Ch14: Burns（烧伤）

Preparatory Mindset

Burns are a unique surgical disease — a combination of local tissue destruction + systemic inflammatory response (fluid shift, hypovolemic shock, infection). The exam tests: depth classification (I°, II°, III°), extent estimation (Rule of Nines / Lund-Browder / palm = 1%), the Parkland formula for fluid resuscitation, and burn complications (infection, sepsis, contractures). The lecture (17 Burns.ppt, legacy binary) is covered by 外科学笔记.txt + prep PDFs.

Exam mindset: "烧伤面积九分法" (Rule of Nines), "三度四分法" (I°, superficial II°, deep II°, III°), and the Parkland formula (4 ml × TBSA% × kg, half in first 8 h) are guaranteed exam items.

Core Concepts

1. Depth classification (MUST KNOW — 三度四分法)

• Key distinction: III° is painless (nerve endings destroyed); deep II° vs III° matters for grafting decisions

2. Extent estimation (MUST KNOW)

• Rule of Nines (成人九分法): head & neck 9%; each upper limb 9%; each lower limb 18% (front 9 + back 9); anterior trunk 18%; posterior trunk 18%; perineum 1% (=100%)
• Lund-Browder chart — more accurate, adjusts for age (children: larger head, smaller legs)
• Palm method: patient's palm (incl. fingers) ≈ 1% TBSA — quick estimate for scattered burns
• Children: head = 18% (age 1) decreasing; legs smaller proportion — use Lund-Browder

3. Burn severity classification (MUST KNOW)

- Partial thickness >20% (adult) / >10% (child) - Full thickness (III°) >5% or involving face, hands, feet, perineum, major joints - Inhalation injury, electrical burns, chemical burns, burns with major trauma, pre-existing disease, extremes of age

• Minor: <10% TBSA (adult) / <5% (child) superficial-partial, no face/hands/feet/perineum involvement
• Moderate: 10-20% (adult) partial; 5-10% (child)
• Major (refer to burn center):

4. Pathophysiology & systemic response (MUST KNOW)

• Local: coagulation necrosis, inflammation, edema; burn wound is sterile initially → colonized by day 3-7 (infection risk)
• Systemic (early): massive capillary leak → fluid loss & hypovolemic shock; tissue edema; decreased cardiac output; hemoconcentration
• Systemic (late): hypermetabolism (↑↑ catabolic state), hyperglycemia, immune suppression → sepsis (leading cause of death in burns), MODS
• Inhalation injury: smoke/heat → upper airway edema (stridor — intubate early), CO poisoning (carboxyhemoglobin), chemical injury → ARDS — major determinant of burn mortality

5. Fluid resuscitation — Parkland formula (MUST KNOW)

- Half in the first 8 hours (from the time of burn, not admission) - Second half over the next 16 hours

• Parkland (Baxter): 4 ml × body weight (kg) × TBSA burn % of Ringer's lactate (平衡盐液) in the first 24 h:
• Children: add maintenance fluids (dextrose-containing)
• Endpoint: urine output 0.5-1 ml/kg/h (adults ~30-50 ml/h; children 1 ml/kg/h); HR/BP/mentation
• Avoid: over-resuscitation (edema, compartment syndrome, ARDS), under-resuscitation (AKI, shock)
• Colloids: added after 24 h (capillary leak resolves); albumin in some protocols
• Note: the burn depth used in Parkland counts partial & full thickness only (II°+III°), not I°

6. Burn wound management (MUST KNOW)

• First aid: stop the burning, cool the wound (running cool water 10-20 min — within 3 h), remove clothing/jewelry, cover with clean dry cloth — do NOT apply ice, butter, toothpaste
• Escharotomy: circumferential full-thickness burns of limbs/chest → eschar constricts → compartment syndrome / respiratory restriction → urgent escharotomy (longitudinal incisions through the eschar)
• Wound care: clean, debride blisters (large), topical antimicrobials: silver sulfadiazine (II°), mafenide acetate (III°/eschar — penetrates), silver dressings; culture & treat infection
• Excision & grafting: early tangential excision of deep burns + split-thickness skin graft (STSG); full-thickness → autograft; meshed grafts; donor sites
• Dressings & grafting principles: clean bed (no infection) → graft take; immobilize the grafted area
• Nutrition: high calories & protein (25-40 kcal/kg, 2-3 g/kg protein) — hypermetabolic
• Tetanus prophylaxis (all burns); analgesia; antibiotics only for documented infection (prophylaxis controversial)

7. Complications of burns (MUST KNOW)

• Early: hypovolemic shock, inhalation injury/CO poisoning, acute kidney injury, electrolyte imbalance, compartment syndrome
• Late: burn wound infection & sepsis (leading cause of death), pneumonia, Curling ulcer (stress ulcer — GI bleeding), hypermetabolism/cachexia, DVT, contractures & hypertrophic scars (scar management: pressure garments, splinting), Marjolin ulcer (SCC in chronic burn scar), psychological trauma

8. Special burns

• Electrical burns: deep tissue injury along the current path ("iceberg" — small entry/exit, extensive deep damage) → rhabdomyolysis, myoglobinuria (AKI), arrhythmias; fluid (more than Parkland predicts), alkalinize urine, fasciotomy, monitor ECG 24-48 h
• Chemical burns: copious irrigation (alkali worse than acid — liquefaction), remove contaminated clothing, neutralize (dilute, don't over-neutralize)
• Tar/asphalt: cool then remove
• Inhalation injury: bronchoscopy, early intubation, 100% O2/CO-oximetry, avoid fluid overload

High-Yield Points

• Depth: I° (red, painful) → superficial II° (blisters, very painful) → deep II° (mottled, less painful, scars) → III° (waxy/charred, PAINLESS, needs graft)
• Rule of Nines: head 9, each arm 9, each leg 18, ant trunk 18, post trunk 18, perineum 1
• Palm = 1% TBSA; children use Lund-Browder (head bigger)
• Parkland: 4 ml × kg × TBSA% RL; half in first 8 h; target urine 0.5-1 ml/kg/h
• III° = painless = grafting; deep II° scars
• Escharotomy for circumferential burns (limb/chest)
• Topical: silver sulfadiazine (II°), mafenide (eschar, penetrates)
• Inhalation injury & sepsis = leading causes of death; intubate early for stridor
• Electrical: hidden deep injury, rhabdomyolysis/myoglobinuria, ECG monitoring
• Curling ulcer = stress ulcer in burns; Marjolin ulcer = SCC in old scar

Topic Summary

Burns are classified by depth (I°, superficial II° blisters painful, deep II° mottled scarring, III° painless full-thickness needing grafting — 三度四分法) and extent (Rule of Nines, palm 1%, Lund-Browder for children). Major burns: >20% partial (adult), >5% full thickness, face/hands/feet/perineum, inhalation/electrical/chemical. Pathophysiology: early capillary leak → hypovolemic shock; late hypermetabolism + sepsis (leading death cause). Parkland resuscitation: 4 ml × kg × TBSA% Ringer's lactate, half in 8 h, urine 0.5-1 ml/kg/h. Wound care: cool first, debride, topical antimicrobials (silver sulfadiazine/mafenide), early excision & grafting; escharotomy for circumferential burns; high-protein nutrition; tetanus prophylaxis. Complications: shock, inhalation injury/CO, AKI, sepsis, Curling ulcer, contractures, Marjolin ulcer. Special: electrical (hidden deep injury, myoglobinuria), chemical (copious irrigation).