Body Electrolytes Clinical Chemistry Practice Flashcards

Flashcards covering the vocabulary and definitions found in Bishop Dominic Wamamba's Clinical Chemistry Notes on Body Electrolytes.

Electrolyte

A chemical substance that dissociates into positively and negatively charged ions when dissolved in water or body fluids, enabling them to conduct electrical current.

Cation

A positively charged ion, such as $Na^{+}$, $K^{+}$, or $Ca^{2+}$.

Anion

A negatively charged ion, such as $Cl^{-}$ or $HCO_{3}^{-}$, which helps maintain electrical neutrality.

Total Body Water (TBW)

The total amount of water in the body, accounting for approximately $60\%$ of body weight in adults and up to $75\text{--}80\%$ in neonates.

Intracellular Fluid (ICF)

Fluid contained within the cells, constituting approximately two-thirds of total body water; its major cation is $K^{+}$.

Extracellular Fluid (ECF)

Fluid outside the cells, including plasma and interstitial fluid, where $Na^{+}$ is the predominant cation.

Osmolality

The concentration of solute per kilogram of water, primarily determined by sodium, chloride, and potassium in the body.

Osmosis

The movement of water across a semipermeable membrane toward an area of higher electrolyte concentration.

Tonicity

The effect of a solution on cell volume, determined by the effective osmolality of the solution relative to plasma.

Hyponatremia

A decrease in serum sodium concentration below $135 \, \text{mmol/L}$, often reflecting a disorder of excess body water relative to sodium.

Hypernatremia

A serum sodium concentration above $145 \, \text{mmol/L}$, almost always reflecting a deficit of body water relative to sodium.

Hypokalemia

A serum potassium concentration below $3.5 \, \text{mmol/L}$, which can predispose patients to cardiac arrhythmias and muscle weakness.

Hyperkalemia

A serum potassium concentration above $5.0 \, \text{mmol/L}$, frequently caused by renal failure and posing a risk of cardiac arrest.

Chloride Shift

A physiological process in red blood cells where $Cl^{-}$ ions are exchanged with $HCO_{3}^{-}$ to facilitate $CO_{2}$ transport and maintain pH.

Bicarbonate ($HCO_{3}^{-}$)

The principal buffer of the extracellular fluid, serving as a marker for metabolic acid-base disorders.

Ionized Calcium

The biologically active, free fraction of serum calcium that accounts for approximately $45\text{--}50\%$ of total calcium.

Hydroxyapatite

The crystalline form of calcium and phosphate, formulated as $\text{Ca}_{10}(\text{PO}_{4})_{6}(\text{OH})_{2}$, that provides structural strength to bones and teeth.

Hypomagnesemia

A reduced serum magnesium concentration (typically $< 0.7 \, \text{mmol/L}$) that often causes refractory hypokalemia and hypocalcemia.

Phosphate ($\text{PO}_{4}^{3-}$)

A major intracellular anion essential for energy metabolism through $\text{ATP}$, bone mineralization, and acid-base buffering.

Sulfate ($\text{SO}_{4}^{2-}$)

A minor extracellular anion derived from sulfur-containing amino acids, relevant in detoxification and high anion gap metabolic acidosis in renal failure.

Anion Gap (AG)

A calculated lab value, typically $\text{Na}^{+} - (\text{Cl}^{-} + \text{HCO}_{3}^{-})$, used to identify unmeasured anions in metabolic acidosis.

Ion-Selective Electrode (ISE)

The standard laboratory method for measuring electrolytes like sodium, potassium, and chloride based on the electrical potential across a selective membrane.

Pseudohyponatremia

An artifactual low sodium result occurring with indirect ISE when excess solids like lipids or proteins reduce the plasma water fraction.

Hemolysis

The breakdown of red blood cells, which falsely elevates potassium, phosphate, and magnesium in a blood sample.

Aldosterone

A hormone from the adrenal cortex that increases $Na^{+}$ reabsorption and $K^{+}$ excretion in the distal nephron.

Antidiuretic Hormone (ADH)

A hormone that regulates water balance by inserting aquaporin-2 channels in the renal collecting ducts.

Westgard Rules

A set of statistical decision rules used to detect random and systematic errors in laboratory quality control.

Delta Check

A quality control procedure comparing a patient's current lab result with previous results to identify significant changes or potential errors.

Basic Metabolic Panel (BMP)

A routine lab test including 8 parameters: sodium, potassium, chloride, bicarbonate, urea, creatinine, glucose, and sometimes calcium.

Chvostek sign

Facial muscle twitching elicited by tapping the facial nerve, indicating latent neuromuscular excitability seen in hypocalcemia.