Laser Doppler imaging in a paediatric burns population
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Laser Doppler imaging in a paediatric burns population
Julie Mill a,*, Leila Cuttle a, Damien G. Harkin b, Olena Kravchuk c, Roy M. Kimble a
aRoyal Children’s Hospital Burns Research Group, University of Queensland, Department of Paediatrics and Child Health,
Royal Children’s Hospital, Herston Rd, Herston, Queensland 4029, Australiab School of Life Sciences and Institute of Health and Biomedical Innovation, Queensland University of Technology,
Kelvin Grove, Queensland 4059, AustraliacSchool of Land, Crop and Food Science, University of Queensland, St Lucia, Queensland 4072, Australia
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1
a r t i c l e i n f o
Article history:
Accepted 26 November 2008
Keywords:
Laser Doppler
Paediatric
24 h
Fast scan
Grafting
Scar management
Re-epithelialisation
a b s t r a c t
Objective: Laser Doppler imaging (LDI) was compared to wound outcomes in children’s
burns, to determine if the technology could be used to predict these outcomes.
Methods: Forty-eight patients with a total of 85 burns were included in the study. Patient
median age was 4 years 10 months and scans were taken 0–186 h post-burn using the fast,
low-resolution setting on the Moor LDI2 laser Doppler imager. Wounds were managed by
standard practice, without taking into account the scan results. Time until complete re-
epithelialisation and whether or not grafting and scar management were required were
recorded for each wound. If wounds were treated with SilvazineTM or ActicoatTM prior to the
scan, this was also recorded.
Results: The predominant colour of the scan was found to be significantly related to the re-
epithelialisation, grafting and scar management outcomes and could be used to predict
those outcomes. The prior use of ActicoatTM did not affect the scan relationship to out-
comes, however, the use of SilvazineTM did complicate the relationship for light blue and
green scanned partial thickness wounds. Scans taken within the 24-h window after-burn
also appeared to be accurate predictors of wound outcome.
Conclusion: Laser Doppler imaging is accurate and effective in a paediatric population with a
low-resolution fast-scan.
# 2008 Elsevier Ltd and ISBI. All rights reserved.
avai lable at www.sc iencedi rec t .com
journal homepage: www.elsevier.com/locate/burns
1. Introduction
Traditional ways for assessing acute burns and subsequent
scarring rely largely on qualitative methods such as total burn
surface area calculation via the Lund and Browder chart
estimation [1] and the Vancouver General Hospital Scar Scale
[2]. While such techniques have been useful, they are unable to
guide us on the clinical status of a burn when decisions about
most appropriate treatments are being made.
Laser Doppler technology originally existed as flowmetry.
Reports at that time found that laser Doppler flowmetry could
* Corresponding author. Tel.: +61 7 3636 9067; fax: +61 7 3365 5455.E-mail address: rchburns@somc.uq.edu.au (J. Mill).
0305-4179/$36.00 # 2008 Elsevier Ltd and ISBI. All rights reserved.doi:10.1016/j.burns.2008.11.016
be used as a clinical predictor tool with burns displaying the
lowest perfusion values on days 0–3 requiring skin grafting or
taking longer than 21 days to re-epithelialise [3,4]. However, as
a small probe was required to be in contact with the burn in
order to take the measurements, this technique was con-
sidered painful and too localised and now laser Doppler
imaging (LDI) which can scan the whole burn area in a non-
contact manner is more popular.
LDI produces a colour-coded image of skin blood perfusion.
A low-intensity red laser light beam penetrates the full dermis
and is reflected by both moving red blood cells and the static
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1 825
tissue. The instrument then assigns perfusion units (PU) to
quantify the movement of blood cells flowing through the
vessels of the skin and the perfusion units are translated into
colours which are transposed on a greyscale digital image of
the scanned area. This provides a valuable indicator of burn
depth and thus severity.
