Med-Surg Endocrine System, part 10: Diabetes Insipidus and SIADH

by Cathy Parkes August 01, 2020

Full Transcript

Alright, in this video we are going to talk about diabetes insipidus, as well as SIADH. These are two very important topics. If you happen to be following along with cards, I'm on card 23, and you'll notice the next four cards, there's a lot of bold and red text on them, because there are several very important nursing concepts for you to know related to these disorders.

So both of these disorders have to do with ADH, either too much ADH, not enough ADH, or the organs in your body aren't responding appropriately to ADH. So let's do a quick review of ADH, and if you want more details about ADH, I did make a whole other video about it. But if you recall, ADH is released by the posterior pituitary gland in response to low blood volume in the body, low blood pressure, or to hypernatremia, or increased blood osmolarity. So if the body senses any of these three things, it will release ADH from the posterior pituitary gland, which will cause the kidneys to reabsorb more water, which helps to bring up that blood pressure, bring up that blood volume, and dilute the blood so that the blood osmolarity is back to a normal level.

So with diabetes insipidus, we have one of two things going on. We may have neurogenic diabetes insipidus, which means that there is some kind of injury or tumor in the hypothalamus or the pituitary gland such that insufficient ADH is being released from the posterior pituitary gland. So if the posterior pituitary gland is not releasing enough ADH, the kidneys aren't getting the signal to reabsorb that water. So that is neurogenic diabetes insipidus.

The other thing we may have going on is something called nephrogenic diabetes insipidus. So in this situation, the posterior pituitary gland is doing its job fine. It's releasing ADH. But there's some problem in the kidneys and they are not responding appropriately to that signal. Right? They're getting the ADH but they're kind of like, "Ehh." They're not reabsorbing more water. This may be due to some kind of kidney infection, or maybe the kidneys have been damaged due to nephrotoxic medications. But this is called nephrogenic diabetes insipidus.

So in terms of signs and symptoms of diabetes insipidus, the key symptom is that the patient will have large amounts of dilute urine. So we're just dumping water. We're just peeing out tons of dilute urine. We're not reabsorbing that water as we should be. The patient will exhibit polydipsia, so this is where they have excessive thirst. And one way that I remember this symptom, if you look at the word diabetes insipidus, diabetes inSIPidus will make you want to SIP more water, because you're super thirsty. Other signs and symptoms include dehydration, hypotension, and anorexia. So in terms of labs, labs are definitely going to be important to know. The urine, like we talked about, is going to be very dilute. So the specific gravity of the urine will be very low, or under 1.005. Also the osmolarity of the urine will also be very low, because it's very dilute. So it will be under 200, and then we would expect kind of decreased sodium levels in the urine as well. In the blood though, that's a totally different story. Because we're getting rid of all those fluids, the blood's going to be really concentrated, so the serum, or blood osmolarity is going to be over 300, and the sodium levels are also going to be really high, so we're going to see hypernatremia.

In terms of diagnosis of diabetes insipidus, we can do a water deprivation test to test the ability of the kidneys to concentrate urine. We can also do a vasopressin test. So vasopressin is essentially the same as ADH. And if we give the patient vasopressin, we would expect their kidneys to reabsorb water. If their kidneys don't do that, then we know it's a problem with the kidneys and we have nephrogenic diabetes insipidus. If we give the patient vasopressin and their kidneys do do their job and reabsorb water, then we know it was an issue with the pituitary gland not producing enough ADH. And if that is the case, then we can provide medications such as vasopressin or desmopressin, which you can find on Pharm card 110 in terms of getting more information about those medications.

Alright. So in terms of nursing care, when a patient has diabetes insipidus, we're definitely going to want to monitor the patient's eyes and nose, as well as their urine specific gravity and their daily weight.

Alright. Let's move on to syndrome of inappropriate ADH, or SIADH. With SIADH, we have excess release of ADH from the posterior pituitary gland due to a brain tumor, head injury, meningitis, or because of a medication. So even though the blood is very dilute, the posterior pituitary gland still releases ADH, even though it should not. So because it's releasing all this extra ADH inappropriately, it's causing the kidneys to reabsorb more water. So signs and symptoms of SIADH will include a very small amount of very concentrated urine. And then we'll have signs and symptoms of fluid volume excess because we have all this extra fluid being reabsorbed. So the patient may exhibit signs and symptoms such as tachycardia, hypertension, crackles, jugular vein distention, as well as weight gain. They may also complain of a headache, weakness, and muscle cramping. And then they may also exhibit confusion because we have hyponatremia due to all this dilution, and that can cause the patient to be confused. So one way to remember what SIADH does, if you look at the first two letters of that, S-I, you can think of super inflated, and that's basically what happens. When you have SIADH, you reabsorb all this extra fluid, and you are super inflated.

Alright. In terms of labs, we're going to have, basically, the exact opposite as we saw with diabetes insipidus. So the urine with SIADH will be super concentrated. So the urine specific gravity will be elevated. It will be over 1.03, and the urine osmolality or osmolarity will also be increased because it's so concentrated the blood or the serum will be a completely different story. It will be very dilute, so the serum osmolality will be decreased. It will be under 270 and we'll see hyponatremia because the sodium is diluted with all this extra fluid volume. In terms of treatment, we're definitely going to give the patient diuretics to try to get rid of some of this excess fluid. We can also give them a vasopressin antagonist, and then we can also give them hypertonic saline to help bring up the sodium levels and allow for those electrolyte levels to be more in balance. In terms of nursing care, again, we're going to want to monitor the patient's eyes and nose, we're going to weigh our patients daily, and we're going to restrict fluids and replace sodium as ordered by the provider. We're going to monitor for fluid volume excess. So if we have too much fluid volume overload, we can end up with pulmonary edema, which is life threatening. So we're definitely going to want to monitor for that. And then we're going to want to continually monitor the patient's neurologic status because of the confusion that can result from hypernatremia, and we're also going to need to implement seizure precautions, because hypernatremia can result in seizures if it gets too bad.

Alright. So hopefully that was useful in terms of a review of diabetes insipidus, and SIADH. If you appreciated this review, be sure to like our video and subscribe to us here. Take care.


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