Page 90 - JSOM Summer 2022

systemic response to burn injury follow a predictable timeline. oxygen partial pressure (PaO ) to the fraction of inspired oxy-
2
The first 24 to 48 hours is referred to as the shock phase. gen (FiO ) as a more reliable indicator of the severity of inha-
2
Edema rapidly forms around the burn site, primarily because lation injury, despite this ratio being impacted by other factors
of microvascular damage, increased microvascular permeabil- such as ventilator settings and resuscitation volume. 19,20 Some
ity, and other processes that derange the fluid balance at that burn centers have reported using a mix of data to grade the
level. This increased permeability leads to a rapid shift of fluid overall inhalation injury severity as mild, moderate or severe.
and plasma proteins from the intravascular space into the in- Taken together, findings of erythema, secretion, casts, and
terstitial space. In turn, loss of plasma proteins causes systemic epithelial sloughing revealed via bronchoscope inform these
hypoproteinemia, which accelerates the loss of fluid across the classifications. 17
microvasculature. Meanwhile, systemic release of inflamma-
tory mediators in larger burns causes increased microvascular Burn-Wound Classification
permeability at sites remote from the burn, causing generalized This section will focus on diagnostic approaches to the burn
edema. In patients with burn size > 10–20% TBSA and in re- wound. The most important indicator of burn-wound severity
sponse to all of these processes, hypovolemic shock develops is percentage of total body surface area burned (TBSA).
over the first several postburn hours. 8,9
Caution should be used in estimating burn size, as a growing
After successful resuscitation of a patient with extensive burns body of literature points to the incorrect estimation thereof in
and beginning after the first 24–48 hours, the body transi- prehospital and non-specialty settings. 18,21 Burns < 20% TBSA
10
tions to a hyperdynamic phase. In this phase, microvascular are more likely to be overestimated and larger burns tend to
permeability decreases, plasma volume is restored, systemic be underestimated. 22,23 This can result in either the over- or
vascular resistance decreases, and cardiac output increases. In under-administration of fluid resuscitation, which can have
24
response to vasodilatory signals, blood flow is redistributed to downstream impacts and complicate future care. TBSA is the
areas of the body with burns. Additionally, a patient’s basal major risk factor for complications such as infection and mul-
metabolic rate increases significantly. The increase in meta- tiple organ dysfunction syndrome (MODS). 25,26 The Wallace
bolic rate can persist for several years postburn. 11 Rule of Nines technique should be used with caution, taking
27
into account differences in age, as well as body mass index.
Using a tool such as the Lund and Browder Chart will ensure
Diagnostics
more accurate TBSA assessment, due to its incorporation of
There has been a recent call for a more standardized approach body-shape changes with age.
to prehospital burn injury diagnosis and intervention. This
12
section will provide a review of several diagnostic approaches. Another critical factor is burn depth. The diagnostic criteria
A review of several techniques and insight from recent litera- of capillary refill, tissue moisture, color, and wound texture
ture will also be highlighted. Before attempting to apply any should be used to assess depth of the injury. A first-degree
diagnostic strategies, the provider must ensure scene safety. A or superficial burn damages only the epidermis. These burns
basic diagnostic approach and notation of any threats to life is are erythematous and may form tiny blisters. An example is
critical before engaging in detailed burn assessment. a mild sunburn. A second-degree or partial-thickness burn
damages the epidermis and a variable degree of the dermis.
Inhalation Injury These may be red, moist, painful, and blistered. With deeper
Approximately 7–10% of burn patients with mild to moderate second-degree burns, fixed hemosiderin staining (due to blood
thermal injuries co-present with inhalation injuries, and this extravasated from damaged capillaries) may be seen. An ex-
incidence tends to increase with age. 13,14 In a recent study of ample is a scald injury. A third-degree or full-thickness burn
combat casualties, inhalation injuries were present in 16.4% destroys all of the epidermis and dermis. These burns are dry,
15
of burn patients. Inhalation injury increases postburn mor- lack capillary refill, are insensate, and have a charred or leath-
bidity and mortality. Generally, direct thermal injury is limited ery appearance. An example is a flame burn from gasoline. 27,28
to the supraglottic airway, due to heat dissipation in the upper Differentiating burn depth during the early postburn hours
airway and the protective mechanism of the glottis. Especially is difficult, because the appearance of the wounds tends to
within the first 24 hours, it is important to monitor patients evolve over time.
for progressively developing airway edema, which may cause
16
rapid airway obstruction. Subglottic inhalation injuries
largely arise due to the noxious and irritant effects of chemi- Treatment
cal exposure. It is important to identify clinical signs such as In the prehospital setting, it is imperative to manage burned
17
wheezing from bronchospasm. A provider should obtain as patients by following a systematic treatment algorithm such
much of a detailed history of injury and exposure as possible, as the MARCH (Massive Hemorrhage, Airway, Respiration,
29
and closely monitor patients for symptoms of potential chem- Circulation, Hypothermia) assessment. This is important be-
ical and irritant exposure. cause burn patients often present with other traumatic inju-
ries, which may go unnoticed due to the distracting nature of
Recent literature has highlighted a high number of potentially burns. In other words, burn patients should initially be treated
unnecessary endotracheal intubations (28–53% of transfers as trauma patients with burns, until non-thermal trauma has
18
to specialized burn care). The diagnostic approach to in- been ruled out.
halation injuries is complicated by the lack of a clear, stan-
dardized diagnostic criteria system. The Abbreviated Injury Inhalation Injuries and Airway Management
Scale diagnostic system is based on bronchoscopic findings Inhalation burns lead to the most immediate life-threatening
and corresponds to increased impairment in gas exchange and injury to the patient due to edema in the supraglottic struc-
mortality. Other studies have noted the ratio of the arterial tures. This upper-airway edema can lead to complete airway

88 | JSOM Volume 22, Edition 2 / Summer 2022