If someone is septic/crashing, running NS wide open through large bore peripheral IV's is the thing to do. Depends on the patient, I have pumped liters and liters into small women with sepsis and they do fine, then I've pumped a couple of liters into larger people and fluffed out their lungs.
The trick is that for volume resuscitation one should give a set amount of fluids, then physically reassess the patient- is their pressure up, is their tachycardia better, do they have JVD, are they starting to get SOB, new O2 req, listen for crackles. Fluids, then reassess, fluids then reassess.
As for maintenance, typically more for children, but the old demented nursing home patient taking poor po, 1/2 NS approximates serum sodium concentration, given at 1ml/kg/hr, and you add D5 to prevent starvation ketoacidosis (which I have mistakenly let happen to many patients).
A key point I learned early on is to never write an order like this: "NS IV at 100cc/hr," ALWAYS write a stop time, even for maintenance fluids, I write "stop at 0600 tomorrow," so I can reassess them in the AM. I can't tell you how many times I have seen surgery patients post op having continuous IVF running forever and nobody following it, just keeps running, happens with MICU transfers a lot too. Pure garbage, always write a start and stop time to fluids, or else you go round the next day and the guy you were supposed to discharge is 4L up with massive edema to the thighs and a new O2 requirement, a lot of times nurses don't question these kinds of things but they are very important.
