00:01
How do we assess the surface area?
There’s lots of different ways of doing it.
00:04
One commonly used one is the rule of nines which is really only valid for adults
and that basically says that the head is 9%,
the front of the torso is 9, the back of the torso’s another 9.
00:16
The front of the abdomen’s 9, the back of the lower back is another 9.
00:21
Each leg is 18, each arm is 9, it all adds up to a hundred
but it’s actually not terribly reliable even though it is easy to remember
especially at extremes of weight.
00:31
So very thin patients or very obese patients,
this doesn’t really give you a good accurate assessment
and there is a pediatric version available
but because these proportions are so growth dependent,
it’s not actually as accurate as we might hope.
00:47
So a little bit more sophisticated approach is the Lund-Browder Chart.
00:51
This is not one that you’re gonna be able to memorize.
00:54
So you would definitely have to pull this up
and refer to it while you’re calculating surface area.
00:59
It’s definitely more complex than the rule of nines
but it does address issues of relative growth for pediatric patients.
01:06
So it shows you visually how the body is broken down
and then, it actually provides you with a chart based on the patient’s age that tells you,
yeah, if you’ve got half the head involved and it’s a baby, it’s gonna be 9.5%,
whereas if it’s a 15 year old, it’s gonna be 4.5%.
01:25
So it addresses the relative sizes of different body parts and different age ranges,
and allows you to more accurately calculate the total percent burned.
01:34
The most commonly used one is the Parkland formula.
01:37
It’s based on lactated ringers and the calculation is 4cc per kilo per percent surface area burned.
01:46
You give half of that in the first 8 hours,
and then, the other half over the next 16 hours.
01:52
Now, there have been a lot of studies looking at the Parkland formula
and it actually results in over-resuscitation in a significant percentage of patients.
02:00
So you wanna be a little bit careful and make sure that you’re monitoring
and titrating the patient’s fluid intake to their urine output.
02:10
A lot of times, people use the Modified Brooke formula
which as you can see, is a little bit less aggressive.
02:15
It’s 2cc per kilo per percent burned for adults and 3% for children.
02:21
So it’s a little bit less than what Parkland gives
Current Advanced trauma, life support
and the American Bar Association
guidelines both endorse
the use of the modified Brooke formula.
02:32
However, the overall goal of fluid resuscitation
is to titrate fluid input to urine output goals.
02:39
but in either case again, you wanna make sure that you’re carefully monitoring urine output.
02:44
We expect half a cc per kilo per hour for adults
and between half a cc and one cc per kilo per hour for children.
02:53
If you’re getting significantly more urine output than that,
you’re probably over resuscitating and wanna back off on your fluids a little bit.
03:00
So just adjust it so that you maintain the expected urine output over time.
03:05
So here’s an example just to go through the calculations for you.
03:08
We’ve got a 29-year-old man who got drunk and fell into a campfire.
03:12
He’s got burns over his entire anterior chest and abdomen,
as well as his bilateral thighs, which gives us a roughly 27% total body surface area burn.
03:24
His weight is 80 kilos.
03:26
So by the Parkland formula, 4 cc per kilo times 80 kilos, times 27% burned
gives us 8640 cc of lactated ringers.
03:40
Now, Parkland tells us to divide that in half.
03:42
We’re gonna give half of that in the first 8 hours.
03:45
So 4320 cc over 8 hours which is 540 cc an hour.
03:50
That’s a lot of fluid, right?
That’s more than half a liter of fluid per hour.
03:55
So it’s a pretty significant volume.
03:56
The remainder, we’re gonna give in the next 16 hours
and that’s gonna take us down to 270 cc per hour after the first 8 hours of resuscitation.
04:05
So let’s say our patient has 300 cc of urine output in a 2-hour period.
04:12
Well, he’s an 80 kilo guy, so we expect him to have half a cc per kilo per hour,
or about 40 cc an hour.
04:21
He’s had 300 cc in 2 hours which is more than three times what we’d expect for him.
04:26
So this is a situation where we would wanna say,
okay, we’ve gotten a little bit overzealous with our fluid.
04:32
Let’s back it down.
04:33
Let’s maybe cut it in half and reassess the urine output in a couple of hours
to keep ourselves on track.