Histological biopsy assessment has long been considered
to be the gold standard of burn depth assessment. LDI has
been shown to correlate well with histopathological markers
of wound depth [5–8], however, this has not been validated in
a paediatric population. Also, biopsies may be inaccurate in
the first few days as the burn wound progresses and more
tissue dies, or recovers. The optimum time that laser Doppler
scanning should be performed post-burn is still a contro-
versial topic. Laser Doppler is widely reported to give
accurate results when performed between 48 and 72 h
[7,9]. Holland et al. 2002 reported that scans at 24 h may
be inaccurate as burned areas which initially appear deep
can later improve. This was based on scans shown in Niazi’s
landmark paper in 1993 [5]. However, another study showed
that laser Doppler flowmetry performed within 24 h post-
burn gave similar flux values to scans taken three days after-
burn [10], indicating that perhaps scans within the 24-h
window may still give accurate readings. This is a theory
supported by others [11] who have also done serial
measurements using LDI.
For this study, we were interested to see if LDI might
provide a reliable indicator (via colour of scan) of burn depth
and therefore outcome when used as early as 0–24 h and
continuing up to 120 h after-burn. We also sought to
determine if a standard resolution (fast) laser Doppler scan
for the paediatric population was accurate. The effect of the
prior application of nanocrystalline silver dressing ActicoatTM
(Smith and Nephew, Hull, UK) and SilvazineTM cream (1%
silver sulphadiazine with 0.2% chlorhexidine digluconate,
Smith and Nephew, Clayton, Australia) to the scan was also
examined.
2. Materials and methods
2.1. Patients
The human research ethics committee of the Royal Children’s
Hospital (RCH) approved the study and all patients had
consent obtained prior any procedures. Subjects were children
who presented to the Stuart Pegg Paediatric Burns Centre,
whose parents consented or the patient assented to the study.
Patients were recruited at any time from 0 to 190 h after burn
injury. Both outpatients and inpatients were enrolled in the
study.
2.2. Laser Doppler scanning
The scanning was done using the MoorLDI-2 laser Doppler
imager (Moor Instruments Limited, Devon, UK), with a laser
wavelength of 633 nm (visible red), scan range (distance from
the wounds) of 35–80 cm, fast scan resolution of 256 � 64 pix-
pixels, and a scan duration of 80 s. The scanner head was
aimed slightly off perpendicular to the skin, to prevent
reflection and non-valid areas, as recommended by the
product manual (p54-55), rather than directly perpendicular
to the skin as suggested by others [12]. Software used was v1.5.
Using the standard colour palette setting XE, the amount of
blood flow (expressed as perfusion units in the range 0–1000)
was translated into specific colours: dark blue (<125 PU), light
blue (125–250 PU), green (250–440 PU), yellow (440–628 PU),
pink (628–812.5 PU), and red (812.5–1000 PU).
LDI was performed with a green drape placed under the
patient, using the standard (fast) scan. The laser Doppler
scan was performed either in the designated laser Doppler
room, burns clinic bathroom or operating theatre. All rooms
are maintained at �25–318 C. Patients wore the standard
goggles supplied by Moor during the scan (if age-appro-
priate), and the door was closed during scanning. For
patients who were non-compliant with the goggles (toddlers
and babies), a green drape was clipped to the scanner head
and the scanner head was lowered into position so that
child was unable to see the scanner red point light, thus
shielding their eyes completely during the scan. Each body
part that was injured was scanned separately and in some
cases lateral and medial surfaces were scanned for
circumferential burns, as suggested by others [9]. Patients
were scanned each time they returned to the outpatients
department, if this fell within the first 200 h.
Use of digital photography to document the wounds was
also utilised as an adjunct to the laser scan, as the colour
photograph representation on a laser Doppler image is
traditionally poor quality compared to a digital photograph
[9]. A digital photograph was taken at 3.0 megapixels with a
Fujifilm E510 Finepix 5.2 Megapixel camera with the flash on,
using the normal automatic setting.
2.3. Patient management
Patients were given standard pain relief used in the burns
outpatient department, most commonly oxycodone and
paracetomol (acetaminophen) orally and for inpatients most
commonly intravenous morphine. Patients who showed signs
of uncontrolled pain during dressing down procedures and
who would benefit from immediate redressing were not
scanned and a digital image only was taken. Age-appropriate
toys were used for distraction to enable to child to relax and
keep still for the scan.
If patients presented out of hours, they were clinically
assessed by the burns registrar without the use of laser
Doppler, a digital photograph was taken and dressings were
applied after discussion with the burns consultant. Routine
dressing care for the RCH Stuart Pegg Paediatric Burns Centre
is to gently cleanse the wound area with 0.1% chlorhexidine
digluconate mixed in warm water, removing any creams, or
dead skin that has lifted.
