Electrolytes and Body Fluids Practice Questions

Q: Which of the following statements about total body water (TBW) is false?

In newborn TBW is 60% of body weight. ***In newborn TBW is 60% of body weight*** - This statement is **false** because newborns have a significantly higher percentage of total body water, typically ranging from **75-80%** of their body weight. - The proportion of total body water decreases with age, from birth through adulthood, as **fat mass increases** and **muscle mass proportionally decreases**. *ICF is 2/3rd of TBW* - This statement is **true** in adults. The intracellular fluid (ICF) compartment accounts for approximately **2/3** of the total body water. - The remaining **1/3** of TBW is found in the extracellular fluid (ECF) compartment. *Premature newborns have more TBW* - This statement is **true**. Premature newborns have an even higher percentage of TBW, often reaching **80-85%**, compared to full-term newborns. - This higher proportion is due to their relatively lower fat content and less developed regulatory systems. *In adults, TBW is 60% of body weight* - This statement is **true**. In healthy adult males, total body water typically constitutes about **60%** of their body weight. - In adult females this percentage is slightly lower due to a higher proportion of adipose tissue.

Q: Mannitol infusion causes increase in

Osmolarity. ***Osmolarity*** - Mannitol is an **osmotic diuretic** that remains in the extracellular space and pulls water from the intracellular space due to its **osmotic effect**. - This increases the **osmolarity of the blood** and tubular fluid. *Blood viscosity* - Mannitol causes water to shift from the intracellular to the extracellular compartment, leading to **hemodilution**, which would decrease, not increase, blood viscosity initially. - While fluid loss through diuresis could ultimately increase viscosity, the immediate effect of mannitol is an increase in plasma volume. *Intraocular pressure* - Mannitol reduces **intraocular pressure** by drawing fluid from the vitreous humor into the blood. - This effect is clinically useful in treating acute angle-closure glaucoma. *Intracranial pressure* - Mannitol significantly **reduces intracranial pressure** by creating an osmotic gradient that draws water from brain tissue into the cerebral circulation. - This is a primary indication for its use in cerebral edema.

Q: What is the effect of infusion of hypotonic saline?

Increased in both ICF and ECF. ***Increased in both ICF and ECF*** - Infusion of **hypotonic saline** introduces water and a small amount of electrolytes, which first expand the **extracellular fluid (ECF)** compartment. - Due to the lower osmolality of the hypotonic solution, water then shifts from the ECF into the **intracellular fluid (ICF)** compartment to maintain osmotic equilibrium, leading to an increase in both. *Increased ICF only* - This option incorrectly suggests that the ECF does not increase, which is contrary to the initial effect of infusing any fluid into the vascular space. - The ECF must first expand before any significant shift into the ICF can occur due to changes in osmolality. *Increased ECF only* - This is incorrect because hypotonic solutions cause a decrease in ECF osmolality, leading to a shift of water into the cells (ICF compartment). - An increase in ECF only would typically be seen with **isotonic fluid** administration, where there is no osmotic gradient to drive water into the cells. *Increased ICF and decreased ECF* - This scenario would imply a net loss of water from the ECF into the ICF exceeding the volume of fluid infused, which is not what happens with hypotonic saline infusion. - A decrease in ECF volume would contradict the fact that fluid has been added to the extracellular space.

Q: Tetany in muscle occurs in spite of normal serum Ca2+ level. Which ion is responsible?

Ionized Ca2+. ***Ionized Ca2+*** - While total serum calcium might be normal, **tetany** is specifically caused by a decrease in the concentration of **ionized (free) calcium** in the extracellular fluid. - Ionized calcium is the physiologically active form of calcium responsible for neuromuscular excitability. *Mg2+* - **Hypomagnesemia** can exacerbate hypocalcemia and contribute to tetany, but it is not the primary ion directly responsible for tetany when **total serum calcium is normal**. - A deficiency in Mg2+ can impair the release of **parathyroid hormone** and reduce target organ responsiveness to PTH. *K+* - Abnormalities in **potassium levels** (hypokalemia or hyperkalemia) primarily affect cardiac and muscular excitability, leading to arrhythmias or muscle weakness/paralysis. - While electrolyte imbalances are interconnected, changes in potassium are not the direct cause of tetany due to calcium's role. *Na+* - **Sodium ions** are crucial for nerve impulse transmission and muscle contraction by establishing the resting membrane potential and initiating action potentials. - However, direct changes in sodium concentration do not typically cause tetany; rather, they can lead to neurological symptoms like seizures (hyponatremia) or altered mental status (hypernatremia).

