Hypermagnesemia
Encyclopedia
Hypermagnesemia is an electrolyte disturbance
in which there is an abnormally elevated level of magnesium
in the blood. Usually this results in excess of magnesium in the body.
Hypermagnesemia occurs rarely because the kidney
is very effective in excreting excess magnesium. It usually develops only in people with kidney failure who are given magnesium salts or who take drugs that contain magnesium (e.g. some antacid
s and laxative
s). It is usually concurrent with hypocalcemia and/or hyperkalemia
.
and metabolism
see hypomagnesemia
.
Arrhythmia and asystole are possible cardiac complications of hypermagnesemia. Magnesium acts as physiologic calcium blocker
, which results in electrical conduction abnormalities.
Clinical consequences related to serum concentration:
Note that the therapeutic range for the prevention of the pre-eclampsic uterine contractions is: 4.0-7.0 mEq/L. As per Lu and Nightingale, serum Mg2+ concentrations associated with maternal toxicity (also neonate depression - hypotonia and low Apgar scores) are:
s, renal failure
(as a result of hypermagnesemia) most often occurs due to prolonged over supplementation or long term use of magnesium containing medications or laxatives.
Definitive treatment of hypermagnesemia requires increasing renal magnesium excretion through:
Electrolyte disturbance
Electrolytes play a vital role in maintaining homeostasis within the body. They help to regulate myocardial and neurological function, fluid balance, oxygen delivery, acid-base balance and much more. Electrolyte imbalances can develop by the following mechanisms: excessive ingestion; diminished...
in which there is an abnormally elevated level of magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
in the blood. Usually this results in excess of magnesium in the body.
Hypermagnesemia occurs rarely because the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
is very effective in excreting excess magnesium. It usually develops only in people with kidney failure who are given magnesium salts or who take drugs that contain magnesium (e.g. some antacid
Antacid
An antacid is a substance which neutralizes stomach acidity.-Mechanism of action:Antacids perform a neutralization reaction, increasing the pH to reduce acidity in the stomach. When gastric hydrochloric acid reaches the nerves in the gastrointestinal mucosa, they signal pain to the central nervous...
s and laxative
Laxative
Laxatives are foods, compounds, or drugs taken to induce bowel movements or to loosen the stool, most often taken to treat constipation. Certain stimulant, lubricant, and saline laxatives are used to evacuate the colon for rectal and/or bowel examinations, and may be supplemented by enemas under...
s). It is usually concurrent with hypocalcemia and/or hyperkalemia
Hyperkalemia
Hyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...
.
Metabolism
For a detailed description of magnesium homeostasisHomeostasis
Homeostasis is the property of a system that regulates its internal environment and tends to maintain a stable, constant condition of properties like temperature or pH...
and metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
see hypomagnesemia
Hypomagnesemia
Hypomagnesemia is an electrolyte disturbance in which there is an abnormally low level of magnesium in the blood. Usually a serum level less than 0.7 mmol/L is used as reference. The prefix hypo- means low . The middle 'magnes' refers to magnesium...
.
Symptoms
- Weakness, nausea and vomiting
- Impaired breathing
- HypotensionHypotensionIn physiology and medicine, hypotension is abnormally low blood pressure, especially in the arteries of the systemic circulation. It is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is the...
- Hypocalcemia
- Arrhythmia and AsystoleAsystoleIn medicine, asystole is a state of no cardiac electrical activity, hence no contractions of the myocardium and no cardiac output or blood flow...
Arrhythmia and asystole are possible cardiac complications of hypermagnesemia. Magnesium acts as physiologic calcium blocker
Calcium channel blocker
A calcium channel blocker is a chemical that disrupts the movement of calcium through calcium channels.CCB drugs devised to target neurons are used as antiepileptics. However, the most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with...
, which results in electrical conduction abnormalities.
Clinical consequences related to serum concentration:
- 4.0 mEq/l hyporeflexiaHyporeflexiaHyporeflexia is the condition of below normal or absent reflexes. It can be tested for by using a reflex hammer. It is the opposite of hyperreflexia....
