Dehydration dilutional hyponatremia ????

[ohbet]

Please,those with greater insight,how can a geriatric patient be admitted with a dx. of dehydration,dt diarrhea and poor po intake,who is then placed on 80cc/hr iv fluid,d5w 1/2 ns, then,after only 2 hrs of this iv fluid intake have the labs show she is hypo-neutremic?,and no,she does not have addison disease.

If your sodium is low its due to,99% of the time,to much water,but this patient only had 160cc fluid intake iv.

So was she missed diagnosed with dehydration?

or am I ignorant and remarkable misinformed and when I get the answer be remardably embarrassed?

Thank you ,ole wise ones.

[tjohnson]

Originally posted by ohbet

Please,those with greater insight,how can a geriatric patient be admitted with a dx. of dehydration,dt diarrhea and poor po intake,who is then placed on 80cc/hr iv fluid,d5w 1/2 ns, then,after only 2 hrs of this iv fluid intake have the labs show she is hypo-neutremic?,and no,she does not have addison disease.

If your sodium is low its due to,99% of the time,to much water,but this patient only had 160cc fluid intake iv.

So was she missed diagnosed with dehydration?

or am I ignorant and remarkable misinformed and when I get the answer be remardably embarrassed?

Thank you ,ole wise ones.

The dx of diarrhea is the key. Where water goes, salt follows. As well as some other electrolytes. The hyponatremia may have been on it's way to occuring when the first lab was drawn, she may have been borderline. Then, by the time the second lab was taken, she was then below borderline giving her the dx of hyponatremia. 80cc per hour is only a KVO (keep vein open) rate, it is pretty low. My guess is that the doctor was trying to reestablish her electrolyte balance which has to be done slowly or the patient will swing the other way, hypernatremia, hyperkalemia, etc. It's like being too aggressive with a diabetic in a bout of hypoglycemia, the result would be hyperglycemia. It would take a little time before the labs would show an improvement on her sodium level with any iv going at that rate, esp since it's half NS. There would also be a risk of fluid volume excess at a rate too high for that patient. I don't know if she has a history of CHF, or some other medical condition.

[ohbet]

Thanks,but I thought where the Salt goes,water goes.

[butters]

Water follows salt. What was her sodium concentration prior to the IV fluids being given?????? A dehydrated person can be hypernatremic or hyponatremic (if ADH is trying to maintain water).

Also, diarrhea can cause hyponatremia. What is weird is either way, in a hypovolemic person you would give Normal Saline (even in the hypernatremic person).

Mathematically, here is how to work it out. A dehydrated person might have 10 L of extracellular fluid (interstitial fluid + plasma). Normal is about 14 L. If her sodium was 145 mmol/L, multiply by 10 L to get 1450 mmols of total salt in her body. 1/2 saline is 77mmol/L. So you said she got 160cc, or 160ml, or .160 L total. Thus she got 77mmol/L X .160 L which equals 12.32 mmol of additional salt.

The total salt she now has is 1450 + 12.32 = 1462.32.

The total water is now 10 L + .160 L = 10.160

Thus the new concentration is 1462.32/10.160 = 143.92 mmol/L.

So yeah, this is pretty insignificant.