• Information
  1. Scope of Problem
  2. Grading of Burns
  3. Complications of Burns
  4. Risk Factors for Poor Outcome
  5. Overview of Treatment
  6. Infection in Burn Injury Patients

A. Scope of Problem

1. Nearly 1.5 million burns per year in USA
2. About 50,000 hospitalizations for burns per year in USA
3. Incidence is declining in USA and other developed countries
4. High risk for death with burns: [2]
   1. Burns over 40% of the body are associated with very high mortality
   2. Inhalation injury - increases risk of death >4 fold
   3. Age >60 - increases risk ~2 fold
5. Overall, most patients will recover from burn injuries

B. Grading of Burns

1. First Degree - superficial burn only, small blister may form
2. Second Degree - invovlement of dermal tissue with moderate to severe blistering
3. Third Degree - destruction of subcutaneous tissue, muscle/nerve; no blistering
4. Fourth Degree - internal organ or bone destruction

C. Complications of Burns

1. Components of Burn Injury
   1. Burn Shock - due to hypovolemia as well as inflammatory cascades
   2. Inhlalation Injury
   3. Burn-Wound
   4. Catabolism - muscle breakdown, sympathetic overdrive
2. Infection / Sepsis
   1. Burn-wound infection - bacteria proliferate rapidly in burned tissue
   2. Systemic immunocompromise - release of multiple cytokines [3]
3. Severe Dehydration
4. Rhabdomyolysis
5. Multiple Organ Dysfunction Syndrome (MODS)
   1. Adult Respiratory Distress Syndrome (ARDS)
   2. Acute Renal Failure
   3. Shock
6. Cosmetic Issues

D. Risk Factors for Poor Outcome

1. Advanced Age
2. Concommitant smoke inhalation
3. Greater size (>15-20% of surface) and depth of burn
4. Pulmonary Dysfunction (ARDS)

E. Overview of Treatment [1,3]

1. Four Phases of Burn Care
   1. Initial evaluation and resuscitation
   2. Initial burn excision and biological closure
   3. Definitive wound closure
   4. Rehabilitation and reconstruction
2. Resuscitation and Supportive Care
   1. Airway protection is critical - mechanical ventilation often required
   2. Breathing - oxygen; carbon monoxide poisoning often present (see below)
   3. Circulation - fluid losses are marked due to capillary leak and skin compromise
   4. Mechanical ventilation for in severe burns and/or with smoke inhalation
   5. Sedatives and pain management also reduce respiratory drive
   6. Intravenous rehydration for "Burn Shock" - Lactated Ringer's is usually preferred
   7. Enteral and/or parenteral nutrition is critical in this highly catabolic state
   8. Hypercatabolic state may be tempered with ß-blockade (propranolol) [4]
3. Inhalation Injury
   1. Smoke inhalation is often accompanied by respiratory distress
   2. Carbon monoxide level is a good marker for extent of inhalation
   3. If carboxyhemoglobin is detectable, then 100% oxygen should be given
   4. Endotracheal intubation may be required to protect airway which will become edematous
   5. Adult respiratory distress syndrome (ARDS) often develops over several days
   6. Bronchiolitis is also not uncommon
4. Burn Shock (Hypovolemia)
   1. Rehydration on day 1 is 2-6mL/kg x Burn % of Body area (mean requirement is 4mL/kg)
   2. About 50% of day 1 fluid requirement should be given in first 8 hours
   3. Smoke inhalation injury can increase fluid requirements >50%
   4. Crystalloids given initially; colloids shoud be generally be avoided
   5. Note that only ~25% of crystalloid will remain in intravascular space
   6. Maintain urine output at around 0.5mL/kg/hr for adults, ~1.0mL/kg/hr for <25kg persons
   7. Fluid requirements on day 2 are about half of those required on day 1 (given above)
5. Wound Therapy
   1. Aggressive surgical debridement and closure of wounds within 1 week
   2. Application of topical anti-microbials (silver sulfadiazine or nitrate, sodium mafenate)
   3. Early wound closure with autografts or skin substitutes (remove eschar)
   4. Frequent, regular (every 48hrs) quantitative wound cultures to monitor bacterial levels
   5. Bacteria levels >100,000 organisms / gram of tissue highly associated with invasion
6. Risk of Infection is increased due to burn induced immunosuppression (see below)
7. Surgical Treatment of Burns [1]
   1. Five general classes of burn operations
   2. Decompression procedures - edema induced constriction of vital tissues
   3. Excision and biologic closure operations - use of skin allografts or condroitin
   4. Definitive closure procedures - replace temporary membranes with permanant grafts
   5. Burn reconstruction - begins when function is impeded by contactures
   6. General supportive procedures - vascular access, tracheostomy, gastrostomy, others
8. Skin Grafting [3,5]
   1. Current procedures usually involve skin autografts
   2. This is problematic with burns covering large part of the body
   3. Growth of autologous skin in vitro is being developed
   4. Integra® is a chondroitin 6-sulfate based skin substitute
   5. The membrane promotes healing and prevents infection
   6. It can be used while waiting for autologous skin cells to grow
9. Reducing Hypermetabolic State
   1. Improves outcomes in burn injuries
   2. Maintaining environmental temperature at 30-32°C
   3. Continuous feeding of high carbohydrate, high protein diet (enteral whenever possible)
   4. Early instiutution of vigorous and aerobic resistive exercise programs
   5. Possible administration of anabolic agents
10. Anabolic Agents
    1. Exogenous continuous low-dose inuslin infusion
    2. Propranolol - non-selective ß-adrenergic blocker, reduces stress-induced catablosim
    3. Oxandrolone - synthetic testosterone analog, helps maintain muscle mass