SilvazineTM cream was the mainstay of treatment for the
RCH Burns Centre until November 2001. Daily cleaning was
required due to the necessity to reapply the cream. The advent
of nanocrystalline silver dressings such as ActicoatTM has
changed the face of burns treatment in our centre. Dressings
are applied and left intact for up to 4 days for ActicoatTM and 7
days for Acticoat7TM [13,14]. The centre also pricks blisters and
expresses the fluid, leaving the blister skin intact until it
Table 1 – The total number of burns included in thestudy, some were on the same patient.
Burn sites Number of patients
1 27
2 10
3 4
4 3
Table 2 – The time post-burn of the laser Doppler scans.
Scan time post-injury (h) Number of wounds
0–24 13
25–48 22
49–72 15
73–120 19
>120 2
Unable to scan 11
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1826
further denudes at later dressing changes [15]. ActicoatTM is
applied using a simple water irrigation system [13,14]. Patients
were then instructed, if managed as outpatients, to return to
the burns outpatient clinic for dressing every 3–7 days.
Patients were recruited immediately into the study if they
presented during business hours and less than 200 h post-
burn. If they presented out of hours, they were recruited if they
returned to the centre for further treatment during this time
frame. A note of dressings such as SilvazineTM and ActicoatTM
used prior to scanning was taken.
The RCH Burns Centre includes five paediatric burn
surgeons. The general consensus amongst our surgeons is
that if a wound takes longer than 2–3 weeks to heal, it will
require a skin graft. It is well recognised that prediction of
burn wound outcome remains especially difficult in chil-
dren, due in part to the prevalence of mixed depth scald
burns, children’s thin skin and their unpredictable response
to injury [12]. If a burn wound appeared to be deep and could
be predicted by the surgeons to take more than 2–3 weeks to
heal, it was grafted as soon as possible. Indeterminate depth
burns were monitored over approximately a 2-week period
to determine if they needed grafting. The patients were
reviewed by the burns consultant and the laser Doppler
image was shown to the medical staff for their interest only,
however, the usual protocol for grafting remained regard-
less of the laser Doppler image. All patients who take longer
than 2–3 weeks to heal and all those who undergo skin
grafting are treated with active scar management, which
includes custom measured pressure garments and silicone
products.
2.4. Database
Patient and injury details were recorded prospectively. The
data included: date and time of burn, mechanism of injury,
provision and nature of dressing treatments, description of
treatments prior to scanning, and total burn surface area
(TBSA). The laser Doppler scan was taken and reviewed by the
first author. The laser Doppler scan was categorised by the
worst scan colour. The outcome of the burn wound was
recorded in days taken to completely re-epithelialise or time
until skin graft and whether or not the wound required
grafting, and/or scar management.
2.5. Statistical analysis
All the healing outcomes and diagnostics data were
analysed using the Minitab Software Package (Minitab,
Release 15, Minitab Inc., Chicago 2006). The associations
between the laser Doppler diagnostics and the wound
healing outcomes were modelled with logistic multiple
regressions (binary or nominal regressions with the logit
link function), in which various patient characteristics such
as age, mechanism of burns, the time to scan and others
were included. In cases where some categories were over- or
under-presented so that the execution of logistic regres-
sions was not possible, the chi-square and exact Fisher’s
test were conducted instead. The significance level was set
at 5% for individual effects; the p-values of the tests are
additionally reported in the text.
3. Results
3.1. Patient and subjects scanning data
There were 48 patients enrolled in the study, with a total of 82
separate burns. Many patients had multiple burn sites as
described in Table 1. The initial laser Doppler scan occurred at
various time points, from 0 to 186 h after-burn. Table 2 details
the number of burns scanned during each timeframe. A large
percentage of burns (42%) were only able to be scanned outside
the recommended 24–72 h timeframe after-burn, and some
burns (11 of 82) were unable to be scanned (13%).
