Wound Healing

Hemostasis Duration

0-24 hours

Inflammatory Phase Duration

1-10 days

Proliferation Phase (Regeneration or granulation) Duration

3 days- 21 days

Remodeling Phase (Maturation) Duration

7 days- 2 years

\
Lasts up to one year for normal healthy adults and **2 years for children, elderly, or immunocompromised patients.**

Hemostasis Phase (Often considered part of the inflammatory phase)

* Tissue injury causes hemorrhage into the wound.
* Platelets aggregate eventually resulting in fibrin clot formation and hemostasis.
* Fibrinolysis to break down fibrin clot

Inflammatory Phase (Phase 2)

* Sequential infiltration of neutrophils and macrophages: mount an acute inflammatory response.
* Neutrophils: clear invading microbes/bacteria and cellular debris in the wound area by phagocytosis
* Macrophages:
* Same as neutrophils
* Also a rich source of biological regulators

Clinical Observation: erythema, warmth, edema and pain

What are the goals for Inflammatory Phase?

* Contain exudate (in wound)
* Reduce edema (in tissues)
* Remove necrotic tissue
* Promote granulation
* Prevent maceration (periwound)

Proliferation Phase (Regeneration or granulation) (Phase 3)

* Granulation, contraction and epithelialization (migration over the matrix within the wound)
* In the dermis, fibroblasts and endothelial cells support capillary growth (angiogenesis), collagen formation, and the formation of granulation tissue at the site of injury.
* Within the wound bed, fibroblasts produce collagen, glycosaminoglycans and proteoglycans (major components of the extracellular matrix)

\
Clinical observation: beefy red granulation, epithelialization

Goals for proliferative phase

* Stimulate angiogenesis
* Promote epithelialization
* Prevent epiboly
* Prevent maceration
* Protect wound
* Maintain moist wound environment

Epithelialization

Epithelial cells migrate in a single layer across a granulated wound surface towards the middle and proliferate.

\
Contact Inhibition: Occurs when new epithelial cells cover the wound

\-rolled or curled edges (epiboly) frequently occur in wounds that have no granular tissue to cross

\
A wound is closed when epithelial integrity is restored, however it is not healed.

Remodeling Phase (Maturation) Phase 4

* Wound is now closed. This phase can last for years.
* Regression of newly formed capillaries
* High fibroblast activity with extracellular matrix remodeling
* Shrinking, thinning, paling of scar
* Scar tissue is only 80% as strong as original tissue

Goals for Maturation Phase

* Educate patient in pressure relief, skin inspection
* Mobilize soft tissue
* Gradual/incremental stress to tissue

How wounds heal

Order of inc complexity:

* Superficial wound healing (sometimes primary)
* Primary Intention
* Secondary Intention- wound granulates
* Tertiary Intention- Delayed primary intention
* Skin graft
* Local Flap/ Free Flap

Primary Intention

Closed by approximation of wound margins (immediately closed)

* Best choice for recent, clean wounds, well-vascularized areas, minimal tissue loss (surgical incision, laceration, puncture, superficial and partial-thickness wounds)
* Typically have minimal scarring and heal quickly
* Specific techniques: sutures, stapes, adhesives.

Primary Intention Complications

Dehiscence: Surgical complication in which the wound ruptures along the suture line

Risk factors:

* Age
* Diabetes
* Poor knotting or grabbing of stitches
* Increased abdominal pressure (lifting)

Secondary Intention

Wound closes on own w/o superficial closure

Wounds: significant tissue loss or necrosis, irregular or nonviable wound margins that cannot be re-approximated, infection or debris contamination. (ex: venous/pressure ulcers)

\
Granulation tissue gradually fills the wound bed to level of surrounding skin with closure occurring by wound contraction and scar formation

\
Large scars

Tertiary Intention/ Delayed Primary Intention

Wound left open, then sutured closed 4-7 days after signs of infection diminished

\-Usually traumatic wounds

\
Occurs when a wound:

\-Is heavily contaminated

\-High risk for infection

Skin Graft

Type of medical grafting involving transplantation of skin. The transplanted tissue is a skin graft.

\
Used to treat:

\-extensive wounds

\-burns

Chronic Wounds

Chronic wounds fail to progress in a timely manner through the normal phases of healing.

\
Time frame: >30 days duration for complete healing

\
“Fail to progress through a normal, orderly, and timely sequence of repair .....”

What phase does chronic wounds tend to get stuck in? Why have chronic wounds inc?

Stuck in inflammatory phase.

\
Inc age, diabetes, more pt survive grave illnesses.

Causes of Delayed Healing: Local factors (wound)

Oxygenation

Infection

Foreign body

Desiccation (extremely dry)

Maceration (wet)

Mechanical stresses

Causes of Delayed Healing: Systemic Factors (individual)

Age

Stress

Co-morbidities

Obesity

Smoking

Medications

Nutrition

Age is associated with decreased….

* Dermal thickness, causing thin sin
* Amount and flexibility of collagen and elastin (wrinkles)
* Size of rete ridges, thus inc risk of skin tears
* Sensation and metabolism
* Sweating due to atrophy of the sweat glands (dry skin)
* Subcutaneous tissue leading to less padding over bony prominences

Age is associated with increased…

* Time for epidermal regeneration (leading to slower healing)


* Damage to skin from the sun

Psychological Stress and ANS

Increased Norepinephrine and epinephrine → Hyperglycemia → Impaired wound healing

Psychological Stress and Hypothalamus

Inc cortisol, glucocorticoid hormones→ Altered immune response → impaired healing

Obesity Local Wound conditions

* Decreased vascularity in adipose tissue
* Skin folds harbor microorganisms
* Friction from skin on skin contact
* Increased wound tension
* Increased tissue pressure
* Venous HTN
* Decreased ability to reposition self

Obesity wound complications

Infection, dehiscence, hematoma and seroma formation, pressure and venous ulcers

Smoking effects on healing

Post-operatively, patients who smoke show delayed wound healing and an increase in infections, wound rupture, wound and flap necrosis, and a decrease in the tensile strength of the wound

Nutrition in wound healing

* Malnutrition or specific nutrient deficiencies impact wound healing.
* Energy, carbohydrate, protein, fat, vitamin and mineral metabolism affect the healing process.
* Fats and carbs help the healing processs

Medications that impact wound healing

* Glucocorticoid Steroids – anti-inflammatory agents.


* Non-steroidal Anti-inflammatory Drugs (NSAIDs)– (long term use)


* Chemotherapeutic Drugs