- >5.0 mEq/l Prolonged atrioventricular conduction
- >10.0 mEq/l Complete heart blockHeart blockA heart block can be a blockage at any level of the electrical conduction system of the heart .* Blocks that occur within the sinoatrial node are described as SA nodal blocks....
- >13.0 mEq/l Cardiac arrestCardiac arrestCardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
Note that the therapeutic range for the prevention of the pre-eclampsic uterine contractions is: 4.0-7.0 mEq/L. As per Lu and Nightingale, serum Mg2+ concentrations associated with maternal toxicity (also neonate depression - hypotonia and low Apgar scores) are:
- 7.0-10.0 mEq/L - loss of patellar reflex
- 10.0-13.0 mEq/L - respiratory depression
- 15.0-25.0 mEq/L - altered atrioventricular conduction and (further) complete heart blockHeart blockA heart block can be a blockage at any level of the electrical conduction system of the heart .* Blocks that occur within the sinoatrial node are described as SA nodal blocks....
- >25.0 mEq/L - cardiac arrestCardiac arrestCardiac arrest, is the cessation of normal circulation of the blood due to failure of the heart to contract effectively...
Causes
Since magnesium is excreted through the kidneyKidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
s, renal failure
Renal failure
Renal failure or kidney failure describes a medical condition in which the kidneys fail to adequately filter toxins and waste products from the blood...
(as a result of hypermagnesemia) most often occurs due to prolonged over supplementation or long term use of magnesium containing medications or laxatives.
Predisposing conditions
- HemolysisHemolysisHemolysis —from the Greek meaning "blood" and meaning a "loosing", "setting free" or "releasing"—is the rupturing of erythrocytes and the release of their contents into surrounding fluid...
, magnesium concentration in erythrocytes is approximately three times greater than in serum, therefore hemolysis can increase plasma magnesium. Hypermagnesemia is expected only in massive hemolysis. - Renal insufficiency, excretion of magnesium becomes impaired when creatinine clearance falls below 30 ml/min. However, hypermagnesemia is not a prominent feature of renal insufficiency unless magnesium intake is increased.
- Other conditions that can predispose to mild hypermagnesemia are diabetic ketoacidosisDiabetic ketoacidosisDiabetic ketoacidosis is a potentially life-threatening complication in patients with diabetes mellitus. It happens predominantly in those with type 1 diabetes, but it can occur in those with type 2 diabetes under certain circumstances...
, adrenal insufficiencyAdrenal insufficiencyAdrenal insufficiency is a condition in which the adrenal glands, located above the kidneys, do not produce adequate amounts of steroid hormones , primarily cortisol, but may also include impaired aldosterone production which regulates sodium, potassium and water retention...
, hyperparathyroidismHyperparathyroidismHyperparathyroidism is overactivity of the parathyroid glands resulting in excess production of parathyroid hormone . The parathyroid hormone regulates calcium and phosphate levels and helps to maintain these levels...
and lithiumLithiumLithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
intoxication.
Therapy
Prevention of hypermagnesemia usually is possible. In mild cases, withdrawing magnesium supplementation is often sufficient. In more severe cases the following treatments are used:- Intravenous calcium gluconateCalcium gluconateCalcium gluconate is a mineral supplement.-Hypocalcemia:10% calcium gluconate solution is the form of calcium most widely used in the treatment of hypocalcemia. This form of calcium is superior to calcium lactate, but it only contains 0.93% calcium ion. Calcium gluconate is a salt of calcium and...
, because the actions of magnesiumMagnesiumMagnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
in neuromuscular and cardiac function are antagonized by calciumCalciumCalcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
.
Definitive treatment of hypermagnesemia requires increasing renal magnesium excretion through:
- Intravenous diureticDiureticA diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...
s, in the presence of normal renal functionRenal functionRenal function, in nephrology, is an indication of the state of the kidney and its role in renal physiology. Glomerular filtration rate describes the flow rate of filtered fluid through the kidney... - DialysisDialysisIn medicine, dialysis is a process for removing waste and excess water from the blood, and is primarily used to provide an artificial replacement for lost kidney function in people with renal failure...
, when kidney function is impaired and the patient is symptomatic from hypermagnesemia