Mag sulphate with preeclampsia

Twinmom06, ASN, APN · Nov 28, 2011

I was on mag and blew up like a balloon - not sure if it is from the mag directly or all the fluids they pumped in - at any rate I actually had bigger ankles when I was discharged than when I went in LOL!

I realize it doesn't help your answer but it is the truth!

klone, MSN, RN · Nov 28, 2011

MgSO4 is not a diuretic. Having a baby is generally a diuretic, and within a couple days of giving birth, the woman usually starts to let go of all her extra fluid.

maelstrom143 · Nov 28, 2011

I am a new nurse who just started working in OB. I had a patient on mag after she had a c section. We had to monitor her urine output every hour. My preceptor said that when the mag "starts working" she will begin to diurese and get rid of "all that fluid she is holding". So, my question...does magnesium somehow cause a reduction in urine output, and if so, why? And then, why should her output increase after she has been on the mag a while? I can't find the answer anywhere, not even from my preceptor!

Mag is usually used in patients w/eclampsia or pre-eclampsia if talking OB. I have used it once on one of my patients. Usually used to decrease risk of seizure activity and (per my preceptor at one facility) helps rid the body of toxins accumulated during pregnancy that can precipitate eclampsia (I am not sure of the mechanism). Since mg sulfate is excreted through kidney function, the urine level (I&O) needs to be strictly monitored. A decrease in urine output increases the risk of mag toxicity and pulmonary edema.

Mag sulfate causes vasodilation. If kidneys functioning properly and vasodilation occurs, mayhap this would increase urine output? On the other hand, one of mag sulfate's side effects can be urinary retention, in which case you can end up w/edema and increased risk of mag toxicity and/or pulmonary edema (same as mentioned above).

Here is another article I read on the subject: http://www.jfponline.com/Pages.asp?AID=3131

Just my :twocents: Haven't had any OB patients in a couple years, though.

obs03_MagnesiumPre-eclampsia_081711.pdf

ERNurse752, RN · Nov 28, 2011

I was on mag for preterm labor and was taken off of it after a week because I gained 10 lbs of fluid. I was on it again a couple weeks later after my c section (breech twins), this time for preeclampsia, and blew up like a balloon...which was also probably from all the fluids I got.

SanFranSRNA · Nov 28, 2011

Magnesium sulfate has many indications. In OB setting, I use magnesium sulfate for tocolytic and seizure prophylaxis. Although the use of magnesium sulfate for the purpose of tocolysis is falling out of favor, the use of seizure prophylaxis is still popular. Magnesium increases the seizure threshold in the case of preeclampsia. Magnesium is excreted through the kidney and renal insufficiency can lead to magnesium toxicity. Therefore, UOP is routinely monitored every hour.

In regarding to your original question, I don't think that magnesium has a direct effect the production or excretion of urine.

cosmicmama, BSN, RN · Nov 29, 2011

Did she get a lot of Pitocin? That will sometimes cause fluid retention. Usually when my mag patients aren't putting out a lot (they are on pit the whole time they are on mag), they diurese like crazy once the pitocin is out of their systems. Just a thought.

hmorgan · Nov 30, 2011

Thanks everybody for the input! Much thanks!

strn96 · Dec 6, 2011

The magnesium doesn't typically cause diuresis, but as mentioned above, closely monitoring UO is very important b/c both magnesium and preeclampsia affect kidney function. Typically, the eventual diuresis takes place after delivery and is a result of delivery (remember that delivery is when preeclampsia starts to improve), not of magnesium. You may see an increase in UO before delivery, but that is usually due to increased fluid intake (IV), not the mag.

Hushi05 · Dec 7, 2011

Mag sulfate in postpartum preeclamptics is for seizure prophylaxis. It is a *mild* vasodilator which accounts for the slight lowering of BP and perhaps mild increase in urine output, but the real reason for the diuresis is that the preeclampsia (a vasospastic condition) is resolving. Mag sulfate is not given to *cure* preeclampsia. It is "working" if the patient does not have a seizure. Monitoring urine output is a way to determine if the preeclampsia is resolving and also to keep an eye on a patient who could become mag toxic if she is not excreting it through her kidneys.