NCLEX-PN Practice: Fluids, Electrolytes, and Metabolic Function

Vocabulary flashcards covering key concepts of fluids, electrolytes, metabolic function, and acid-base balance for NCLEX-PN review.

Intracellular compartment

The fluid space inside cells that contains approximately two thirds of total body water, with potassium as the principal cation and phosphate as the principal anion.

Third spacing

The shift of fluid into a compartment where it is not available to the circulation, such as the peritoneal cavity in ascites.

Insensible fluid loss

Unmeasurable and unnoticed evaporation from the skin and exhaled air, totaling roughly $500$ to $1,000\,mL$ daily in adults.

Active transport

A process that uses energy ($ATP$) to move particles against their concentration gradient, such as the sodium-potassium pump.

Facilitated diffusion

A passive process where molecules like glucose move from higher to lower concentration using protein carriers, often increased by insulin.

Filtration

The movement of water and dissolved substances out of a capillary driven by hydrostatic pressure against the vessel wall.

Colloid osmotic pressure (Oncotic pressure)

The pulling force exerted by plasma proteins, chiefly albumin, that holds or draws fluid back into the vascular space.

Antidiuretic hormone (ADH)

A hormone from the posterior pituitary that increases water reabsorption in the renal collecting ducts, resulting in concentrated urine and lower serum osmolality.

Aldosterone

A mineralocorticoid from the adrenal cortex that acts on the distal tubule to reabsorb sodium and water while excreting potassium.

Atrial natriuretic peptide (ANP)

A hormone released by stretched atrial cells in response to fluid overload that promotes the excretion of sodium and water.

Renin-angiotensin-aldosterone system (RAAS)

A compensatory sequence triggered by low renal perfusion where renin converts angiotensinogen to angiotensin I, then to the potent vasoconstrictor angiotensin II, which stimulates aldosterone release.

Serum osmolality

A measure of the concentration of particles in the blood, with a normal range of approximately $275$ to $295\,mOsm/kg$.

Hyponatremia

A serum sodium level below $135\,mEq/L$ that can cause cerebral edema, headache, confusion, and seizures.

Hypernatremia

A serum sodium level above $145\,mEq/L$ that causes water to shift out of cells, leading to cellular shrinking and intense thirst.

Hypokalemia

A serum potassium level below $3.5\,mEq/L$ that causes muscle weakness, leg cramps, and dangerous cardiac dysrhythmias.

Hyperkalemia

A serum potassium level above $5.0\,mEq/L$ that threatens cardiac conduction and can lead to fatal cardiac arrest.

Trousseau sign

A carpal spasm induced by inflating a blood pressure cuff, indicating hypocalcemia and neuromuscular irritability.

Kussmaul respirations

Deep, rapid breathing used by the body to blow off $CO_2$ and reduce carbonic acid to compensate for metabolic acidosis.

Basal metabolic rate (BMR)

The energy the body uses at rest, which is driven by thyroid hormone and decreases as lean muscle mass declines with aging.

Respiratory acidosis

An acid-base imbalance characterized by a $pH$ below $7.35$ and a $PaCO_2$ above $45\,mm\,Hg$, typically caused by alveolar hypoventilation or retained $CO_2$.

Metabolic alkalosis

An acid-base imbalance characterized by a $pH$ above $7.45$ and a bicarbonate ($HCO_3$) above $26\,mEq/L$, often caused by prolonged vomiting or gastric suction.

Isotonic solution

An intravenous fluid like $0.9\%$ sodium chloride or lactated Ringer's that has an osmolality near plasma and expands the extracellular fluid without shifting water out of cells.

Hypotonic solution

An intravenous fluid like $0.45\%$ sodium chloride with an osmolality lower than plasma, causing water to move into cells and hydrate them.

Hypertonic solution

An intravenous fluid like $3\%$ sodium chloride that pulls water out of the cells into the vascular space, used for severe hyponatremia.

Spironolactone

An aldosterone antagonist diuretic that reduces sodium reabsorption but spares potassium, carrying a risk of hyperkalemia.

Furosemide

A loop diuretic used for fluid volume excess that wastes potassium and magnesium, often requiring the monitoring of serum electrolytes.

Catabolism

The breakdown of body protein for energy, which lowers serum albumin and raises blood urea nitrogen ($BUN$).