Help with symptomatic hyponatremia management

[sliceofbread136]

This is something I’ve actually never taken care of so I feel somewhat clueless about it and would appreciate some help.

the intial part seems fairly straight forward, 3-5ml/kg of hts until symptoms abate, which will usually involve a correction of 2-4. It’s the part after that I’m not sure about

hypovolemic hyponatremia- anticipating a free water dump start low dose vaso or ddavp. Then calculate fluid you would give to correct volume deficit and sodium deficit with goal correct of around 6-8 for day. Next day let them drink or infuse isotonic saline and make sure they self correct well (like another 6)

euvolemic hyponatremia such as siadh- fluid restrict to 60% maintenance and watch while self correct (goal around 6 for day)

hypervolemic hyponatremia- also start fluid restriction, maybe even need to give lasix to remove extra volume of your hypersal blouses.

Did I get anything wrong here??

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[sliceofbread136]

So for a hypovolemic hyponatremia example: say we have a 10kg patient with a sodium of 115 that is corrected to 118 by a hyper sal bolus.

Say I’m not vaso: then for maintenance for the day I have 1L free water (4 per kilo per hour) and 30meq sodium (3meq/kg/day). Then my sodium deficit is ~20meq for a good slow correct. So I want to give around 50meq in 1l volume, so I can approximate this at running maintenance rate of 1/2 NS which if correcting to fast I will decrease to 1/4NS.

if I give vaso: then for maintenance I lose free water only from insensible (which is 1/kg in this case) and 30meq sodium (3meq/kg/day). Deficit is still ~20. So now I want to give 50meq Na in 250ml fluids which I will approximate by giving normal saline at 10cc/hr.

Really not sure if I’m right or off base here. Thanks for any guidance!!!

 

[sliceofbread136]

Alternatively I can just use this calculator to guide my desired correction:

Sodium Correction Rate in Hyponatremia and Hypernatremia - MDCalc

The Sodium Correction Rate for Hyponatremia Calculates recommended fluid type, rate and volume to correct hyponatremia slowly (or more rapidly if seizing).

www.mdcalc.com

This gives me a very different answer but I feel is more correct

 

[SurfingDoctor]

You really shouldn’t be giving Vasopressin out a true HPA axis issue.

Yes, 3% NaCl for hyponatremic seizures at the dose you stated.

I’m struggling to understand what you are asking here. The context of the disease matters how you correct electrolytes.

 

[sliceofbread136]

You really shouldn’t be giving Vasopressin out a true HPA axis issue.

Yes, 3% NaCl for hyponatremic seizures at the dose you stated.

I’m struggling to understand what you are asking here. The context of the disease matters how you correct electrolytes.

sorry I think it’s hard to effectively communicate this through typing. What I’m trying to understand is what you do after you give hypersal. For clarity let’s focus on hypovolemic hypernatremia. Say we have corrected the seizures/symptoms and our sodium raised 4-6. What’s the next step???

 

[sliceofbread136]

As far as the vasopressin I got that from here:

The cause as a cure? The Case for a DDAVP clamp in severe Hyponatremia — NephJC

This week, we will discuss an observational study - a very large series of using DDAVP for treatment of hyponatremia. Yes, you read that right. Read the paper for free thanks to Am J Med and join us on March 27/28 to discuss.

www.nephjc.com

uptodate also seems to recommend ddavp or vaso while treating hyponatremia in a reversible disease (specifically from hypovolemia or hpa axis issues)

 

[SurfingDoctor]

sorry I think it’s hard to effectively communicate this through typing. What I’m trying to understand is what you do after you give hypersal. For clarity let’s focus on hypovolemic hypernatremia. Say we have corrected the seizures/symptoms and our sodium raised 4-6. What’s the next step???

Hypernatremic hypovolemia doesn’t typically cause seizures. Use mean hyponatremia?

If you stop the seizures, then most people will try some isotonic fluid at a rate that corrects the total free water deficit. But it doesn't really matter because whatever you calculate and so forth will be invariably wrong. The most important thing is keeping an eye on the Na+ every 2 to 4 hours depending on the severity of the Na+ imbalance and altering the rate or the Na+ content so as to not correct faster than 0.5 to 1 mEq/hr.

 

[sliceofbread136]

Hypernatremic hypovolemia doesn’t typically cause seizures. Use mean hyponatremia?

If you stop the seizures, then most people will try some isotonic fluid at a rate that corrects the total free water deficit. But it doesn't really matter because whatever you calculate and so forth will be invariably wrong. The most important thing is keeping an eye on the Na+ every 2 to 4 hours depending on the severity of the Na+ imbalance and altering the rate or the Na+ content so as to not correct faster than 0.5 to 1 mEq/hr.

yes I meant hypo. Sorry about that.

