Olde NBME clarification - hyponatremia

[sahell]

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An alcoholic with serum Na 99mg/dl is treated with 0.9% saline and develops quadriparxsis, dysarthria and slurred speech.

Most answers say it's central pontine myelinolysis but that would be because of rapid correction of hyponatremia. That would require hypertonic saline.

0.9% is isotonic so I think it's a consequence of cerebral edema.

 

[ASM student]

Not necessarily with hypertonic saline, correction of hyponatremia must be in a rate of 1-2 mEq/L per hour with maximum of 8mEq/L in the first 24 hours. It's the rate of the correction rather than the amount of sodium you're adding.

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[sahell]

You mean that the total amount of sodium we're infusing at a given time makes the difference and not the concentration of the sodium in the fluid? So if I infuse 3% really slowly, it would be equivalent to a faster NS infusion? And no problems as long as it's not too fast?

 

[ASM student]

Regardless of what you're using if it corrected the osmolarity faster than it should, it can cause CPM. Remember that he is hypotonic so isotonic saline to him is hypertonic and it will raise the osmolarity and even if it was to a level lower than the normal the rate has to be in check. Yes the rate of the correction matters more than the level you're going for.

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[sahell]

Brilliant! I was actually thinking that NS would be relatively hypertonic for him after your first reply but wasn't sure. Thank you for clarifying that.

 

[Surgeria]

Regardless of what you're using if it corrected the osmolarity faster than it should, it can cause CPM. Remember that he is hypotonic so isotonic saline to him is hypertonic and it will raise the osmolarity and even if it was to a level lower than the normal the rate has to be in check. Yes the rate of the correction matters more than the level you're going for.

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Great, Thank you for the part that isotonic saline for a patient with hyponatremia will be hypertonic!! kind of easy stuff, but sometimes can't clarify by yourself