Advances in Burn Wound Treatment: Some Thoughts
P E Banwell BSc MB BS FRCS
Department of Plastic Surgery, Radcliffe Infirmary, Oxford, UK
INTRODUCTION
The last half century has heralded a new approach to burns care and
has seen several major developments. Before this time there were no
resuscitation regimes, no antibiotics and no burns units. Blood transfusion
and skin grafting were in their infancy. Patients with large burns died,
and those with deep burns were left with months of treatment and lifelong
severe scarring. The study of burns was not considered worthwhile, and
preventative measures for burns in the home and work-place were non-existent.
Today, patients with more than 90% burns can survive, the treatment
is more rapid and less painful, and accidents in the workplace and at
home have been reduced by legislation and by improved standards in design
and manufacture. The modern ‘high-tech’ treatment of burns,
however, is expensive, and these changes have only been possible in
the developed world.
What recent changes have brought about this improvement, and where is
burn care going in the next decade?
PREVENTION
Prevention campaigns or legislation must be based on good epidemiology
to be effective. Epidemiological data is collected systematically in
the United States but poorly throughout Europe. In most countries of
the world, it is not collected at all. With the advent of modern computers
and database systems there is now no excuse for not collecting information
about the causes of burns. It is estimated in the UK that at least half
of all burn deaths are caused by smoking materials. It is possible to
make cigarettes that do not set light to furniture and furnishings.
In many parts of the world, we do not have the data to support effective
prevention campaigns. The collection of this data and continued education
is one of the challenges for the next decade.
RESUSCITATION
The improved resuscitation of major burns has proved to be a decisive
factor in the reduced mortality figures seen in such patients. Debate
still continues worldwide, regarding the preferred use of colloid or
crystalloid in resuscitation regimes, although a recent systematic review
supports the latter. However, various artificial colloids have also
been developed over the last few years but none have been formally tested
in large burns, and their place in future treatment has yet to be assessed.
Recent data from the United States confirm mortality rates are dependent
on age, depth and size of burn but also introduce a new variable: inhalational
injury. Such injuries often require intubation and ventilation and are
more prone to systemic complications such as adult respiratory distress
syndrome (ARDS) and systemic inflammatory response syndrome (SIRS).
New treatment modalities for respiratory complications are now being
introduced including early use of bronchoscopy as a diagnostic and therapeutic
tool and the use of extracorporeal membrane oxygenation (ECMO) for patients
with severe respiratory failure.
Intensive care management of the burned patient, especially those with
a respiratory problem or systemic complication, has had a dramatic impact
on care. However, perhaps the most important unanswered question in
major burn resuscitation is whether the patient should be intensively
monitored during the resuscitation phase. This requires a large number
of intravascular lines to record the information on which to base the
resuscitation. This is in contrast to the older teaching in burn care
that all intravenous long lines should be avoided because of the risk
of infection. However, the outcomes of intensive resuscitation have
not, as yet, been fully reported. There is no known prospective trial
comparing the two methods, but this would be of enormous value.
There have been some interesting publications on the use of selective
digestive tract decontamination. This technique was first developed
in Intensive Care Units and showed markedly improved outcome figures
in severely ill patients; its adoption in Burn Units has been less rapid
and encouraging early results in some units have not been confirmed
by randomised trials.
Great advances have also been made in recognising the need for adequate
nutritional supplementation in the acute burn injury. Many authors have
shown that if feeding is started within six hours of the injury, gastro
intestinal complications and weight loss due to the massive catabolic
state are reduced. Many units have subsequently adopted a policy of
using naso-gastric tubes and feeding as part of the initial resuscitation.
Paul Banwell |
IMMUNOLOGY
One of the primary characteristics of the skin is its role as an immunocompetant
organ. Non-specific inflammatory reactions within the skin are characterised
by the activation of humoral inflammatory cascades, such as complement
and the prostaglandins, followed by neutrophil migration. The skin also
plays an integral part in the adaptive immune responses which are centred
around antigen recognition and lymphocyte-mediated responses to that antigen.