3.2. Patient burn data
The patients ranged in age from 9 months to 14.6 years, with
the median age of 3 years 6 months and the mean age 5 years 5
months. The spread of mechanisms of burn was typical to that
seen in our total burn population, with 41.5% scalds, 22.0%
contact burns, 28.1% flame burns, 6.1% hot oil burns and 2.4%
friction burns. As expected, the colour of the laser scan was
found not to be associated with the patient age, TBSA, burn
mechanism or the time of the scan after-burn. There were a
total of 11 burns (from 9 patients) which were unable to be
scanned. These burns were not significantly different from the
scanned burns in terms of the healing time, grafting/scar
management outcomes, TBSA or age of the patients.
3.3. Grafted burns
There was a significant relationship between the colour of the
scan and whether the wounds were grafted (p < 0.001),
indicating that the colour could be used as a good predictor
for grafting. Fig. 1 shows the predominant scanned colour for
the grafted and non-grafted wounds. All five dark blue
scanned wounds were grafted, none of the 20 green scanned
wounds were grafted and only one of the yellow/pink/red
scanned wounds were grafted. This yellow/pink/red wound
was judged by the consultant to be deep and grafting was
performed as a precautionary measure as the patient lived
Fig. 1 – The predominant colour scanned and perfusion
units (PU) for the wounds and whether or not they were
grafted. All dark blue scanned wounds required grafting,
while no green scanned wounds were grafted. Light blue
scanned wounds were predominantly not grafted and one
yellow/pink/red wound was grafted erroneously.
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1 827
remotely. However, a biopsy of the tissue removed during the
grafting procedure found that the tissue was viable and the
surgeon’s prediction of deep burn depth was wrong. For the
light blue scanned wounds, the decision not to graft was
slightly more prevalent (58%). The light blue wounds that were
not grafted were predominantly contact and flame burns. The
light blue grafted burns were predominantly scald burns, with
only one out of 8 contact burns and 3 out of 10 flame burns
grafted. This mechanism effect was significant (p = 0.015),
demonstrating that prior knowledge of burn mechanism does
affect clinical judgement of the requirement for grafting,
especially for indeterminate depth burns.
3.4. Scar management
The need for active scar management was also found to be
significantly associated with the colour of the laser scan
(p = 0.003), indicating that the laser scan colour can be used for
predicting the need for scar management. The scan colour of
the wounds treated with scar management is shown in Fig. 2.
All dark blue wounds received scar management, whereas
only 50% of green wounds also received this treatment. Patient
Fig. 2 – The predominant colour scanned for the wounds
and whether or not they received active scar management.
All dark blue scanned wounds required scar management,
while 87% of light blue scanned wounds, 50% of green
wounds and 20% of yellow/pink/red wounds received scar
management.
age and TBSA were found to be significant factors influencing
scar management in the green group (p = 0.004), with younger
patients with greater burn TBSA more likely in need of scar
management. For the light blue wounds, the mechanism
significantly effected the requirement for scar management
(p = 0.038), in particular the majority of flame burns required
scar management (although they did not require grafting).
3.5. Effect of dressings on the scan
Prior to scanning, most wounds (72 of 82) received treatment
with SilvazineTM or ActicoatTM at either the primary referral
centre or in the RCH. Of these, 45.1% received SilvazineTM,
57.3% received ActicoatTM and 14.6% received both.
Statistical analysis showed that although the prior use of
ActicoatTM did not affect the relationship between scan colour
and expected outcome, the prior use of SilvazineTM may have
affected this relationship. If wounds that scanned green or
light blue were treated with SilvazineTM prior to the scan, they
tended to not need grafting (for light blue) or scar management
(for green), whereas wounds pre-treated with ActicoatTM had
significant trends for requiring grafting and scar management.
This may indicate that pre-treatment with SilvazineTM makes
the wound scan at a deeper depth than it really is, and it may
heal slightly better than expected from the scan colour. Or it
may indicate that prior use of SilvazineTM alters the clinical
appearance of the wound and clinicians tend to underestimate
the need for grafting or scar management, although the LDI
may indicate they are required.
