Burgess John asked:
I hope the subject might get your attention but I guess as a Doc....!
Question..as a matter of survival and in dire need of fluids without potable drinking water would an anal infusion of sea water work?† If it would how much fits down there, a glass, a litre?
I know of an occurrence where brackish water was administered that way to avoid the stomach upset and consequent problems drinking it would have resulted in.
Great show, Dave's kitchen science gets my vote.
We put this to Miles Parks, Gastroenterologist, and Ari Ercole, Intensivist, both from Addenbrookes Hospital...
Miles - Using the rectum as a means of administering fluid replacement in dehydrated individuals is an interesting idea. The colon or large bowel functions primarily to absorb fluid, normally doing so of course as material enters to the cecum from the small intestine, the material which has not been digested, fibrous products and so on, together with a substantial amount of fluid and solute enters into the colon, and the fluid is then sucked out as the material goes around the 4 feet or so of the colon to form up the stool. And so, you can see the colon is well designed for absorbing liquid but it really needs to do so in the context also of transport of solute, thatís to say of sodium and chloride ions, and so on. Itís the absorption of these, of the solute itself which then creates the osmotic gradient which sucks fluid across the lining of the bowel, and into the bloodstream. So, bearing these things in mind, I do think that water enemas on their own or water on its own is perhaps unlikely to be absorbed in a clinically significant quantities, and of course, itís just likely to come out of the rectum again whereas, I think administering saline or something of that type would potentially lead to quite a significant absorption of fluid.
Diana - Water on its own probably wouldnít do very much, but a saline solution could give one a better chance of a drink. But what if you're stuck for saline drips and all you've got is a much saltier seawater?
Ari - Unfortunately, giving yourself a seawater enema for hydration if you've had the misfortune to be stranded at sea is a complete thermodynamic nonstarter. The problem is that the salt in seawater is much more concentrated than the concentration of all the various solutes found in body tissues. Since, to a first approximation at least, the gut can be thought of as a sort of semipermeable membrane, this will lead to water molecules tending to move from the body through the gut wall, and into the seawater to reduce the concentration difference. This process where water moves along its own concentration gradient across a semipermeable membrane is called osmosis, and itís very important in biology. In this case it will actually result in you becoming increasingly dehydrated. The situation is reversed with freshwater which would be successfully absorbed. Having said that, neither procedure would be very safe especially if the water was dirty. So, giving yourself a seawater enema if you're trapped at sea is likely to make you lose water. Of course, giving yourself a seawater enema if you're trapped at a cocktail party is likely to make you lose friends as well.
When I saw the title of this question, I was sooooo tempted to write 'shove it up your a**e and find out', but I shall refrain from such an undignified and ungracious way to treat a guest. Don_1, Tue, 29th Sep 2009
Do I understand your question correctly? You are asking if, Knowing that you can't drink sea water, but being in danger of dehydrating, could you survive by shoving it up your rectum?
It seems that some people may have done the experiment in a way.
My tortoises can 'drink' (perhaps not the best term to use here) via their cloaca (vent). Whether they could filter out salt in the process, I really don't know.
This forum's great; you guys ask the strangest questions. peter125, Thu, 18th Mar 2010
I've heard that if you are unfortunate enough to drop from a great height into water, it's a good idea to try to go "feet first" and it is also imporant to clench your butt as tight as possible on entry. Geezer, Thu, 18th Mar 2010
I believe that much of the problem with drinking salty sea-water is that people don't do it until they're already dehydrated, by which time the body is too dehydrated to deal with the salts. LeeE, Fri, 19th Mar 2010
There is a TV show on the Discovery TV Channel were a former British Special Forces member (or whatever they are called) named Bear Gryll is the host. It is named "Man vs. Wild"
There's no way I'm clicking on either of those links.
Come on Geezer - Live LARGE! JimBob, Fri, 19th Mar 2010
I agree with CliffordK. I think, if the experiment were done with seawater, the high salt concentration would result in an osmotic diarrhoea owing to the net movement of water OUT of the body and into the intestinal lumen to dilute the hypertonic solution.
I think the idea is to use urine granpa, Tue, 30th Nov 2010
But, in dehydration states, urine's always going to be hypertonic (saltier) than body fluids, thus accelerating the dehydration...
Or better still, diabetes insipidus... chris, Fri, 3rd Dec 2010
so if you are stuck at sea the better thing to do would be to try to catch a seagull or fish and drink the blood? JnA, Sat, 4th Dec 2010
The best thing to do is to try to find a way to capture, recover, or distill fresh water including capturing the morning dew if there is some.
I thought I'd look up some of the numbers... it is a little hard to find everything, but, looking at Sodium and Chloride ions. Note, the urine also is the primary balance for Nitrogen (Urea), and other water soluble toxins. But regulation of Sodium (salt) is important when considering it with respect to sea water.