Burns cause an oxygen-derived free radical (OFR) driven injury response
and normal mechanisms for OFR scavenging are impaired by the reduction
in vascular supply. The inflammatory response and subsequent neutrophil
activation lead to further ischaemia and necrosis. In small burns this
remains localised but larger burns result in a more generalised inflammatory
response. This so-called systemic inflammatory response syndrome (SIRS)
can cause remote organ damage to the renal, respiratory, gastro-intestinal
and reticulo-endothelial systems. Controlling this response is potentially
a target for therapeutic intervention, which in turn, should reduce the
need for intensive care,
Despite attempts at targeting each of the pro-inflammatory mediators by
various pharmacological agents, there is to date no effective way of reducing
the harmful effects of the burn inflammatory response. Current suggestions
include ways of blocking neutrophil-mediated damage by using neutrophil
adhesion molecule antibodies and protease inhibitors. Whilst animal studies
have been encouraging in this field, clinical studies need to confirm
these results.
Uncontrolled local inflammation may also be responsible for the phenomena
of delayed microvascular damage, whereby the depth of partial thickness
burns slowly increases in the first 48 hours after insult. Reducing this
damage would potentially keep scarring to a minimum; this is particularly
relevant in scalds which mainly affect children.
Burns also affect the lymphocyte function and ultimately patients with
large burns are immunosuppressed. Whilst this is beneficial in the use
of allografts, infection is a major cause of death in resuscitated large
burns. The altered structure of burned skin acts as a highly potent immunogenic
stimulus activating humoral and cellular responses. Analysis of the dermal
products reveals the presence of a highly toxic compound, called lipid
protein complex (LPC), which has been detected intravenously in humans
following burn injury. The concept of early burns surgery has done much
to reduce this unwanted immunosuppression but there is no therapeutic
management available at present. Ultimately, the best method of eliminating
this will lie in early burn wound excision whilst providing immediate
immuno-competent skin cover.
BURN DEPTH
To date, clinical assessment has been considered to be the most convenient
method of estimating burn depth. It is based upon the clinical appearance
of the wound, gross assessment of the dermal microvasculature as determined
by capillary refill, and the presence or absence of sensation. Classic
descriptions of the three depths of burn are presented below.
Superficial Partial Thickness Burns
These burns have damage to the epidermis and papillary dermis only. The
clinical features are erythema with vesicle formation. The capillary return
is normal or quicker than normal and pinprick sensation is normal or hyperalgesic.
There is no fixed staining visible if examined within the first few hours.
Such burns heal without residual scarring in two weeks.
Deep partial thickness (deep dermal) burns
These have damage down to the deeper parts of the reticular
dermis and clinically the epidermis is lost. Capillary return is slower
than normal and pin-prick sensation is impaired. Fixed capillary staining
is usually present. They take longer than two weeks to heal and leave
residual scarring.
Full thickness burns
These burns have damage to the entire thickness of the dermis.
Clinically they may produce a hard leathery appearance and feel to the
skin. The epidermis can be present or absent. The colour varies from white
to charred black depending upon the intensity of the heat. There is no
capillary return and subcutaneous thrombosed veins can often be seen.
The skin is totally anaesthetic. Due to complete destruction of all epithelial
elements, natural healing can only occur by contraction of the wound and
epithelial migration. Large full thickness burns will not heal without
treatment.
In general, the diagnosis of very superficial burns and very deep burns
is uncomplicated; problems arise however, when assessing mixed thickness
burns or burns described as ‘indeterminate thickness’. Surface
appearance alone is very deceptive as Jackson and others have reported.
The presence of a dermal circulation, as measured by capillary refill
at 24 hours post-injury does not necessarily mean the burn will remain
superficial partial thickness. Conversely, absence of visible circulation
is not a criterion of total skin destruction. A detailed history may therefore
provide additional clues; information relating to the nature, intensity
and duration of the burn and the part of the anatomy affected, may also
give an indication as to the severity of the injury. In addition, the
presence or absence of hairs along with the sensation of pain and resistance
associated with plucking them may also indicate whether the deeper dermis
is viable.
