Chapter 10: Fluid and Electrolyte Balance

A set of vocabulary flashcards covering key terms and concepts from the Fluid and Electrolyte Balance notes.

Total-body water (TBW)

The total amount of water in the body; about 60% of body weight.

Intracellular fluid (ICF)

Fluid inside cells; roughly 40% of body weight.

Extracellular fluid (ECF)

Fluid outside cells; roughly 20% of body weight.

Interstitial fluid

Fluid in the interstitial spaces between cells; part of the extracellular fluid.

Plasma

Intravascular fluid within blood vessels; roughly 3.5 L.

Transcellular fluid

Fluid in special compartments (e.g., CSF, synovial, pericardial).

Osmolarity

Concentration of solute particles in a solution; measured in mOsm/L.

Electrolyte

Substances in body fluids that carry electrical charges; include cations and anions.

Cation

Positively charged ion (e.g., sodium, potassium, calcium, magnesium, hydrogen).

Anion

Negatively charged ion (e.g., chloride, bicarbonate, phosphate, sulfate, protein ions).

mEq/L

Milliequivalents per liter; unit used for electrolyte concentration.

Diffusion

Movement of solutes from an area of higher concentration to lower concentration.

Filtration

Movement of water and solutes from areas of high hydrostatic pressure to low hydrostatic pressure.

Active transport

Energy-dependent movement of substances across membranes.

Sodium–potassium pump

Na+/K+ ATPase; maintains higher extracellular Na+ and intracellular K+.

I&O (intake and output)

Balance of fluids taken in and excreted.

Daily weight

Regular weight measurement used to monitor fluid status.

Renin–Angiotensin–Aldosterone System (RAAS)

Hormonal system that regulates blood pressure and fluid balance.

Antidiuretic Hormone (ADH)

Hormone that promotes water reabsorption in the kidneys, reducing urine output.

Osmoreceptors

Sensing receptors that detect changes in osmolality and influence ADH release.

Natriuretic Peptides

Hormones that promote natriuresis and diuresis to reduce volume.

Third-space fluid shift

Fluid moves into nonfunctional spaces (e.g., pleural, peritoneal, edema).

Hypovolemia (Fluid Volume Deficit)

Loss of extracellular fluid exceeding intake; electrolytes lost in normal proportions.

Hypervolemia (Fluid Volume Excess)

Excess fluid volume in the extracellular compartment due to retention of sodium and water.

Oliguria

Reduced urine output.

Isotonic solution

IV fluids with osmolality similar to plasma; expand volume without changing osmolality.

Hypotonic solution

IV fluids with lower osmolality than plasma; water moves into cells.

Hypertonic solution

IV fluids with higher osmolality than plasma; draws water out of cells.

Colloid

IV fluids containing larger molecules (e.g., albumin) that pull fluid into the intravascular space.

Hyponatremia

Serum sodium < 135 mEq/L; often related to water imbalance.

Hypernatremia

Serum sodium > 145 mEq/L; can indicate water deficit or excessive sodium.

Hypokalemia

Serum potassium < 3.5 mEq/L; can cause ECG changes and muscle symptoms.

Hyperkalemia

Serum potassium > 5.0 mEq/L; risk of dysrhythmias.

Hypocalcemia

Serum calcium < 8.6 mg/dL; signs include tetany and Chvostek/Trousseau signs.

Hypercalcemia

Serum calcium > 10.5 mg/dL; may cause weakness, constipation, stones.

Hypomagnesemia

Serum magnesium < 1.8 mg/dL; can cause neuromuscular irritability.

Hypermagnesemia

Serum magnesium > 2.6 mg/dL; may cause diminished reflexes and CNS depression.

Hypophosphatemia

Phosphorus < 2.5 mg/dL; can cause muscle weakness and respiratory issues.

Hyperphosphatemia

Phosphorus > 4.5 mg/dL; often related to kidney dysfunction and hypocalcemia.

Hypochloremia

Chloride < 98 mEq/L; associated with GI losses and diuretics.

Hyperchloremia

Chloride > 106 mEq/L; can accompany dehydration or metabolic acidosis.

Trousseau sign

Clinical sign of hypocalcemia/hypomagnesemia: carpal spasm with blood pressure cuff inflation.

Chvostek sign

Facial twitching with tapping of facial nerve; sign of hypocalcemia/hypomagnesemia.

Calcium gluconate

IV calcium used in emergent hyperkalemia or hypocalcemia management.