Electrolytes and Body Fluids Practice Questions

Q: All of the following are true about potassium, except

Leaves the cell in the presence of insulin. ***Leaves the cell in the presence of insulin*** - Insulin promotes the uptake of **potassium into cells**, primarily by stimulating the Na+/K+-ATPase pump. - Therefore, insulin actually causes potassium to enter the cell, not leave it, which helps to **lower extracellular potassium levels**. *Mostly concentrated inside the cells* - **Potassium (K+)** is the primary intracellular cation, with concentrations approximately 30 times higher inside cells than outside. - This high intracellular concentration is crucial for maintaining **resting membrane potential** and cellular functions. *Plasma concentration increases at time of metabolic acidosis* - In **metabolic acidosis**, hydrogen ions (H+) shift into cells in exchange for potassium ions, which move out of cells into the extracellular fluid. - This H+/K+ exchange mechanism leads to an **increase in plasma potassium concentration**. *Ingestion of acetazolamide results in potassium loss* - **Acetazolamide** is a carbonic anhydrase inhibitor that acts on the proximal tubule of the kidney. - It inhibits bicarbonate reabsorption, leading to increased delivery of sodium and water to the collecting duct, which promotes **potassium secretion and loss**.

Q: Which of the following is NOT true about body fluids:

Synovial fluid is transcellular fluid. ***Synovial fluid is transcellular fluid*** - This statement is **NOT true** according to most standard classifications. - **Synovial fluid** is classified as a component of **interstitial fluid**, not transcellular fluid. - **Transcellular fluid** refers to specialized fluids formed by active transport across epithelial membranes and includes cerebrospinal fluid (CSF), pleural fluid, peritoneal fluid, pericardial fluid, and digestive secretions. - Synovial fluid, while specialized, is formed by ultrafiltration of plasma and secretion by synoviocytes, and is considered part of the interstitial compartment. *ECF volume of 70 kg adult man would be approximately 14 L* - This statement is **TRUE**. - **Extracellular fluid (ECF)** constitutes approximately **20% of total body weight** in adult males. - For a **70 kg man**: 20% × 70 kg = **14 kg ≈ 14 L** of ECF. *The total body fluid per unit body weight is more in infants as compared to adults* - This statement is **TRUE**. - **Infants** have approximately **75-80% total body water (TBW)** compared to adults with **50-60% TBW**. - This is due to higher metabolic rate, less fat tissue, and different body composition in infants. *Intracellular fluid is 40% of total body weight* - This statement is **TRUE**. - **Intracellular fluid (ICF)** represents approximately **two-thirds of total body water**, which equals about **40% of total body weight** in adults. - ICF is the largest fluid compartment in the body.

Q: Which of the following is not a general compartment of body fluid?

Peritoneal. ***Peritoneal*** - The **peritoneal fluid** is a component of the **extracellular fluid**, but it is not considered one of the *general* body fluid compartments in the typical physiological classification. - General compartments refer to the broad categories of **intracellular** and **extracellular fluid**, with extracellular being further divided into **interstitial fluid** and **blood plasma**. *Blood plasma* - **Blood plasma** is a major component of the **extracellular fluid** compartment, specifically the **intravascular fluid** that circulates within blood vessels. - It is crucial for **transporting nutrients**, waste products, hormones, and blood cells throughout the body. *Interstitial* - **Interstitial fluid** is a part of the **extracellular fluid**, located in the spaces between cells. - It acts as an **interface** between blood plasma and intracellular fluid, facilitating the exchange of substances. *Intracellular* - **Intracellular fluid (ICF)** is the fluid found *inside* cells and constitutes about two-thirds of the total body water. - It is a primary compartment, essential for **cellular metabolism** and maintaining cell volume.

Q: Interstitial fluid volume can be determined by:

Radioactive sodium and radioactive labelled albumin. ***Radioactive sodium and radioactive labelled albumin*** - **Interstitial fluid volume** (ISF) is the difference between **extracellular fluid** (ECF) and **plasma volume**. - **Radioactive sodium** can be used to estimate ECF, and **radioactive labelled albumin** can be used to estimate plasma volume. *Radioactive iodine and radiolabelled water* - **Radioactive iodine** (often as iodide) is used for **extracellular fluid** (ECF) measurement, not directly for ISF alone. - **Radiolabelled water** (e.g., tritiated water) is used to measure **total body water** (TBW), which includes intracellular and extracellular components. *Radioactive sodium and radioactive water* - **Radioactive sodium** is used to measure **extracellular fluid** (ECF) due to its limited entry into cells. - **Radioactive water** (e.g., tritiated water) measures **total body water** (TBW), not specifically interstitial fluid. *Radioactive water and radiolabelled albumin* - **Radioactive water** measures **total body water** (TBW), which encompasses all fluid compartments. - **Radiolabelled albumin** measures **plasma volume** because albumin remains within the vascular space.

