Acid-Base Imbalance

Vocabulary flashcards covering key terms and definitions related to acid-base balance, buffering systems, ABGs, and related physiology.

Homeostasis

The body's ability to maintain a stable internal environment, including regulation of pH and acid-base balance.

Acid-base balance

Regulation of hydrogen ion concentration (H+), bicarbonate (HCO3-), and CO2 to keep body fluids’ pH in the normal range (7.35–7.45).

pH

A measure of hydrogen ion concentration; lower pH = more acidic, higher pH = more basic; expressed as the negative logarithm of [H+].

Hydrogen ion concentration (H+)

Amount of free hydrogen ions in solution; determines acidity.

Bicarbonate (HCO3-)

A base that buffers acids in the blood; part of the bicarbonate–carbonic acid buffering system.

Carbon dioxide (CO2)

A gas whose partial pressure drives respiration; combines with water to form carbonic acid in buffering.

Acidemia

Arterial blood pH < 7.35.

Alkalemia

Arterial blood pH > 7.45.

Acidosis

Process that adds acid or removes base from the body, lowering pH.

Alkalosis

Process that removes acid or adds base to the body, increasing pH.

Buffer

Molecules that react with acid and base to prevent large pH changes (e.g., bicarbonate, phosphate, hemoglobin, proteins).

Bicarbonate–carbonic acid buffer system

Principal buffering system; CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-; helps maintain pH.

Phosphate buffer

Buffer important for intracellular buffering.

Hemoglobin-oxyhemoglobin buffer

Buffer that maintains pH in venous and arterial blood.

Protein buffer

Buffers that bind or release H+ via amino acid residues in proteins.

Anion gap

Difference Na+ − (HCO3- + Cl-); helps identify cause of metabolic acidosis; normal ≈12; increased with lactic or ketoacidosis; decreased with hyperchloremic acidosis.

Base excess (BE)

Measure of the total buffer base in blood; normally ±2 mEq/L; ~50 mEq/L of buffer available.

Compensation

Physiologic mechanisms (respiratory or renal) that minimize pH changes without correcting the underlying disorder.

Correction

Resolution of the underlying disorder leading to normalization of pH.

ABG (Arterial Blood Gases)

Test that measures pH, PaCO2, HCO3-, BE, and O2 to assess acid-base status and gas exchange.

PaCO2

Partial pressure of carbon dioxide in arterial blood; reflects ventilatory status.

HCO3- (bicarbonate)

Primary metabolic buffer in plasma; its level helps define metabolic components of acid-base disorders.

pH in ABG

Indicates acidity or alkalinity (normal arterial pH 7.35–7.45).

Respiratory acidosis

pH < 7.35 with PaCO2 > 45 mmHg; due to hypoventilation or impaired gas exchange.

Respiratory alkalosis

pH > 7.45 with PaCO2 < 35 mmHg; due to hyperventilation.

Metabolic acidosis

pH < 7.35 with HCO3- < 24 mEq/L; due to bicarbonate loss or excess acid.

Metabolic alkalosis

pH > 7.45 with HCO3- > 28 mEq/L; due to bicarbonate gain or acid loss.

Respiratory compensation

Lungs adjust ventilation to minimize pH change in metabolic disturbances (does not fully normalize pH).

Renal compensation

Kidneys adjust reabsorption/secretion (HCO3-, H+, ammonium) to restore pH.

K+ shifts in acidosis/alkalosis

Acidosis: K+ moves out of cells (risk of hyperkalemia); alkalosis: K+ moves into cells (risk of hypokalemia).

Kussmaul respiration

Deep, rapid breathing typically seen in metabolic acidosis (e.g., DKA) as a compensatory mechanism.

ROME mnemonic

Respiratory disorders produce opposite changes in pH and PaCO2; Metabolic disorders produce equal changes in pH and HCO3-.

Oxygenation

Ability to take in oxygen (O2) and deliver it to tissues.

Ventilation

Ability to remove carbon dioxide (CO2) through breathing.

Carbonic acid

H2CO3; formed from CO2 and H2O; part of the buffering equilibrium.

Anion gap normal value

Normal anion gap ≈ 12 mEq/L; used to differentiate causes of metabolic acidosis.