12.03 Magnesium Sulfate

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Study Tools



  1. Used as an anticonvulsant in the pregnant patient
    1. Decreases risk of preeclampsia from turning into eclampsia
  2. Has been used as a tocolytic, but research shows there are other more effective options
  3. May suppress uterine contractions in the laboring patient

Nursing Points


  1. If given in an actively seizing patient, it is an emergency.  
    1. IV bolus given
    2. IM injections
    3. Then continuous IV infusion.
  2. Given in a preeclamptic patient to prevent seizure
    1. May be continued up to 24 hours postpartum


  1. Closely monitor mag levels
    1. Normal serum mag level is 1.5-2.5 mEq/L
    2. Target therapeutic range for this indication is 2.5-7.5 mEq/L
    3. Mag over 12 mEq/L can be fatal
  2. Closely monitor vitals per protocol/order set
    1. Hypotension
  3. Closely monitor deep tendon reflexes, respiratory function, heart monitor
    1. Patellar reflex = legs hanging over bed, use reflex hammer to hit the quadricep tendon, do it on both legs and rate.  Suppressed reflex can be a sign of impending respiratory arrest!
      1. 0 – no response
      2. 1 –  sluggish
      3. 2 – normal
      4. 3 – more brisk, slightly hyperactive
      5. 4 – brisk, hyperactive
    2. Call if RR is less than 12/min
    3. Check RR + reflex before IV doses.  Reflex MUST be present and RR greater than 16 before each IV dose (unless hospital policy reflects otherwise).
  4. Watch renal function on BMP or CMP and urinary output (med eliminated by kidneys

Therapeutic Management

  1. Titrating magnesium based on assessment findings
  2. Calcium gluconate easily accessible
    1. Antidote for Magsulfate

Nursing Concepts

  1. Pharmacology
  2. Lab values
  3. Safety

Patient Education

  1. Side effects
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In this lesson I will explain the uses of magnesium sulfate and the role in this population.
So I want to go over a few points to help everything click and make sense. Mag sulfate causes vasodilation which causes hypotension and flushing and sweating. I think of it as slowing everything down so respiration become depressed. It is given for active seizures as well as to prevent seizures in a preeclamptic patient. You can refer to the lesson on preeclampsia but remember that’s a patient that has high blood pressure and can become eclamptic, which means they have seized. So mag sulfate is given prophylactically to prevent seizures. This patient will need close monitoring so let’s see what that will look like.
We want to watch for magnesium toxicity so we are going to be closely monitoring mag levels. The target therapeutic range for is 2.5-7.5 mEq/L. Renal function needs to be monitored since the medication is eliminated by the kidneys. Obviously if the kidneys aren’t functioning properly then the mag level can build up and become toxic. So it must be watched. Vital signs are going to be closely monitored. Magnesium has a side effect of hypotension which is great for our patient suffering with preeclampsia but we need to keep assessing the blood pressure. Respirations need to be monitored and let the provider know if the client is breathing less than 12 a minute or whatever the hospital policy asks for. Remember everything slows down and we don’t want respirations to be too low. Closely monitor deep tendon reflexes, respiratory function, heart monitor. Reflexes will be frequently checked. Everything is slowed down so if magnesium levels are too high then we will see diminished reflexes and suppressed reflex can be a sign of impending respiratory arrest!
Our management will include titrating magnesium based on assessment findings. So either keeping the dose going or stopping or reducing if toxicity is occurring. Calcium gluconate should be easily accessible because it is the antidote for magnesium sulfate. Education should be on the side effects. Mag sulfate can make a patient feel miserable. They are flushed, lethargic, weak, have headaches, and hypotensive to name a few so letting them know what to expect before hand can help them be prepared.
Pharmacology, lab values, and safety are the nursing concepts because we are talking about a drug that is going to need lab monitoring and it is all for the safety of the patient.
Our key points for magnesium sulfate are that it is used for the preeclamptic patient to prevent eclampsia from occurring which is when a patient seizes so we are preventing seizures from occurring. The patient will be monitored for magnesium toxicity with frequent labs and reflex checks. Calcium gluconate should be available as an antidote if needed. A few of the side effects are hypotension, headache, lethargy, flushed, weak and can prolongs labor.
Make sure you check out the resources attached to this lesson and review the key points. Now, go out and be your best selves today. And, as always, happy nursing.

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