SilvazineTM is not used for burn treatment in this hospital,
however, almost all burns are treated with ActicoatTM. Here,
ActicoatTM gave no observed detrimental effect on scanning
quality, despite the nanocrystalline silver deposition from this
dressing. An example of how ActicoatTM treatment did not
interfere with laser scanning can be seen in Fig. 3. This patient
was scanned at 0 h and then treated with ActicoatTM. At 0 h,
some dark blue areas can be seen. He was scanned again at
200 h post-burn, after two ActicoatTM dressing changes and
the dark blue area was still present and more demarcated. At
200 h, there is no evidence of silver deposition into the wound
and no apparent decrease in efficacy of the scan. At 22 days
this dark blue area was grafted, with good results.
3.6. Re-epithelialisation
For re-epithelialisation results, the grafted wounds were
excluded as the true time for complete re-epithelisation could
not be determined for these wounds. Importantly, there was a
significant relationship between time taken for re-epithelia-
lisation and scar management, with wounds that healed
slowly requiring scar management more often (p < 0.001).
There was also found to be a significant relationship between
the scan colour and the time taken for re-epithelialisation
(p < 0.003) in wounds both pre-treated with, and without
Silvazine. Silvazine treatment appeared to make the light blue
wound outcome less conclusive with three out of 15 light blue
wounds in that group, however, this effect was not found to be
significant (p > 0.10). Similarly, although light blue scanned
wounds that were pre-treated with Silvazine had a mean re-
epithelialisation of 19.3 days, compared to wounds that did not
Fig. 3 – Laser Doppler scanning of a hot tea scald treated with ActicoatTM. (A) The scan and picture of the burn taken at 0 h
post-burn. The patient had no SilvazineTM prior to this scan. He was dressed with ActicoatTM from this time. (B) The scan
and picture of the burn taken at 200 h, after 2 subsequent changes of ActicoatTM dressing. Note that there is no evidence of
silver deposition onto the wound and no apparent decrease in the efficacy of the scan after ActicoatTM has been used. (C)
The outcome of the burn at 50 days. The patient was grafted at 22 days, in the areas only where the laser Doppler scan
showed dark blue perfusion units. The wound outcome could be accurately predicted at the time of the 0 h scan; however,
the usual course of 2–3 weeks of dressing treatment was followed before grafting.
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1828
have Silvazine applied prior to scanning, with an average of
22.7 days, that difference was not significant (p > 0.10).
The mean times for re-epithelialisation (of non-grafted
wounds) for each colour are shown in Table 3. The re-
epithelialisation times reported here are similar to those
reported in the laser Doppler product manual (v2.0).
Fig. 4 shows the time to re-epithelialisation when wounds
are sorted by scan colour. The majority of light blue wounds
(72.2%) took >14 days to re-epithelialise or required grafting.
The light blue wounds that healed in <15 days were mostly
flash flame burns where the initial swelling may have
impeded the scan accuracy. The green wounds healed
around 14 days (mean was 13.8 days). The yellow/pink/red
wounds all healed within 15 days, except for one wound
which was erroneously grafted. The burns which were
unable to be scanned were not related to the time taken for
complete re-epithelialisation
3.7. Prediction of wound outcome
The data from this study comply well with the outcomes
suggested in the laser Doppler product manual (v2). We
Fig. 4 – The times taken for complete re-epithelialisation of
the wounds when they are sorted based on their
predominant scan colour. The majority of the light blue
wounds took >14 days to re-epithelialise or required
grafting. Green wounds did not require grafting but many
still required up to 21 days to re-epithelialise. All except
one of the yellow/pink/red wounds healed within 14 days,
this wound was grafted erroneously.
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1 829
support that predictions of the wound outcomes can be made,
based on the scan colour of the wound as shown in Table 4.
3.8. Time to scan
In this study, scans were taken at 0–186 h after the burn. The
predictability of wound outcome based on scan colour was not
significantly affected by the time of the scan. For scans taken
less than 24 h post-burn, the association between scar
management, time to heal and the colour of the scan did
not change significantly compared to other time points.
However, a larger sample size is needed to confirm that scans
are completely reliable during the first 24 h.