F. Infection in Burn Injury Patients

1. Burn Induced immunocompromise
   1. Burns over ~40% of the body surface cause generalized immunosuppression
   2. Breakdown in normal intestinal barriers increase enteric bacterial infection
   3. Intubation with mechanical ventilation increase risk of pneumonia
   4. Hospital acquired infections are common and often extremely serious
   5. The wounds themselves can become infected leading to local and systemic problems
2. Related to increased Interleukin 4 production, reduced IL2 and IFNgamma production
3. Local and systemic infections are common
4. Local Infections
   1. Early colonization of burn wounds with usual skin flora
   2. Staphylococcus aureus is often the major problem
   3. Methicillin resistance of S. aureus is increasing
   4. Currently used topical anti-bacterials can lead to highly resistant bacteria
   5. Colonization of burn wounds inhibits autograft "take" and slows local healing
   6. Use of skin substitutes and/or enhancing epithelialization could reduce infections
5. Pulmonary Infections
   1. Patients with major burns are at high risk of developing ARDS
   2. This is thought to be due to overall systemic inflammatory response in burn patients
   3. In addition, toxic fume exposure can cause ARDS and/or bronchiolitis obliterans
   4. Pain or low level of consciousness increases risk of atelectasis and bacterial invasion
   5. Mechanical ventilation carries relatively high risk of pulmonary infection
6. Systemic Infections
   1. Often due to breakdown of normal gut bacterial containment mechanisms
   2. Wound colonization with high levels of bacteria increases risk of invasion
   3. Most common systemic infections in burn patients are due to gram negative rods
   4. Pseudomonas aeruginosa and Enterobacter cloacae are not uncommon
   5. Invasive S. aureus infection, increasing methicillin resistance, is a problem

References

1. Sheridan RL, Schultz JT, Ryan CM, McGinnis PJ. 2004. NEJM. 350(8):810 (Case Record)
2. Ryan CM, Schoenfeld DA, Thorpe WP, et al. 1998. NEJM. 338(6):362
3. Monarfo WW. 1996. NEJM. 335(21):1581
4. Herndon DN, Hart DW, Wolf SE, et al. 2001. NEJM. 345(17):1223
5. Singer AJ and Clark RAF. 1999. NEJM. 341(10):738