“Introduction to Burn Physiology” by Robert Sheridan, MD for OPENPediatrics
15
October

By Adem Lewis / in , , , , /


The purpose of this video is to provide general
information and education about the care of a critically ill child. It is in no way a substitute for the independent
decision making and judgment by a qualified health care professional. The information contained in this video should
not be used to make a diagnosis or to overrule the advice of a qualified healthcare provider,
nor should it be used to provide advice for emergency medical treatment. Introduction to Burn Physiology by Dr. Robert
Sheridan. Please note that in this video, we will be
following the guidelines used at Shiners Hospitals for Children, Boston. Some of this information may need to be modified
based on the equipment, guidelines, and practices in place in your institution. Warning: some of the content of this video
is extremely graphic, as it depicts the injuries associated with severe burns. Viewers unfamiliar with such injuries may
find this material disturbing. Hello my name is Rob Sheridan, and I work
in the burn unit at the Shiners Hospital in Boston. What we’re going to do is briefly talk about
burn physiology. We’re first discuss the local response to
a burn. We’ll talk briefly about the systemic response
to a burn. And then, briefly, the various important aspects
of pediatric and geriatric physiology as it relates to recovering from a burn. Local Response. I will talk briefly about the local response
to burn injury. What happens, you know, there’s the thermal
energy causes direct coagulaton of the tissue, but then there’s a peripheral area where there’s
damage that potentially is reversible. A lot gets made of this zone of stasis and
hyperemia where this potentially salvageable areas of injured, but not necrotic skin. And there may be something to this. I think that where it comes into play most
frequently is if there is a wound with some peripheral areas that are not full thickness. If the patient doesn’t have a good quality
fluid resuscitation, there may be some progression of the wound in those areas that are threatened,
but not necrotic. So this is the local response to the burn. A small burn, the response pretty much stays
local. And how do you manage the local response? Well, you want to prevent hypoperfusion. You want to do good resuscitation. You want to prevent desiccation of the wound. The purpose of the epithelium, in part, in
large part, is to prevent desiccation of the underlying dermis. So you want to prevent that with your topical
wound care plan. And you want to prevent infection. The epidermis also keeps the bacteria out,
so you need to help the body along with that issue. So to manage the local injury, those are your
goals: prevent hypoperfusion, desiccation, and infection. As the wounds get bigger, there becomes not
just a local response, but a systemic response. Exactly when this happens, and what burn size
this happens, and what burn severity this happens, is not entirely clear. But it is quite common in burns under 15%
or so the you see a relatively minimal systemic response. As the burns get bigger than that, the systemic
response can become quite profound and quite a problem. And, again, there’s a lots of ways to manage
the goals of hypoperfusion prevention, desiccation prevention, and infection. There are a topical salves, topical ointments,
topical liquids that can be put on. There are membrane dressings, like illustrated
here. And we’ll talk about these in more detail
later. But those are your goals as regards to local
response. Systemic Response. So as the burns get bigger, the local response
triggers a systemic response that can become an increasing issue as the burns get larger. This was initially well described by Cuthbertson,
a Scott, a nutritionist. And, he’d use the phrases as ebb and flow
phases. The ebb phase, referring kind of to the tide,
being a period of hypoperfusion. This is a period of hypotension related to
hypovolemia, fluid gets lost through the wounds. And we obscure this nowadays frequently with
the fluid that we administer intravenously. So the ebb phase is not quite as dramatic
as it is in a setting in which a fluid resuscitations are not done. And, then he described the flow phase, which
falls about 72 hours later in patients who do survive the ebb phase. And this is a period of increasing hyperdynamic
circulation, increasing catabolic metabolism. And this flow phase, or this hyperdynamic
phase, will persist until well after wounds are closed. And in patients with very large injuries,
it can persist a year or so after wound closure. And this period is characterized by hyperdynamic
circulation, protein catabolism, and glucose intolerance. How do you address the systemic response? Well, the best way to do it is to remove the
eschar as soon as it’s obvious where it is full thickness. Close those wounds physiologically somehow. And then support the hyperdynamic physiology
as best you can. There’ll be increased needs for substrate. There will be increased needs for volume. So, to support those needs with nutritional
