Sodium and Heart Rate

Sodium is essential to a number of life-sustaining processes, including brain and heart function. Along with chloride, it is the principal ion in the fluid outside of cells (extracellular fluid), including blood plasma.

Function

• The body uses sodium to regulate blood pressure and blood volume. Sodium is also critical for the functioning of muscles and nerves, and plays an important role in the absorption of chloride, amino acids, glucose and water.

Values

• Blood sodium level is normally between 135 and 145 mEq/L (milli-equivalents per liter). In hypernatremia (excess body sodium), sodium is higher than 145 mEq/L. Hyponatremia (low sodium) is defined as a concentration of less than 135 mEq/L and is considered severe when sodium content is below 125 mEq/L.

Blood Volume Control

• When sensors in the heart, blood vessels and kidneys detect high sodium content, they stimulate the kidneys to increase sodium excretion. Conversely, low sodium content triggers mechanisms to retain sodium and increase blood volume.

Hypernatremia

• Hypernatremia usually results from excess water loss. Severe hypernatremia may lead to: edema (swelling), high blood pressure, rapid heart rate (tachycardia), difficulty breathing, convulsions, coma and death.

Hyponatremia

• In addition to impaired brain function, hyponatremia can lead to hypotension (low blood pressure) and tachycardia (rapid heart rate). However, far-advanced signs of hyponatremia can include bradycardia (slow heart rate).

Considerations

• At rest, normal heart rate values are between 60 and 80 beats per minute (bpm), but can be less than 50 bpm for athletes. Sodium imbalances can impair brain function, but must usually be severe to cause abnormal heart rates.