Burns Flashcards
What is a burn?
A burn is an injury resulting in damage to skin and underlying tissue secondary to an external stimulus which may be:
- thermal
- radiation induced
- chemical
- electrical
Burn injuries provoke a local physiological response - represented by Jacksons burn wound model (1953)
- Inner zone of COAGULATION - usually coagulative necrosis
- Intermediate zone of STASIS
- Outer zone of HYPERAEMIA
In major burns the zone of hyperaemia may be extensive resulting in systemic effect.
Tell me about Jacksons Burn Wound Model?
Jacksons burn wound model (1953) describes the physiological changes which occurs following a burn.
Inner zone of COAGULATION
- epicentre of burn
- immediate coagulative necrosis
- unsalvageable
Intermediate zone of STASIS
- adjacent area with sub-lethal injury
- damage to microcirculation - tissue hypoxia/ischaemia
- susceptible to progressive necrosis BUT potentially salvageable with appropriate management
1. Effective fluid resuscitation
2. Adequate tissue oxygenation
3. Prevention of oedema
Outer zone of HYPERAEMIA
- tissue furthest away from injury
- hyperaemia
- salvageable - will usually recover
What is a major burn?
A major burn is a burn over ~20% which results both local AND systemic pathological response
- causing result in hypermetabolic response with multi organ involvement
What is the local tissue response to a burn?
- Tissue necrosis
- immediate coagulative necrosis - Inflammation
- cell damage and protein denaturation
- release of various proinflammatory mediators e.g prostaglandins, histamine, thromboxane, bradykinin, etc.
- chemotaxis of inflammatory cells to area incl. neutrophils, macrophages - Oedema
- release of proinflammatory mediators result in increased microvascular permeability
- reduced vascular integrity
- fluid shifts from intravascular to interstitial space with local fluid sequestration and localised oedema
What is the systemic response to a burn?
Systemic effects occur when the pt sustains more than 20% TBSA burns i.e. major burn
- conceptually whole body becomes “zone of hyperaemia”
- release of local inflammatory mediators with spillage into systemic circulation
- widespread changes in vascular integrity with resultant fluid shifts
- resultant widespread oedema incl non- burned tissues and depletion of intravascular volume
- hypovolaemia “BURN SHOCK”
- resultant effects or other organ systems
- if left untreated progression to MOF and death
NB. The greatest fluid shifts occur within the first 24 hrs post burn with peak at 8-12hrs
Tell me about fluid resuscitation in burns pts?
Fluid resuscitation is required if
> 15% TBSA in adults
> 10% TBSA in children
The goals of fluid resuscitation are
- To treat burn shock and restore circulating volume
- To preserve tissue perfusion
- To avoid ischaemic progression of the burn wound
Requires large volumes of salt containing fluids
BUT “Catch-22”
- burn oedema drives burn shock which requires fluid resuscitation
- fluid resuscitation drives burn oedema
Optimal fluid resuscitation therefore aims to support organ perfusion with the least amount of fluid necessary at the least physiological cost
Consider:
Under resuscitation - leads to poor perfusion, progression of circulatory shock, MOF and death
Over resuscitation (“fluid creep”) - leads to increased oedema, raised compartment pressures, pulmonary oedema/ARDS, MOF and death
Optimal regime for fluid resuscitation is controversial
Many fluid replacement regimes available with conflicting evidence
Most widely accepted is modified Parklands formula
= 2-4mls Hartmanns / kg / %TBSA in 24hrs
Half given in first 8 hrs from injury
Half given over next 16hrs from injury
Titration to UO
- Adults 0.5mls/kg
- Child 1ml/kg
Can be doubled in high voltage electrical injury
Additional physiological parameters incl
- BP/MAP
- HR
- RR /Sats
- peripheral perfusion
- core-peripheral temp gradient
Tell me about the hypermetabolic response in burns?
The hypermetabolic response is divided into 2 phases
“EBB” and “FLOW” - described by Cuthbertson
EBB
- first 48hrs
- reduced metabolic rate
FLOW
- persists up to 2yrs
- characterised by hypermetabolism with hypercatabolism and hyperdynamic circulation
Characterised by:
- hyperthermia with core temp 1-2 degrees above normal
- hyperdynamic circulation with increased cardiac output
- hypermetabolism with increased O2 consumption and CO2 production
- hypercatabolism with increased production of catabolic stress hormones creating a “diabetic like state”
> increased glucose consumption
> increased glycogenolysis and gluconeogenesis using protein stores (“carbohydrate cycling”)
> loss of lean muscle mass and decreased nitrogen balance
NB. Metabolic demands can exceed 2x normal in large burns
- response is proportional to size (up to 60%)
The clinical effects of the hypermetabolic response are
- weight loss
- muscle weakness
- immunosuppression
- impaired wound healing
BUT The hypermetabolic response can be modulated by various factors
- essentially “ HEAT ‘EM, FEED’ EM & KEEP ‘EM COMFORTABLE!
- Environmental control
- Nutrition
- Medications and hormone modulation
- Prevention of sepsis
- Early wound closure
How do you do a tracheostomy?
Pt consented (if feasible)
GA
Sandbag under shoulders
Mark 1/2 way between cricoid and sternal notch
Transverse skin crease incision
Retract strap muscles
Expose thyroid isthmus - suture ligation and division
Bjork flap - inferiorly based flap 1/2 to 2/3 width of trachea
- transverse portion incised with 15 blade between 1st/2nd tracheal rings - must preserve 1st to prevent subglottic stenosis
- vertical extensions with scissors
- hinged on tissue between 3rd/4th rings
- sutured to skin with silk
- ET tube exchanged for tracheostomy tube once anaesthetist ready
What are the advantages of a tracheostomy?
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What are the complications of high voltage electrical injuries?
Think in terms of organ systems…
EARLY
INTERMEDIATE
LATE
How do electrical injuries cause damage?
Heat is the byproduct of current flowing through high resistance tissue
What first aid should be given to a pt with a burn?
Guidance from BBA first aid position statement
- Stop the burning process
- 20mins running water (Bartlett 2008)
- Shower probably better than tap
- Tepid water ideally 15 degrees (Cuttle 2008)
- Effective within first 3 hours
- No evidence that more is better i.e. no need to continue and risk hypothermia.
i. e KEEP PT WARM & BURN COOL
How do you classify burn alopecia?
McCauley classification of burn alopecia (1990)
Based on pattern and extent of alopecia
Grade 1-4 based on PATTERN 1 - single area 2 - multiple areas 3 - patchy 4 - total
Grade a-d based on EXTENT
a - 75%
Principles of management:
If single small areas - may treat with serial excision
If larger single areas - may benefit from tissue expansion
If more than one area - may be amenable to sequential expansion
If large patchy areas or total alopecia then usually not amenable to tissue expansion