support does help your patients survive that phase of his care. In patients in whom nutritional support is
inadequate to this task, you really get into a late systemic phase where there is a lot
of catabolism. And this really complicates their recovery. It makes healing of their wounds and donor
sites pretty much impossible. It very much exaggerates the immune compromise
that burn patients suffer. And, so, very early, very aggressive attention
to nutritional support of somebody with a medium to large wound is really critical in
avoiding this sort of late phase, catabolic illness. Pediatric Considerations. Briefly, pediatric considerations are– children
are commonly burned. The mechanisms are often a little bit different–
a lot more scalding, bathing, and cooking accidents. Airway is always an issue. The pediatric airway, as you know, is much
smaller than the adult airway. As edema occurs in the head and neck, occlusion
of the airway due to edema is much more rapid than an adult with a full size trachea. Children have higher energy needs per surface
area unit. They have a thinner skin. They have exaggerated temperature loss. All these things need really focused attention
early on. And from a practical perspective, they have
smaller blood vessels. Vascular access is more difficult and needs
a little more attention to detail. Having said that, there’s no reason that children
should have a higher mortality with the same size injury as a young adult. It’s also very important to really keep in
the forefront of your head that kids will get cold easily, especially small children
with thin skin, not a lot of insulation. They’re evaporating through their wounds. They’ll really get cold quickly. You won’t get cold. They’ll be cold. This is particularly important in the operating
room, because hypothermia will lead to coagulopathy. And if you’re doing an operation, it really
demands an intact coagulation cascade to have a successful outcome. You really want to pay attention to this detail. Constantly monitor the temperature of the
child. Injuries of abuse do occur in all age groups,
probably more common in small children. There are certain classic patterns and stories
you want to be alert for. This is one such, the flexor sparing across
a popliteal fossa. We’ll talk a little bit more about this later. But to have this in your mind as you go through
the initial evaluation of patients is important. And finally, kids grow. And they outgrow their scars. They outgrow their grafts. And to keep them functioning normally requires
periodic visits for reconstruction. These operations are very straightforward
in most cases. They’re very easy to do. They’re very well tolerated. But they’re best done as soon as they manifest
rather than waiting. Geriatric Considerations. Geriatric considerations, again, the mechanisms
tend to be a little different. Sometimes, when very old patients are burned,
it’s part of their global deterioration in their ability to interact with their environment. They frequently have co-morbid issues. They frequently have a reduced reserve. There are sometimes advance directives or
health care proxies that need to be brought into the overall planning. This ideally should be done extremely early
so inappropriate things aren’t done and inappropriate paths not taken. And, finally, they have very thin skin. Like little children, they have an atrophic
skin. It doesn’t heal well. It doesn’t tolerate donor site harvests very
well. And we’ll talk later about some of the specific
ways to address that operatively to get a good outcome. Finally, rehab can be more difficult for elderly
patients. They do best in their home environment. Sometimes, that’s very difficult, depending
on the physical characteristics of the home environment and who’s living there and who
can help. And thinking about and planning a placement
and the rehabilitative needs of elderly patients is really important if you’re going to give
them a quality outcome. Summary. So, to summarize burn physiology, really there
are local issues, there are systemic issues, there are pediatric and geriatric unique aspects. But really, it’s all about the wound. If you can address the wound efficiently,
quickly, and with minimal morbidity related to the operative event, you can really truncate
the physiologic aberrations here very well. And so if you can address the wound efficiently,
everything else will get better. That concludes our video on Introduction to
Burn Physiology. Please help us improve the content by providing
us with some feedback. What did or didn’t you like about this video? Was the content too simple, just right, or
too difficult? Was the length too short, just right, or too
long? Any additional comments? You can either click the Start a New Discussion
button and type in feedback or send us an email at [email protected] hildrens.harvard.edu. Note, feedback is not required to complete
this activity in the guided learning pathway.


Leave a Reply

Your email address will not be published. Required fields are marked *