Wound Management

"Golden Period": First 6-12 hours post-injury; after this, bacterial colonization (>10^5 organisms/gram tissue) increases infection risk significantly; heavily contaminated wounds may have 3-4 hour window

Healing Stages and Timeline

Phase 1 - Inflammatory (0-3 days)

• Hemostasis, fibrin clot formation, neutrophil infiltration
• Clean wound: Minimal bleeding; sealed by day 1
• Contaminated wound: May continue oozing; risk of infection peaks day 3

Phase 2 - Proliferative (3-21 days)

• Angiogenesis, fibroblast proliferation, collagen deposition
• Epithelialization from wound edges inward
• Primary closure: Re-epithelialized by day 7; 70% original strength by day 21
• Second intention: Slower; may take weeks to months

Phase 3 - Remodeling (21 days-1 year+)

• Collagen cross-linking, scar maturation
• Wound reaches ~80% strength at 3 months, 90%+ at 1 year
• Species variation: Dogs heal faster than cats; young animals faster than geriatric

Debridement Principles

Mechanical Debridement (wet-to-dry bandaging, wet-to-moist, surgical):

• Remove devitalized tissue, foreign material, bacteria
• Surgical debridement: Scalpel/electrocautery under anesthesia; fastest, most complete
• Wet-to-dry: Non-selective; removes granulation tissue along with necrotic debris (limit duration)
• Wet-to-moist: More selective; granulation tissue adheres less; preferred for prolonged debridement

Enzymatic Debridement (hydrogel, papain-urea):

• Slower than surgical; useful adjunct for chronic wounds
• Does not remove foreign material

Antiseptic/Antimicrobial Agents (chlorhexidine 0.05%, dilute povidone-iodine):

• Initial wound flush (surgical preparation)
• Avoid concentrated solutions (cytotoxic to fibroblasts)
• Repeat daily during open management phase

Bandaging Types and Indications

Wet-to-Dry Dressing

• Composition: Sterile gauze moistened with saline applied wet; allowed to dry completely (12-24 hours)
• Mechanism: Non-selective debridement as dressing dries; dead tissue adheres and is mechanically removed at dressing change
• Indications: Heavy exudate, significant devitalized tissue, early wound management (first 3-7 days)
• Limitations: Painful dressing change; non-selective (removes granulation tissue too); labor-intensive; risk of maceration if edges sealed

Wet-to-Moist Dressing

• Composition: Gauze moistened with saline (or antimicrobial solution) kept moist at all times
• Mechanism: Selective debridement; maintains moist environment for healing; gauze removed while still wet (before drying)
• Indications: Transitional phase (days 3-10); less necrotic tissue remaining; promotes granulation
• Change frequency: BID-TID (more labor than wet-to-dry)

Tie-Over Bandage (Donut/Bolus)

• Composition: Sterile gauze/telfa pad, soft padding, outer wrap; tied over surgical incision or laceration
• Mechanism: Compression dressing; maintains suture approximation; protects from contamination
• Indications: Head/neck wounds (difficult to bandage); high-motion areas; early post-operative (first 2-3 days)
• Change frequency: Typically q3-5 days until suture removal

Negative Pressure Wound Therapy (NPWT)

• Mechanism: Controlled suction applied via foam/gauze interface; promotes angiogenesis, reduces edema, increases bacterial clearance
• Indications: Large wounds, high-motion areas, chronic wounds, post-operative infection prevention
• Protocol: 75-125 mmHg continuous or intermittent; dressing change q2-3 days
• Efficacy: Accelerates healing by ~20% in controlled studies; expensive; requires specialized equipment

Advanced Dressings (Hydrogel, Calcium Alginate, Foam)

• Hydrogel: Maintains moist environment; non-adherent; good for shallow wounds with moderate exudate
• Calcium alginate: Absorbs heavy exudate; changes to gel as fluid absorbed; biodegradable
• Foam dressing: Absorbs moderate exudate; maintains moisture; non-adherent
• Indications: Chronic wounds, wounds with adequate blood supply, clean granulating wounds

Drain Placement

Indications: Dead space >2-3 cm, heavy exudate, infection risk, contaminated wounds

Types:

• Passive drain (Penrose, latex tubing): Gravity/capillary action; simple, inexpensive; less effective than active
• Active drain (Jackson-Pratt, Blake drain): Closed system; maintains negative pressure; superior drainage; higher infection risk if sealed prematurely

Technique: Place in dependent location; secure with suture; cover with padded bandage Maintenance: Monitor output daily; strips, color, volume; remove once output <0.5 mL/kg/day

Species-Specific Healing Differences

Dogs

• Healing rate: Rapid; epithelialization by day 7 (clean wounds)
• Primary closure: Safe up to 12-16 hours post-injury if clean
• Second intention: Smaller wounds can heal acceptably; larger wounds (>5 cm) benefit from closure
• Suture removal: 10-14 days; skin removes sutures at day 10-12 safely

Cats

• Healing rate: Slower than dogs; epithelialization by day 8-10
• Primary closure: More conservative approach; 8-12 hours recommended
• Infection risk: Higher than dogs; more sensitive to bandage stress; early mobility complicates healing
• Suture removal: 12-14 days recommended; high risk of re-opening if removed early

Rabbits/Small Mammals

• Healing rate: Rapid epithelialization but fragile skin
• Closure: Primary closure preferred when possible; secondary healing slow and cosmetically poor
• Complications: High risk of self-mutilation; E-collar essential; analgesia critical to prevent chewing
• Bandaging: Difficult due to small body size; splinting sometimes necessary

Horses

• Healing rate: Slow; exuberant granulation common (proud flesh formation)
• Chronicity: Leg wounds can take months; risk of contracture and poor cosmesis
• Second intention: Requires aggressive management to prevent proud flesh; bandaging critical
• Closure: Primary/delayed primary closure preferred if anatomically feasible

Wound Infection Risk Factors

High Risk:

• Contamination with soil, feces, water (Gram-negative, anaerobic risk)
• Crush injury, devitalized tissue
• Foreign body retention
• Delay >12-24 hours to closure/debridement
• Immunosuppression (diabetes, corticosteroid use, FIV/FeLV)
• Joint space involvement

Antibiotic Approach:

• Clean wound, early closure: Prophylactic single dose (pre-operative cephalosporin)
• Contaminated wound: Therapeutic antibiotics (7-14 days); culture if infection signs develop
• Prophylactic antibiotics NOT standard for all bite wounds (controversial); consider species (human bites, high risk; dog bites lower risk if early drainage)

Wound Healing Complications

Dehiscence (premature opening): Inadequate suturing, early suture removal, excessive motion, infection Seroma/Hematoma: Continued fluid accumulation; may require drainage if >5 cm or expanding Infection: Fever, purulent discharge, swelling, delayed healing; culture, sensitivity, systemic antibiotics Proud Flesh (excessive granulation, horses): Bandaging, topical corticosteroids, cautery as last resort Contracture: Scar tissue contraction limiting mobility; more common in chronic wounds Keloidal Scarring: Excessive collagen deposition; cosmetically poor but functionally acceptable

Workflow

1. Assess wound: Location, contamination level, time post-injury, underlying structures
2. Debride under anesthesia if needed; remove foreign material
3. Classify wound (clean/contaminated/dirty)
4. Decide: Primary closure (clean, <12 hours), delayed primary (contaminated, >12 hours), or secondary (infection, excessive contamination)
5. Place drain if dead space significant
6. Suture/bandage; select appropriate dressing based on healing phase
7. Change dressing per protocol; assess healing progression daily
8. Remove sutures at species-appropriate interval (dogs 10-12, cats 12-14 days)

Limitations

• Wound classification: Judgment-based; gray area between categories complicates closure decision
• Healing rate variation: Age, nutrition, underlying disease, medications all affect timeline; individual variation significant
• Infection prediction: Bacterial burden difficult to assess clinically; culture definitive but delayed
• NPWT cost: May exceed cost of standard dressing changes in small animals; not universally available
• Secondary healing: Cosmetics generally poor; larger defects (>5 cm) often benefit from grafting (beyond primary veterinary scope)
• Referral: Complex wounds, joint involvement, high-motion areas, failed primary healing → surgical specialist consideration