Use of the pin-prick test can also provide useful information, even in
children. This ‘low-tech’ clinical method for assessing burn
depth was first described by Dupuytren in 1832 but was later refined and
popularised by Bull in 1949. The retention of sensation is a useful indicator
of depth, but does require a significant degree of patient compliance
and, some authors argue, may not be appropriate for the very young, elderly
or confused. While full thickness burns are anaesthetic, deep partial
thickness burns show diminished or absent mechanical pain detection but
still retain the ability to perceive the pin prick as touch. Superficial
partial thickness burns can have reduced mechanical, heat and pain detection
thresholds, as measured by von Frey hairs and heated probes. The advantages
of this technique lie in its simplicity: perception of a sharp prick indicates
a 2° superficial burn; a perception of touch only indicates a 2°
deep burn; and a 3° full-thickness burn is insensate. In disagreement,
Bennett and Dingman comment that ‘ the test is not sensitive enough
to differentiate between a full thickness burn and an anaesthetic or hyperaesthetic
partial thickness burn which is potentially capable of healing without
grafting’.
A number of authors have investigated the reliability of clinical assessment
for burn depth using the above parameters. All such studies have estimated
that the accuracy of clinical assessment, in the hands of an experienced
surgeon, to be between 50–65%. Despite these obvious limitations,
Peter Shakespeare has argued that visual examination will remain as the
first line method of assessment, at least for the present time.
SKIN COVER
There has been a definite move over the past 20 years towards earlier
surgery. It is now very clear that better functional and cosmetic results,
as well as lower morbidity and mortality can be obtained by early excision
of the burn wound, and immediate cover. This needs to be done within five
days before infection occurs, and it may well be that surgery even earlier
than this has advantages. Although used as a standard technique in most
developed countries, it has not always proved possible to introduce the
method to developing countries, partly because of resources as well as
the special skills required. The technique, however, is dependent on recognising
which burn needs to be excised.
If the burn surface area exceeds 30% of the body, there is a shortage
of donor skin available. Various techniques of skin graft expansion are
available. These can have both functional and cosmetic disabilities. Within
the last few years there have been enormous developments in trying to
produce ‘artificial skin’. The earliest work was cell culture
of keratinocytes taken from a small area of the person’s own skin.
This has been reported as giving some good results, but in general the
results have been less than ideal, with the added disadvantages of a three
week delay waiting for sufficient skin to grow, and of course, high costs.
Both animal and human cadaver skin have also been used to great effect,
either treated by freeze drying or glycerol preservation. Graft treated
by either method acts as a biological dressing. The cadaveric ‘allograft’
skin can also be used either on its own, or as a cover to a widely meshed
autologous graft. Over the last decade or so, tremendous advances have
occurred in the development of various dermal substitutes, which are either
covered by keratino-cytes, or by delayed skin grafting. These techniques
have dramatically altered the management of patients with large burns.
REHABILITATION
In the field of rehabilitation, perhaps the most important development
has been the recognition of Post Traumatic Stress Disorder as a psychiatric
entity. Another important development has been Burn Camps which badly
scarred children can attend, and in effect receive group therapy. Following
the Bradford football fire in 1985, it became common for people involved
in major disasters, including fires, to receive counselling. In response
to such challenges, Changing Faces, an international charitable organisation
offers support to those with disfigurement and aims to educate the general
public about coping with such difficulties.
RECONSTRUCTION
The well tried method of treating burn scar contractures by cross cutting
and split skin grafting is now being replaced in many cases by the use
of local tissue using a combination of fascio-cutaneous flaps and tissue
expansion, and of distant tissue using microsurgery, often with pre-fabirication
. These changes have led to far better functional and cosmetic results,
shorter hospital stays and very much less pain from the operation which
would normally not be expected to require a second skin graft donor site.
It is possible that the role of artificial dermis mentioned above may
be found to be much more useful for reconstruction than for primary skin
cover in the future, as one is then dealing with an uninfected surgical
wound.
FUTURE
There is no doubt that as we move into the new millenium our understanding
of burns and their pathophysiogy will enable us to devise new methods
to optimise patient care. Already, advances in tissue engineering has
provided technology to aid the development of pre-formed structures for
anatomical reconstruction which will inevitably be refined with time.
The prospect of replacement ‘off-the-shelf’ skin is now also
becoming reality. Burn care is undoubtedly moving forward into a new era.
Acknowledgements: Grateful thanks to the Odstock Burns,
Wound Healing & Reconstructive Surgery Research trust, Stoke Mandeville
Burns & Reconstructive Surgery Research Trust, Royal College of Surgeons
of England, The McAlpine Foundation.
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