MJ-15

MEq/L

The term MEq/L stands for milliequivalents per liter. It is a unit of measurement used in chemistry and medicine to express the concentration of electrolytes in a solution. This unit is particularly important in the field of medicine, where it is used to quantify the concentration of ions in biological fluids such as blood serum, plasma, and urine.

1. 1. Definition

A milliequivalent (mEq) is one-thousandth of an equivalent. An equivalent is a measure of reactive capacity, which is based on the number of moles of a substance that can react with or supply one mole of hydrogen ions (H⁺) in an acid-base reaction, or one mole of electrons in a redox reaction. The concept of equivalents is used to account for the valency of ions in solution.

The formula to calculate milliequivalents is:

\[ \text{mEq} = \frac{\text{mg of substance}}{\text{molecular weight}} \times \text{valence} \]

Thus, mEq/L is calculated as:

\[ \text{mEq/L} = \frac{\text{mg/L of substance}}{\text{molecular weight}} \times \text{valence} \]

1. 1. Importance in Medicine

In clinical settings, mEq/L is used to measure the concentration of electrolytes such as sodium (Na⁺), potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl⁻), bicarbonate (HCO₃⁻), and phosphate (PO₄³⁻) in the blood. These electrolytes are crucial for maintaining various physiological functions, including nerve conduction, muscle contraction, and acid-base balance.

1. 1. 1. Sodium (Na⁺)

Sodium is the primary extracellular cation and plays a key role in maintaining fluid balance and osmotic pressure. Normal serum sodium levels range from 135 to 145 mEq/L.

1. 1. 1. Potassium (K⁺)

Potassium is the main intracellular cation and is vital for cardiac and neuromuscular function. Normal serum potassium levels range from 3.5 to 5.0 mEq/L.

1. 1. 1. Calcium (Ca²⁺)

Calcium is essential for bone health, muscle function, and blood coagulation. Normal serum calcium levels range from 8.5 to 10.5 mg/dL, which can be converted to mEq/L using the valence of calcium.

1. 1. Calculation Example

To calculate the mEq/L of a solution containing 40 mg/L of potassium chloride (KCl):

1. Determine the molecular weight of KCl: Potassium (K) = 39.1 g/mol, Chloride (Cl) = 35.5 g/mol, so KCl = 74.6 g/mol. 2. The valence of K⁺ is 1. 3. Use the formula:

\[ \text{mEq/L} = \frac{40 \text{ mg/L}}{74.6 \text{ g/mol}} \times 1 = 0.536 \text{ mEq/L} \]

1. 1. Clinical Relevance

Abnormal levels of electrolytes can lead to various medical conditions:

- Hyponatremia: Low sodium levels, which can cause confusion, seizures, and coma. - Hyperkalemia: High potassium levels, which can lead to cardiac arrhythmias. - Hypocalcemia: Low calcium levels, which can cause tetany and muscle spasms.

1. 1. Also see

- Electrolyte imbalance - Acid-base homeostasis - Serum osmolality - Blood chemistry

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Source: Data courtesy of the U.S. National Library of Medicine. Since the data might have changed, please query MeSH on MJ-15 for any updates.

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