Dehydration - is it really *that* bad?

[w ripley]

Dives of an hour or less, unless in a terribly stressed situation, probably aren't a big deal, IMO, as far a hydration goes. Once you get to 3 hours and beyond, I think it becomes very important. Probably more so - on those longer dives - for those of us that are older.

The biggest mistake I see divers of both sexes make is to deliberately not consume fluids before dives because they refuse to install and use a pee valve. It's just stupid, IMO. Combine that with sitting on a hot deck perspiring in a drysuit, waiting for the boat to open the pool for example, and you're really stacking the deck against you.

Smart divers hydrate. Divers with longer profiles also carry hydration packs, and usually mixed with one of the smarter additives referenced above. For me, it's the Hammer line of endurance fuels. And, for long dives, there's proper restoration of your body once you get out of the water. Once out of the water even Gatorade's Recover is fine, sugars and all, again IMO.

You don't jump in the water with low tanks, so why would you jump in under-hydrated?

 

[DevonDiver]

Looking at this from another angle: I believe it is common practice for hyperbaric chambers to typically hydrate patients using IV. That leads me to the assumption that there are benefits to having a robust blood/fluid volume in the treatment of DCS. If valuable for treatment, then why not for prevention.

Understood.. that's a very simple assumption - maybe someone of the medical profession can explain that treatment, and the rationale behind it?

 

[tajkd]

So after all that the answer is; no one knows if dehydration really causes an increased risk of DCS but it might, no one can accurately measure nor do they know how much it takes to be "hydrated", but some of you think you need to drink a lot before diving just in case. Oh and I'm not smart if I don't hydrate according to at least one person. Hmmm
.

 

[w ripley]

So after all that the answer is; no one knows if dehydration really causes an increased risk of DCS but it might, no one can accurately measure nor do they know how much it takes to be "hydrated", but some of you think you need to drink a lot before diving just in case. Oh and I'm not smart if I don't hydrate according to at least one person. Hmmm
.

All I know is that after 3 hours without hydration + an energy source, I tend to become less patient and more likely to make mistakes. Having changed that, and hydrating every 2 hours in a dive, I am more relaxed and more patient when issues arise. All of that means I'm more clear headed to solve a problem. I also notice a huge difference when exiting the water and having to carry all of my gear to my truck: it's just easier & I'm not as tired - even after a 6-hour cave dive.

 

[TSandM]

If you want a measure of adequate hydration, do a specific gravity examination on your urine. Assuming normal food intake and normal renal function, you are almost certainly adequately hydrated if your urine specific gravity is 1.010. If it's 1.020 or higher, you are concentrating your urine to maintain volume or correct electrolyte abnormalities due to water loss.

But I don't think most people want to carry around a device for measuring urine spec grav, so a reasonable proxy is urine volume and urine color. Between a liter and a liter and a half of urine every 24 hours is the absolute MINIMUM you can get down to and still clear toxins from the blood. Assume, then that 2.5 liters of urine is a reasonable goal, and you're looking at a little more than 100 cc of urine an hour. The average bladder will start requesting to be emptied at around 250 cc, so if you are urinating every 2 to 3 hours, with light colored urine, you are almost certainly replacing your fluid losses adequately.

More than you wanted to know?

 

[Mr Carcharodon]

I believe it is common practice for hyperbaric chambers to typically hydrate patients using IV. That leads me to the assumption that there are benefits to having a robust blood/fluid volume in the treatment of DCS. If valuable for treatment, then why not for prevention.

Patients who suffer trauma due to auto accidents and cancer patients receive fluids by IV too. Is good hydration preventive of auto accidents and cancer? If not is DCS different?

 

[Thalassamania]

I don't know the origins of it, but in the late 1960s I was taught by Dumas (Calypso's chief diver) to drink was came to be known at the "French Cocktail" before every dive, that was a baby aspirin washed down by a liter of Orange juice. I have done this, or something similar, all my life. I have never had any form of DCS, and I have usually dove the U.S. Navy Tables with an ascent rate of 60 fpm. I watch the color of my urine on dive days as best I can and try to keep it on the light and clear side. Now ... this is all anecdotal, nothing more, take it ... or leave it.

P.S. My physician parents tell me that I might have been running the risk of an ulcer doing that.

 

[eponym]

[tangent]

I've enjoyed reading this discussion. It has reminded me of a study I read in the 1970s which made a lasting impression. I can't locate or cite it, but from memory . . .

The protocol involved man & dog teams. Each team was hydrated to their own satisfaction, then sent out on a long hike in warm weather.
When each team returned, they were asked to drink water until sated (okay, the dogs were just given access to water).
Measurements indicated that while the dogs uniformly re-hydrated to their pre-hike weight, the men replaced on average only half their water loss.

I'd guess that a similar experiment today would have different results. Awareness of hydration has I think changed a great deal (in the US at least) since the 70s.

[/tangent]

 

[CaveMD]

Dives of an hour or less, unless in a terribly stressed situation, probably aren't a big deal, IMO, as far a hydration goes. Once you get to 3 hours and beyond, I think it becomes very important. Probably more so - on those longer dives - for those of us that are older.

The biggest mistake I see divers of both sexes make is to deliberately not consume fluids before dives because they refuse to install and use a pee valve. It's just stupid, IMO. Combine that with sitting on a hot deck perspiring in a drysuit, waiting for the boat to open the pool for example, and you're really stacking the deck against you.

Smart divers hydrate. Divers with longer profiles also carry hydration packs, and usually mixed with one of the smarter additives referenced above. For me, it's the Hammer line of endurance fuels. And, for long dives, there's proper restoration of your body once you get out of the water. Once out of the water even Gatorade's Recover is fine, sugars and all, again IMO.

You don't jump in the water with low tanks, so why would you jump in under-hydrated?

I personally consider doing any mandatory decompression dives in a dry suit without either a pee-valve or a diaper to be frankly negligent.

 

[Bubbletrubble]

Just a few comments to add to the various lines of discussion in this thread...

• Muscle cramping has many different causes. Muscle cramping in scuba divers isn't just caused by dehydration or electrolyte imbalance. I would speculate that many cases of cramping in divers may be attributed to a lack of conditioning, particularly in older divers and those who aren't accustomed to the level of physical exertion encountered on dives.
• I would not characterize average recreational scuba divers as elite athletes. Elite endurance athletes exert themselves strenuously over extended periods of time. They are very aware of their sweat rate and energy needs during a race. Consequently, they optimize fluid/electrolyte replacement and nutrition intake to maximize performance.
• Tech divers conducting long (multi-hour?) dives probably should have some sort of plan in place to maintain proper hydration status. Normal, healthy OW recreational divers (not vomiting due to seasickness and not suffering from diarrhea) who are conducting 30-60 minute dives really don't need to be obsessing about drinking fluids all the time during surface intervals. They would be much better served moderating the known factors associated with increased DCS risk.
• I'd be willing to bet that a dry mouth post-dive influences a diver's perception of his/her hydration status. If anything, I would expect divers to overestimate their state of dehydration.
• Theoretically speaking, there may be a danger of over-hydrating before a dive, particularly in the segment of the diving population that has certain heart conditions or that takes meds affecting cardiac function.
• The diuretic effect of a caffeine-containing beverage is minimal (if it exists at all) for a person who is habituated to a that level of caffeine intake.
• There is evidence to suggest that the intake of a moderate amount of caffeine by certain types of athletes can actually be performance-enhancing.