Pathophysiology: Acid-Base, Electrolytes, and Fluid Homeostasis Flashcards

Vocabulary practice flashcards covering foundational pathophysiology concepts including acid-base balance, arterial blood gas interpretation, electrolyte imbalances, fluid volume dynamics, and homeostatic regulation.

Acidosis

A state in which blood pH drops below $7.35$ due to an excess of acid in the blood.

Alkalosis

A state in which blood pH rises above $7.45$ due to an excess of base in the blood.

Chemical Buffer Systems

Immediate chemical mechanisms, including the bicarbonate-carbonic acid system, phosphate buffers, and protein buffers, that bind or release free hydrogen ions to prevent sudden pH shifts.

Carbonic Acid Equation

The chemical reaction $CO_2 + H_2O \rightleftharpoons H_2CO_3 \rightleftharpoons HCO_3^- + H^+$ facilitated by carbonic anhydrase, illustrating how carbon dioxide functions as an acid in the bloodstream.

$$PaCO_2$$

The partial pressure of arterial carbon dioxide with a normal range of $35$ to $45\text{ mmHg}$, serving as the primary respiratory indicator regulated entirely by the lungs.

$HCO_3^-$ (Bicarbonate)

The primary metabolic indicator with a normal range of $22$ to $26\text{ mEq/L}$, serving as a base produced and regulated by the kidneys.

Respiratory Acidosis

An acid-base imbalance driven by arterial $CO_2$ retention resulting from hypoventilation, airway constriction, or brainstem damage.

Respiratory Alkalosis

An acid-base imbalance driven by excessive $CO_2$ elimination through hyperventilation, commonly caused by anxiety, high altitude, or early asthma exacerbation.

Metabolic Acidosis

An acid-base imbalance caused by a loss of bicarbonate or accumulation of metabolic acid, seen in severe diarrhea, kidney failure, diabetic ketoacidosis, or excessive alcohol ingestion.

Metabolic Alkalosis

An acid-base imbalance caused by a loss of acid or gain of excess bicarbonate, driven by severe vomiting, prolonged gastric suctioning, diuretics, or sodium bicarbonate overuse.

ROME Mnemonic

A mnemonic standing for Respiratory Opposite, Metabolic Equal, indicating that $PaCO_2$ moves in the opposite direction of pH in respiratory disorders, while $HCO_3^-$ moves in the same direction in metabolic disorders.

Uncompensated Blood Gas

An arterial blood gas state where the pH is abnormal and only one compensating system ($PaCO_2$ or $HCO_3^-$) is abnormal, while the other remains within normal limits.

Partially Compensated Blood Gas

An arterial blood gas state where the pH remains abnormal, but both $PaCO_2$ and $HCO_3^-$ are abnormal because the secondary system has begun responding.

Fully Compensated Blood Gas

An arterial blood gas state where the pH has returned to the normal range ($7.35$ to $7.45$), but both $PaCO_2$ and $HCO_3^-$ remain abnormal.

Sodium-Potassium ATPase Pump

An active transport pump burning ATP to keep sodium primarily in the extracellular fluid and potassium in the intracellular fluid by pumping $3$ sodium ions out for every $2$ potassium ions in.

Hyponatremia

A serum sodium level below $135\text{ mEq/L}$, leading to a hypotonic extracellular environment that causes water to rush into cells, resulting in cellular swelling and neurological symptoms.

Hypernatremia

A serum sodium level above $145\text{ mEq/L}$, creating a hypertonic extracellular environment that pulls water out of cells, resulting in cellular shrinkage and neuronal dehydration.

Hypokalemia

A serum potassium level below $3.5\text{ mEq/L}$, causing cell membrane hyperpolarization, delayed cardiac repolarization, and overall muscle weakness.

Hyperkalemia

A serum potassium level above $5.0\text{ mEq/L}$, causing partial cell membrane depolarization, early neuromuscular excitability, and high risk of fatal cardiac dysrhythmias.

Hypocalcemia

A serum calcium level below $8.5\text{ mg/dL}$, removing the normal sedative effect on voltage-gated sodium channels and causing neuromuscular hyperexcitability, tetany, and paresthesias.

Hypercalcemia

A serum calcium level above $10.5\text{ mg/dL}$, acting as a neuromuscular sedative that depresses reflexes, slows muscle responsiveness, and leads to lethargy and confusion.

Chvostek's Sign

A clinical indication of hypocalcemia characterized by facial muscle twitching when tapping the facial nerve in front of the ear.

Trousseau's Sign

A clinical sign of hypocalcemia manifested as carpal spasm and contraction of the hand and wrist when inflating a blood pressure cuff on the upper arm.

Saponification

A process occurring in acute pancreatitis where released lipase breaks down fat into free fatty acids that bind free calcium ions to create soap in the retroperitoneum, precipitating severe hypocalcemia.

Refeeding Syndrome

A condition in malnourished or alcoholic patients re-fed with carbohydrates, where a sudden insulin spike forces phosphate into cells, causing severe hypophosphatemia and critical ATP depletion.

Tonicity

The ability of an extracellular solution to alter cell volume by affecting the direction and rate of osmosis based on relative solute concentrations across a membrane.

Hypotonic Solution

A solution with a lower solute concentration and higher water concentration than the inside of the cell, causing water to flow into the cell and resulting in cell swelling.

Isotonic Solution

A solution with a solute concentration equal to that of the cell interior, resulting in no net movement of water across the membrane and maintaining stable cell shape.

Hypertonic Solution

A solution with a higher solute concentration and lower water concentration than the inside of the cell, causing water to leave the cell and resulting in cell shrinkage.

Dehydration

An osmolar fluid imbalance characterized by altered concentration and cellular hydration shifts, rather than purely an intravascular volume loss.

Hypovolemia

An isotonic fluid volume deficit involving proportional loss of both water and electrolytes from the intravascular compartment.

Oliguria

A clinical state characterized by abnormally low or decreased urine production.

Polyuria

A clinical state characterized by excessive or abnormally high volume urine production.

Hemodilution

A condition in fluid volume excess where expanded plasma volume dilutes circulating red blood cells and plasma proteins, lowering hematocrit and serum sodium concentrations.

Pulmonary Crackles

Popping sounds heard during lung auscultation when air moves through fluid-filled alveoli, serving as a critical indicator of fluid volume excess and pulmonary edema.

Homeostasis

A dynamic equilibrium in which the body utilizes negative feedback loops to continuously monitor variables and execute minute-by-minute corrections within dynamic normal ranges.

Intracellular Fluid (ICF)

Fluid residing inside cells, making up approximately two-thirds ($\frac{2}{3}$) of total body water.

Extracellular Fluid (ECF)

Fluid residing outside cells, making up one-third ($\frac{1}{3}$) of total body water and divided into intravascular, interstitial, and transcellular spaces.

Osmosis

The passive movement of water across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.

Renin-Angiotensin-Aldosterone System (RAAS)

An endocrine and renal dynamic pathway activated by low blood pressure, low sodium, or reduced renal perfusion to promote systemic vasoconstriction and renal sodium and water reabsorption.

Insensible Losses

Unmeasurable fluid output escaping the body through skin evaporation (sweat) and humidified air expired by the lungs.