Electrolytes

a

Ions capable of carrying a positive charge and migrating toward the cathode are classified as:

a) Cations

b) Anions

c) Zwitterions

d) Neutrons

e) Positrons

b

Which of the following is classified as a major intracellular electrolyte?

a) Sodium

b) Potassium

c) Calcium

d) Chloride

e) Bicarbonate

c

Which of the following represents the most abundant cation in the extracellular fluid (ECF)?

a) Calcium

b) Potassium

c) Sodium

d) Magnesium

e) Phosphate

d

What is the normal reference value for plasma osmolality, which is primarily determined by the concentration

of sodium?

a) 135 mmol/L

b) 145 mmol/L

c) 280 mmol/L

d) 295 mmol/L

e) 310 mmol/L

e

Which hormone released by the adrenal gland directly regulates sodium concentration by stimulating direct

renal reabsorption of sodium?

a) Cortisol

b) Antidiuretic hormone (ADH)

c) Calcitonin

d) Parathyroid hormone (PTH)

e) Aldosterone

a

Approximately what percentage of filtered sodium is reabsorbed in the proximal convoluted tubules of the

kidney?

a) 80%

b) 20-25%

c) 50%

d) 10%

e) 99%

a

Which of the following represents the normal reference range for sodium in serum or plasma specimens?

a) 135 – 145 mmol/L

b) 135 – 150 mmol/L

c) 140 – 220 mmol/L

d) 98 – 107 mmol/L

e) 3.5 – 5.1 mmol/L

b

Which of the following conditions is classified as a cause of hyponatremia due to increased sodium loss?

a) SIADH

b) Addison's Disease (Hypoaldosteronism)

c) Acute/Chronic Renal Failure

d) Hepatic Cirrhosis

e) Congestive Heart Failure

c

Which of the following conditions is a primary cause of hyponatremia due to increased water retention rather

than sodium loss?

a) Ketonuria

b) Prolonged vomiting or diarrhea

c) Congestive Heart Failure

d) Thiazide diuretic use

e) Salt-losing nephropathy

d

Under which subcategory of hyponatremia causes is SIADH classified in clinical regulation?

a) Increased Sodium Loss

b) Increased Water Retention

c) Pseudohyponatremia

d) Water Imbalance

e) Primary Hypoparathyroidism

e

Pseudohyponatremia occurs when sodium is measured using indirect ion-selective electrodes (ISE) in

patients with hyperproteinemia and hyperlipidemia. What is the most common cause of

pseudohyponatremia?

a) High blood urea nitrogen

b) Marked hyperglycemia

c) Extreme leukocytosis

d) In-vitro thrombocytosis

e) In-vitro marked hemolysis

a

Which category of hyponatremia based on osmolality is considered the most common?

a) Low osmolality

b) Normal osmolality

c) High osmolality

d) Isosmotic hyponatremia

e) Hyperosmotic hyponatremia

b

Which of the following electrolyte imbalances is associated with normal osmolality hyponatremia?

a) Mannitol infusion

b) Hypermagnesemia

c) Hyperglycemia

d) Severe ketonuria

e) Addison's disease

c

Which of the following is associated with high osmolality hyponatremia?

a) SIADH

b) Lithium excess

c) Hyperglycemia

d) Hyperproteinemia

e) In vitro hemolysis

d

Which of the following conditions is classified under hypernatremia due to excess water loss?

a) Conn's Disease (Hyperaldosteronism)

b) Sodium bicarbonate infusion

c) Ingestion of sea water

d) Diabetes insipidus

e) Cushing's Syndrome

e

Which of the following causes hypernatremia primarily through increased sodium intake or retention?

a) Diabetes insipidus

b) Severe dehydration

c) Profuse sweating

d) Prolonged diarrhea

e) Hyperaldosteronism (Conn's Disease)

a

In a patient presenting with hypernatremia, a urine osmolality of <300 mOsm/kg is indicative of which

condition?

a) Diabetes insipidus (DI)

b) Osmotic diuresis

c) Gastrointestinal loss of hypotonic fluid

d) Extrarenal loss of water

e) Partial defect in AVP secretion

b

A urine osmolality of 300-700 mOsm/kg in a hypernatremic patient is clinically associated with which of the

following?

a) Gastrointestinal loss of hypotonic fluid

b) Partial defect in AVP secretion or defect in response to AVP

c) Complete diabetes insipidus

d) Excess oral intake of sodium chloride

e) Primary loss of thirst

c

Which of the following conditions is associated with a urine osmolality of >700 mOsm/kg in a patient with

hypernatremia?

