Magnesium Sulfate

Magnesium Sulfate

Electrolyte, Antiarrhythmic, Smooth Muscle Relaxer

December 29, 2023

Welcome to the final installment of UH EMS-I’s Pharmacy Phriday for the year 2023. As we close out this year’s series, we look at another call from the health EMS archives to introduce our topic of review.

Our squad was dispatched to a mid-morning call for a 78-year-old female in respiratory distress for the past day. The squad arrived to find the patient in obvious distress with labored breathing, audible wheezes, tripod positioning, and the inability to speak more than one or two-word responses. The patient informed the crew of a history of asthma and COPD, as well as a cardiac history. The patient admitted the use of her personal inhaler several times without any relief and was wearing home oxygen via a nasal cannula at 4 lpm (normal for the patient). The patient’s initial vitals were a BP of 160/96, pulse of 89, respiratory rate of 28 and labored, and an SPO2 of 80% on the 4 lpm of oxygen. 

Crews provided treatments that included an increase in oxygen and two DuoNeb treatments with no changes in the patient’s condition. SOLU-MEDROL was also administered appropriately (a treatment that will not provide immediate results yet is still a very important treatment discussed in an early installment this year). Due to the patient’s age and previous cardiac condition, Epinephrine was not considered. What other treatments within the UH protocol could be considered?

Oxygen, beta-agonists, bronchodilators, and steroids are mainstays in the treatment of respiratory distress. Though not required in every respiratory distress call, Magnesium Sulfate may be considered since Magnesium can aid in the relaxation of constricted bronchioles, especially for those patients who do not respond to first-line treatments.

Magnesium is a salt that has many effects on the body. In previous installments, we discussed Magnesium’s role in cardiac calls (Torsades) and in obstetrics cases (pre-eclampsia and eclampsia). Now, we consider Magnesium Sulfate for respiratory calls. For these cases, high doses of Magnesium Sulfate can be used to take advantage of the pharmacologic effects of the medication, physiologically a calcium channel blocker, to assist in treating some of our patients by causing smooth muscle relaxation of the bronchioles.

Within the UH protocols, Magnesium Sulfate is indicated in respiratory distress and bronchoconstriction with minimal relief from other treatments. The dosing in such cases is 2 grams IV/IO over 20-60 minutes. In the upcoming 2024 protocol updates, the dosing of Magnesium Sulfate is being simplified and will direct an infusion over 20 minutes in such cases. (See the chart below for the simplified standards for Magnesium administration coming in the 2024 protocols). The pediatric dose is referenced in the “Pediatric Respiratory Distress Lower Airway” protocol and is 50 mg/kg IV/IO to a max of 2 grams.

Contraindications to administering Magnesium Sulfate include shock, dialysis patients, and the presence of third-degree heart blocks. Possible side effects such as flushing, sweating, and drowsiness can occur. Patients should be monitored throughout administration for these, as well as more concerning respiratory depression, bradycardia, arrhythmias, and hypotension. 

In the case mentioned above, an IV infusion of 2 grams of Magnesium Sulfate was started en route to the Emergency Department. The patient arrived in some distress but with an improved respiratory rate of 24 and an SPO2 of 99%. Great job!!

Have a safe New Year’s weekend! See you in 2024!!


The UH EMS-I Team

University Hospitals

August 4, 2023

Magnesium Sulfate in OB Emergencies

Welcome back to UH EMS-I’s Pharmacy Phriday.  In an earlier edition, we discussed the use of Labetalol in cases of Eclampsia and Preeclampsia.  In this installment, we will review one of the primary medications for such cases.  Do you know the medication?  Do you know the proper dosing for each? We begin the review with actual case presentations from our UH records.


In our first case, EMS was dispatched to the report of a 22-year-old female, 32 weeks pregnant, not feeling well.  The patient complained of feeling dizzy and experiencing a headache (described as 10/10 on the pain scale), vision loss in her right eye, and severe abdominal pain on her right side (8/10 on the scale).  Her vitals were as follows; BP 178/81; Pulse 104; Respirations 20; SpO2 95%; Glucose 94; and a GCS of 15.  Following protocol, the squad administered an IV infusion of 4 grams of Magnesium Sulfate over 20 minutes.  The patient’s blood pressure resolved to 135/90 but did still complain of pain.  Medical direction was contacted and ordered fentanyl for the patient’s pain.

In case #2, EMS was dispatched to the report of a 29-year-old female complaining of a severe headache, abdominal pain, shortness of breath, nausea, and vomiting.  During the exam, EMS found the patient to be two weeks post-partum. She explained she had a history of preeclampsia with a previous pregnancy.  Her vitals were a BP of 161/125; Pulse 66; Respirations 50; SpO2 100%; EtCO2 23. After contacting medical direction, the patient was administered 4 grams of Magnesium Sulfate over 20 minutes as well as 10 mg of Labetalol.


In the final case, EMS was called to a local business for the report of a pregnant female having a seizure.  Upon arrival on scene, the EMS crew found the female unconscious and actively seizing.  Though a full history could not be obtained, the crew was able to determine that the patient was apparently on a blood pressure medication due to her pregnancy and had a previous seizure during this pregnancy.  An IV was established, O2 was administered, and the monitor was applied.  A BP of 136/71 and a pulse of 100 were documented.  The crew administered 4 grams of Magnesium Sulfate over 4 minutes, with the seizures resolving at the end of the administration of the medication.

A major cause of mortality and morbidity in the pregnant patient is hypertension which can be an early sign of and lead to preeclampsia or eclampsia.  Such OB emergencies are very serious, threatening the lives of both the mother and fetus.  Though such conditions can resolve following delivery, they can also be seen in the post-partum setting as witnessed in case #2 above. 

