Hypomagnesemia

 

Original Editors -Shawn Abraham & Sean Joyce- Students from Bellarmine University's Pathophysiology of Complex Patient Problems project.

Top Contributors - Shawn Abraham, Sean Joyce, Lucinda hampton, Kim Jackson, Elaine Lonnemann, Selena Horner, 127.0.0.1 and WikiSysop  

Definition/Description

Magnesium (Mg) is a principal cation (ie an electrolyte) in the intracellular fluid that is an essential part of many enzyme systems associated with energy metabolism. Hypomagnesemia is an electrolyte imbalance with inadequate levels of magnesium in the bloodstream. Serum magnesium levels are rarely deficient in healthy individuals because magnesium is abundant in foods and water and its excretion through urine is limited by the kidneys. However, certain medical conditions and medications can cause excessive loss of magnesium resulting in deficiency.

Etiology

Hypomagnesemia can be:

• Secondary to decreased intake, as seen in: Starvation; Alcohol use disorder; Critically ill patients who are receiving total parenteral nutrition
• Secondary to the following medications: Loop and thiazide diuretics; Proton pump inhibitors; Aminoglycoside antibiotics; Amphotericin B; Digitalis; Chemotherapeutic drugs, such as cisplatin, cyclosporine
• Induced by gastrointestinal and/or renal losses, including but not limited to the following conditions: Acute diarrhea; Chronic diarrhea (Crohn disease, ulcerative colitis); Hungry bone syndrome (an increased magnesium uptake by renewing bone following parathyroidectomy or thyroidectomy, causing a decrease in serum magnesium); Acute pancreatitis; Gastric bypass surgery.

Epidemiology

The risk of hypomagnesemia depends on multiple characteristics in various healthcare settings, with the following being the latest incidences:

• 2% in the general population
• 10% to 20% in hospitalized patients
• 50% to 60% in intensive care unit patients
• 30% to 80% in persons with alcohol use disorder
• 25% in outpatients with diabetes

There have been no recent studies identifying which age groups are at higher risk of hypomagnesemia.

Characteristics/Clinical Presentation

Patients with symptomatic magnesium depletion can present in many ways. The major clinical manifestations include neuromuscular and cardiovascular manifestations and other electrolyte abnormalities. Specific signs and symptoms are outlined below.

• Electrolyte abnormalities: Hypokalemia; Hypocalcemia
• Neuromuscular: Hyperirritability; Carpopedal spasm; Tetany; Muscle cramps; Muscle fasciculations; Fascial muscle spasms induced by tapping the branches of the facial nerve.
• Neurologic: Vertigo; Nystagmus; Aphasia; Hemiparesis; Depression; Delirium; Choreoathetosis
• Cardiovascular: Ventricular arrhythmias; Torsade de points; Superventricular tachycardia; Enhanced sensitivity to digoxin; Vasomotor changes; Occasionally Hypertension
• Central Nervous System: confusion; delusions; hallucinations; seizures; Abnormal eye movements

Treatment

Magnesium deficiency is commonly encountered in clinical practice. The key is to find the primary cause.

• Asymptomatic patients can be managed with supplements prescribed as outpatients.
• Symptomatic patients need admission and parenteral magnesium. The prognosis for most patients with a reversible cause is excellent.

It is important to treat hypomagnesemia. Dangerously low levels of magnesium have the potential to cause fatal cardiac arrhythmias. Moreover, hypomagnesemia in patients with acute myocardial infarction puts them at higher risk of ventricular arrhythmias within the first 24 hours.

Clinicians, nurses, and pharmacists must coordinate care to find a rapid resolution to magnesium deficiency. This often involves education of the patient, family, and a team approach from the health practitioners.

Patients with hypomagnesemia should be encouraged to eat the following foods:

• Green vegetables, such as spinach
• Beans
• Peas
• Nuts
• Seeds
• Unrefined grains

Diagnostic Tests/Lab Tests/Lab Values

The average adult holds approximately 25 g magnesium. 50% to 60% is found in the bones and most of the rest is found in soft tissue, the remaining less than 1% of magnesium is found in blood serum. Normal serum magnesium levels fall between 0.75 and 0.95 mmol/L. Hypomagnesemia is characterized as serum levels falling below 0.75 mmol/L.

Systemic Involvement

Hypomagnesemia has a systemic link to other electrolyte deficiencies, especially hypokalemia and hypocalcemia.

Hypokalemia has been found to occur in 40-60% of cases of hypomagnesemia cases. This is related to underlying disorders that cause magnesium and potassium losses like diuretic therapy and diarrhea. The mechanism for hypomagnesemia-induced hypokalemia relates to the intrinsic biophysical properties of renal outer medullary potassium channels mediating potassium secretion in the thick ascending limb and the distal nephron.

The mechanism of hypocalcemia is multifactorial. Parathyroid gland function is abnormal, largely because of impaired release of parathyroid hormone. Impaired magnesium-dependent adenyl cyclase generation of cyclic adenosine monophosphate mediates the decreased release of parathyroid hormone. Skeletal resistance to this hormone in magnesium deficiency has also been implicated. Hypomagnesemia additionally changes the heteroionic exchange of calcium and magnesium at the bone surface, causing increased bone release of magnesium ions in exchange for an increased skeletal uptake of calcium from the serum.

Physical Therapy Management (current best evidence)

There are no direct physical therapy interventions for hypomagnesemia. Patient will be referred to physical therapy for treatment of impairments that may be a cause of hypomagnesemia such as decline in muscle strength, fatigue, or abnormal eye movements. (See Clinical Presentation)

Physical therapists can take a team approach with medical management through patient education on:

• Foods high in magnesium
• Importance of following medical recommendations for magnesium intake
  
  

Differential Diagnosis

Hypomagnesemia can be masked as other electrolyte imbalances. Therefore, obtain magnesium levels with other electrolytes (eg, potassium, calcium, phosphorus) when ordering laboratory tests.

• hypocalcemia
• hypokalemia

Case Reports/ Case Studies

1. Bircan I, Turkkahraman D, Dursun O, Karaguzel G. Successful management of primary hypomagnesaemia with high-dose oral magnesium citrate: A case report. Acta Paediatrica [serial on the Internet]. (2006, Dec), [cited April 7, 2016]; 95(12): 1697-1699. Available from: Academic Search Complete.

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2. Daskalakis G, Marinopoulos S, Mousiolis A, Mesogitis S, Papantoniou N, Antsaklis A. Gitelman syndrome-associated severe hypokalemia and hypomagnesemia: case report and review of the literature. Journal Of Maternal-Fetal & Neonatal Medicine [serial on the Internet]. (2010, Nov), [cited April 7, 2016]; 23(11): 1301-1304 4p. Available from: CINAHL.

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3. Hypomagnesaemia in an elderly patient: case report. Reactions Weekly [serial on the Internet]. (2011, Aug 27), [cited April 7, 2016]; (1366): 23-24. Available from: Academic Search Complete.

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4. Wang A, Sharma S, Kim P, Mrejen-Shakin K. Hypomagnesemia in the intensive care unit: Choosing your gastrointestinal prophylaxis, a case report and review of the literature. Indian Journal Of Critical Care Medicine [serial on the Internet]. (2014, July), [cited April 7, 2016]; 18(7): 456-460. Available from: Academic Search Complete.

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Resources

ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/ - Magnesium Fact Sheet for Health Professionals (NIH)

- Informational video on Hypomagnesemia