Cool Under Fire – Burn Surgery Vocabulary

Fundamentals of Burn Pathophysiology

Skin Anatomy & Burn Depth

• Layers: epidermis → dermis → subcutaneous fat → muscle → bone

• Classic depth terminology
  • First-degree (epidermal)
  • Superficial second-degree (papillary dermis)
  • Deep second-degree (reticular dermis)
  • Third-degree (full thickness to sub-Q)
  • Fourth-degree (extends into muscle/bone)

Zones of Burn Injury

• Zone of coagulation (central, irreversible)

• Zone of stasis (ischemic but salvageable)

• Zone of hyperemia (peripheral inflammation)

Clinical Depth Determination & Initial Rx

1. First-degree
   • Dry, erythematous, no blisters, painful
   • \to Frequent lotion, NSAIDs

2. Superficial 2°
   • Moist, bright red, painful, brisk capillary refill
   • \to Serial dressings, analgesia

3. Deep 2°
   • Pale, sluggish refill, moist, painful
   • \to Dressings ± skin-cell suspension ± autograft

4. Third-degree
   • Leathery/white/charred eschar, insensate
   • Circumferential risk \to compartment syndrome (5 Ps) ⇒ escharotomy
   • \to Early excision, dermal substitute, grafting (often staged)

Escharotomy Essentials

• Indicated for circumferential third-degree burns compromising perfusion/ventilation

• Tools: bovie cautery, frequently performed bedside during hydrotherapy

• High peak inspiratory pressures ⇒ chest escharotomy

Burn Size Estimation (Total Body Surface Area, TBSA)

• Rule of Nines (adult) vs. Lund-Browder adjustment (pediatric)
  • Adult head 9\%, each arm 9\%, chest 18\%, back 18\%, each leg 18\%, perineum 1\%
  • Child head 18\%, legs 13.5\% each, other values similar

• Heuristic: \%\text{TBSA} \approx \text{minimum inpatient days}

Determinants of Burn Mortality

• Age extremes ↑ risk

• TBSA ↑ (surface area) ↑ death

• Depth ↑ (full thickness %) ↑ death

• Inhalation injury multiplies risk 15{-}17\times for same TBSA

• Comorbidities (CHF, ESRD, DM II, PVD, immunosuppression) complicate resuscitation/healing

• Missed concomitant trauma = leading early post-survival cause of death

Inhalation Injury

• Pathophysiology: super-heated gases & toxic combustion by-products

• Incidence: 33\% overall, 8\% even in small burns; enclosed spaces highest risk

• Clinical clues: hoarseness, stridor, facial burns, carbonaceous sputum, soot, hypoxia

Management

• Early, skilled endotracheal intubation (anticipate edema)

• Nebulized “HAM” regimen
  • Heparin ⇢ lyse fibrin casts
  • Albuterol ⇢ bronchodilation
  • Mucomyst (N-acetylcysteine) ⇢ mucolysis

• ARDS ventilation (“3\text{Ps}+V”)
  • \text{PEEP}
  • Prone positioning
  • Paralysis (short course)
  • Low tidal V_t

• Toxins
  • Carbon monoxide (CO) ⇢ 100\% \text{FiO}_2
  • Cyanide (HCN) ⇢ hydroxocobalamin

• Outcome data: 73\% respiratory failure, 20\% ARDS, 70\% pneumonia, 18\% mortality

• Special note: brief combustion on home oxygen rarely produces true inhalation injury; avoid reflex intubation in COPD patients.

Acute Burn Resuscitation

2010 ABA Consensus Formula (>20\% TBSA)

• Adults: \text{Fluid}=2\,\text{cc}\times\text{kg}\times\%\text{TBSA} (goal UO 0.5\,\text{cc/kg/hr})

• Pediatrics: 3\,\text{cc/kg/%TBSA} (goal UO 1\,\text{cc/kg/hr})

• High-voltage electrical: 4\,\text{cc/kg/%TBSA} (goal UO 1{-}1.5\,\text{cc/kg/hr})

• Example flame burn 100 kg, 50\% TBSA:
  • Total =2\times100\times50=10{,}000\,\text{mL}
  • 50\% given first 8 h ⇒ 625\,\text{cc/hr}, then 312\,\text{cc/hr} for next 16 h

Limitations & Modern Practice

• Formula ignores obesity (consider IBW)

