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Thursday, April 3, 2014

Resuscitation Fluids and formulae……….



Doc, how much fluids should be given to a burn patient and can a person survive if fluids are given if the patient comes to the hospital many hours after the burn incident?
Shawn, California
As we discussed in an earlier post, burn wounds loose body fluids from the wound surface as the skin integrity is damaged. Greater the surface area of the burn, more the fluid loss. In general the body is able to tackle the fluid loss that occurs from a less than 15 percent TBSA (total burn surface area) in an adult, and less than 10 percent TBSA in a child. Beyond this the body’s internal mechanisms are unable to handle this loss and the patient will end up in shock if the lost body fluids are not replaced. Once we understand this concept then we are faced with two questions:
a) At what rate should we administer the intravenous fluids?
b) What is the type of fluid that we should administer?

Parkland formula
Charles Baxter from parkland hospital (Texas, USA) made a large contribution to the management of burns by his studies on the fluid loss in burns and their replacement. He observed that the first 24 hours were critical to the survival of burn patients and the replacement of fluids was to be done in the first 24 hours itself. In this the first 8 hours were crucial as the blood vessels and capillaries lost their integrity totally and therefore the intravascular fluids leaked out on a large scale. In the second 8 hours after the burn the capillaries regained their integrity and the leaks were controlled to a great extent. Keeping this in mind Charles Baxter suggested a fluid resuscitation formula in burn patients at 4 ml/kg/TBSA for the first 24 hours. The type of fluid suggested was Ringer Lactate.  Of the total fluid calculated for 24 hours, half of the volume was to be given in the first 8 hours and the rest in the next sixteen hours. 

Why did Baxter suggest Ringer Lactate as the resuscitation fluid?
  Obviously because he observed that it was more physiological and had many advantages:
a) Ringer lactate has a lower sodium concentration (130mEq/L) than normal saline. 
b)The metabolized lactate had a buffering effect on associated metabolic acidosis in burns. 
c)Ringer lactate is an Isotonic crystalloid solution
 
Example for fluid calculation:
Let’s take an example here – a patient with a body weight of 65 kg  comes to the ER with flame burns of 45 percent TBSA.
TBSA 45%
Weight of the patient- 65 kg
Therefore the fluid calculation by parkland formula-
4x% TBSA x body weight
i.e. 4 x 45 x 65
i.e.  11,700 ml for 24 hours
Half of this has to be given in the first 8 hours
i.e. half of 11,700 – which is 5850 ml for 8 hours
Therefore for each hour in the first 8 hours the patient needs 5850/8 ie 731.25 ml or approximately 730ml per hour

For the next 16 hours the remaining 11700 ml needs to be spread out
So 5850/16 is 365 ml needs to be given each hour for the next 16 hours

Thus the patient must receive 730 ml per hour for the first 8 hours post burn and for the remaining 16 hours of the first day the patient must receive 365 ml per hour. 

Coming to the second part of the question- the fluid calculated has to be replaced in the time specified. However some patients appear later than the time of the burn and therefore the fluids which were not administered will have to be replaced at a higher rate but taking care to see that we do not overload the patient and put him into cardiac failure or pulmonary edema.

It must be noted that the calculation of fluids by this formula is only a guide line and a number of factors must be taken into consideration which administering fluids which we shall discuss in another post …..

(An original initiative in burn care and education from asktheburnsurgeon++)

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