Plastic Surgery SC030: An Ugly Wound: Wound Healing, Wound Infection, Anti-septic Technique Flashcards
***Etiology of Wound
External:
- Traumatic
- Thermal
- Chemical (e.g. extravasation of contrast / chemotherapy causing burn)
- Surgical
Local:
- Vascular (e.g. Arterial insufficiency)
- Pressure
- Neuropathic (e.g. DM)
- Infective
- Malignant
***Wound healing
Ways of healing:
Fetus:
- Regeneration (i.e. No scar)
Neonate - Adult:
- Fibrosis / Scarring
Complex interactive process involving a variety of **cell types, **soluble factors, ***matrix components
Phases (biologically distinct from one another, but overlapping):
1. Haemostasis (immediate - day 3)
- start immediately when injury to tissue
- aim to stop bleeding
- tissue injury —> Tissue factor activate extrinsic clotting cascade —> platelets clump —> platelet plug —> intrinsic clotting cascade —> Fibrinogen to Fibrin —> end result: platelet plug + fibrin mesh (provide a scaffold for cell migration for wound healing)
- Inflammatory phase (immediate - day 5)
- new framework for blood vessel growth
- start before haemostasis ends
- Platelet degranulate —> PDGF (platelet derived growth factor), TGF-β —> attract neutrophils + macrophages —> **phagocytosis + **remove devitalised tissue
- macrophage can also release cytokines for wound healing - Proliferative / Granulation phase (day 4-21)
- pull the wound closed
- fibrin matrix replaced by granulation
—> **Fibroblasts (proliferate, migrate and deposite ECM —> **Type 3 collagen)
—> Macrophages (PDGF, TGF-β)
—> Endothelial cells (neovascularisation —> vascular wound (bleeds))
- **Re-epithelialisation: **Keratinocyte migration —> if whole wound covered by keratinocytes —> considered healed - Remodeling / Maturation phase (day 21 - 1 year)
- final proper tissue
- programmed **regression of blood vessels and granulation
- **Wound contraction by Myofibroblasts
- Collagen remodeling: Type 3 collagen replaced by ***Type 1 collagen
—> scar less red, raised, itchy, painful, more supple
***Tensile strength of healing wound
Collagen content in wound:
- rise and reaches plateau at the end of proliferative phase
Tensile strength in wound:
- not increase much in proliferative phase
- shoot up during and reach maximum at the end of remodeling phase (can up to 2 years) (i.e. wound won’t be strong until the end of remodeling phase i.e. 2 years)
- never goes back to 100% (80% maximum)
Pathological wound healing
Arrested in inflammatory phase
—> Chronic inflammatory wound (wound without healing >= a few weeks)
Arrested in proliferative phase
—> Fibroblast keep proliferating and laying down collagen
—> Hypertrophic / Keloid scar
***Factors affecting wound healing
Local factors:
- Infection
- Pressure
- Edema (e.g. dependent area)
- Dessication (e.g. moist area promote wound healing, dry scap e.g. slough, necrotic tissue impede wound healing ∵ keratinocyte cannot migrate across dessicated / devitalised tissue)
- Colonisation
- Hypoxia (post-RT, arterial insufficiency)
Systemic factors:
- Old age
- Obesity (even if lost weight)
- Chronic diseases (e.g. DM, anaemia, chronic renal diseases)
- Malnutrition, Malabsorption
- Genetic factor (e.g. Ehlers-Danlos disease)
- Smoking
- Medications (e.g. steroid, immunosuppressants, chemotherapy)
Wound infection
Definition:
- Bacterial growth >100,000 organisms per gram of tissue (10^5 / g)
Mild wound infection:
- pain, erythema, edema, increased temperature
- can be managed locally —> wound dressing, local dressing material, local antibiotic, systemic antibiotic
Severe wound infection
- skin necrosis, pus formation
Anti-septic technique: Prevention of wound infection
Every surgical wound is contaminated by bacteria
3 sources of bacteria:
1. Surgical team
2. Patient’s own flora
3. Operative environment
- Surgical team
- PPE (Universal precaution)
- Mask
- Gloves
- Eye shield / goggles
- Face shield
- Barrier gowns - Scrubbing
- Betadine (Povidone-iodine): rapid onset of action, broad spectrum, short effect
- Chlorhexidine gluconate: longer acting - Brushes (controversial)
- may cause skin abrasions (may increase wound infection) - Meticulous surgical techniques
- gentle tissue handling, minimal tissue trauma —> less edematous wound bed + less devitalised tissue —> heal better
- careful haemostasis to prevent haematoma formation —> good medium to culture bacteria - Irrigation of surgical field to dilute / reduce bacterial load
- amount more important than types of irrigant
- Patient preparation
- Longer the hospital stay —> Higher chance of hospital acquired infection (e.g. HAI, antibiotic-resistant bacteria)
Sources of infection:
- Pre-existing pneumonia
- Drip site
- Other catheterisation (Foley, Central line, A line)
- Colonisation by antibiotic-resistant bacteria
Special attention:
- Smoker
- Immunocompromised patients (DM, CRF, Immunosuppressant)
- Aspirin / Anticoagulants (higher chance of bleeding / haematoma formation)
- Shaving
- Hair adjacent to operative site to be removed
- Shaving often cause injury to the skin —> increasing wound infection rates
- Perform as near to the time of surgery as possible
- Clippers - Anti-sepsis
- Use sterilised sponge forceps to apply
- Povidone-iodine / Aqueous-based chlorhexidine gluconate / Alcohol-based chlorhexidine gluconate (beware of accumulation —> when surgery use diathermy —> subsequent burn injury) - Drapes
- Protect from contamination from periphery
- Sterilised cotton drapes —> Protection diminished when wet
- Plastic disposable drapes - Prophylactic antibiotic
- Dirty trauma wounds
- Entry into nasal cavity / oropharynx / bowel etc.
