Fluid, Electrolyte, and Acid-Base Balance

Fifty vocabulary flashcards covering key terms from fluid, electrolyte, and acid-base balance lecture notes.

Homeostasis

The body’s natural state of equilibrium maintained by adaptive responses within narrow fluid and electrolyte limits.

Body Water Content

Percentage of body weight that is water; varies with age, gender, and fat—higher in infants, lower in older adults.

Intracellular Fluid (ICF)

Fluid inside cells; about 40 % of body weight and two-thirds of total body water.

Extracellular Fluid (ECF)

All body fluid outside cells; includes interstitial, intravascular, and transcellular compartments.

Interstitial Fluid

ECF located in the spaces between cells.

Intravascular Fluid

ECF within blood vessels; plasma component of blood.

Transcellular Fluid

Specialized ECF in spaces such as cerebrospinal, synovial, pleural, and peritoneal cavities.

Osmolarity

Total milliosmoles per liter of solution (mOsm/L).

Osmolality

Milliosmoles per kilogram of water (mOsm/kg); normal 280-295, >295 = water deficit, <275 = water excess.

Isotonic Solution

IV fluid with the same tonicity as plasma; expands ECF without shifting water between compartments.

Hypotonic Solution

IV fluid with lower osmolality than plasma; moves water from ECF into cells.

Hypertonic Solution

IV fluid with higher osmolality than plasma; pulls water from cells into vascular space, raising serum sodium.

First Spacing

Normal distribution of fluid between ICF and ECF.

Second Spacing

Abnormal accumulation of interstitial fluid—edema.

Third Spacing

Fluid trapped in areas where it is difficult to exchange with ECF, e.g., ascites or pleural effusion.

Antidiuretic Hormone (ADH)

Pituitary hormone that tells kidneys to reabsorb water, reducing urine output.

Thirst Mechanism

Hypothalamic drive that increases fluid intake when osmolality rises or volume falls.

Aldosterone

Adrenal cortical hormone that promotes sodium and water reabsorption and potassium excretion by the kidneys.

Atrial Natriuretic Peptide (ANP)

Hormone released by atria when stretched; inhibits RAAS and ADH, promoting sodium and water excretion.

Brain Natriuretic Peptide (BNP)

Hormone from ventricles signaling fluid overload; actions similar to ANP.

Hypovolemia

ECF volume deficit from fluid loss, inadequate intake, or plasma-to-interstitial shift.

Hypervolemia

ECF volume excess from fluid intake, retention, or interstitial-to-plasma shift.

Maintenance IV Fluids

Solutions given to meet daily fluid and electrolyte needs when oral intake is insufficient.

Replacement IV Fluids

Solutions administered to correct existing fluid or electrolyte losses.

Normal Saline (0.9 % NaCl)

Isotonic fluid; expands IV volume, compatible with blood products, higher overload risk.

Lactated Ringer’s Solution

Isotonic balanced electrolyte fluid containing lactate, K, Ca; treats burns/GI losses; avoid in liver dysfunction or hyperkalemia.

Dextrose 5 % in Water (D5W)

Provides 170 kcal/L; free water moves into cells; treats hypernatremia but supplies no electrolytes.

3 % Saline

Hypertonic saline used for severe hyponatremia; requires close monitoring for fluid overload and neurologic changes.

D5 ½ Normal Saline

Dextrose 5 % in 0.45 % NaCl; hypertonic maintenance fluid often supplemented with KCl.

D10W

10 % dextrose in water; hypertonic, 340 kcal/L; maximum dextrose strength suitable for peripheral infusion.

Colloid Solution

IV fluid containing large molecules (e.g., proteins, starches) that remain in the intravascular space.

Plasma Expanders

Colloid products such as albumin, plasma, or packed RBCs that raise osmotic pressure and increase vascular volume.

Osmotic Pressure

Force exerted by solutes to draw water across a semipermeable membrane.

Hyponatremia

Serum sodium <135 mEq/L; usually from water excess or sodium loss; causes confusion, seizures.