Even though you say the calculations are invariably wrong do you mind sharing how you do the calculations? I feel like what ever I read online gives me a very different answer as to the appropriate method

 

[SurfingDoctor]

yes I meant hypo. Sorry about that.

Even though you say the calculations are invariably wrong do you mind sharing how you do the calculations? I feel like what ever I read online gives me a very different answer as to the appropriate method

What calculation? The free water deficit?

(You can skip all the steps beyond 3)

Again though, this is like the Parkland formula for burn resuscitation. It’s a starting point. You have to measure the serum sodium regularly to make sure you’re not over/under correcting.

 

[sliceofbread136]

What calculation? The free water deficit?
View attachment 301617
(You can skip all the steps beyond 3)

Again though, this is like the Parkland formula for burn resuscitation. It’s a starting point. You have to measure the serum sodium regularly to make sure you’re not over/under correcting.

I know the formulas for both free water deficit and sodium deficit, but how does that translate to the fluids that you use while also taking into account their maintenance fluid requirements?

For example, a 30 kg child with a free water deficit of 1.2L?

Or for a hypernatremic example, a 30 kg child with a sodium deficit of 180 meq?

 

[SurfingDoctor]

I know the formulas for both free water deficit and sodium deficit, but how does that translate to the fluids that you use while also taking into account their maintenance fluid requirements?

For example, a 30 kg child with a free water deficit of 1.2L?

Or for a hypernatremic example, a 30 kg child with a sodium deficit of 180 meq?

Isotonic fluids is never the wrong answer.

You can read this if you’d like a more in-depth reading with the caveat that it recommends 0.2% NaCl which I my opinion, should never be given to a patient.

Pediatric Fluid and Electrolyte Therapy

Managing fluids and electrolytes in children is an important skill for pharmacists, who can play an important role in monitoring therapy. Fluid therapy is divided into maintenance, deficit, and replacement requirements. The Holliday-Segar equation remains ...

www.ncbi.nlm.nih.gov

 

[sliceofbread136]

Isotonic fluids is never the wrong answer.

You can read this if you’d like a more in-depth reading with the caveat that it recommends 0.2% NaCl which I my opinion, should never be given to a patient.

Pediatric Fluid and Electrolyte Therapy

Managing fluids and electrolytes in children is an important skill for pharmacists, who can play an important role in monitoring therapy. Fluid therapy is divided into maintenance, deficit, and replacement requirements. The Holliday-Segar equation remains ...

www.ncbi.nlm.nih.gov

That article is what I was taught in medical school. When I do those calculations I always get fluids that I would never use like 1/4 NS which what has led to my confusion. I like the idea of just using isotonic fluids much more.

2 more questions...

1. For hyponatremia how do you calculate the rate of NS you will use to correct a deficit? For example with the child with 180 meq Na deficit do you take 180 meq/24 hour to get 7.5 meq per hour which would be 50 cc/hour NS (15.4 mEq Nacl/100ml)?

2. How do you give free water with an isotonic fluid? Wouldnt you have to use atleast 1/2 NS?

Once again thanks for the help!

 

[SurfingDoctor]

That article is what I was taught in medical school. When I do those calculations I always get fluids that I would never use like 1/4 NS which what has led to my confusion. I like the idea of just using isotonic fluids much more.

2 more questions...

1. For hyponatremia how do you calculate the rate of NS you will use to correct a deficit? For example with the child with 180 meq Na deficit do you take 180 meq/24 hour to get 7.5 meq per hour which would be 50 cc/hour NS (15.4 mEq Nacl/100ml)?

2. How do you give free water with an isotonic fluid? Wouldnt you have to use atleast 1/2 NS?

Once again thanks for the help!

I’ll give you an honest answer, outside of free water deficit, I don’t do any calculations (and again that’s just a ballpark estimate of where to start). The fluids I pick depend on how high the Na+ is. If it’s greater than 160, I’ll use something like LR or plasmalyte (or 0.9 NS if they are hypochloremic, which is rare). I do this because I worry more about cerebral edema at the higher end of the hypernatremia spectrum (though I don’t think it’s evidence based). Once they hit 150s, I switch to 1/2 NS because I’m less worried about cerebral edema in that range. For children with intact thirst mechanisms though, it becomes easier because you put them on the same fluids until they wake up and then you let them drink and auto regulate.

Again, this is all in the context of frequent Na+ checks. If it’s not dropping 2-4 mEq every 4 hours, you give more hypotonic fluids. If it’s faster than that, you give isotonic fluids. It’s almost impossible to hurt someone with isotonic fluids, it’s just the rate of correction which is slowed. Personally, I prefer slow and steady as opposed to fast and potentially harmful.

