Chapter 3 Fluids, Electrolytes, and Acid-Base Balance (Pathophysiology)

Vocabulary flashcards covering functional fluid compartments, water movement, edema mechanisms, key electrolytes, acid-base balance, and related disorders from Chapter 3.

Intracellular fluid (ICF)

Fluid inside cells; about two-thirds of total body water; separated from extracellular fluid by cell membranes.

Extracellular fluid (ECF)

Fluid outside cells; includes plasma and interstitial fluid; about one-third of total body water.

Capillary hydrostatic pressure (Pc)

Pressure exerted by capillary blood on its walls; promotes filtration from capillaries to the interstitium.

Capillary oncotic pressure (piC)

Osmotic pressure exerted by plasma proteins; pulls water into capillaries.

Interstitial hydrostatic pressure (Pi)

Pressure within the interstitial space; generally opposes capillary filtration.

Interstitial oncotic pressure (piI)

Osmotic pressure from proteins in the interstitial fluid; tends to draw water out of capillaries.

Starling forces

Net filtration pressure across capillary walls determined by Pc, piC, Pi, and piI that governs fluid exchange.

Edema

Excess fluid accumulation in the interstitial space; can be localized or generalized.

Filtration (water movement between plasma and interstitial fluid)

Movement of fluid from capillaries to interstitium driven by capillary hydrostatic pressure.

Reabsorption (water movement between plasma and interstitial fluid)

Movement of water from interstitium back into capillaries driven by capillary oncotic pressure.

Total body water (TBW)

Sum of all body water; about 60% of body weight in adults; divided into ICF (~40% BW) and ECF (~20% BW).

Two functional fluid compartments

Intracellular fluid (inside cells) and extracellular fluid (outside cells).

Normal water gains (age and size related)

Water intake and production that vary with age and body size; TBW proportion highest in infancy.

Hypotonic alteration

Low osmolality state often from sodium deficits or water excess; can cause cellular swelling.

Isotonic alteration

Normal osmolality with changes in total body water; volume depletion or overload without osmotic shift.

Hypertonic alteration

High osmolality due to water deficit or sodium gain; causes cellular dehydration.

Water and solute imbalances: isotonic

Isotonic gains/losses with proportional Na and water shifts; e.g., isotonic dehydration or overload.

Water and solute imbalances: hypotonic

Hypotonic state with relatively more water than solute; often hyponatremia.

Water and solute imbalances: hypertonic

Hypertonic state with relatively more solute than water; often hypernatremia.

Sodium (Na+)

Major extracellular cation; regulates plasma osmolality and extracellular fluid volume.

Chloride (Cl-)

Major extracellular anion; follows sodium; participates in acid-base balance.

Potassium (K+)

Major intracellular cation; crucial for membrane potential and cellular function; kidney-regulated.

Calcium (Ca2+)

Important for bones and signaling; tightly regulated by PTH, vitamin D, and calcitonin.

Phosphate (PO4^3-)

Intracellular anion important for energy storage and bone mineralization; regulated with calcium.

Magnesium (Mg2+)

Intracellular cation involved in enzyme function and neuromuscular activity; kidney-regulated.

Hypernatremia

Elevated serum sodium; hypertonic state usually from water loss or sodium gain.

Hyponatremia

Low serum sodium; hypo-osmolality; can cause brain edema and neurologic symptoms.

Hyperchloremia

Elevated chloride level; often accompanies hypernatremia or metabolic acidosis.

Hypochloremia

Low chloride level; can accompany metabolic alkalosis or vomiting.

Hyperkalemia

Elevated serum potassium; risk of cardiac arrhythmias; often due to renal failure or acidosis.

Hypokalemia

Low serum potassium; muscle weakness and arrhythmias; can result from diuretics or losses.

Hypomagnesemia

Low magnesium; can cause neuromuscular excitability and cardiovascular effects.

Hypermagnesemia

High magnesium; usually from renal failure; can cause decreased reflexes and hypotension.

Hypocalcemia

Low calcium; tetany, seizures, and neuromuscular irritability; often due to hypoparathyroidism or vitamin D deficiency.

Hypercalcemia

High calcium; symptoms include stones, bones, groans; often from hyperparathyroidism or malignancy.

Hypophosphatemia

Low phosphate; weakness and impaired energy production; common in malnutrition.

Hyperphosphatemia

High phosphate; often with renal failure; may cause hypocalcemia and soft tissue calcification.

Water deficit (dehydration)

Insufficient water intake or excessive loss; hypernatremia; manifestations include thirst and dry mucous membranes.

Water excess (water intoxication)

Excess water intake or impaired excretion; hyponatremia; edema and confusion in severe cases.

Hydrogen ion concentration (pH)

Amount of H+ in body fluids; determines acidity/alkalinity and cellular function.

Plasma buffering systems

Bicarbonate/carbonate, protein buffers, cellular ion exchange, respiratory and renal buffering that stabilize pH.

Lungs and kidney in acid-base balance

Lungs regulate CO2 (respiratory buffer); kidneys regulate HCO3- (metabolic buffer) and compensate.

Metabolic acidosis

Low pH with decreased HCO3-; excess acid or bicarbonate loss; compensation via increased ventilation.

Metabolic alkalosis

High HCO3-; high pH; compensation via reduced ventilation and renal adjustments.

Respiratory acidosis

Low pH with elevated CO2 from hypoventilation; kidneys compensate by increasing HCO3-.

Respiratory alkalosis

High pH with low CO2 from hyperventilation; kidneys compensate by lowering HCO3-.

Compensation vs correction

Compensation is physiological adjustment by another system; correction resolves the underlying cause.