Experience From - Rob Gryfe , Rich Schick , Norm Yarger , Matt Mahoney , George Beinhorn , Scott Weber ,
While I have no study to back up my comments, I think that it is very unlikely that receiving IV rehydration causes any sort of dependence on the need for future IV rehydration. That being said, the CAUSE for needing intravenous rehydration may recur (i.e. inability to take in oral fluids, large gastrointestinal or urinary losses in ill patients, or ultra runners who are prone to dehydration). Basically, receiving IV fluid should not influence whether you'll ever need it again or not, but the reason for needing it in the first place may certainly influence future needs.
If you need IV's during or as a result of an ultra there are several possible explanation. The most common is you failed to take adequate fluids until you got to the point of no return where you could no longer take oral fluids. The solution is simple. Drink more early in the race. This can become habit forming if you fail to learn from your mistakes. A second possibility is you got sick during the race and developed diarrhea or vomiting for whatever reason. If this becomes habitual you need to see an MD and find out what's wrong with your gut. Third possibility is that the medical folks at the race just love to start IV's and plugged in anyone who said they felt weak, thirst or dehydrated. Really not much wrong with this, good practice for the EMT's or whoever, but IV's aren't required unless the patient is unable to take fluids by mouth. Gatorade, Powerade or any other electrolyte drink is perfectly good (Though most are better tolerated and just as good diluted to 1/2 strength with water).
Extremes of heat and distance should not result in the need for IV's. In my opinion one should drop out before getting to the point of requiring an IV. By the time you actually need one it is in fact a medical emergency -- you could possibly die or permanently injure yourself, in general this is senseless. About the only way this would make sense is if a runner got in trouble and it was a long way to the next aid station.
Regarding this thread, some time back I saw an article by a Doctor. He attempted to experiment with IV verses oral replacement (drinking). Often the medics would apply the IV anyway, but his conclusions were that taking water generally was better than the IV and led to more rapid recovery. Of course there are those cases where the condition is truly life threatening, but for the rest, if possible try drinking cold water first.
Disclaimer: I am not a doctor and I do not play one on TV either. Just For What its Worth.
An IV contains water, salt, potassium, and glucose. All of these ingredients are found in foods. None are addictive. It shouldn't make any difference whether you get them through the stomach or a vein in the arm.
I've had IV's (usually 1-2 liters) twice after Ironman-length events and once after a half-Iron. This was several years ago before I figured out that the best thing to eat in long endurance events to prevent nausea is regular food instead of liquid carbos. I did not suffer any withdrawl symptoms after getting an IV and I never needed one after an ultra. You do feel better fast after an IV, but I would still prefer not to need one in the first place.
You'd better IV if you're clinically dehydrated. You'll be vomiting and feel real, real bad. It'll cost you $170+ at the ER, but it'll be worth it.
In the Hi-Tec Badwater, it USED to be legal to IV on the course and continue racing. I got the lesson of how effective it was when one runner came blasting by me at near 10 K pace climbing the super steep sections of the Whitney Portals road at mile 130. I kept wondering where all that energy came from at being hammered by the cousrse for well over 48 hours. I later found out this guy got IV'ed at the start of the climb.
If you need an IV, then, you bet, do it. And, take yourself out of the race (usually madatory; but in some cases, like above, a personal choice). I have never been IV'ed during any of my efforts at Badwater by the way. I don't say that to be boostful, I just say it to let you know I put "my money where my mouth is".
Badwater would become a joke if the IV thing was allowed to go on. It would make sense to be IV'ed before the race right up to the start. Then, at every rest stop, to load up again. I think of it like oxygen at Everest. You go to Badwater to confront the heat; you go to Everest to confront the altitude. IV'ing and Oxygen just compromise the accomplishment.
But, when you're in trouble, save your ass before you die.