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In this lesson, we'll go over the medication magnesium sulfate, sometimes referred to as simply mag sulfate, and all of its effects, including indications, precautions and contraindications, and adult dosages. At the end of the lesson, we conclude our look at STEMI.

Magnesium sulfate affects the SA node by slowing down its impulse rate, and it also reduces the automaticity in partially depolarized cells. Magnesium sulfate causes vasodilation, and when administered rapidly, can also create hypotension.

Magnesium Sulfate Indications

Now let's take a look at magnesium sulfate indications.

Magnesium sulfate is effective as an anticonvulsant and antiarrhythmic and is used to treat polymorphic ventricular tachycardia with a pulse

Magnesium sulfate is recommended for use in cardiac arrest only in cases of torsade's de pointes or suspected cases of hypomagnesemia. Whenever you see these conditions present, this is when you would use magnesium sulfate.

Magnesium sulfate is also indicated for life threatening ventricular arrythmias due to digitalis toxicity.

Pro Tip: Digitalis toxicity (DT) occurs when you take too much digitalis (also known as digoxin or digitoxin), a medication used to treat heart conditions. Signs of toxicity include nausea, vomiting, and an irregular heartbeat.

Magnesium Sulfate Precautions and Contraindications

Magnesium sulfate is contraindicated for patients with central nervous system depression or hypermagnesemia. And caution must be taken when used on patients with renal impairment as well.

Routine administration of magnesium sulfate in hospitalized patients with acute myocardial infarction is also not recommended.

Adult Dosage of Magnesium Sulfate

Now let's look at the adult dosage of magnesium sulfate.

The administration of magnesium sulfate in pulseless cardiac arrest is 1 to 2 grams (or 2 to 4ml) of a 50 percent solution diluted in 10ml of D5W or normal saline via slow IV or IO push over 5 to 20 minutes.

When dealing with adult patients with torsade's with a pulse or acute myocardial infarction with hypomagnesemia, a loading dose will be required of 1 to 2 grams mixed in 50 to 100ml of D5W or normal saline via IV over a 5 to 60-minute period.

This should then be followed with a .5 to 1 gram per hour IV titrated to control torsade's de pointes.

A Word About STEMI

We provided an introduction into ST-Elevation Myocardial Infarction (STEMI) in the last Word section of the Lidocaine lesson. In this Word, we'll dig a little deeper into STEMI.

Early Reperfusion Therapy

Healthcare providers should rapidly identify patients with STEMI and quickly screen them for indications and contraindications to fibrinolytic therapy by using a fibrinolytic checklist if appropriate.

The first qualified physician who encounters a patient with STEMI should interpret or confirm the 12-lead ECG, determine the risk vs. benefit of reperfusion therapy, and direct administration of fibrinolytic therapy or activation of the PCI (percutaneous coronary intervention) team.

Early activation of PCI can occur with established protocols. The following time frames are recommended by the American Heart Association:

  1. For PCI, the goal for ED door-to-balloon inflation time is 90 minutes. In patients presenting to a non-PCI-capable hospital, the time from first medical contact to device should be less than 120 minutes when primary percutaneous coronary intervention is considered.
  2. If fibrinolysis is the intended reperfusion, an ED door-to-needle time (needle time relates to the beginning of infusion of a fibrinolytic agent) of 30 minutes is the goal that's considered the longest acceptable time. It goes without saying that systems should strive to achieve the shortest time possible.
  3. Patients who are ineligible for fibrinolytic treatment should be considered for transfer to a PCI facility regardless of the delay. The system should strive for a door-to-departure time of 30 minutes after a transfer decision has been made.

Adjunctive treatments can also be indicated.

Use of PCI

The most frequently used form of percutaneous coronary intervention is coronary intervention with stent placement. Optimally performed primary PCI is the preferred reperfusion strategy over fibrinolytic administration.

Rescue PCI should be used early after fibrinolytics in patients who may have persistent occlusion of the infarct artery, although this term has been recently replaced by the term pharmacoinvasive strategy. PCI has been shown to be superior to fibrinolysis in the combined end points of death, stroke, and reinfarction in many studies for patients presenting between 3 and 12 hours after onset.

However, these results have been achieved in experienced medical settings involving skilled healthcare providers at skilled PCI facilities – those performing more than 200 PCl's for STEMI with cardiac surgery capabilities.

Considerations for the use of PCI include the following:

  1. PCI is the treatment of choice for the management of STEMI when it can be performed effectively with a door-to-balloon time of less than 90 minutes from first medical contact by a skilled provider at a skilled PCI facility.
  2. Primary PCI can also be offered to patients presenting to non-PCI-capable healthcare centers if PCI can be initiated promptly within 120 minutes from first medical contact. The TRANSFER AMI (Trial of Routine Angioplasty and Stenting After Fibrinolysis to Enhance Reperfusion in Acute Myocardial Infarction) trial supports the transfer of high-risk patients who receive fibrinolysis in a non-PCI center within 12 hours of symptom onset to a PCI center within 6 hours of fibrinolytic administration to receive routine early coronary angiography and PCI if indicated.
  3. For patients admitted to a hospital without PCI capabilities, there may be some benefit associated with transfer for PCI versus administration of on-site fibrinolytics in terms of reinfarction, stroke, and a trend to lower mortality when PCI can be performed within 120 minutes of first medical contact.
  4. PCI is also preferred in patients with contraindications to fibrinolytics and is indicated in patients with cardiogenic shock or heart failure complicating myocardial infarctions.