Hyponatremia: Management

by Amy Sussman, MD

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    00:01 When it comes to the management of our patients with hypotonic hyponatremia, then it's really going to depend on the underlying cause.

    00:10 So in our patients who have hypovolemic hypotonic hyponatremia, what we want to do is correct the intravascular volume with isotonic fluid.

    00:19 By doing that we will release the stimulus for ADH.

    00:23 So typically in that situation, we want to give our patients isotonic fluids like 0.9% or normal saline.

    00:30 Now, we have to be very careful when doing so because remember, as you start to repeat that patient's vascular volume, you will turn off ADH.

    00:39 And that patient will now have a significant water diuresis.

    00:43 So you will have to follow their serum sodium very closely so that you don't overcorrect those patients.

    00:49 In our patients who have euvolemic hypotonic hyponatremia, it's important to correct the underlying cause, so treating hypothyroidism.

    00:56 Or having patients increase their solute intake.

    00:59 If they are tea and toast dieter, or somebody who has beer potomania.

    01:04 For SIADH, we strive to correct the underlying cause if it's identifiable.

    01:09 But if not, an ADH remains present, there's a couple of things that we have to keep in mind.

    01:14 Number one, we want to free water restrict our patients.

    01:17 So that means really reducing water intake, and that's all hypotonic fluids to somewhere between 0.8 and 1.2 liters of water daily.

    01:27 We want to increase their solute intake.

    01:29 Remember, by increasing solute intake, we increase our osmolar generation.

    01:34 And the more osmoles we make then the more water we can excrete, because of that obligate osmolar excretion.

    01:43 We can give our patients things like loop diuretics.

    01:46 That's going to abolish the medullary gradient, and that will help us also excrete more free water.

    01:52 And then finally, we can give our patients V2 receptor antagonists.

    01:55 Medications like conivaptan or tolvaptan, which directly antagonize V2 receptors.

    02:01 Now, they're available, but they are costly.

    02:03 And it's something that we can use in our patient population.

    02:06 In our hypervolemic hypotonic hyponutrimic patients, remember they have total body sodium access or ECB access.

    02:14 So we want to manage those patients with diuretics.

    02:16 And we also want to fluid restrict them as well.

    02:20 Now, there is something I want you to keep in mind when it comes to correcting patients who have chronic hypotonic hyponatremia.

    02:26 That means that they've been hyponatrimic for greater than 48 hours period of time.

    02:31 That sodium correction should never exceed greater than 8 milliequivalents within a 24 hour period of time.

    02:37 If it does, that patient can be at risk for osmotic demyelination syndrome.

    02:43 We'll talk about that in just a moment.

    02:45 Alternatively, what I do want to tell you is that if the patient is symptomatic, and they have life threatening seizures because of cerebral edema.

    02:52 It is okay to raise their serum sodium rather quickly by about four to six milliequivalents to get them out of the danger zone with hypertonic saline.

    03:00 Now, let's review what happens with osmotic demyelination syndrome.

    03:05 Just to remind us what happens in the situation of hyponatremia.

    03:09 Remember, water is going to be primarily distributed to the intracellular fluid volume.

    03:14 Now that's fine, but when it comes to our neuronal cells, they are enclosed by a rigid calvarium.

    03:21 Therefore, when they expand, patients will experience cerebral edema.

    03:25 They might feel nauseated, they might vomit or have confusion because of that cerebral edema.

    03:31 And our bodies being elegant as they are have that adaptive mechanisms.

    03:35 So acutely, we will use things like sodium, potassium, and chloride to the extracellular fluid volume, water follows and shrinks those cell volumes down to the normal size.

    03:45 If this is happening chronically, meaning greater than 48 hours, then we start to lose organic osmolytes into the extracellular fluid volume.

    03:52 Again, water follows.

    03:54 So it brings our cells back to the normal volume.

    03:57 Now, let's think about what happens if we all of a sudden try to restore patient's serum osmolality back to the normal.

    04:04 So if we have something that is hypertonic to their plasma osmolality, then what's going to happen? Water is going to move from that intracellular compartment to the extracellular fluid compartment.

    04:17 These cells remember, already have lost organic osmolytes.

    04:21 So they start to shrink even further.

    04:23 And when that happens that stimulates osmotic demyelination.

    04:28 The way that patients manifest is it can happen anywhere from two to three days after the event up to two to three weeks.

    04:34 And they oftentimes will have severe debilitating neurological symptoms, including choreiform movements or even locked-in syndrome.

    04:42 So it's extremely debilitating.

    04:44 And the people who are most at risk are going to be your malnourished patients and females that are typically middle to older age.

    About the Lecture

    The lecture Hyponatremia: Management by Amy Sussman, MD is from the course Water Balance: Hypo- and Hypernatremia.

    Included Quiz Questions

    1. Normal saline (0.9% NaCl)
    2. Hypertonic saline (3% NaCl)
    3. Half-normal saline (0.45% NaCl)
    4. Hypotonic saline (0.3% NaCl with dextrose)
    1. Water restriction
    2. ADH antagonist
    3. Aldosterone antagonist
    4. SSRIs
    5. Salt restriction

    Author of lecture Hyponatremia: Management

     Amy Sussman, MD

    Amy Sussman, MD

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