Infection — bacteria compete for oxygen and nutrients and prolong inflammation indefinitely.
• Mechanical stress — repeated pressure, friction, shear, or tension across the suture line.

Assessing a wound

Describe what you see; do not conclude. Size in centimetres including depth and any undermining. Wound bed — red granulation, yellow slough, black eschar. Exudate — amount, colour, odour. Peri-wound skin — intact, macerated, indurated, erythematous. Pain — including any change in character.

Red is healthy. Yellow needs debridement. Black is necrotic and needs review before anything else happens to it.

Escalate now

Finding	Why it matters
Purulent drainage, foul odour, spreading erythema	Infection — needs culture and systemic treatment, not a dressing change
New fever with a wound that had been settling	Possible systemic involvement
Sudden increase in serosanguineous drainage from a surgical wound	Classic warning sign that dehiscence is imminent
Wound edges separating	Dehiscence
Viscera visible or protruding	Evisceration — a surgical emergency

For evisceration: cover the organs with sterile gauze moistened with sterile normal saline, position the patient supine with knees bent to reduce abdominal tension, keep them nil by mouth, and call the surgical team. Never attempt to push the viscera back in, and never let the gauze dry out.