4. Discussion
This paediatric study found significant relationships between
LDI scan colour, time for complete re-epithelialisation and
requirement for grafting and scar management. Based on the
data from this study, laser Doppler scanning was used as an
accurate prediction tool for determining wound depth and
outcome and assisting with clinical management. In this
observational study it is important to note that the surgeons
were not blinded to the laser Doppler scan, and this may have
introduced some bias to the resulting clinical judgment and
course of treatment. However, we believe, as do others [7,12]
that the use of the laser Doppler prevents unnecessary surgery
or expedites treatment such as skin grafting and scar
management, leading to decreased hospital stays and there-
fore costs to the patient and hospital. Here we found that the
consultants would often wait, erring on the side of caution and
wounds which scanned as light or dark blue were commonly
left to heal as long as possible, when we could now predict that
they would not heal without grafting and/or scar manage-
ment. This is similar to work by others, who have also found
laser Doppler to be very accurate for assessing wound depth
compared to clinical assessment alone [7,9,12,16]. As clin-
icians become more comfortable with the use of this device
Table 4 – Predictions of wound outcome based on scan colourwith the prediction ability—for the light blue wounds, althoughre-epithelialisation time was <14 days for 3 out of 12 Silvazin
Colour Skin grafting Scar manag
Dark blue <125 PU Yes Yes
Light blue 125–250 PU Yes Yes
Green 250–440 PU No Yes/no (shou
Yellow/pink/red 440–628–1000 PU No No/yes (may
Table 3 – The mean times for re-epithelialisation (of non-graftethe laser Doppler product manual.
Colour of scan Time to re-epithelialisein this study
Light blue 20.5 � 8.3 days
Green 13.8 � 4.9 days
Yellow 10.0 � 2.6 days
Pink 10.0 � 2.6 days
Red 10.0 � 2.6 days
and its accuracy, this may also make it easier to explain to
patients and carers that grafting is warranted for the best long-
term outcome of their burn.
In our experience using the standard colour palette in v1.5 of
the Moor software, we found that if the wound scanned yellow
(440–628 PU),pink (628–812.5 PU) orred (812.5–1000 PU), it would
heal within 14 days and not require grafting or scar manage-
ment. If the wound was green (250–440 PU) it would heal in
approximately 14 days without requiring skin grafting, but
may require scar management. If the wound was light blue
(125–250 PU) it would take approximately 19 days to re-
epithelialise, may require skin grafting and would definitely
requirescar management. If thewound was dark blue (<125 PU)
of the wound. The prior application of Silvazine interferedthe prediction for scar management was 100% correct, the
e treated wounds.
ement Re-epithelialisation Success % of predictions
NA 100
>14 days or grafted 83
ld need) <21 days 100
need) <14 days 100
d wounds) for each colour as reported in this study and in
Time to re-epithelialise as reportedin Moor Manual v2.0
>21 days
�21 days
14–21 days
�14 days
<14 days
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1830
it would require skin grafting and scar management. Thus, the
predominant scan colour can be used to accurately predict
wound outcome and optimal clinical management. Interest-
ingly, for the light blue wounds, there is no way to accurately
predict a need for grafting. Certainly, prior experience with burn
mechanisms by the clinician can assist with clinical judgment
of the requirement for grafting. However, flash/flame burns can
be difficult to clinically judge as initially they may appeardeeper
in depth and here we saw that although the majority of light
blue flame wounds required scar management, they were not
grafted. The light blue wounds took approximately 3 weeks to
heal, and almost all required scar management, suggesting that
perhaps they could have all been grafted. However, there is no
evidence to date that wounds which take more than 3 weeks to
heal would have had a better cosmetic outcome if they had been
grafted. We were also surprised to see that three yellow/pink/
red wounds required scar management even though they all
healed in�14 days. Burns treatment is not an exact science and
rules as to which children require skin grafting and scar
management should not be rigorously applied. Surgeons and
therapists will always use their judgement based on experience
and some children will receive scar management even though
their burns heal within 2 weeks. This is because we know that
the occasional wound will ‘‘break the rules’’ and scar with
resulting contractures without appropriate management.
There were some situations for which LDI did not seem to
be entirely accurate. We found, similar to others [17] that
blisters are unable to be scanned and wet wounds may also
result in reflection artefacts. Interestingly, we found that pre-
treatment with SilvazineTM may make clinical interpretation
more difficult. Possibly this is due to the residual pseudo-
eschar layer that SilvazineTM can leave behind on a wound
even after it is removed. In a previous study comparing
SilvazineTM and ActicoatTM [14], we found that significantly
many more children who received SilvazineTM as their
treatment went on to be skin grafted (25.6% vs 15.4%,
p = 0.001). These patients were treated in our unit before
acquisition of the LDI device; however, perhaps treatment of
their wounds would have been different with the LDI tool as an
adjunct to management.
