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Hypomagnesemia & Hypermagnesemia

This week we will be focusing on the fluid and electrolyte imbalances hypomagnesemia and hypermagnesemia. We will cover causes, signs and symptoms, treatment, and nursing considerations for these imbalances.

If you are already read the post on hypocalcemia and hypercalcemia, then this information should come fairly naturally to you; there are a lot of similarities between the manifestations of the imbalance of calcium and magnesium.

Once you finish reading this post, be sure to download this PDF cheat sheet that highlights the “need to know” information of hypomagnesemia and hypermagnesemia.

As always, let’s break down the words hypomagnesemia and hypermagnesemia.

Hypo= low mag= magnesium emia= in the blood

Hyper= high mag= magnesium emia= in the blood

The normal lab level for magnesium is 1.3-2.1 mEq/L.

Therefore, hypomagnesemia= <1.3 mEq/L and hypermagnesemia is >2.1 mEq/L.

Magnesium

Most magnesium is stored in the bone and cartilage and is regulated by the kidneys and intestines.

Magnesium is a membrane stabilizer and has an important role in the following:

• Skeletal muscle contraction
• Blood coagulation
• Carbohydrate metabolism
• Cell growth

You will see that most of the issues that occur with an imbalance with magnesium is related to its involvement in skeletal muscle contraction.

Magnesium is necessary for the secretion of parathyroid hormone (PTH) from the parathyroid. Due to this relationship, hypomagnesemia can cause too little parathyroid hormone to be secreted. This can cause a secondary condition of hypocalcemia.

As a review, this is how PTH normally works in order to increase calcium levels in the blood:

Magnesium plays a key role in the contraction and relaxation of muscle.

Too little magnesium causes nerve transmission to occur more easily without much stimulation. Hypomagnesemia could be viewed as “too much contraction”.

Too much magnesium causes nerve transmission to occur less often and require more stimulation. Hypermagnesemia could be viewed as “too much relaxation”.

Hypomagnesemia

<1.3 mEq/L

Causes:

• Malnutrition/dietary- if not enough magnesium rich foods are eaten, then over time there will be a magnesium deficit.

• Intestinal disease- in intestinal diseases such as Celiac or Crohn’s disease, the intestines are not able to properly absorb the magnesium that is present in food. Over time, this reduced absorption of magnesium in the intestines can lead to hypomagnesemia.

• Alcoholism- alcohol has a diuretic effect, therefore increased amounts of magnesium are excreted in the urine leading to hypomagnesemia.

Signs/symptoms:

*Remember, decreased magnesium= increased nerve impulse transmission=increased muscle contraction. “too much contraction”*

• Hyperactive DTRs- the deep tendon reflexes will be overactive and the patient could experience severe muscle contractions and tetany (increased muscle contraction)

• Chvostek’s sign– this is a twitching of facial muscles whenever the patient’s face is lightly tapped over the facial nerve. This will be present if hypomagnesemia is accompanied by hypocalcemia.

• Trousseau’s sign– this is a carpal spasm that occurs when a blood pressure cuff is inflated on the arm. This will be present if hypomagnesemia is accompanied by hypocalcemia.

• Seizures- increased nerve impulse transmission can cause this “uncontrolled electrical disturbance in the brain” (MayoClinic)

• Psychological alterations- psychosis or confusion can occur due to the increased nerve impulse transmission. The change in psychological state can come in many different forms.

• Paresthesia- an abnormal sensation of numbness and tingling due to increased nerve impulse transmission

• Decreased intestinal peristalsis, constipation- this one may seem a little counterintuitive considering the involvement of smooth muscle in intestinal peristalsis. However, magnesium draws water into the intestines allowing stool to pass more easily. If there is not enough magnesium present, then the stool may become hard and more difficult to pass, thereby causing constipation.

Treatment:

• IV magnesium- if the magnesium deficiency is severe, then IV magnesium may be utilized to increase the magnesium levels. *Patient should be closely monitored when this medication is infusing*

• Oral magnesium- if the magnesium deficiency is mild, then oral magnesium may be utilized to increase the magnesium levels. Encourage patients to consume foods that are high in magnesium (green leafy vegetables, fruits, nuts, vegetables, etc.)

Hypermagnesemia

>2.1 mEq/L

Causes:

• Dietary- too much magnesium intake, antacids– too much magnesium intake in the form of magnesium supplements or antacids can cause hypermagnesemia to occur.

• IV magnesium infusion- hypermagnesemia can occur easily during an IV magnesium infusion if the patient is not carefully monitored.

• Kidney disease- if kidney disease is present, then magnesium will not be excreted in the urine as it normally is; this causes hypermagnesemia to occur.

Signs/symptoms:

*Remember, too much magnesium= decreased nerve impulse transmission=decreased muscle contraction. “too much relaxation”*

• Hypoactive or absent DTRs, muscle weakness- the deep tendon reflexes will be hypoactive or absent and the patient may experience severe muscle weakness (decreased muscle contraction)

• Bradycardia, vasodilation, hypotension- the cardiac alterations in hypermagnesemia can be fatal. As mentioned, magnesium “relaxes” the body. In this case it is relaxing things a bit too much and causing vasodilation which causes hypotension. One sign you may notice is that the patient is flushed in their face due to the vasodilation.

• Drowsy/lethargic- the neurons in the brain will be experiencing decreased nerve impulse transmission so the patient may exhibit drowsiness.

• ECG changes- prolonged PR interval, widened QRS complexes

• Decreased respiratory rate- this is due to the decreased muscle contraction of the respiratory muscles. The respiratory muscles may become weakened to the point of respiratory failure.

Treatment:

• IV fluids- magnesium free IV fluids may be administered to help reduce magnesium levels if the patient does not already have kidney failure.

• Loop diuretics- diuretics such as furosemide (Lasix) will encourage urination and excretion of excess magnesium. Ensure kidney function before administering and continue to monitor urine output during utilization of loop diuretics. This treatment should be coupled with adequate IV fluid replacement to prevent further electrolyte imbalances.

• IVP calcium gluconate- calcium gluconate will not lower the levels of magnesium, but it will help with the neuromuscular and cardiac manifestations associated with hypermagnesemia.

• Dialysis- if the hypermagnesemia is severe, then dialysis may need to be initiated

Nursing Considerations:

Implement seizure precautions for patients with hypomagnesemia.

• Quiet room with dim lights, keep noise to a minimum
• Oxygen and suction at bedside
• IV access
• Bed in lowest position, mattress on floor beside the bed

Assess kidney function of a patient receiving IV magnesium. If the patient has a decreased in urinary output during the infusion, the infusion should be stopped; severe hypermagnesemia could occur if the infusion continues running.

Assess DTRs hourly in a patient who is receiving IV magnesium to ensure that hypermagnesemia does not result. If DTRs become weakened or absent stop the infusion and notify the physician.  

Monitor cardiac function closely of a patient with hypermagnesemia. HIGH risk for cardiac arrest if severe levels. Ensure cardiac monitoring has been initiated.

Administer IVP calcium gluconate slowly (5-10 minutes depending on the dose).

If you haven’t already checked out my other posts on the other fluid and electrolyte imbalances, you can click the links below to be taken to each of the individual posts. Each of them have a downloadable cheat sheet so be sure to grab those!

• Hypokalemia & hyperkalemia
• Hypocalcemia & hypercalcemia
• Hypophosphatemia & hyperphosphatemia
• Hyponatremia & hypernatremia

As always, feel free to contact me if you have any questions!

Happy Nursing!