hypernatremia

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Definition

The normal concentration of sodium in the blood plasma is 136–145 mM. Hypernatremia is defined as a serum sodium level over 145 mM. Severe hypernatremia, with serum sodium above 152 mM, can result in seizures and death.

Description

Sodium is an atom, or ion, that carries a single positive charge. The sodium ion may be abbreviated as Na⁺ or as simply Na. Sodium can occur as a salt in a crystalline solid. Sodium chloride (NaCl), sodium phosphate (Na₂HPO₄) and sodium bicarbonate (NaHCO₃) are commonly occurring salts. These salts can be dissolved in water or in juices of various foods. Dissolving involves the complete separation of ions, such as sodium and chloride in common table salt (NaCl).

About 40% of the body's sodium is contained in bone. Approximately 2–5% occurs within organs and cells and the remaining 55% is in blood plasma and other extracellular fluids. The amount of sodium in blood plasma is typically 140 mM, a much higher amount than is found in intracellular sodium (about 5 mM). This asymmetric distribution of sodium ions is essential for human life. It makes possible proper nerve conduction, the passage of various nutrients into cells, and the maintenance of blood pressure.

The body continually regulates its handling of sodium. When dietary sodium is too high or low, the intestines and kidneys respond to adjust concentrations to normal. During the course of a day, the intestines absorb dietary sodium while the kidneys excrete a nearly equal amount of sodium into the urine. If a low sodium diet is consumed, the intestines increase their efficiency of sodium absorption, and the kidneys reduce its release into urine.

The concentration of sodium in the blood plasma depends on two things: the total amount of sodium and water in arteries, veins, and capillaries (the circulatory system). The body uses separate mechanisms to regulate sodium and water, but they work together to correct blood pressure when it is too high or too low. Too high a concentration of sodium, or hypernatremia, can be corrected either by decreasing sodium or by increasing body water. The existence of separate mechanisms that regulate sodium concentration account for the fact that there are numerous diseases that can cause hypernatremia, including diseases of the kidney, pituitary gland, and hypothalamus.

— Tom Brody, PhD

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n.
An abnormally high plasma concentration of sodium ions.

[HYPO- + New Latin natrium, sodium (from French natron, natron; see natron) + -EMIA.]

The presence of an abnormally high sodium concentration in the blood plasma. It may occur as a result of excessive sweating and inadequate fluid intake.

(hī'pur-nə-trē'mē-ə)
n

An abnormally elevated concentration of serum sodium. It may occur rarely in nephrosis, congestive heart failure, and Cushing’s disease and after administration of adrenocorticotropic hormone (ACTH), cortisone, or deoxycorticosterone. Normal adult range of serum sodium is 135 to 145 mEq/L.

An abnormally high sodium ion concentration in the blood (usually diagnosed as being greater that 150 mmol L⁻¹). It may occur as a result of excessive sweating or inadequate fluid intake.

An excess of sodium in the blood, indicative of water loss exceeding the sodium loss.

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