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CHAPTER10 Burn depth assessment
Clinical assessment
Table 10.1 provides an overview of the clinical assessment for burns.
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Yes Brisk
Highly
sensitive/
painful
3– 4days
kerationcytes
regenerate damage
blistered
Yes Brisk
2– 3 weeks Sensitive/
Scald Red/ Blistered
painful
Moist
Slow
Fixed
Staining
decreased
Contact Dark shade of red >3 weeks Sensation
CLINICAL ASSESSMENT
Absent
Absent
blanching
blanching
Absent Non
Never unless very
small
Never Absent Non
Leathery
Leathery
Flame White/ black
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Table10.1 Clinical assessment table forburns
Classication Degree Layer of skin involved Examples Appearance Time to heal Sensation Blanching Bleeding
Supercial 1st degree Epidermis Sunburn Redness but not
Epidermis+
2nd degree
Supercial Partial
Papillary Dermis
(2a)
Thickness
Epidermis +
Reticular dermis
2nd degree
(2b)
Deep partial
thickness (deep
dermal)
involves underlying
structures
Full thickness 3rd Degree All layers involved Flame White/ Black
Catastrophic 4th degree Through skin and
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CHAPTER10 Burn depth assessment
Technology
There are three main areas in which technology is being used in burns depth
assessment. These are:
• Tissue perfusion
• Surface colour
• Structural analysis
Extremely important is the concept that the burn wound is dynamic not
static and assessment at one point in time should be interpreted with this
in mind. There remain considerable dierences of opinion in regard to the
role of clinical vs. objective measures of burn depth assessment and some
believe that NICE guidelines in favour of laser Doppler assessments have
over- reached.
Tissue perfusion
It is assumed that a deeper burn will correlate with a lower blood perfusion
due to blood vessels either being destroyed or thrombosed. Clinically we
judge this by the blanching of the skin.
The problem with all tissue perfusion measurement is that a number of
other factors can eect tissue perfusion. These include:
• Hypothermia
• Room temperature
• Vasoconstructive drugs
• Tourniquets
• Hypovolaemia
• Respiratory rate
• Patient’s emotional state
Laser Doppler
Laser Doppler technology uses the measurement in alteration in light to
measure the velocity and number of moving particles.
Laser Doppler owmetry
Initially laser dopplers were introduced in 1975 and required contact with
the burn wound– this is known as laser Doppler owmetry (LDF). This
method was proven to be 70- 100% accurate in predicting healing within
21days and 93– 100% accurate in predicting failure to heal.
However, a number of problems were identied with the method, which
included:
• Contact needed with burn wound, leading to increased infection risk
and pain
• Pressure with probe, leading to occlusion and articial results
• Only a small area could be scanned (1mm area)
Laser Doppler imager
Owing to the problems of the LDF requiring contact with the patient laser
Doppler imagers (LDIs) were introduced in the 1990s. LDIs could scan a
larger area and used a non- touch technique. The laser typically penetrates
1– 2mm. Before 48 hours accuracy in indeterminate depths is less than 80%
and this compares to a 60– 70% clinical accuracy. They have therefore been
recommended for scanning between 2– 5days.
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NICE guidelines (2011) recommend LDI use for all intermediate depth
burn wounds. However, many burns surgeons feel that this guidance came
prematurely and assessment and treatment of intermediate depth burns is
both controversial and varied amongst burns surgeons.
Depending on the make and local hospital policies safety goggles may
need to be worn.
There are two types of commercially available LDIs:
• Scanning LDI
• Alaser is reected onto the skin by moving mirrors to produce a scan
of the area. Reected light from the skin is then mirrored back to the
photodiodes
• Speckle LDI
• The laser source hits the surface of the skin and forms a speckle
pattern. This reects the coherence of the source and the
microcirculation of the skin. The pattern is received over a time
period and relayed to the screen
Interpretation
Laser dopplers measure inammatory response therefore a high reading
would be expected in supercial burns.
Unburnt skin has low blood ow and therefore will appear to look like
a deep burn.
As the LDI depends on blood ow they are only accurate before the inammatory phase of the burn declines and the dermal circulation stabilizes.
This occurs between 48 hours and 5days.
The results of the machines are recorded in perfusion units. Traditionally
these perfusion units are scaled against healing times (see Table 10.2)
LDI problems
Movement of the patient or machine, however small, gives an inaccurate
image of perfusion. Therefore a deep burn can appear more supercial,
because the machine will analyse the movement as blood ow and thereby
lead to misdiagnosis.
Undebrided, tattooed, and darker pigmented skins eect the penetration
of the laser and therefore will give low readings.
