WRT the ratio of fluid; after infusing 1L of NS, only about 200ml is left in the vasculature at the end of that hour. The rest goes interstitial. The same amount of colloid, 1L of say hetastarch will increase the vascular volume to about 1600ml. Now don't go and give someone 1L of colloid at once, this is just for ease of understanding the ratios here. After 8 hours, you have about the same amount of fluid in the vasculature from the colloid. If you have infused 1L of NS every hour for 8 hours (Lets hope that the casuatly is catheterized if you're giving that much fluid) at 200ml remaining intravascular per hour, then you've got about 1600ml in the vascualture in that 8 hours. We don't give 1L boluses of hetastartch or pentastarch, we give them 500ml, then if that doesn't work we try 500ml more, then stop it for a couple reasons. Higher amounts can have adverse effects and if he needs more then he is probably bleeding internally and anymore fluid will make him bleed more. Better to use it on someone else that is salvageable. The colloid molecule is too big to diffuse into the interstitium. So you come out with a ratio of 4L NS to about 500ml of Hextend/Pentaspan. The equivalent of HSD to Hextend/Pentaspan is about half, so 250ml. I hope this is an understandable explaination. Maybe it should be in the fluid resus thread.
The days of following the ATLS guideline in a tactical environment should be forgotten. We are not in a hospital, we are far from it, thats why this research is being done. Treating a number of say 90mm Hg is not a good practice. Filler up and blow the clot. Especially if the hemorrhage is internal. Theraputic hypovolemia can be benificial. The AMMED fluid resus algorhythm is pretty good all things considered.
The other problem with filling somone full of 8L of NS is that someone who is hypovolemic is probably acidotic. The periferi is shut down, acid is being produced from anerobic cellular metabolism. Lets say hypovolemic shock assumes slight acidosis. The pH of NS is about 5.5, so you are filling someone who is acidotic with alot (8L) of acid, as opposed to a little bit (250ml) of acid. Another reason that it may be more benificial.
With the hypertonic solutions, cellular dehydration is an obvious problem, the hypertonicity of the fluid pulls body fluids from the interstitial and then intracellular spaces into the vasculature. This is why it is called a "volume expander" but the celular dehydration is secondary of concern to vascular volume expansion and oxygen tranport to the cells. Anemia isn't usually a problem as fairly low hematocrit levels are generally tolerated. Perfusion is priority #1. You're right, medics will still have to carry NS to rehydrate hyperthemics and other conditions, but these fluids allow much more sustained care - read longer CASEVACs and CASEVAC delays, as well, can carry fluid to treat more casulties. Yes, this fluid would also be benificial in a non-combat SAR environment when the SAR-Tech has to treat casualties in isolated locations with CASEVAC delays.
Cost shouldn't be that big of an issue. We're not drinking the stuff for breakfast. We don't hang 10 bags a day like you're average city ambulance. And as to the temperature durability, I will see what I can find.
On another note, when is the CF going to issue eveyone in theatre a manufactured tourniquet? Is this not negligence on their part to not provide this item to everyone? They know what they number one preventable casue of battlefield death is, yet they are painfully slow in doing anything about it. Is this not called negligence?