What is Jackson’s burns model?
Jackson described the zones of burn injury in 1970
Zone of COAGULATION (NECROSIS)
Zone of STASIS (OEDEMA)
Zone of HYPERAEMIA (INFLAMMATION)
Tell me about the epidemiology of burns
How has outcome and mortality rate improved ?
0.5-1% UK pop burnt each yr 10% require admission 10% of admissions are life threatening children - scalds most common adult - flame burns most common
% TBSA associated with death of 1/2 of cohort (LD 50, median lethal dose) age 21
1950 = 45% TBSA
1990 = 85% TBSA
plot of burn size s mortality shows a sigmoid distribution
Due to
Why do blisters form?
damage to dermo-epidermal junction → leakage of plasma → separation of dermis from epidermis
blister fluid contains inflammatory mediators and should be regarded as open wound
What is the pathophysiology of burn wounds?
divided into local and systemic effects
Local
- inflammatory mediators (from cap walls, WBC and plts)
- vasodilation, leak, fluid in interstitial space
Systemic
Reduced cardiac output
Increased SVR
- catecholamines, ADH, angiotensin II
Pulmonary oedema
- inc pulmonary vasc resistance, cap pressure, cap permeability, LHF, hypoproteinaemia, inhalational injury, ARDS
Renal
dec renal perfusion, inc ADH & aldosterone, inc Na H20 retention
Liver / pancreas
GI
What is eschar and pseudo-eschar?
Eschar - considered an open wound and may compromise wound healing, as it is
Pseudo-eschar
- formed when topical antimicrobials e.g. SSD (polypropylene glycol carrier) / flammacerium (cerium nitrate) chelates with wound exudate
Indications for ventilation
history inc RR, confusion, distressed, tiring H&N burns supraglottic oedema high COHb Anaesthetic assessment prophylactic Abx and steroids not indicated
Inhalational injury
a) History
b) Examination
c) Types
a) history - enclosed space, unconscious
symptoms - hoarse voice, carbonaceous sputum, stridor, restlessness, respy difficulty, SOB, wheeze
b) singed nasal hairs, soot in nose and throat, burns in airway, swollen upper airway, inc RR, accessory muscles, hypoxia, pulmonary oedema, ARDS, altered consciousness
c) supraglottic (due to heat)
subglottic - due to products of combustion
systemic - toxic compounds: carbon monoxide, cyanide poisoning
Smoke inhalation pathophysiology
increases mortality by 40%, 70% w pneumonia
inflammatory mediators are released
increased pulmonary artery blood flow
bronchoconstriction TXA2, increased airway resistance
VQ mismatch
decreased pulmonary compliance
interestitial oedema, fibrin casts, infection, distal atelectasis
Late - pseudomembrane, permanent airway fibrosis and stenosis
What cases should be referred to burns unit?
PT >10% adult, >5% children FT >5% adult burns to specialised areas burn requiring decompression significant chemical or electrical injury ?NAI associated major trauma significant co-morbidities
Treatment of inhalation injury
CO - high affinity for Hb, O2 dissociation curve shifted left
- also binds cytochromes (sick cell syndrome)
CoHb >5% = inhalation injury, >20% toxic symptoms (headache), death >60%
Rx - 100% O2 (reduces 1/2 life of CO from 250mins to 40-60mins)
Cyanide - inhibit cytochrome oxidase, uncouples oxidase phosphorylation
Rx - 100% O2 humidified
hydroxycobalamin
sodium thiosulphate
Treatment of inhalational injury Humidified O2 Intubation early Increase fluid resus Mechanical ventilation, avoid barotrauma, even if PaCO2 is slightly higher (permissive hypercapnia)
ABG, fibreoptic bronchoscopy and BAL, CXR, chest physio, sputum culture, antibiotics, bronchodilators, N-acetyl cysteine, tracheostomy, PPI
How do you assess depth of burns?
Erythema - epidermis intact, no blistering, blanches
Superficial partial thickness - papillary dermis loss, sensate, blanches, blisters, skin appendages intact
Deep dermal - reticular dermis, decreased sensation, fixed staining, poor cap refill
Full thickness - entire dermis and adnexal structures damaged, insensate, leathery, dry
What do you ask the referring A&E to do before referring to burns unit?
EMSB guidelines
ATLS protocol if patient suffered concurrent trauma
What investigations may be useful to assess burns?