Q: Osmolality of plasma in a normal adult:

280-290 mOsm/L. ***280-290 mOsm/L*** - The normal range for **plasma osmolality** in adults is generally accepted to be between 280 and 295 mOsm/L, with 280-290 mOsm/L falling squarely within this range. - This physiological value helps maintain **fluid balance** and cellular integrity throughout the body. *260-270 mOsm/L* - This range is **hypoosmolar**, indicating a lower concentration of solutes in the plasma. - Values in this range would typically suggest **overhydration** or conditions leading to **dilutional hyponatremia**. *300-310 mOsm/L* - This range is slightly to moderately **hyperosmolar**, meaning a higher concentration of solutes. - Values here could indicate **dehydration**, **hyperglycemia**, or other conditions causing increased solute load. *320-330 mOsm/L* - This range represents a significantly **hyperosmolar** state, which is clinically concerning. - Such high osmolality would usually be seen in severe **dehydration**, uncontrolled **diabetes mellitus**, or specific intoxications.

Q: In an adult man weighing 70 kg, the Total body water volume will be about -

42L. ***42L*** - Total body water (TBW) in an adult male is approximately **60% of body weight**. - For a 70 kg man, this calculates to 0.60 * 70 kg = **42 L**. *12L* - This volume is significantly **lower** than the typical total body water volume for an adult man. - 12L would represent around 17% of body weight, which is not physiologically accurate for total body water. *25L* - This value is more representative of the **intracellular fluid (ICF)** volume, which is about 40% of body weight. - It does not account for the total body water, which includes both intracellular and extracellular fluid. *15L* - This volume is generally closer to the **extracellular fluid (ECF)** volume, which is about 20% of body weight. - It significantly underestimates the total body water content of an adult male.

Q: A patient with severe dehydration exhibits decreased skin turgor and sunken eyes. What is the primary mechanism responsible for these symptoms?

Isotonic fluid loss. ***Isotonic fluid loss*** - **Severe dehydration** with decreased skin turgor and sunken eyes indicates **significant extracellular fluid (ECF) volume depletion**. - **Isotonic fluid loss** occurs when water and electrolytes are lost in proportional amounts (e.g., from **diarrhea, vomiting, hemorrhage, or burns**). - Loss of ECF leads to **decreased interstitial fluid volume**, causing **decreased skin turgor** (loss of tissue elasticity) and **sunken eyes** (reduced periorbital fluid). - These are classic **physical examination findings** of volume depletion affecting the extracellular compartment. *Hypertonic fluid loss* - Occurs when **water loss exceeds electrolyte loss** (e.g., diabetes insipidus, excessive sweating). - Initially affects the **intracellular compartment** more than ECF, with relatively preserved blood volume. - Primary symptoms include **intense thirst, altered mental status, and hypernatremia**, rather than the prominent ECF depletion signs described. *Hypotonic fluid gain* - Results from **excessive water intake** or hypotonic IV fluids causing **hyponatremia**. - Leads to **cellular swelling**, presenting with confusion, seizures, and cerebral edema. - Would not cause dehydration signs like decreased skin turgor. *Hypertonic fluid gain* - Uncommon scenario involving gain of **hypertonic fluid** (high solute concentration). - Would increase plasma osmolarity and potentially cause **cellular dehydration** with thirst. - Does not cause the **ECF volume depletion** signs seen in this patient.

Q: A patient presents with confusion and muscle cramps after running a marathon. His serum sodium level is 125 mEq/L. Which physiological process is primarily responsible for his condition?

Increased water retention. ***Increased water retention*** - The patient's symptoms (confusion, muscle cramps) and a **serum sodium level of 125 mEq/L** indicate **hyponatremia**, most likely **exercise-associated hyponatremia (EAH)**. - In EAH, excessive fluid intake (often hypotonic fluids) during prolonged exercise, coupled with antidiuretic hormone (ADH) release, leads to **dilution of plasma sodium** due to increased water retention. *Increased sodium absorption* - This option would typically lead to **hypernatremia** (high sodium levels), not the **hyponatremia** observed in the patient. - Sodium absorption in the GI tract or kidneys does not directly explain a low serum sodium level in this context. *Decreased potassium levels* - While **hypokalemia** (low potassium) can cause muscle cramps and weakness, it does not directly lead to the **hyponatremia** described. - The primary issue here is the low sodium concentration in the blood, not potassium. *Increased renal excretion of sodium* - While **renal sodium loss** can contribute to hyponatremia due to volume depletion, this patient's presentation after a marathon, especially with confusion and cramps, suggests **dilutional hyponatremia** from water retention. - In EAH, kidneys often retain water rather than actively excrete a significant amount of sodium to cause such a drastic drop.

Q: A 55-year-old patient with hypertension is found to have hypernatremia. What is the likely effect on his body fluid compartments?