• Hour 23 identical to hour 2 despite accumulating data; prefer dynamic management

• Colloid (FFP or 5\% albumin) started early to limit “fluid creep”

• Continuous hourly titration guided by urine output; electronic tools like Burn Navigator support decision-making

The “C” Causes of Resuscitation Failure

\text{Carbon Monoxide},\;\text{Cyanide},\;\text{Concomitant Trauma},\;\text{Comorbidities},\;\text{Cardiac/CHF},\;\text{Can’t pee (BPH/ESRD)},\;\text{Calculation Error},\;\text{Congenital Heart},\;\text{Compartment Syndrome}

• Fluid of choice: Lactated Ringer’s.

• Normal Saline is acidotic ⇒ hyperchloremic metabolic acidosis when used in large volumes.

Burn Shock

• Subtype of distributive shock driven by cytokine/catecholamine surge

• Immunosuppression proportional to \%\text{TBSA}

• Under-resuscitation ⇒ multiorgan failure; over-resuscitation ⇒ edema, ACS, pulmonary failure

• Early (<24 h) surgical excision markedly blunts inflammatory load

Hypermetabolism & Long-Term Physiologic Sequelae

• Severe burns induce the highest metabolic rate of any critical illness; may persist 3{-}5 years

• Multimodal countermeasures
  • Early excision/closure
  • Early/robust PT & OT
  • High-protein nutrition
  • Propranolol (\beta-blockade) to dampen catecholamine surge
  • Anabolic agents, micronutrient optimization
  • Psychotherapy

• Sepsis is the leading in-hospital killer; no prophylactic antibiotics initially

Operative Burn Care & Emerging Technologies

Standard of Care

• Tangential excision to viable dermis + split-thickness autograft (STSG)

• Each OR trip increases total wound burden & donor-site pain

Skin Cell Suspension Autograft (ReCell)

• Harvest 6{-}8/1000-inch STSG \approx1\,\text{cm}^2 ⇒ 1\,\text{mL} cell suspension ⇒ treats 80\,\text{cm}^2 (expansion 80{:}1)

• Trypsin digestion to single cells (keratinocytes, melanocytes, fibroblasts, myofibroblasts)

• Sprayed onto wound or interstices of meshed grafts; enhances re-epithelialization

Enzymatic Debridement (Bromelain – pine-apple enzyme)

• Office/bedside application, obviates OR, minimizes blood loss

• Enables earlier wound bed preparation but is painful

Cultured Epithelial Autografts (CEA)

• FDA-approved for >30\% TBSA

• Requires full-thickness biopsy ⇒ $3-week lab culture

• Take rate \approx75\%, graft is extremely fragile

• Experimental bilayer constructs (epidermis + dermis) are under development

Skin Substitutes

• Hundreds on market: cadaveric allograft, xenograft, biologic/synthetic matrices

• Functions
  • Temporize until patient stabilizes
  • Seal fluid/protein loss
  • Cover tendon/bone
  • Restore contour
  • Scaffold for subsequent autograft take

Reconstruction & Rehabilitation Continuum

1. Acute Injury & Resuscitation

2. Primary Wound Coverage

3. Rehabilitation (begins Day 1)

4. Social Reintegration

5. Long-term Reconstruction & Laser Scar Therapy

• Hypertrophic scar contracture can generate tremendous tissue tension (illustrated by wound gaping once incised).

• Modern lasers (fractional CO_2, IPL) modulate scar pliability and pigmentation.

• Rehab goals
  • Restore ADLs, vocational capacity
  • Splinting and stretching to prevent contractures
  • Lifelong psychosocial support (PTSD, body image)

ABA Burn Center Referral Criteria (Key Points)

• Immediate consult/transfer
  • Full-thickness burns
  • Partial-thickness >10\% TBSA
  • Deep burns to face, hands, feet, genitalia, perineum, major joints
  • Inhalation injury
  • Electrical (>1{,}000 V) or lightning
  • All chemical burns
  • Pediatric burns (\le14 yr or \<30 kg)
  • Burns with major comorbidities or concomitant trauma
  • Poorly-controlled pain

• Consultation recommended
  • Partial-thickness \<10\% TBSA but potentially deep
  • Low-voltage electrical for latent complications

• “No Silvadene, please!” — outdated topical; modern centers favor bacitracin, mupirocin, or silver foam dressings.