Not specific to just hypernatremic dehydration, but in hyperosmolar dehydration (ie DKA), standard protocols for fluid management across the US are isotonic fluids for the first 8 to 12 hours followed by 1/2 NS for the maintenance. Clearly, once you give Insulin, the ongoing losses dissipate, so it’s quite the same as say osmotic diarrhea, but the general concepts can still be followed, since isotonic fluids (Na+ concentration of 130-154 mEq/L) are hypotonic and thus have free water, in comparison to someone whose serum Na+ is greater than 155 mEq/L.

 

[Stitch]

Just want to echo what Surfing doc points out. There are a lot of calculations that you can find, but clinically it matters that you check often and adjust as needed. You really can't hurt someone with isotonic fluids, so that's always a decent starting point no matter where you are. You can give more or less sodium in fluids as needed. The big lesson I teach residents is to know what's in your IV fluids. It's amazing to me how few people know what the electrolyte and pH composition of the fluids they are writing for. Learn and understand that.

 

[WheezyBaby]

The equations are bull**** because you're not operating in a closed system - the kidneys **** with everything you do. In correcting hypovolemic hyponatremia, you have an unpredictable risk. This is a high ADH state and your urine should be maximally contentrated. As you infuse crystalloid, you replenish your intravascular volume and eventually your ADH switch is going to turn off. You're subsequently going to dump free water at a different rate that you have been and you can see unexpected sodium swings. Vasopressin infusion is a strategy to lock out the kidneys and gain more control over sodium correction with the use of hypertonic. Hyponatremia in the setting of something like polydipsia is a different situation, your urine is going to be in the direction of maximally dilute, and when you introduce a sodium load you can see fluid dumping and unexpected sodium changes, but vasopressin could be used here as well.

Here is a more fleshed out article on the pathophysiology and rationale for vasopressin

Taking control of severe hyponatremia with DDAVP

. Introduction with a case . Imagine an elderly patient presenting with hypovolemic hyponatremia (sodium of 115 mM) and moderate confusion. How would you

emcrit.org

In general though, I think the important points are (1) rapidly correct symptomatic hyponatremia and (2) primum non nocere aka don't **** up your good work after you achieve number 1. To accomplish point 2, tailor your therapy to the underlying pathophysiology, go slow, check frequently, and be prepared to change your strategy / correct overcorrection should it develop. My general strategy is gentle LR for hypovolemia, fluid restriction to a degree that isn't torture for the patient and then salt tabs for SIADH, some combination of diuresis and fluid restriction for hypervolemia usually with an emphasis on the former

 

[sliceofbread136]

The equations are bull**** because you're not operating in a closed system - the kidneys **** with everything you do. In correcting hypovolemic hyponatremia, you have an unpredictable risk. This is a high ADH state and your urine should be maximally contentrated. As you infuse crystalloid, you replenish your intravascular volume and eventually your ADH switch is going to turn off. You're subsequently going to dump free water at a different rate that you have been and you can see unexpected sodium swings. Vasopressin infusion is a strategy to lock out the kidneys and gain more control over sodium correction with the use of hypertonic. Hyponatremia in the setting of something like polydipsia is a different situation, your urine is going to be in the direction of maximally dilute, and when you introduce a sodium load you can see fluid dumping and unexpected sodium changes, but vasopressin could be used here as well.

Here is a more fleshed out article on the pathophysiology and rationale for vasopressin

Taking control of severe hyponatremia with DDAVP

. Introduction with a case . Imagine an elderly patient presenting with hypovolemic hyponatremia (sodium of 115 mM) and moderate confusion. How would you

emcrit.org

In general though, I think the important points are (1) rapidly correct symptomatic hyponatremia and (2) primum non nocere aka don't **** up your good work after you achieve number 1. To accomplish point 2, tailor your therapy to the underlying pathophysiology, go slow, check frequently, and be prepared to change your strategy / correct overcorrection should it develop. My general strategy is gentle LR for hypovolemia, fluid restriction to a degree that isn't torture for the patient and then salt tabs for SIADH, some combination of diuresis and fluid restriction for hypervolemia usually with an emphasis on the former

So for hypovolemic hyponatremia what would you consider gentle LR? Half maintenance? And if they start dumping urine maybe switch to a vasopressin and hypersal drip?

 

[WheezyBaby]

So for hypovolemic hyponatremia what would you consider gentle LR? Half maintenance? And if they start dumping urine maybe switch to a vasopressin and hypersal drip?

I think it depends on their po intake, but total daily fluids between IV/PO somewhere between 1 and 1.5 maintenance is a reasonable target. I'd personally target the lower end of that if they're not po'ing much. For your second question I think it depends what your practice setting is. Vaso and hypertonic are ICU therapies for hyponatremia in my opinion, unless you're a nephrologist. If it was a floor / stepdown patient and I thought they hit that ADH switch and were autocorrecting in a scary way, I'd stop my fluids, do D5W, and consider an ICU transfer if needed for appropriate care e.g. Frequency of sodium checks.