Dehydration vs volume depletion

[Daitong]

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Hi,

Can some one explain the conceptual difference between the two, and why it matters? It feels that intuitively they are the same thing, and I wouldn't know how to discern any related pathologies between them.

Best,

 

[chillaxbro]

Dehydration you're losing volume that's hypotonic, leaving your body hypertonic
Volume depletion is more like bleeding so you're losing volume thats isotonic and your body remains isotonic

 

[worldbeater]

Hi,

Can some one explain the conceptual difference between the two, and why it matters? It feels that intuitively they are the same thing, and I wouldn't know how to discern any related pathologies between them.

Best,

Dehydration you're losing volume that's hypotonic, leaving your body hypertonic
Volume depletion is more like bleeding so you're losing volume thats isotonic and your body remains isotonic

This didn't look right I first saw it, because they are both "low volume" profiles, so I looked up the dehydration specifically. When your are sweating, you are losing sodium, so you are actually hyponatremic. That makes you more likely to depolarize (meaning more positive), because even though your losing sodium, the driving force of calcium into the cell is now uninhibited (sodium usually gets in calcium's way) to make the cell more positive, and there is just enough sodium, even though it's low, to make the cell more likely to depolarize. That's why after exercise, you have increased muscle cramps, increased urge to defecate, etc.

Losing blood is a low volume profile as well, so low serum sodium, low chloride, low potassium, increased BP, and an alkalotic pH. I would think both conditions have the same profile.

 

[chillaxbro]

This didn't look right I first saw it, because they are both "low volume" profiles, so I looked up the dehydration specifically. When your are sweating, you are losing sodium, so you are actually hyponatremic. That makes you more likely to depolarize (meaning more positive), because even though your losing sodium, the driving force of calcium into the cell is now uninhibited (sodium usually gets in calcium's way) to make the cell more positive, and there is just enough sodium, even though it's low, to make the cell more likely to depolarize. That's why after exercise, you have increased muscle cramps, increased urge to defecate, etc.

Losing blood is a low volume profile as well, so low serum sodium, low chloride, low potassium, increased BP, and an alkalotic pH. I would think both conditions have the same profile.

When you sweat, you secrete isotonic solution at first and as the sweat goes down the duct, it reabsorbs Cl (and Na follows) so you end up losing a hypotonic solution. Therefore you lose more water than salt, so you become hyperosmotic

When losing blood, everything you lose is the same composition in terms of electrolytes so you end up hypovolemic but isotonic