- Cardiac indications (e.g. heart valves, vegetations) - Cover up source of containation
- Nipple shield in breast implant insertion (∵ nipple ducts harbour lots of bacteria —> cannot be disinfected effectively by antiseptics)
- Operative environment
Concepts of zones:
1. Aseptic zone: operating area
2. Clean zone: area between reception and theatre suite
3. Outer zone: patient reception area
4. Dirty zone: disposal areas and corridors
Design of operating theatre:
Airflow
- maintain humidity / temp / air circulation
- too humid / high temp: increase bacterial growth
- laminated + unidirectional air flow
- air pumped into room via filters
- passed out through vents in the periphery and does not return
Behaviour in the theatre:
- minimal no. of people should be in the operating room
- must not contaminate the sterile instruments
- separate instruments / areas for clean and contaminated items
Preparation of operating instruments / Sterilisation of instruments:
- complete destruction + removal of all viable microorganisms, including viruses, bacteria, spores
- damage to organic substances
- applied to inanimate objects only
Sterilisation by steam
- ***Autoclaves
- Steam under pressure
—> 134oC (30 lb in. ^-2) for a hold time of 3 mins
—> 121oC (15 lb in. ^-2) for a hold time of 15 mins
- effective against bacteria (including TB), viruses (HBV, HCV, HIV), heat-resistant spores (Clostridium tetani, C. perfringens)
Sterilisation by Ethylene oxide
- C2H4O
- **low temp 20-60oC, 2-24 hours
- highly penetrative, non-corrosive, broad-spectrum cidal action
- toxic, irritant, mutagenic, carcinogenic
- for **delicate items e.g. electrical equipments, flexible fibre endoscopes etc.
Sterilisation by Irradiation
- gamma rays / accelerated electrons
- dosage of 25 kGy
- suitable for sterilisation of ***large batches of similar products (catheters, syringes etc.)
- expensive, not readily available
Management of wound infection
- Wound assessment
- Clinical
- Imaging (esp. for deep seated wound) - Adequate debridement of devitalised tissue (necrotic skin, slough) / Removal of foreign body
- Wound swab send for culture + sensitivity
- guide antibiotic use - Empirical antibiotics
- broad-spectrum antibiotic
- streamline after culture results available - Dressing of wound
- for open wound - Irrigation of a cavity / sinus
***Wound debridement (傷口清創)
Definition:
- Removal of necrotic tissue from wound bed to promote wound healing
Natural process that occurs in all wounds (by neutrophils, macrophages) (even without surgical intervention)
End point of debridement:
- Healthy wound bed obtained to **promote granulation (Fibroblast proliferation, Neovascularisation) + epithelialisation (Keratinocyte migration)
- Healthy wound for **reconstruction: skin grafts / flaps
***Purpose of debridement:
1. Remove foreign body (hair, sutures, dirt)
- foreign body is a physical barrier against epithelialisation
2. Reduces bacterial burden
3. Remove exudate
4. Promotes effective inflammatory response for healthy granulation tissue
Evidence:
- More frequent debridement —> shorten time to wound healing
Classification:
1. Autolytic
2. Sharp
3. Enzymatic
4. Mechanical
5. Biological
6. Surgical
Surgical debridement
- By surgeons
- Non-selective (may remove healthy tissue as well), requiring anaesthesia, larger wound
Ways:
1. Sharp debridement
- by scalpel, scissors, curette
- Tangential debridement
- by Watson’s knife, Goulian knife
- e.g. in burn wound removing partial thickness of skin - Hydrosurgery (Versajet)
- a high pressure, high velocity stream of sterile saline through an opening of hand piece
- venturi effect creates a local vacuum on the debriding surface - USG debridement (Sonoca)