TECHNOLOGY
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Table10.2 Interpreting laser Doppler results
Inammatory response/ velocity
of red blood cells
High Red <14days
Medium Yellow 14– 21
Same as unburnt skin or lower Blue >21
Reproduced from Pape etal. (2012) Burn wound healing time assessed by laser Doppler imaging
(LDI). Part1:Derivation of a dedicated colour code for image interpretation Burns 38(2):187– 94
with permission from Elsevier
LDI colour Potential healing time
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CHAPTER10 Burn depth assessment
Angle artefact
The LDI must be parallel to the area skin to be scanned to get the maximum recording of the reected light. If this angle changes you do not get
the full reection of the laser, leading to an lower, inaccurate reading. This
can happen on small areas (eg. ngers), where a body part curves away (eg.
ank, arm, leg), or if the laser is not set up correctly.
• Dierent areas of the body have dierent perfusions therefore an area
may be misdiagnosed
• Topical agents disrupt LDI readings as they form a barrier to laser
penetrance
• Distance measured can also eect readings
Other measures oftissue perfusion
• Injection techniques of either radioactive isotopes or dyes. Presence
would imply good perfusion and a supercial burn. However these are
invasive, expensive and not readily available.
• Video microscopy
• Uses a visual evaluation of vessel integrity
• Thermography
• It is a non- contact technique which uses infrared radiation produced
by the skin to assess burn depth. However environmental factors
can sometimes dramatically eect readings. Progress continues to be
made in this area.
• LDI is very expensive, and after a wave of purchasing and enthusiasm,
some units no longer use the equipment in favour of clinical
assessments
Surface colour
Part of a clinical assessment is the colour of the wound bed, which can
indicate the burn depth. Two scientic ways exist of conducting this are
photography and spectrophotometry.
• Photography is increasing in popularity due to the increase in
telemedicine usage. In obvious supercial and deep burns it is purported
to have a 90% accuracy. However without the ability to test blanching,
etc., it is of questionable use in dicult to determine wounds. This does
however facilitate the storage of images
• Spectrophotometry. This judges the wound surface colour by sending
light from a spectrometer and the reected light intensity is assessed by
the photometer
• Photography and telemedicine with an experienced eye can be
surprisingly accurate
Structural analysis
The gold standard is considered to be histological analysis by punch biopsy.
However for obvious reasons this is conned mostly to a research environment. This is due to the fact they only show the area biopsied, processing
can take several days, needing expert knowledge and can leave additional
scarring.
Ultrasound at high frequencies has been shown to be of some use how-
ever it requires contact with the burn and is dicult to interpret.
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TECHNOLOGY
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CHAPTER10 Burn depth assessment
Further reading
Hoeksema H, Baker RD, Holland AJ, etal. A new, fast LDI for assessment of burns:a multi- centre
clinical evaluation. Burns 2014;40:1274– 82.
Javed M, Shokrollahi K. VACUETTE(®) for burn depth assessment— a simple and novel alternative
use for a ubiquitous phlebotomy device. Burns 2012;38:1084– 5.
Hop MJ, Moues CM, Bogomolova K, etal. Photographic assessment of burn size and depth:reliability
and validity. Journal of Wound Care 2014;23:144– 5, 148– 52.
Shokrollahi K, Sayed M, Dickson W, Potokar T. Mobile phones for the assessment of bur ns:we have
the technology. Emergency Medicine Journal 2007;24:753– 5.
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Chapter11
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Fluid resuscitation
inburns
Introduction to uid resuscitation in burns 90
Calculation of uid requirement 92
Further reading 94
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CHAPTER11 Fluid resuscitation inburns
Introduction tofluid resuscitation
inburns
Burns injury demands uid resuscitation when total body surface area
(TBSA) exceeds 15% in adults and 10% in children.
There are two key mechanisms underlying this:
• Alarge volume of uid is lost from the wound when the integrity of the
epidermis is lost. The greatest loss is in the rst 12 hours post burn
• Inammatory mediators are released into the wound causing
vasodilation. This process becomes systemic with burns >20% resulting
in intravascular hypovolaemia. The altered capillary permeability that
drives this tends to recover from 36 hours post burn
Full thickness burns develop three areas zones of decreasing injury
(Jackson’s burn wound model):
• Central zone of coagulative necrosis
• Intermediate zone of stasis of blood ow
• Outer zone of vasodilation and hyperaemia
The primary function of uid resuscitation is to
• Prevent burn shock by giving adequate uid without overloading the
vascular system or causing excessive oedema
• Maintain circulatory volume in the face of losses due to the burn— this is
essential for cardiac output, renal perfusion and tissue perfusion
• Provide metabolic water
• Maintain tissue perfusion to the zone of stasis and prevent the burn
from deepening
With limited physiological reserve resuscitation must commence in children
>10% TBSA and be accompanied by additional background uid support.
Inhalation injury further increases uid requirement and can represent
up to an additional 20% TBSA.
There is no clear evidence to favour one resuscitation uid over another,
but most units use easily accessible crystalloid such as Hartmann’s solution
(Parkland).
Albumin is also often used via a dierent protocol (Muir and Barclay).
The crystalloid vs. colloid debate continues.
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INTRODUCTION TOFLUID RESUSCITATION INBURNS
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www.merseyburns.com
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