Fluid, Electrolyte, and Acid-Base Imbalances – Core Vocabulary

A comprehensive set of vocabulary flashcards covering key fluids, electrolytes, hormones, imbalances, and acid-base concepts from Chapter 2. Use them to test recognition of terms and their clinical significance.

Intracellular Fluid (ICF)

The fluid located inside body cells; largest single fluid compartment.

Extracellular Fluid (ECF)

All body fluid outside cells, including plasma, interstitial, cerebrospinal, and transcellular fluids.

Intravascular Fluid (IVF)

The plasma portion of blood found within blood vessels.

Interstitial Fluid (ISF)

Fluid that bathes and surrounds tissue cells, lying between capillaries and cells.

Cerebrospinal Fluid (CSF)

Clear fluid circulating in and around the brain and spinal cord; part of the ECF.

Transcellular Fluid

Specialized secretions such as synovial, peritoneal, pleural, and ocular fluids.

Hydrostatic Pressure

The pushing force exerted by a fluid against the walls of its container, driving filtration out of capillaries.

Osmotic Pressure

The pulling force created by solute concentration differences, drawing water toward higher solute areas.

Osmoreceptor

Hypothalamic sensor that detects plasma osmolarity and activates thirst.

Antidiuretic Hormone (ADH)

Posterior pituitary hormone that promotes water reabsorption in kidney tubules.

Aldosterone

Adrenal cortex hormone that increases sodium and water reabsorption and potassium excretion.

Atrial Natriuretic Peptide (ANP)

Cardiac hormone that lowers blood volume by increasing renal sodium and water loss.

T-type Natriuretic Peptide

Myocardial peptide that, like ANP, helps regulate fluid, sodium, and potassium balance.

Filtration

Movement of water and solutes from blood (high hydrostatic pressure) to ISF (low pressure) across a membrane.

Osmosis

Passive movement of water from an area of low solute concentration to high solute concentration across a semipermeable membrane.

Edema

Excess fluid accumulation in the interstitial compartment causing tissue swelling.

Pitting Edema

Indentation (“pit”) that remains after finger pressure due to excess interstitial fluid.

Pulmonary Edema

Fluid accumulation in alveoli and lung interstitium, often from increased capillary hydrostatic pressure.

Hypovolemia

A state of reduced circulating blood volume often accompanying dehydration.

Dehydration

Deficit of body water resulting from inadequate intake, excessive losses, or both.

Third-Spacing

Fluid shift from the vascular space into a body cavity or tissue where it is trapped and unavailable for circulation.

Sodium (Na⁺)

Primary ECF cation crucial for fluid balance, nerve conduction, and muscle contraction.

Hyponatremia

Serum sodium <135 mEq/L; often causes cellular swelling and cerebral edema.

Hypernatremia

Serum sodium >145 mEq/L, usually from water loss or sodium gain, producing cellular dehydration.

Potassium (K⁺)

Major intracellular cation essential for nerve impulse transmission and cardiac rhythm.

Hypokalemia

Serum potassium <3.5 mEq/L, leading to muscle weakness and dangerous cardiac dysrhythmias.

Hyperkalemia

Serum potassium >5 mEq/L, producing muscle paralysis and life-threatening cardiac arrest.

Calcium (Ca²⁺)

Important extracellular cation for bone structure, nerve stability, muscle contraction, and blood clotting.

Hypocalcemia

Low serum calcium causing tetany, muscle twitching, and weak heart contractions.

Hypercalcemia

Elevated serum calcium leading to muscle weakness, lethargy, and dysrhythmias.

Magnesium (Mg²⁺)

Predominantly intracellular ion involved in enzyme reactions and neuromuscular function.

Hypomagnesemia

Low magnesium, often from malnutrition or alcoholism, causing increased neuromuscular excitability.

Hypermagnesemia

High magnesium, usually due to renal failure, resulting in depressed reflexes and respiration.

Phosphate (PO₄³⁻)

Ion vital for ATP, bone mineralization, and acid-base buffering; inversely related to calcium.

Hypophosphatemia

Low serum phosphate from malabsorption, diarrhea, or excessive antacids.

Hyperphosphatemia

High phosphate level, commonly seen in renal failure patients.

Chloride (Cl⁻)

Major extracellular anion linked to sodium and inverse with bicarbonate in acid-base shifts.

Hypochloremia

Low chloride, often with vomiting-induced alkalosis.

Hyperchloremia

Excess chloride from high sodium chloride intake, potentially causing acidosis.

Electrolyte

Ionized substance in body fluids that conducts electricity and maintains physiologic functions.