a) Osmotic diuresis

b) Partial defect in AVP secretion

c) Loss of thirst

d) Complete diabetes insipidus

e) SIADH

d

At what concentration of serum sodium do gastrointestinal (GI) symptoms such as nausea and vomiting

typically present?

a) 135 – 140 mmol/L

b) 130 – 135 mmol/L

c) 120 – 125 mmol/L

d) 125 – 130 mmol/L

e) 115 – 120 mmol/L

e

Neuropsychiatric symptoms of hyponatremia, such as headache, lethargy, ataxia, seizures, and coma,

typically manifest when sodium levels drop below what value?

a) 135 mmol/L

b) 130 mmol/L

c) 120 mmol/L

d) 115 mmol/L

e) 125 mmol/L

a

Severe hypernatremia with a serum sodium concentration exceeding 160 mmol/L is associated with what

mortality rate?

a) 60-75%

b) 10-20%

c) 30-40%

d) 45-55%

e) 80-90%

b

What is the expected effect of marked in-vitro hemolysis on sodium measurements in serum or plasma?

a) Falsely increases sodium due to cellular release

b) Falsely decreases sodium due to a dilutional effect

c) No change, as sodium is extracellular and unaffected by lysis

d) Interferes with electrode potentiometry by coating the membrane

e) Causes rapid oxidation of uranyl acetate reagent

c

In Flame Emission Photometry, sodium ions emit light of what characteristic color when excited in a flame?

a) Violet

b) Red

c) Yellow

d) Green

e) Orange-red

c

The routine and most commonly used method for sodium analysis is Ion Selective Electrode (ISE). What

membrane material is utilized in the sodium measuring electrode?

a) Liquid membrane impregnated with valinomycin

b) Polycrystalline silver halide-silver sulfide membrane

c) Glass aluminum silicate / ion exchange membrane

d) Calmagite-impregnated organic membrane

e) Titan yellow dye-lake membrane

d

Which method of Ion Selective Electrode (ISE) preparation is preferred in hyperlipidemic and

hyperproteinemic samples to prevent the pseudohyponatremia effect?

a) Indirect ISE, because of dilution of interfering proteins

b) Atomic Absorption Spectrometry

c) Fiske-Subbarow Method

d) Direct ISE, because undiluted samples interact with the membrane

e) Schales and Schales mercuric nitrate titration

a

In the Albanese and Lein / Sunderman and Delory colorimetric method for sodium, what is the end product

formed after adding water to the precipitate?

a) Yellow Solution

b) Yellow-Brown Complex

c) Blue-Violet Solution

d) Reddish Complex

e) Stable Red Lake

b

The Trinder colorimetric method for sodium precipitates the ion using Magnesium Uranyl Acetate. What

reagent is subsequently added to produce a yellow-brown complex?

a) Diphenylcarbazone

b) Thioglycolic Acid

c) Mercuric Thiocyanate

d) 8-hydroxyquinoline

e) Polyvinyl Alcohol

b

Potassium is the major intracellular cation. How does its intracellular concentration compare to its plasma

concentration?

a) Intracellular concentration is 20x less than extracellular concentration

b) Intracellular concentration is 20x greater than extracellular concentration

c) Intracellular concentration is 50x greater than extracellular concentration

d) Intracellular concentration is 100x greater than extracellular concentration

e) Intracellular concentration is equal to extracellular concentration

d

Which anatomical structure of the kidney serves as the principal determinant of urinary potassium excretion

under the influence of aldosterone?

a) Glomerulus

b) Proximal tubule

c) Loop of Henle

d) Distal tubules and collecting ducts

e) Ascending thick limb

e

Which of the following compounds promotes the cellular uptake of potassium from extracellular fluid by

increasing Na-K ATPase pump activity?

a) Propranolol

b) Digitalis

c) Digoxin

d) Captopril

e) Epinephrine

a

Which of the following drugs impairs potassium cellular uptake by directly decreasing Na-K ATPase pump

activity?

a) Digitalis

b) Epinephrine

c) Insulin

d) Spironolactone

e) Captopril

b

What is the normal reference range for potassium in serum or plasma specimens?

a) 135 – 145 mmol/L

b) 3.5 – 5.1 mmol/L

c) 33 – 86 mmol/d

d) 8.8 – 10.3 mg/dL

e) 0.63 – 1.0 mmol/L

c

Which of the following is a cause of hypokalemia classified under renal loss?

a) Diarrhea

b) Alkalosis

c) Cushing Syndrome

d) Malabsorption

e) Insulin Overdose

a

Leukocytosis is associated with pseudohypokalemia (falsely decreased potassium) because of which

mechanism?