Magnesium sulfate is the preferred treatment in cases of preeclampsia and eclampsia.  It is a salt that breaks down into Magnesium and sulfate when administered.  The Magnesium is an essential element in numerous biochemical reactions.  In a previous Pharmacy Phriday, we discussed Magnesium and its effects on the heart.  In OB emergencies such as preeclampsia and eclampsia, Magnesium acts as a depressant on the CNS and a smooth muscle relaxant that can reverse some of the vasospasm associated with preeclampsia and eclampsia.  The goal in the treatment is resolving the hypertension, preventing or stopping seizures, and maintaining placental perfusion.

Magnesium Sulfate is indicated in the “Obstetrical Emergencies Pre and Post-Partum” protocol as the first line medication for a pregnant female seizing.  In the case of preeclampsia, the medication is indicated for the patient experiencing symptoms such as edema, a headache, visual disturbances, and epigastric pain with a systolic blood pressure of >140 and/or a diastolic of >90. 

The dose of Magnesium Sulfate is 4-6 grams in both cases but note the difference in the timing of administration.  In cases of actual seizures, the medication is given as a rapid infusion over 2-4 minutes.  In cases of preeclampsia, the medication is given over a 20-60 minute time frame. 

Contraindications to the use of Magnesium Sulfate include heart blocks, shock, and a sensitivity to the medication.  The most immediate danger or side effect to its use is respiratory depression. The paramedic should monitor the patient’s EKG, vital signs, and respiratory effort during administration.  If respiratory depression is noted, the provider should provide appropriate ventilatory support and call medical direction to consider Calcium Chloride as a possible antidote (hypermagnesemia). 

Have a great day, and stay safe!


The UH EMS-I Team

University Hospitals

May 26, 2023

Dear colleagues:

Welcome back to UH EMS-I’s Pharmacy Phriday.  Over the past few installments, we have reviewed some of the medications within the protocols that directly affect and treat heart arrhythmias.  Last week we reviewed Amiodarone, a medication used for ventricular arrhythmias.  In this edition, we will review another antiarrhythmic medication that is typically specific to one rhythm or a specific condition.  Let’s begin by looking at a few cases from the UH archives on Health EMS. 

The first case involves a 78-year-old male that called 911 because he had not been feeling well throughout the day.  The patient was found sitting in his chair by EMS providers, alert and oriented. The physical exam of the patient was unremarkable, and vital signs were B/P 130/74, pulse 110, respirations 18, and a SpO2 of 99% on room air.  The initial rhythm on the EKG was sinus tachycardia. While EMS continued their assessment, the patient became short of breath with obvious dyspnea. An EKG was repeated, and the patient was found to be in Torsades de Pointes.  Vitals were repeated as well and remained stable.  What actions would you consider at this point? What medication and dose come to mind? 

The second case involves a 65-year-old male that complained to his wife of sudden chest pain while at a football game.  Shortly after the complaint, the patient became unconscious.  Upon arrival of EMS personnel, the patient was found to be in cardiac arrest. CPR was initiated, the monitor applied, and the initial rhythm was recognized as Ventricular Fibrillation.  The patient was immediately defibrillated at 200 joules, and CPR was continued.  After gaining vascular access, 1mg of epinephrine was administered.  The second rhythm check revealed Torsades de Pointes, and the patient was again defibrillated, this time at 300 joules.  CPR was continued, and the rhythm remained the same. What actions would you consider next?  What medication and dose are you considering?

In both cases, 2 grams of Magnesium Sulfate was administered with positive results! Why was Magnesium Sulfate helpful in these instances?

Magnesium is a cation (positively charged ion) that has many effects within the body.  It plays an essential role in the movement of ions across cell membranes, a process that is important to nerve impulse conduction, muscle contraction, and in the heart, a normal rhythm.  The medication has the pharmacologic effect of acting as a calcium channel blocker, which then affects the movement of sodium and potassium, thus affecting cellular action potential, depolarization, repolarization, and physiologic response of muscle cells in the body.  (For a better understanding of this process, follow HERE.)  

In the heart, the excitability of the cells is diminished by Magnesium Sulfate, reducing arrhythmias, especially Torsades de Pointes.  Low serum magnesium level is a known cause leading to this arrhythmia. That is why the provider finds in the protocol the use of Magnesium Sulfate administration in a patient with Torsades de pointes or cardiac arrest due to Torsades.  The medication is also suggested in cases of alcoholism or malnutrition due to potentially low magnesium levels in the body. The dosing of Magnesium Sulfate for these cardiac cases is 1-2 grams IV/IO.  In the arrest patient, the administration is as a slow IV push.  In the patient with a pulse, the administration is an infusion over 5-60 minutes. 

Contraindications for using Magnesium Sulfate include:

Side effects can include:

Be sure to monitor your patient, including ECG and capnography, while administering Magnesium Sulfate.  In cases of severe bradycardia, severe respiratory depression, or severe hypotension (signs of magnesium intoxication) following the administration of the medication, Calcium Chloride or Calcium Gluconate can be considered as an antidote (refer to UH’s Cardio Toxic Protocols).

Magnesium Sulfate does have other uses within our UH protocols that include Cardio-Toxic events, eclampsia or pre-eclampsia, and in respiratory distress with asthma or COPD where epinephrine has failed. These uses will be reviewed in upcoming installments of Pharmacy Phriday.

Until the next edition of UH’s Pharmacy Phriday, stay safe! 


The UH EMS-I Team

University Hospitals