Water Content of the Body

[Aagramn]

A friend of mine had some sort of fitness test yesterday at a sports centre. One of the results he was given was that his body is 44% water. Does this sound plausible, or is this a duff reading? I always thought the body was about 2/3 water, and didn’t know it could vary this much. Note that he didn’t exercise just before the test, so he shouldn’t have been unsually dehydrated.

[groman]

Well that’s not totally out of range, but as far as I remember most healthy people should have somewhere between 55 to 75 % water. It goes down as you age though(starting at 85% for babies, IIRC).

[picunurse]

Yes that IS totally out of range. A normal, healthy adult is around 80% water, and infant is 90% and a senior is drier, at around 70%.
At 44% your friend would be probably be unconscious, if not approaching death.

[picunurse]

Just to clarify, the range is pretty narrow 20% can certainly be the difference between walking around and circling the drain (Medical slang for trying to die)

[KarlGauss]

@picunurse

Yes that IS totally out of range. A normal, healthy adult is around 80% water, and infant is 90% and a senior is drier, at around 70%.
At 44% your friend would be probably be unconscious, if not approaching death.

Notwithstanding your cite, I disagree.

Men are around 60% water.

Women are around 50 to 55% water.

Here is one reference. There are many, many more.

[KarlGauss]

I neglected to mention that a very obese person will have a significantly lower precentage body weight as water. I don’t see 44% as outrageous in such a situation.

[raz]

I read somewhere that the body is about 75% water, but most of that water is inside of your cells. So how would they be able to measure the water content of the body if this is true?

[KarlGauss]

@KarlGauss

Here is one reference. There are many, many more.

Here are some more:

Australian Anesthesia Education Website

National Academies Press

“Dr. Carmen”

UNC at Charlotte

Albany Medical Center Anesthesiology

etc.

[picunurse]

KarlGauss I apologize. I went back to my real references… my books, and my memory has failed me again. (I don’t remember signing up for this getting old thing, first my figure, now my memory. :rolleyes: )
My texts do have it a bit higher than your sources, but my books are pretty old, and more research is being done all the time.
I do stand by the narrow balance, however. Losing 20% of one TBW would cause a serious electrolyte imbalance and probably symptomatic hypovolemia.
One of your cites does have some questionable text. It speaks of using D[sub]5[/sub]W as a fluid replacement, which, in the clinical setting, isn’t done.That’s just free water and, as such, would go directly into the cells. ICV maintains itself at all cost, so free water isn’t necessary, and can cause more problems than it solves. D[sub]5[/sub]W is used in steady states to maintain hydration, but not to increase ECV.

Sometimes fluids are isotonic in the bottle (or bag, now), Figure 4, but become hypotonic following metabolism, e.g., 5% dextrose in water (D5W). When this is infused into the body, the ECF expands about 33%. The ICF expands about 67%. The infusion of this solution reduces the osmotic pressure of these two fluid compartments. Hence, the water infused is “free” water. Therefore, it maintains fluid needs and** is used for replacing volume loss**.

(my bold) This is misleading. It would be used to maintain a steady state volume, never to replace it.

This cite is actually trying to show that D[sub]5[/sub]W is not an acceptable volume replacement.

For example, assume that a 70-kg patient has suffered an acute blood loss of 2000 ml, approximately 40% of the predicted 5-liter blood volume. The formula describing the effects of replacement with 5% dextrose in water (D5W), lactated Ringer’s solution, or 5 or 25% human serum albumin is as follows:

To restore blood volume using D5W:

2 liters is the desired PV increment, 42 liters is the TBW in a 70-kg person, and 3 liters is the normal estimated PV.

2 liters x 42 liters/3 liters =** 28 liters**

To restore blood volume using LR:
14 liters is the ECV in a 70-kg person.

2 liters x 14 liters/3 liters = 9.3 liters

abreviations used: Total body water (TBW) Intracellular volume (ICV) Extracellular volume (ECV) Plasma volume (PV)

(again my bold) It would take 28 liters to regain homeostasis from a 2 liter deficit. that’s dangerous.

[Aagramn]

Mystery solved. He gave me the wrong information, his test results were that his body contains 44 litres of water (about 60% of his body mass), not 44%.