a) Active white blood cells take up potassium from serum at room temperature

b) Active leukemic cells secrete water which dilutes serum potassium

c) WBCs compete for binding with the valinomycin electrode membrane

d) Leukocytes precipitate with potassium sodium cobaltinitrite in-vitro

e) Leukemic cells produce an enzyme that degrades potassium ions

b

Which of the following drugs causes hyperkalemia by acting as a potassium-sparing diuretic?

a) Captopril

b) Spironolactone

c) Digoxin

d) Heparin

e) Cyclosporine

c

Which of the following patient or pre-analytical factors is associated with pseudohyperkalemia (falsely

elevated potassium)?

a) Severe leukemia in room temperature storage

b) Marked leukocytosis

c) Thrombocytosis

d) Storing the blood specimen at room temperature

e) Excessive intake of sodium bicarbonate

d

What is the anticoagulant of choice for measuring potassium when attempting to avoid false elevations from

thrombocytosis?

a) EDTA

b) Oxalate

c) Citrate

d) Heparin (Plasma)

e) Sodium Fluoride

e

What is the clinical effect of storing whole blood specimens on wet ice prior to centrifugation?

a) It promotes intracellular shift of potassium

b) It precipitates magnesium uranyl acetate

c) It prevents in-vitro hemolysis

d) It stimulates Na-K ATPase activity

e) It promotes the release of potassium from RBCs into plasma

a

A slight hemolysis (50 mg/dL hemoglobin) will falsely increase serum potassium levels by approximately

what percentage?

a) 3% increase

b) 30% increase

c) 10% increase

d) 15% increase

e) 1% increase

e

Which potassium colorimetric method relies on potassium reacting with sodium tetraphenylboron to form a

colloidal suspension of potassium tetraphenylboron?

a) Lockhead and Purcell method

b) Schales and Schales method

c) Albanese and Lein method

d) Trinder method

e) Hoffman method

e

The ion-selective electrode (ISE) method is the routine method for potassium analysis. What specific

molecule is impregnated in its liquid ion-exchange membrane to selectively bind potassium?

a) Diphenylcarbazone

b) Silver Chloride

c) 8-hydroxyquinoline

d) Titan Yellow

e) Valinomycin

d

Chloride is the major extracellular anion. It is unique as the only known inorganic anion that serves as an

essential activator for which enzyme?

a) Lipase

b) Alkaline Phosphatase

c) G6PD

d) Amylase

e) Creatine Kinase

d

To maintain electroneutrality, red blood cells participate in the 'Chloride Shift'. This physiological process

involves the uptake of Chloride in exchange for which ion?

a) Sodium (Na+)

b) Potassium (K+)

c) Phosphate (PO43-)

d) Bicarbonate (HCO3-)

e) Calcium (Ca2+)

d

In the Schales and Schales (Mercuric Nitrate Titration) method for chloride analysis, what indicator is added

to yield a blue-violet end product of mercuric chloride?

a) Mercuric Thiocyanate

b) Titan Yellow

c) Triethanolamine

d) Diphenylcarbazone

e) 8-hydroxyquinoline

c

Approximately what percentage of total serum calcium circulates in its physiologically active, free ionized

form (Ca2+)?

a) 99%

b) 40%

c) 45%

d) 15%

e) 55%

c

What is the clinical effect of alkalosis on the concentration of physiologically active free ionized calcium in

blood?

a) Alkalosis decreases protein binding, increasing ionized calcium

b) Alkalosis increases vitamin D activity, increasing ionized calcium

c) Alkalosis promotes increased protein binding, decreasing ionized calcium

d) Alkalosis inhibits PTH release, causing severe hypercalcemia

e) Alkalosis causes direct bone resorption, increasing ionized calcium

e

Which of the following regulatory hormones is secreted by the medullary cells of the thyroid gland in

response to hypercalcemia to inhibit parathyroid hormone (PTH) and vitamin D activity?

a) Aldosterone

b) Growth Hormone

c) 1,25-dihydroxycholecalciferol

d) Thyroxine

e) Calcitonin

e

Magnesium regulation is primarily renal. What is the major renal regulatory site for magnesium reabsorption,

where 50% to 60% of filtered magnesium is reabsorbed?

a) Proximal convoluted tubule (PCT)

b) Distal convoluted tubule (DCT)

c) Glomerulus

d) Collecting duct

e) Loop of Henle (Henle's loop)

b

Due to the circadian rhythm of inorganic phosphorus, when are blood concentrations typically at their

highest level?

a) Early morning

b) Late morning

c) Evening

d) Midnight

e) Afternoon