Quote from traumamedic
But wouldn't it still be a problem in dehydrated patients because wouldn't it be drawing fluid out of the cells?
You are thinking along the right lines; however...
do not confuse hypovolemia with dehydration. hypovolemia is a loss of intravascular or circulating fluids either actual loss such as bleeding or relative loss to redistribution (i.e. third spacing). dehydration is a fluid concentration disorder where there is not enough h2o relative to Na concentration.
The hypertonic fluid does indeed cause h20 to come out of the cell and technically cause a relative dehydration of the cell. remember a couple of things here
-hypovolemia does not necessarily equal dehydration
-the goal of trauma fluid resuscitation is to maintain some sort perfusion of oxygenated hemoglobin to vital organs
-2/3rds of total fluid in the body is intracellular so it is a potential source of h20 that can be utilized in the intravascular space
-do you really care about a relative dehydration in a patient requiring this type of fluid resuscitation...clinical decision time
250cc of hypertonic may get you 500cc from intracellular volume into the vasculature but how long will this fluid last before it either ends up on the floor or thirdspaced? if a patient is losing so much volume that you cannot maintain any sort of hemostasis with blood component, isotonic crytalloid, and colloid fluid... is a touch of hypertonic fluid going to be the silver bullet and saves the day? On the other hand, the patient is clearly having a bad day so why not try all of the guns in your arsenal.