Unlike others [11], we did not have a problem with scans
after the use of ActicoatTM dressing. Although in that
publication they report visible silver deposition on the wounds
causing interaction with the laser light, we encountered no
such problems, possibly due to our unique irrigation techni-
que, which keeps the dressing moist [13,14]. All scans after the
use of ActicoatTM were accurate for predicting wound depth
and therefore outcome. Although it has been shown that laser
Doppler scanning is not possible through the actual ActicoatTM
dressing [18], this does not interfere with our current
treatment protocol as we are able to scan patients every 3–4
days at the dressing change. It is good to know, however, that
scanning is still accurate through plastic cling wrap [18], as
many patients who suffer from pain during dressing changes
are often alleviated by the simple use of plastic wrap placed
onto the wound.
At what point LDI imaging is deemed not only accurate but
also predictive of the clinical outcome varies within the
literature. In general, 24–72 h is considered the optimal time
frame after-burn. However, in this study approximately half of
the patients were initially only able to be scanned outside of
the 24–72-h window after-burn. The issue, then of when laser
Doppler scanning is still accurate is important. In this study,
we have found that scans taken within 24 h after-burn were as
accurate in predicting clinical outcome as burns taken within
the 24–72 h timeframe. Scans of wounds taken after 72 h were
also accurate. Although burn wound dynamics may continue
to change over 72 h after-burn, making biopsies (which
measure tissue viability) inaccurate, this technology (which
measures tissue blood flow and vessel patency) still seems to
accurately predict wound outcome outside of this timeframe.
It may be that LDI is a more reliable indicator of depth of injury,
especially in the first few hours post-burn. However, as this
area still remains controversial, more work with a larger burn
population is warranted.
In this study there were some patients or burns on patients
which were unable to be scanned. These burns were not
different to the scanned burns in terms of TBSA, depth,
mechanism, anatomical position or patient age. Burns were
often unable to be scanned because the patients were in pain
and we wanted to expedite the dressing. In our centre, we use
age-appropriate toys for distraction, as well as the use of a
musical play specialist. We also have access to other novel
augmented reality distraction tools [19,20], which supple-
ment the use of analgesics. Unfortunately, in our unit we do
not have access to nitrous oxide, which others have found to
greatly benefit their scanning incidence rate [12]. However, in
this study the low-resolution setting was used for all scans
and this takes a maximum of 80 s to complete. We found that
these fast scans were accurate for predicting wound outcome,
and were therefore an excellent option for increasing the
chances of obtaining a scan even when the paediatric patient
was in pain. Other techniques used for younger children
included using a green drape around the scanner head so they
were unable to see the scan in progress, or using a drape to
block their view. These techniques all helped to ensure that
patient treatment proceeded as quickly and pain free as
possible.
LDI is proving to be a useful technology, and many
researchers and clinicians are still trying to work out
specifically how scanned perfusion units relate to wound
outcome. However, we have found that different systems from
different companies and even different versions of the same
system allocate different perfusion units to the same colour
palette. This can make it difficult to compare outcomes
between studies. Having different systems which seem to
arbitrarily assign colour palettes and researchers who do not
report perfusion units in their publications (and only colours
or ‘‘low’’ or ‘‘high’’ flux) make it difficult to clarify this
important research.
In conclusion, we found laser Doppler imaging to be
accurate for predicting wound outcome and we believe it to be
an essential tool for effective wound management. It can be
used accurately as early as within the first 24 h post-burn and
using the low-resolution/fast-scan setting. Laser Doppler
scans are also accurate despite the prior use of ActicoatTM
and SilvazineTM, meaning it can be well integrated into current
wound management regimes. This technology is simple to use
and consistently proving to be a valuable clinical management
tool for paediatric burns.
b u r n s 3 5 ( 2 0 0 9 ) 8 2 4 – 8 3 1 831
Conflict of interest statement
There are no conflicts of interest for any of the authors.
Acknowledgements
This project was supported by funding received from the CASS
Foundation Science and Medicine Grants scheme, Queensland
University of Technology, and Tissue Therapies Ltd.
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