Hypernatremia

Serum sodium >145 mEq/L; results from water deficit or sodium gain; causes intense thirst and restlessness.

Hypokalemia

Serum potassium <3.5 mEq/L; leads to muscle weakness, dysrhythmias, and U-wave ECG changes.

Hyperkalemia

Serum potassium >5.0 mEq/L; causes muscle cramps, peaked T waves, and potential cardiac arrest.

ECG Changes in Hyperkalemia

Tall peaked T waves, widened QRS, prolonged PR interval, and flat P waves.

Hypocalcemia

Total calcium <8.6 mg/dL; manifests as tetany, positive Chvostek’s/Trousseau’s signs.

Hypercalcemia

Total calcium >10.2 mg/dL; produces weakness, decreased reflexes, and risk of kidney stones.

Hypomagnesemia

Serum magnesium <1.5 mEq/L; causes neuromuscular irritability and ventricular dysrhythmias (torsades de pointes).

Hyperphosphatemia

Serum phosphate >4.5 mg/dL; often with renal failure and accompanies low calcium levels.

Metabolic Acidosis

pH <7.35 with low HCO₃; caused by DKA, diarrhea, renal failure; features Kussmaul respirations.

Metabolic Alkalosis

pH >7.45 with high HCO₃; commonly from vomiting, diuretics, or GI suctioning.

Respiratory Acidosis

pH

Respiratory Alkalosis

pH >7.45 with PaCO₂ <35 mm Hg caused by hyperventilation (anxiety, pain, PE).

Kussmaul Respirations

Deep, rapid breathing pattern that compensates for metabolic acidosis by blowing off CO₂.

ROME Mnemonic

Guide for ABG analysis: Respiratory Opposite, Metabolic Equal changes in pH vs. PaCO₂/HCO₃.

Arterial Blood Gas (ABG)

Laboratory test measuring pH, PaO₂, PaCO₂, and HCO₃ to assess acid-base and oxygenation status.

Tic-Tac-Toe Method

Stepwise grid technique used to interpret ABG values quickly and determine acid-base disorders.

Homeostasis

The body’s natural state of equilibrium maintained by adaptive responses within narrow fluid and electrolyte limits.

Body Water Content

Percentage of body weight that is water; varies with age, gender, and fat—higher in infants, lower in older adults.

Intracellular Fluid (ICF)

Fluid inside cells; about 40 \% of body weight and two-thirds of total body water.

Extracellular Fluid (ECF)

All body fluid outside cells; includes interstitial, intravascular, and transcellular compartments.

Interstitial Fluid

ECF located in the spaces between cells.

Intravascular Fluid

ECF within blood vessels; plasma component of blood.

Transcellular Fluid

Specialized ECF in spaces such as cerebrospinal, synovial, pleural, and peritoneal cavities.

Osmolarity

Total milliosmoles per liter of solution (mOsm/L).

Osmolality

Milliosmoles per kilogram of water (mOsm/kg); normal 280-295, >295 = water deficit, <275 = water excess.

Isotonic Solution

IV fluid with the same tonicity as plasma; expands ECF without shifting water between compartments.

Hypotonic Solution

IV fluid with lower osmolality than plasma; moves water from ECF into cells.

Hypertonic Solution

IV fluid with higher osmolality than plasma; pulls water from cells into vascular space, raising serum sodium.

First Spacing

Normal distribution of fluid between ICF and ECF.

Second Spacing

Abnormal accumulation of interstitial fluid—edema.

Third Spacing

Fluid trapped in areas where it is difficult to exchange with ECF, e.g., ascites or pleural effusion.

Antidiuretic Hormone (ADH)

Pituitary hormone that tells kidneys to reabsorb water, reducing urine output.

Thirst Mechanism

Hypothalamic drive that increases fluid intake when osmolality rises or volume falls.

Aldosterone

Adrenal cortical hormone that promotes sodium and water reabsorption and potassium excretion by the kidneys.