ICF volume decrease. ***ICF volume decrease*** - **Hypernatremia** increases the **osmolality** of the extracellular fluid (ECF). - Water will move from the intracellular fluid (ICF), where osmolality is lower, to the ECF to re-establish **osmotic equilibrium**, leading to a decrease in ICF volume. *ICF volume increase* - An increase in ICF volume would generally occur with **hyponatremia**, where ECF osmolality is lower than ICF, causing water to move into cells. - This option is incorrect because hypernatremia would draw water out of the cells. *ECF volume decrease* - While fluid shifts occur, hypernatremia usually results in an **increased ECF osmolality**, which can lead to a shift of water from the ICF to the ECF, and thus, the ECF volume may *increase* or remain similar, not decrease, unless there's a significant overall fluid deficit. - **ECF volume decrease** is more commonly associated with conditions like dehydration where both water and sodium are lost. *ECF volume unchanged* - It is unlikely for ECF volume to remain completely unchanged in hypernatremia; the **osmotic shift** of water from the ICF into the ECF directly impacts ECF volume. - The ECF volume tends to **increase** due to the fluid shift from cells, unless accompanied by significant overall body water loss.

Q: A patient with severe burns covering 40% of his body surface area presents with hypotension and tachycardia. Which of the following is the most likely cause of his symptoms?

Increased capillary permeability. ***Increased capillary permeability*** - Severe burns cause extensive damage to the **endothelial cells** of capillaries, leading to a significant increase in their **permeability**. - This increased permeability allows **plasma proteins** and fluid to leak out of the intravascular space into the interstitial space, resulting in **hypovolemia**, hypotension, and tachycardia. *Increased systemic vascular resistance* - While initial sympathetic response to shock can cause some vasoconstriction, severe burn shock leads to profound **fluid loss** and **reduced cardiac output**, which would typically lead to a **decrease** in effective systemic vascular resistance due to inadequate vascular filling, not an increase as the primary cause of hypotension. - Increased SVR would generally cause hypertension, not hypotension, unless coupled with severe pump failure, which isn't the primary mechanism in early burn shock. *Increased plasma protein levels* - In severe burns, plasma proteins leak out of the capillaries, leading to a **decrease** in plasma protein levels, especially albumin. - This reduction in plasma oncotic pressure further exacerbates fluid shifts out of the intravascular space. *Increased cardiac output* - Severe burn injury leads to significant **fluid loss** and a large decrease in **preload**, which consequently causes a **decrease** in cardiac output despite compensatory tachycardia. - An increased cardiac output would typically raise blood pressure, not lead to hypotension.

Question 1

All of the following are true about potassium, except

Accepted Answer

Leaves the cell in the presence of insulin

Answer

Mostly concentrated inside the cells

Answer

Plasma concentration increases at time of metabolic acidosis

Answer

Ingestion of acetazolamide results in potassium loss

Question 2

Which of the following is NOT true about body fluids:

Accepted Answer

Synovial fluid is transcellular fluid

Answer

ECF volume of 70 kg adult man would be approximately 14 L

Answer

The total body fluid per unit body weight is more in infants as compared to adults

Answer

Intracellular fluid is 40% of total body weight

Question 3

Which of the following is not a general compartment of body fluid?

Accepted Answer

Peritoneal

Answer

Blood plasma

Answer

Interstitial

Answer

Intracellular

Question 4

Interstitial fluid volume can be determined by:

Accepted Answer

Radioactive sodium and radioactive labelled albumin

Answer

Radioactive iodine and radiolabelled water

Answer

Radioactive sodium and radioactive water

Answer

Radioactive water and radiolabelled albumin

Question 5

Osmolality of plasma in a normal adult:

Accepted Answer

280-290 mOsm/L

Answer

260-270 mOsm/L

Answer

300-310 mOsm/L

Answer

320-330 mOsm/L

Question 6

In an adult man weighing 70 kg, the Total body water volume will be about -

Accepted Answer

42L

Answer

12L

Answer

25L

Answer

15L

Question 7

A patient with severe dehydration exhibits decreased skin turgor and sunken eyes. What is the primary mechanism responsible for these symptoms?

Accepted Answer

Isotonic fluid loss

Answer

Hypertonic fluid loss

Answer

Hypotonic fluid gain

Answer

Hypertonic fluid gain

Question 8

A patient presents with confusion and muscle cramps after running a marathon. His serum sodium level is 125 mEq/L. Which physiological process is primarily responsible for his condition?

Accepted Answer

Increased water retention

Answer

Increased sodium absorption

Answer

Decreased potassium levels

Answer

Increased renal excretion of sodium

Question 9

A 55-year-old patient with hypertension is found to have hypernatremia. What is the likely effect on his body fluid compartments?

Accepted Answer

ICF volume decrease

Answer

ICF volume increase

Answer

ECF volume decrease

Answer

ECF volume unchanged

Question 10

A patient with severe burns covering 40% of his body surface area presents with hypotension and tachycardia. Which of the following is the most likely cause of his symptoms?

Accepted Answer

Increased capillary permeability

Answer

Increased systemic vascular resistance

Answer

Increased plasma protein levels

Answer

Increased cardiac output

Electrolytes and Body Fluids — MCQs

Electrolytes and Body Fluids — MCQs

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