Fluid and Electrolytes

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Hello,

Im having trouble understanding Fluid and Electrolytes. My main problem is with Isotonic, Hypertonic, and Hypotonic. Ive been looking online for some help but cant find anything that "clicks". I'm looking for pictures or anything that has helped u in the past.

Thanks for your time.

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While I don't have a picture for you, think of your terms as how they relate to the "Solute" (Sodium..etc..)

hypo- means low or less

hyper - means more

so if something is hypotonic - that means less solute

if it is hypertonic - that means more solute

Then if it is isotonic, that's the normal balance.

Hope that helps some..

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Specializes in ER, ICU, Medsurg.

OK I'm gonna try and draw a picture verbally but let's start at the beginning. Remember water chases salt. For the sake of simplicity, let's just say our solute is salt. When you have a hypo (hypo, low) tonic solution you have low salt solution. Picture a cell, outside the cell you have low salt with a hypotonic solution, inside the cell is more salt. So if water chases salt, the hypotonic is going to move into the cell where there is more salt. So the cell is going to swell.

Now on the other hand, if you have a hypertonic (high salt) solution outside the cell the water that is in the cell is going to move outside and cell will shrink.

Water is going to go where the salt is. So if you have a hyper solution infusing the cell will shrink, and visa versa.

Isotonic is happy. There is the same amount of salt inside the cell as there is outside the cell. Think "I so happy" Isohappy.

Hope this helps. Wish I could draw a picture for you. lol

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Specializes in LTC, MDS, ER.

I had a lot of difficulty understanding this until I realized I had to look at the solute (sodium chloride) content of my solution. I think it's a lot easier to understand when you use IV solutions and their relation to red blood cells. (Remember, the inside of the red blood cell is normally 0.9% sodium chloride and 99.1% water, and the RBC is being bathed in the IV solution). Also, water will go where there is a higher concentration of solutes, or sodium chloride in this case. (Water follows sodium).

Simple version:

ISOTONIC: 0.9% Normal Saline. 0.9% sodium chloride, 99.1% water. Inside of the RBC is the same. No swelling or shrinkage because it's equally concentrated on both sides of the red blood cell.

HYPOTONIC: 0.45% Normal Saline. 0.45% sodium chloride, 99.55% water. RBC: 0.9% sodium chloride, 99.1% water. Which has more sodium chloride? The inside of the RBC. Water follows the sodium chloride into the RBC, and the RBC swells.

HYPERTONIC: 1.2% Normal Saline. 1.2% sodium chloride, 98.8% water. RBC: 0.9% sodium chloride, 99.1% water. Which has more sodium chloride? The solution on the outside of the RBC. Water follows the sodium chloride out of the RBC, and it shrinks.

0.9% Normal Saline is ISOTONIC. This solution is 0.9% sodium chloride and 99.1% water (100-0.9=99.1). Water goes in and out of the red blood cell at the same rate, so normal saline is considered isotonic. Picture a red blood cell. Water is going in at the same rate as water is going out, so the red blood cell isn't getting any bigger or any smaller. The reason for this is because there is the same amount of sodium chloride solutes inside the red blood cell as there is on the outside. (The membrane of the red blood cell is the impermeable membrane; the red blood cell is being bathed in the IV solution).

0.45% Saline is HYPOTONIC. This is 0.45% sodium chloride and 99.55% water. Remember, this fluid is on the outside of the red blood cell. If you put a red blood cell in a hypotonic solution, there will be 0.9% sodium chloride inside of the red blood cell, but 0.45% on the outside. Which has more solutes? The inside of the cell. So the water will go inside the red blood cell, making it swell.

1.2% Saline is HYPERTONIC. This is 1.3% sodium chloride and 98.2% water. Bathe a RBC in this solution, where will the water go? There's 1.3% sodium chloride on the outside of RBC, but 0.9% on the inside. Which side has more sodium chloride? The outside of the RBC; all the water will run out of the RBC and it will shrink.

What would happen if you put a RBC in a solution of sterile water (100% water, no sodium chloride)? (Remember, water follows sodium).

Good luck! =)

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Specializes in being a Credible Source.

Try this:

The ocean is hypertonic... if you spend a lot of time in the ocean you become dehydrated because the water in your body is drawn into the hypertonic solution (the ocean).

Distilled water is hypotonic... it doesn't have anything dissolved in it... it's just pure water... all the minerals normally found in tap water (take a look at your faucets and you'll see 'em crusted on there) are removed.

Isotonic... well, ocean water is isotonic with ocean water... distilled water is isotonic with distilled water... normal saline is isotonic with normal blood chemistry.

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Specializes in med/surg, telemetry, IV therapy, mgmt.

there is information on this on these sticky threads:

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