1. Pathophysiology of the burn wound Skin biology Pathophysiologic changes with thermal injury

2. Skin biology Epidermis Multifunctionality: –Barrier function –UV protection –Immune responses Five keratinocyte layers –Stratum basalis (regenerative), stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum (barrier function) Melanocytes –Produce melanin for ultraviolet protection Langerhans cells –BM derived antigen presenting cells with phagocytic capability Sensory nerves

3. Skin biology Basement membrane Basement membrane –Connects epidermis to dermis via epidermal projections Keratinocyte-derived collagen VII anchoring fibrils anchor epidermis to dermis –Following epithelialization, fibril formation may take weeks to months to mature with increased risk for shearing and blistering –Rete ridges and dermal papillae also contribute to epidermal-dermal adhesion

4. Skin biology Dermis Heterogeneous layer of skin with multiple functions: –Mesenchymal elasticity and durability –Vascularity –Immunity Two basic layers separated by a vascular plexus –Superficial papillary dermis –Deep reticular dermis

5. Pathophysiologic changes of thermal injury –Jackson’s zones of Injury Zone of coagulation (center of wound) Zone of stasis (‘at risk’ for conversion) Zone of hyperemia (outer periphery)

6. Jackson’s 3 zones of injury on an ankle burn: (a) the zone of coagulation; (b) the zone of stasis, and (c) the zone of hyperemia.

7. Assessment of burn depth 1 st -degree burn Superficial burn –Epidermis only –Heals in 3–4 days –e.g. sunburn

8. Assessment of burn depth 2 nd -degree burn Superficial dermal burn –extends into the papillary dermis –pink/moist wound, hypersensitive and blanching –heals in 2–3 weeks –e.g. scald burn or flash burn Deep dermal burn –extends into reticular dermis –pale/dry wound, decreased sensation, and sluggish capillary refill –if not healed by 3 weeks grafting usually indicated –e.g. grease burn, flash burn, prolonged scald exposure

9. Lower extremity burn having components of a superficial dermal burn (a) with a wet, pink and moist appearance, as well as a deeper dermal burn; (b) with mottled pink and white areas.

10. Assessment of burn depth ≥ 3 rd -degree burn Full thickness burn –Extends through the skin to the SQ or deeper –Black or charred, leathery, insensate –Excise and graft early to reduce risk of infection and scarring –e.g. flame burns, contact burns

11. Deep contact burn in an elderly patient who was unconscious next to a space heater. Arrows denote the imprints of the space heater grill on his lateral thigh.

12. Assessment of burn depth Adjuncts to clinical judgment Experienced burn surgeon 46–67% accurate in determining which burns will heal on PBD 1 Additional techniques proposed to identify non- healing wounds: –laser Doppler imaging –thermography –MRI –biopsy –ultrasound –light reflectance No technique has proven superior to serial exams

13. Mechanisms of thermal injury Flash and flame burns Scalds Contact burns Chemical burns Electrical burns

14. Mechanisms of thermal injury Flash and flame burns Responsible for more than half of burn injuries Etiology –House fires –Outdoor fires with use of accelerants propane, gasoline, and kerosene 28% related to alcohol use Flash burn Typically superficial to partial dermal burns with preservation of skin covered by clothing Flame burn –Typically deep dermal or full thickness burns Inhalation injury likely with gasoline fire and/or house fire

15. Mechanisms of thermal injury Scalds Second most common burn injury-related admission Depth of scald injury depends on –Water temperature (>110ºF) –Duration of contact consistency of liquid (i.e. soup vs coffee vs grease) –Skin thickness based on age and anatomical location Clothed areas may have deeper burns due to retention of heat and longer contact with skin –e.g. diapers or socks Other sources of scald burns –Grease/oil typically deep dermal or full thickness burns

16. Mechanisms of thermal injury Contact burns Typically small areas due to hot metal, plastic, glass or coals Burn depth related to –Temperature of material –Duration of contact –Patient-related disabilities (e.g. neuropathy) Commonly responsible for pediatric palm burns Grafting of palm can lead to life-long disability and timing of surgery is controversial –Early grafting restores function quickly but destroys unique palmar nerve endings and palmar fasciocutaneous ligaments

17. Mechanisms of thermal injury Chemical burns Acids cause tanning with impermeable barrier limiting deep penetration –e.g. cleaning solvents –Hydrofluoric acid burns unique in need for calcium treatment Topical Intravenous – for life-threatening hypocalcemia Intra-arterial – for comfort and hypocalcemia Alkalis combine with lipids (saponification) and dissolve tissue –e.g. cement or drain openers Etiologies –Work-related –Assault –Improper use of household products and harsh solvents Progressive damage diluted with copious H 2 0 irrigation –15–20 minutes –pH test of skin until neutral –Attempts to neutralize causes exothermic reaction and thermal injury

18. Mechanisms of thermal injury Electrical burns Due to very high intensity localized heat as body becomes an ‘accidental’ resistor High voltage injuries (>1000 volts) –many work-related –deep tissue necrosis –arrhythmia (typically atrial fibrillation) –cognitive deficits –acute and delayed neuromuscular degeneration carpal tunnel injuries compartment syndromes early surgical intervention indicated for acidosis ± signs of rhabdomyolysis or deterioration of neuro-sensorimotor exam –cataract formation Low voltage injuries (<440 volts) –Typically small deep burns at contact points with rare systemic injury, –Classic pediatric injury involves oral commissure with risk of delayed oral artery bleed

19. Criteria for transfer of a burn patient to a burn center Second-degree burns greater than 10% total body surface area (TBSA) Third-degree burns Burns that involve the face, hands, feet, genitalia, perineum, and major joints Chemical burns Electrical burns including lightning injuries Any burn with concomitant trauma in which the burn injuries pose the greatest risk to the patient Inhalation injury Patients with pre-existing medical disorders that could complicate management, prolong recovery, or affect mortality Hospitals without qualified personnel or equipment for the care of critically burned children.

20. Guidelines for referral to a burn center Partial-thickness burns greater than 10% TBSA Burns involving the face, hands, feet, genitalia, perineum, or major joints Third-degree burns in any age group Electrical burns, including lightning injury Chemical burns Inhalation injury Burn injury in patients with complicated pre-existing medical disorders Patients with burns and concomitant trauma in which the burn is the greatest risk. If the trauma is the greater immediate risk, the patient may be stabilized in a trauma center before transfer to a burn center. Burned children in hospitals without qualified personnel for the care of children Burn injury in patients who will require special social, emotional, or rehabilitative intervention