Total Body Water

Combined volume of water in all body compartments; ~60 % of adult male weight.

Insensible Water Loss

Continuous water vapor loss from lungs and skin that is not consciously perceived.

Diuresis

Increased urine output leading to fluid and electrolyte loss.

Specific Gravity (Urine)

Measurement reflecting urine concentration; low in fluid excess, high in dehydration.

Hematocrit

Percentage of blood volume occupied by red blood cells; rises in dehydration, falls in edema.

Albumin

Plasma protein that creates colloid osmotic pressure; loss contributes to edema formation.

Lymphatic Obstruction

Blockage preventing protein-rich fluid return, causing localized edema.

Histamine

Inflammatory mediator that increases capillary permeability and promotes localized edema.

Ischemia

Reduced blood flow leading to tissue oxygen deprivation and possible breakdown.

Thirst Mechanism

Hypothalamic response that stimulates fluid intake when osmolarity rises.

Diabetic Ketoacidosis (DKA)

Serious diabetes complication with hyperglycemia, ketone production, and fluid–electrolyte loss.

Milk-Alkali Syndrome

Hypercalcemia resulting from excessive calcium and absorbable alkali ingestion.

Tetany

Continuous muscle contraction due to hypocalcemia-induced neuromuscular excitability.

Orthostatic Hypotension

Drop in blood pressure upon standing, common in fluid deficit.

Pulmonary Congestion

Fluid accumulation in lungs, producing cough and rales in fluid excess states.

Acid-Base Balance

Maintenance of serum pH within 7.35–7.45 through buffers, lungs, and kidneys.

Buffer

Chemical pair that resists pH changes by accepting or releasing hydrogen ions.

Sodium Bicarbonate–Carbonic Acid Buffer

Major ECF buffer system regulated by respiration and renal function.

Hydrogen Ion (H⁺)

Proton determining acidity; excess causes acidosis, deficit causes alkalosis.

Bicarbonate Ion (HCO₃⁻)

Alkaline component of buffer systems; kidney reabsorption or loss alters metabolic pH.

Carbonic Acid (H₂CO₃)

Weak acid formed from CO₂ and H₂O; respiratory control adjusts its level.

Respiratory Acidosis

pH disturbance from CO₂ retention due to hypoventilation or lung disease.

Metabolic Acidosis

Decrease in bicarbonate or acid gain from renal failure, DKA, diarrhea, or shock.

Respiratory Alkalosis

pH increase from excessive CO₂ loss caused by hyperventilation.

Metabolic Alkalosis

pH elevation from bicarbonate excess or acid loss (e.g., vomiting, antacids).

Compensation (Acid-Base)

Physiologic adjustment by lungs or kidneys to restore normal serum pH ratio.

Decompensation (Acid-Base)

Failure of compensatory mechanisms resulting in life-threatening pH imbalance.

Hyperventilation

Rapid, deep breathing that lowers CO₂ and may induce respiratory alkalosis.

Buffer Systems

Multiple chemical pairs (bicarbonate, phosphate, hemoglobin, protein) that stabilize pH.

Kidney Role in pH

Organ adjusts acid excretion and bicarbonate reabsorption; slow but powerful control.

Respiratory System Role in pH

Regulates CO₂ (carbonic acid) levels through rate and depth of breathing.

Serum pH

Measure of blood acidity/alkalinity; normal range 7.35–7.45, incompatible with life below 6.8 or above 7.8.

Homeostasis

Dynamic equilibrium of internal environment, requiring proper fluid, electrolyte, and pH balance.

Osmotic Pressure Shift into Cells

Water movement into cells when ECF osmolarity drops, as in hyponatremia, causing swelling.

Capillary Exchange

Process of filtration, diffusion, osmosis, and active transport across capillary walls.

Specific Gravity High

Concentrated urine indicating dehydration or fluid deficit.

Specific Gravity Low

Dilute urine associated with fluid excess or diabetes insipidus.

Albumin Loss

Decrease in plasma protein lowering osmotic pressure and promoting edema.

Lymphatic Circulation

Return pathway for filtered proteins and fluid; obstruction causes edema.

Water Balance

Equivalence between fluid intake and loss—about 2500 mL daily in adults.

Insufficient ADH (Diabetes Insipidus)

Hormonal deficiency causing large volumes of dilute urine and possible hypernatremia.

Histamine-Induced Edema

Localized swelling produced by increased capillary permeability during inflammation.

Seizures (Electrolyte)

Neurologic event often precipitated by severe hyponatremia or alkalosis.

Coma (pH)

Severe CNS depression resulting from decompensated acidosis or alkalosis.