Textbook of Basic Nursing: Fluid and Electrolyte Balance

Flashcards covering vocabulary, electrolyte values, and physiological mechanisms of fluid and electrolyte balance based on the Rosdahl and Kowalski Nursing foundations transcript.

Homeostasis

The dynamic process through which the body maintains balance by constantly adjusting to internal and external stimuli; literally means "controlling sameness."

Intracellular fluid (ICF)

Fluid inside the cells, constituting about two thirds ($66\%$) of the total body fluid in an adult; serves as a stabilizing agent for cell parts and helps maintain cell shape.

Extracellular fluid (ECF)

Fluid outside the cells, constituting about one third ($34\%$) of the total body fluid in an adult; the fluid most important in maintaining fluid balance.

Interstitial fluid

A subcompartment of extracellular fluid ($27\%$ of total body fluid) found between the cells.

Intravascular fluid

A subcompartment of extracellular fluid ($7\%$ of total body fluid) consisting of the watery fluid of the blood known as plasma.

Antidiuretic hormone (ADH)

A hormone released from the posterior pituitary gland that regulates the amount of water the kidneys absorb by decreasing urine production and increasing water reabsorption.

Renin–Angiotensin–Aldosterone (RAA) System

A fluid regulation cycle where renin is released by the kidneys to eventually stimulate aldosterone, which controls the reabsorption of sodium and water.

Atrial Natriuretic Peptide (ANP)

A hormone released from the right atrium of the heart that promotes renal diuresis (excretion) of sodium and water to correct fluid overload.

Edema

Excess accumulation of fluid in the interstitial tissue spaces, also known as third-space fluid.

Ascites

The excess accumulation of fluid specifically within the peritoneal cavity.

Anasarca

A term for severe generalized edema.

Dehydration

A deficiency of body water or excessive loss of water from the body where output is greater than intake; also known as fluid volume deficit.

Hydrostatic pressure

The pressure exerted by water against the walls or vessels that contain it, occurring because water has weight and volume.

Isotonic

Solutions that exert equal pressures on opposite sides of a membrane, such as normal saline ($0.9\%\,NaCl$).

Hypertonic

Stronger or more concentrated solutions compared to those on the opposing side of a membrane; causes blood cells to shrink as osmosis draws fluid out.

Hypotonic

Weaker or less concentrated solutions compared to an opposing solution; causes blood cells to swell as fluid moves into them.

Electrolyte

An element or compound that dissociates into ions when dissolved in water and is able to conduct a weak electric current.

Cation

A positively charged ion, such as $Na^+$ or $K^+$.

Anion

A negatively charged ion, such as $Cl^-$ or $HCO_3^-$.

Potassium ($K^+$)

The most dominant intracellular cation, with a normal serum level of $3.5$ to $5.0\,mEq/L$; essential for the functioning of neurons and muscle cells including the heart.

Sodium ($Na^+$)

The most important extracellular cation, with a normal serum level of $135$ to $145\,mEq/L$; maintains osmotic pressure and fluid balance.

Hyponatremia

A less than normal concentration of sodium in the blood (less than $134\,mEq/L$), potentially causing headache, fatigue, and muscle weakness.

Hypernatremia

A greater than normal concentration of sodium in the blood (greater than $145\,mEq/L$), often resulting in dry mucous membranes and cellular dehydration.

Chvostek's sign

A test for hypocalcemia involving a contraction of facial muscles in response to a light tap over the facial nerve in front of the ear.

Trousseau's sign

A sign of hypocalcemia consisting of a carpal spasm induced by inflating a blood pressure cuff above the systolic pressure for several minutes.

Diffusion

The passive transport mechanism characterized by the random movement of molecules from an area of higher concentration to an area of lower concentration.

Osmosis

The diffusion of water across a semipermeable membrane where water moves from an area of higher water concentration to lower water concentration.

Filtration

The transport of water and dissolved materials through a membrane from an area of higher pressure to an area of lower pressure requiring mechanical force.

Active Transport

A transport process requiring energy ($ATP$) used when molecules are too large or specialized to pass through passively; example includes the sodium–potassium pump.

Insensible water loss

Water loss that is not perceptible to the senses, such as water vapor from the lungs or sweat that evaporates immediately.

pH scale

A scale ranging from $0$ to $14$ measuring hydrogen ion concentration; $7$ is neutral, below $7$ is acidic, and above $7$ is basic (alkaline).

Buffer

A chemical system, such as the carbonic acid/bicarbonate system, that helps maintain the serum pH within a narrow range.

Acidosis

A state where there are too many hydrogen atoms, resulting in a serum pH below $7.35$.

Alkalosis

A state where there is an excess of bicarbonate ions or a loss of acids, resulting in a serum pH above $7.45$.

Arterial Blood Gases (ABGs)

Laboratory tests of arterial blood used to determine the status of a patient's acid–base balance and the extent of buffer system compensation.