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XxAyoo_RyanX's avatar

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I need help on my lab analysis question. in my school, im doing the diffusion and osmosis lab. there is one question on the analysis that im not sure of. the question is " You are in the hospital and need intravenous fluids. You read the label on the IV bag, which lists all of the solutes in the water. Why is it important for an IV solution to have salts in it? What would happen if you were given pure water in an IV?" please help me.
Dr Dimari's avatar

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Its quite simple. If you don't have the salts in the IV bag, the water would automatically diffuse by osmosis out of the blood vasculature into the interstitial tissue space.

((IV fluids that have salts such as saline or hartmann's, tend to still have the water diffuse out of the blood, but much slower than if it was plain water - there is a lot of argument about which fluids should be used for what clinical situation))
Blood has natural osmotic pressure which is not zero. By injecting pure water with zero osmotic pressure, you would lower this blood's osmotic pressure, causing all kinds of havoc (edemas..).
To re-word a previous answer; injecting distilled water into someones veins would cause their cells to explode. Diluting the salt concentration would change the osmotic gradient causing fluid to rush into the cell as water molecules travel from high to low, leading to cell lysis.
A picture might make it more intuitive

http://chemistry.about.com/od/imagesclipartstructures/ig/Science-Clipart/Osmosis---Blood-Cells.htm

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