Atrial Natriuretic Peptide (ANP)

Hormone released by atria when stretched; inhibits RAAS and ADH, promoting sodium and water excretion.

Brain Natriuretic Peptide (BNP)

Hormone from ventricles signaling fluid overload; actions similar to ANP.

Hypovolemia

ECF volume deficit from fluid loss, inadequate intake, or plasma-to-interstitial shift.

Hypervolemia

ECF volume excess from fluid intake, retention, or interstitial-to-plasma shift.

Maintenance IV Fluids

Solutions given to meet daily fluid and electrolyte needs when oral intake is insufficient.

Replacement IV Fluids

Solutions administered to correct existing fluid or electrolyte losses.

Normal Saline (0.9 % NaCl)

Isotonic fluid; expands IV volume, compatible with blood products, higher overload risk.

Lactated Ringer’s Solution

Isotonic balanced electrolyte fluid containing lactate, K, Ca; treats burns/GI losses; avoid in liver dysfunction or hyperkalemia.

Dextrose 5 % in Water (D5W)

Provides 170 kcal/L; free water moves into cells; treats hypernatremia but supplies no electrolytes.

3 % Saline

Hypertonic saline used for severe hyponatremia; requires close monitoring for fluid overload and neurologic changes.

D5 ½ Normal Saline

Dextrose 5 \% in 0.45 \% NaCl; hypertonic maintenance fluid often supplemented with KCl.

D10W

10 \% dextrose in water; hypertonic, 340 kcal/L; maximum dextrose strength suitable for peripheral infusion.

Colloid Solution

IV fluid containing large molecules (e.g., proteins, starches) that remain in the intravascular space.

Plasma Expanders

Colloid products such as albumin, plasma, or packed RBCs that raise osmotic pressure and increase vascular volume.

Osmotic Pressure

Force exerted by solutes to draw water across a semipermeable membrane.

Hyponatremia

Serum sodium <135 mEq/L; usually from water excess or sodium loss; causes confusion, seizures.

Hypernatremia

Serum sodium >145 mEq/L; results from water deficit or sodium gain; causes intense thirst and restlessness.

Hypokalemia

Serum potassium <3.5 mEq/L; leads to muscle weakness, dysrhythmias, and U-wave ECG changes.

Hyperkalemia

Serum potassium >5.0 mEq/L; causes muscle cramps, peaked T waves, and potential cardiac arrest.

ECG Changes in Hyperkalemia

Tall peaked T waves, widened QRS, prolonged PR interval, and flat P waves.

Hypocalcemia

Total calcium <8.6 mg/dL; manifests as tetany, positive Chvostek’s/Trousseau’s signs.

Hypercalcemia

Total calcium >10.2 mg/dL; produces weakness, decreased reflexes, and risk of kidney stones.

Hypomagnesemia

Serum magnesium <1.5 mEq/L; causes neuromuscular irritability and ventricular dysrhythmias (torsades de pointes).

Hyperphosphatemia

Serum phosphate >4.5 mg/dL; often with renal failure and accompanies low calcium levels.

Metabolic Acidosis

pH <7.35 with low HCO_3; caused by DKA, diarrhea, renal failure; features Kussmaul respirations.

Metabolic Alkalosis

pH >7.45 with high HCO_3; commonly from vomiting, diuretics, or GI suctioning.

Respiratory Acidosis

pH

Respiratory Alkalosis

pH >7.45 with PaCO_2 <35 mm Hg caused by hyperventilation (anxiety, pain, PE).

Kussmaul Respirations

Deep, rapid breathing pattern that compensates for metabolic acidosis by blowing off CO_2.

ROME Mnemonic

Guide for ABG analysis: Respiratory Opposite, Metabolic Equal changes in pH vs. PaCO2/HCO3.

Arterial Blood Gas (ABG)

Laboratory test measuring pH, PaO2, PaCO2, and HCO_3 to assess acid-base and oxygenation status.

Tic-Tac-Toe Method

Stepwise grid technique used to interpret ABG values quickly and determine acid-base disorders.