[ [quote] quote=marduk]
Unfortunately in survival situations if someone is ill enough or has injuries such that oral rehydration isn’t possible, they may not survive.


Absolutely, unarguably true. But mostly, this forum is about finding ways to not die in a situation that would be greatly simplified by death. Some of the medical techniques that worked in the late 19th and early 20th centuries might be adaptable to survival scenarios in which current therapies fail due to lack of resources. Next topic: field surgery under ether anesthesia.

IIRC, most water absorption in the colon is pretty independent of salt content. Most ions and what-not are absorbed fairly early in the small intestine. The rectum is purely fecal storage, so you'd need to get the fluids up at least 10 inches or so (NO, you don't have to push a tube in 10 inches....)

The colon also uses sodium transport to absorb water, which it does very efficiently.

I don't know exactly where you'd draw the line as far as concentration goes, but sea water is too salty to work as an enema. Your body wouldn't be able to create a big enough osmotic gradient to absorb much water from the salty sea water. Actually, you'd probably end up dehydrating yourself even more as water was drawn into your colon from your body tissues by the sea water enema.

I stand corrected; you're right regarding sodium and water transport.

I'd have to agree about hypertonic enema's though; very likely to dehydrate the person!