Fluid, Electrolyte, and Acid-Base Alterations and Pharmacotherapy

Vocabulary practice flashcards covering fluid compartments, transport mechanisms, fluid imbalances, electrolyte disturbances, and intravenous therapy principles.

Intracellular Fluid (ICF)

Water contained inside cells, in which potassium ($K^+$) functions as the principal intracellular cation.

Extracellular Fluid (ECF)

Water outside cells, composed primarily of plasma within the vascular space and interstitial fluid between tissue cells, with sodium ($Na^+$) serving as the principal cation.

Diffusion

The net movement of solute down its concentration gradient, which influences osmotic forces affecting water distribution.

Active Transport

The energy-dependent movement of solutes against a concentration gradient, exemplified by the $Na^+/K^+$ pump maintaining ECF and ICF electrolyte concentration differences.

Osmosis

The net movement of water across a selectively permeable membrane toward the compartment with a higher effective solute concentration.

Filtration

The pressure-driven movement of fluid across a barrier, such as capillary hydrostatic pressure driving fluid from the intravascular compartment into the interstitium.

Reabsorption

The movement of fluid and solutes back into a compartment, such as renal tubular fluid returning to the blood to conserve water and electrolytes.

Starling Forces

The balance and interaction of hydrostatic and oncotic pressures across capillary walls that govern fluid movement between plasma and the interstitium.

Osmolality

The physical measurement describing the concentration of dissolved solute particles per kilogram of water.

Tonicity

The property describing the sustained osmotic effect of a solution on cell volume, determined specifically by effective, poorly penetrating solutes.

Aquaporins

A family of water-channel proteins embedded in cell membranes that increase membrane permeability to water.

Edema

Excessive accumulation of fluid in interstitial spaces, caused by increased capillary hydrostatic pressure, decreased capillary oncotic pressure, increased capillary permeability, or lymphatic obstruction.

Third Spacing

The sequestration of fluid in body compartments where it is not readily available to support effective circulating volume.

Natriuretic Peptides

Endogenous peptides (including ANP, BNP, and urodilatin) that inhibit RAAS, reduce renal tubular sodium reabsorption, and promote sodium and water excretion to lower blood volume and pressure.

Antidiuretic Hormone (ADH)

A hormone released from the posterior pituitary triggered by increased osmolality or depleted circulating volume that increases renal water reabsorption.

Isotonic Hypovolemia

Proportionate loss of ECF water and electrolytes (from hemorrhage, wound drainage, or diaphoresis) causing weight loss, dry mucosa, decreased urine output, tachycardia, flattened neck veins, and normal or low blood pressure without a sustained osmotic shift across cell membranes.

Isotonic Hypervolemia

Proportionate gain of ECF (from excessive sodium-containing IV fluids, excess aldosterone, corticosteroids, or kidney disease) manifesting as weight gain, edema, distended neck veins, elevated blood pressure, and dilutional falls in hematocrit and plasma proteins.

Hypernatremia

A state of elevated serum sodium ($>145\,\text{mEq/L}$) relative to water, creating hypertonic ECF that draws water out of cells to cause cellular shrinkage, thirst, oliguria, weakness, hyperreflexia, twitching, confusion, and seizures.

Hyponatremia

A state of decreased serum sodium ($<135\,\text{mEq/L}$ or $<136\,\text{mmol/L}$) relative to water, producing hypotonic ECF that drives water into cells to cause cellular swelling, headache, lethargy, confusion, nausea, vomiting, seizures, and coma.

Hypokalemia

A serum potassium level $<3.5\,\text{mEq/L}$ ($<2.5\,\text{mEq/L}$ classified as severe) caused by low intake, renal losses, or ECF-to-ICF shifts, manifesting as skeletal muscle weakness, smooth-muscle atony, prolonged PR, ST depression, flat T waves, and prominent U waves.

Hyperkalemia

A serum potassium level exceeding $5.0\,\text{mEq/L}$ ($>5.5\,\text{mEq/L}$ in teaching deck) resulting from excess intake, renal failure, or ICF-to-ECF shifts, manifesting as irritability, intestinal cramping, paralysis, peaked T waves, low/absent P waves, widened QRS, and ventricular fibrillation.

Hypocalcemia

A total serum calcium level $<8.5\,\text{mg/dL}$ ($<2.1\,\text{mmol/L}$) causing increased neuromuscular excitability, tingling, muscle spasms, Chvostek and Trousseau signs, tetany, convulsions, and a prolonged QT interval.

Hypercalcemia

A total serum calcium level $>10.5\,\text{mg/dL}$ ($>2.5\,\text{mmol/L}$) causing reduced neuromuscular excitability, muscle weakness, fatigue, lethargy, anorexia, nausea, constipation, dysrhythmias, and pathological fractures.

Hypophosphatemia

A serum phosphate level $<2.0\,\text{mg/dL}$ ($<1.0\,\text{mmol/L}$) presenting with impaired oxygen release to tissues, skeletal muscle weakness, osteomalacia or rickets, platelet dysfunction, and altered leukocyte function.

Hyperphosphatemia

A serum phosphate level $>4.7\,\text{mg/dL}$ ($>1.5\,\text{mmol/L}$) commonly caused by renal disease or chemotherapy-related cell lysis, manifesting with hypocalcemia-like symptoms and soft-tissue calcification.

Hypomagnesemia

A serum magnesium level $<1.5\,\text{mEq/L}$ ($<0.65\,\text{mmol/L}$) characterized by increased neuromuscular excitability, behavioral changes, hyperreflexia, muscle cramps, ataxia, tetany, seizures, and an increased risk of cardiac dysrhythmias.

Hypermagnesemia

A serum magnesium level $>3.0\,\text{mEq/L}$ ($>1.05\,\text{mmol/L}$) presenting with lethargy, diminished or absent deep-tendon reflexes, nausea, vomiting, hypotension, bradycardia, respiratory depression, and heart block or arrest.

Crystalloids

Intravenous electrolyte solutions composed of small solutes that distribute freely across capillary walls into interstitial and intravascular spaces, categorized as isotonic, hypotonic, or hypertonic.

Colloids

Intravenous plasma-volume expanders containing high-molecular-weight substances or proteins (such as $5\%$ albumin, dextran, or hetastarch) that generate oncotic pressure to retain and recruit fluid within the vascular space.

D5W (5% Dextrose in Water)

An intravenous crystalloid solution that is approximately isotonic in the container but supplies electrolyte-free water and exerts a hypotonic physiologic effect once glucose is metabolized by tissues.