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HWN Suggests

Multi-Talented Magnesium Sulfate

On-label, off-label and over-the-counter: Magnesium is one of the simplest medications imaginable, but its mechanisms are still not fully understood...

For repletion in hypomagnesemia, dosing ranges from 1-8mg IV depending on severity. Mild hypomagnesemia can also be treated with PO magnesium oxide (250-500mg). Reduce dose by 50% in patients with renal dysfunction, as the magnesium will be excreted more slowly, and could build up to toxic levels.

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Featured

 Hidden Hypomagnesemia...

Why doesn’t a BMP or CMP come with a magnesium level? And who do you order these magnesiums on? Let’s talk about how hypomagnesemia is more hidden than you think…

 Magnesium: the forgotten electrolyte

Hypomagnesaemia can cause hypokalaemia and hypocalcaemia. It is also associated with hyponatraemia and hypophosphataemia.

 Replace/Correct the Magnesium Deficiency Before Potassium (Hypokalemia)!

Let’s wrap it up. Potassium cannot go from plasma into the cells of the kidney unless the Na-K-ATPase channel is working. Magnesium helps this channel work. So if you don’t have enough magnesium, you can do whatever you want but the Na-K-ATPase pump isn’t going to properly. At the same time the intracellular concentration of potassium is going to remain low. Why exactly? It is not described. Quite frustrating really.

Articles of Interest

Disorders of Magnesium Metabolism: Hypomagnesemia and Hypermagnesemia

Hypomagnesemia is seen in hospitalized and community dwelling subjects. Hypermagnesemia is less common than hypomagnesemia.

Magnesium sulphate in the Emergency Department: an old, new friend

Up to now the use of Mg in the Emergency Department (ED) has entered the daily routine in the treatment of many conditions. However, this is often due to personal experiences and not to codified international guidelines...

Pearl of the Day: Hypomagnesemia

Likely underdiagnosed as levels are rarely drawn.

Resources

Core EM

Hypomagnesemia leads to increased K+ renal wasting and concurrent repletion of these electrolytes should be considered, especially if hypokalemia is refractory.

EMCrit

management of life-threatening hypomagnesemia (e.g. Torsade de Pointes, seizures): Initial loading dose of four grams: 2 grams IV magnesium sulfate over 5-15 minutes. 2 additional grams IV over 30-60 min.

Life in the Fastlane

Normal serum magnesium levels are generally considered to be 0.8 – 1.0 mmol/L. Hypomagnesaemia, defined as a level < 0.8 mmol/L, is associated with QT interval prolongation and an increased risk of ventricular arrhythmias.

Empendium

In patients with asymptomatic hypomagnesemia, administer oral magnesium such as magnesium oxide (in patients with normal GI magnesium absorption). All oral magnesium formulations cause diarrhea (extended-release formulations least commonly), which may worsen magnesium deficiency.

WikEM

Asymptomatic: Oral repletion with magnesium oxide 400mg PO, Magnesium oxide 400mg = 2g of MgSO4. Symptomatic (or no POs): 2g MgSO4 IV over 1 hour

StatPearls

The treatment of patients with hypomagnesemia is based on a patient’s kidney function, the severity of their symptoms, and hemodynamic stability. If a patient is hemodynamically unstable in an acute hospital setting, 1 to 2 grams of magnesium sulfate can be given in about 15 minutes. For symptomatic, severe hypomagnesemia in a stable patient, 1 to 2 grams of magnesium sulfate can be given over one hour. Non-emergent repletion of the adult patient is generally 4 to 8 grams of magnesium sulfate given slowly over 12 to 24 hours. In pediatric patients, the dose is 25 to 50 mg/kg (with a maximum of 2 grams).