Facial
- fluorescein eye exam
Inhalational injury
Compartment syndrome
Electrical injuries
Chemical injuries
- pH
Laser Doppler (EG, Chelsmford) Videomicroscopy (Canniesburn)
what is an adult and newborn’s skin surface area?
adult - 1.5 - 2 m2
newborn - 0.2 - 0.3 m2
What is a child and adult’s circulating blood volume?
adult = 60ml/kg
child 80ml/kg
How do you estimate TBSA?
palm = 0.8%, hand ~1%
Lund and Browder charts (adults and children)
Wallaces rule of 9s
Modified for children - 18% head, 14% leg, take away 1% from head and add to legs for each yr
What is the initial management of burns?
EMSB guidelines
ATLS protocol if patient suffered concurrent trauma
Burns resuscitation - adults 15%, child 10%
Fine line b/t adequate resuscitation and fluid overload - frequent adjustments required.
Parkland formula (1st 24hrs) - crystalloid
(Charles Baxter Parkland Hospital Texas 1968)
Adults - 4mls/kg/%/24hrs half given first 8 hrs from burn, Hartmann’s (2mls for kids)
Paeds - Add maintenance (oral/NG/iv) → 4% glucose /saline – oral/NG/i.v. - For 24 hours: o 100ml/kg first 10kg o 50ml/kg next 10kg o 25ml/kg next 10kg
What is used to measure end points for resuscitation?
End Points
How do you assess volaemic status?
initially - UO
after 24hrs - less accurate due to glucose intolerance, SIADH and respy losses
- plasma Na & U
- CVP
What fluid resuscitation formulas can be used after Parkland formula?
What alternative fluid resuscitation formulas are there?
After Parklands
Brooke formula (colloid)
5% albumin (24hrs) = 0.5ml / kg / %TBSA for 24hrs
Free water (ml/hr) = (25 + percentage burn) X BSA (m2)
ALTERNATIVE FLUID RESUS FORMULAS Muir and Barclay Formula - Colloid (1974 - Mt Vernon) 4.5% albumin %TBSA x wt / 2 = 1 ration 1 ration per 4/4/4/6/6/12 Monitor for hypernatraemia - free water may be needed
Evans - NS at 1 mL/kg per %burn, 2000 mL D5W*, and colloid at 1 mL/kg per %burn
Slater - RL at 2L/24h + FFP at 75 mL/kg/24 h
What other fluids can be used?
Why is Ringer’s Lactate (Hartmanns) better than isotonic saline?
Other fluids = Dextran (Demling), FFP (Slater), bld tx
RL is better than isotonic saline because lower Na conc (130 vs 154mEq/L) and higher pH concentration (6.5 vs 5.0) = more physiologic. RL metabolized lactate also has buffering effect on associated metabolic acidosis.
What is fluid creep?
1st described by Pruitt 2000
Saffle J Burn Care Res 2007
Occurs when pts receive more resus than predicted by Parklands formula, and more than actually required.
Reasons include
1. Parkland not accurate in large burns
2. clinicians are slow/reluctant to reduce ivi when UO is high
3. opioid creep: opiates CVS effects include partial antagonisation of adrenergic stress response
4. influence of goal-directed resus
Deleterious effects of over resuscitation
Aim is to give least amount of fluid to maintain tissue perfusion (prevent burns shock) and avoid complications of over-rescusitation (burn oedema).
Burns e.g. 15-20% TBSA w/o inhalation injury usually doesn’t initiate systemic inflammatory response. These pts may be resuscitated more modestly, via oral route.
Explain the colloid vs cystalloid debate.
Colloid
Cochrane Injuries Group 1998 - metaanalysis of 30 studies comparing alb vs crys resus in hypovolaemia, burns and hypoproteinaemia.
Showed albumin Rx increased mortality (increased pulmonary oedema and renal dysfunction) - but criticism to report =
- very dissimilar cohorts
- only 3 burns studies (80% survival in paeds >95% TBSA)
Alderson 2004 - Follow-up reports from Cochrane Injuries Group have failed to support earlier claims that albumin administration increases mortality
The SAFE Study Investigators 2004
Vincent J-L 2004
- metanalysis concluded that albumin administration significantly reduces morbidity in ill hospitalised patients, including patients with burn injury
How do you classify the timing of burns reconstruction?
Emergency, essential and elective
Emergency - urgent when vital organs exposed e.g. cornea
Essential - significantly improve function and appearance e.g. microstomia, jt contractures, scarring affecting growth
Elective - aesthetics