Wound Study Guide

📖 Core Concepts Wound – any disruption of skin, mucosa, or organ tissue. Acute vs. Chronic – Acute: predictable healing, usually < 3 mo. Chronic: stalls in one or more phases, persists > 3 mo. Open vs. Closed – Open breaches skin; closed damages tissue beneath an intact skin surface. Healing Phases – Hemostasis (minutes‑hours), Inflammatory (1‑3 days), Proliferation (days‑1 mo), Remodeling (12 mo‑2 yr). Classification Systems – CDC surgical wound (clean → dirty/infected), Gustilo‑Anderson (open fractures), Tscherne (soft‑tissue injury), AO/OTA (numeric fracture code). Key Terms – Necrotic tissue: dead tissue (eschar = black, slough = yellow‑creamy). Granulation: pink, vascular tissue filling defect. Exudate: wound fluid; amount guides dressing choice. --- 📌 Must Remember Chronic wound definition: > 3 months without progression. CDC wound classes: Clean, Clean‑contaminated, Contaminated, Dirty/infected. Gustilo‑Anderson Types: I (< 1 cm, clean), II (> 1 cm, no extensive loss), IIIA (adequate periosteal cover), IIIB (needs flap), IIIC (arterial repair). ABI/TBI cut‑off for PAD: ABI < 0.9 (or toe‑brachial index). Irrigation volume: $50\text{–}100\ \text{mL/cm}$ wound length with normal saline. NPWT pressure range: $-75$ to $-125\ \text{mm Hg}$. Pressure‑induced ischemia: > 30 mm Hg for > 2 h → tissue necrosis. PUSH score: Lower score = healing; combines size, exudate, tissue type. --- 🔄 Key Processes Hemostasis Vessel spasm → platelet plug → fibrin clot (minutes‑hours). Inflammation Neutrophils (0‑24 h) → macrophages (days 1‑3) clean debris, release cytokines. Proliferation Fibroblast migration, collagen deposition, angiogenesis, granulation, epithelial cell migration. Remodeling Collagen type III → type I, tensile strength ↑, scar matures (12 mo‑2 yr). Debridement (selective) Assess → choose technique (autolytic, mechanical, enzymatic, sharp, biological) → remove necrosis → re‑assess. Primary Closure Decision Evaluate contamination, vascularity, time since injury, patient comorbidities → close within “golden period” if clean & well‑vascularized. --- 🔍 Key Comparisons Incised vs. Laceration – Clean cut by sharp object vs. irregular tear from blunt force. Primary vs. Delayed Primary Closure – Immediate edge approximation vs. 3–5 day delay for drainage/ infection control. Autolytic vs. Enzymatic Debridement – Body’s own enzymes in moist environment vs. topical collagenase applied externally. Gauze vs. Foam Dressings – Highly absorbent, may adhere → painful removal vs. semi‑occlusive, absorbent inner layer, less trauma. Clean vs. Contaminated (CDC) – No break in sterile technique vs. major breach or dirty trauma. --- ⚠️ Common Misunderstandings “All acute wounds close within 6 h.” – No absolute cut‑off; closure depends on contamination and patient factors. “Tap water is unsafe for wound irrigation.” – Low‑risk wounds may be irrigated with tap water; sterile saline is gold standard. “All slough must be removed surgically.” – Autolytic or enzymatic methods can safely clear slough. “Negative pressure always speeds healing.” – Benefits are greatest for large defects, graft fixation, or infection control; not indicated for all wounds. --- 🧠 Mental Models / Intuition “The 4‑S Rule for Wound Assessment” – Size, Shape, Surface (tissue type), Surrounding skin → quick snapshot of severity. “Healing as a Construction Project” – Hemostasis = foundation laying, Inflammation = site cleanup, Proliferation = building walls (granulation), Remodeling = interior finishing (collagen remodeling). “Pressure‑Perfusion Balance” – When external pressure > capillary perfusion pressure (≈ 30 mm Hg), tissue dies → think of a clogged hose. --- 🚩 Exceptions & Edge Cases Deep tissue infection – Surface swab may miss organisms; deep tissue biopsy is gold standard. High‑dose iodine – Cytotoxic; dilute to 10 % (1 % available iodine) for safety. Diabetic foot ulcers – May be neuropathic (painless) or neuro‑ischemic (painful, ischemic signs). Sharp debridement in coagulopathy – May cause bleeding; consider enzymatic/autolytic alternatives. --- 📍 When to Use Which Irrigation: Low‑pressure saline for all wounds; pulsatile flow when heavy bacterial load suspected. Debridement Technique: Autolytic – moist, low‑exudate chronic wounds. Mechanical – heavily exudative, need rapid bulk removal. Enzymatic – patients who cannot tolerate surgery. Sharp – urgent removal of necrosis, contaminated wounds. Biological – chronic ulcers with abundant slough, patient consents. Dressings: Hydrocolloid – moderate exudate, need moist environment. Foam – heavy exudate, need absorbency + protection. Alginate/Hydrofiber – very heavy exudate (> 10 mL/24 h). Film – low exudate, need visualization. NPWT – large defects, graft fixation, infection control. Closure Method: Primary – clean, minimal tissue loss, within 6–8 h if favorable. Delayed Primary – contaminated or high‑risk infection. Secondary Intention – large tissue loss, infection, or patient contraindications. --- 👀 Patterns to Recognize “Staged ulcer pattern” – Venous ulcers → shallow, irregular, medial malleolus; Arterial ulcers → well‑demarcated, painful, distal toe; Neuropathic ulcers → painless, callused base. “Red‑flag infection signs” – Pain > appearance, foul odor, increasing erythema, warmth, purulent exudate. “Exudate‑dressing mismatch” – Excessive drainage with gauze → consider foam/alginate; minimal drainage with film → may be over‑moist. “Edge morphology clues” – Rolled edges → chronic, non‑healing; sharp, everted edges → recent incised wound. --- 🗂️ Exam Traps Distractor: “All contaminated wounds must be classified as dirty/infected.” – Incorrect: CDC separates contaminated (fresh, major break) from dirty/infected (old, devitalized tissue). Distractor: “Povidone‑iodine 10 % is the safest concentration for all wounds.” – Incorrect: Full‑strength iodine is cytotoxic; dilute to 1 % available iodine for most uses. Distractor: “Negative pressure therapy is contraindicated in all infected wounds.” – Incorrect: NPWT can be used with appropriate antimicrobial dressings; absolute contraindications are untreated osteomyelitis, malignancy, exposed vessels. Distractor: “Primary closure must be done within 6 h after injury.” – Incorrect: No rigid cut‑off; decision based on contamination, tissue viability, and patient status. ---