Q: What is the typical pH range of intracellular fluid (ICF) compared to extracellular fluid (ECF)?

Typically around 7.0, slightly less than ECF. ***Typically around 7.0, slightly less than ECF*** - The **intracellular fluid (ICF)** tends to be slightly more acidic due to metabolic processes within cells that produce **acidic byproducts**. - This makes its pH typically around **7.0–7.2**, which is subtly lower than the extracellular fluid. *Typically around 7.4, slightly more than ICF* - A pH of approximately **7.4** is characteristic of **extracellular fluid (ECF)**, which includes plasma and interstitial fluid. - The ECF is maintained within a **narrow, slightly alkaline** range to support cellular function and enzyme activity throughout the body. *Approximately equal to ECF* - While both fluid compartments are maintained within a **narrow physiological range**, their pH values are not exactly equal. - This slight difference is essential for various biological processes, including maintaining **membrane potential** and **enzyme efficiency**. *Significantly higher than ECF* - The ICF pH is **not significantly higher** than ECF; in fact, it is slightly lower. - Maintaining too high a pH intracellularly would disrupt **cellular metabolism** and **protein structure**.

Q: Result of liquorice ingestion

Hypokalemic alkalosis. ***Hypokalemic alkalosis*** - **Licorice** contains **glycyrrhizic acid**, which inhibits **11β-hydroxysteroid dehydrogenase** in the kidneys, preventing the conversion of cortisol to inactive cortisone. - This leads to increased cortisol acting on **mineralocorticoid receptors**, mimicking **aldosterone excess**, resulting in **sodium reabsorption**, **potassium excretion** (hypokalemia), and **hydrogen ion excretion** (metabolic alkalosis). *Hyperkalemic alkalosis* - This option is incorrect because licorice ingestion leads to **hypokalemia** due to increased potassium excretion, not hyperkalemia. - While it does cause alkalosis, the associated potassium imbalance is the opposite of this choice. *Hypokalemic acidosis* - This option is incorrect because licorice ingestion causes a **metabolic alkalosis** due to increased hydrogen ion excretion, not acidosis. - Although it correctly identifies hypokalemia, the acid-base disturbance is wrong. *Hypernatremic acidosis* - This option is incorrect as licorice ingestion initially causes **sodium and water retention** (which can lead to hypernatremia in severe cases, but is not the primary driver of the acid-base), but primarily leads to **metabolic alkalosis**, not acidosis. - The combination of hypernatremia and acidosis is not characteristic of licorice toxicity.

Q: What is the average daily water loss in sweat during normal physical activities in temperate conditions?

500 - 700 ml. ***500 - 700 ml*** - Under normal physical activities in temperate conditions, **sensible perspiration (sweat)** typically ranges from **500 to 700 ml** per day. - This represents active secretion from sweat glands for thermoregulation during baseline daily activities without significant exertion. - This is distinct from insensible water loss (~300-400 ml/day), which is passive diffusion through the skin. *200 - 400 ml* - This range represents **insensible water loss** through the skin by passive diffusion, not active sweating. - While this is a normal component of daily water loss, it does not reflect the active sweat production during physical activities. *50 - 100 ml* - This volume is too low for average daily sweat loss during normal activities. - This might represent minimal sweating in completely sedentary conditions or very cool environments. *1000 - 1200 ml* - This represents significant sweat production, typically seen during **moderate to strenuous exercise**, hot climates, or febrile conditions. - It exceeds the average daily sweat loss during normal physical activities in temperate conditions.

Q: Plasma volume is measured by ?

Evans blue. ***Evans blue*** - **Evans blue** is a dye that binds to plasma proteins and **does not readily cross capillary membranes**, making it an effective tracer for measuring plasma volume. - After intravenous injection, its concentration can be measured to calculate the dilution space, which corresponds to the **plasma volume**. *Inulin* - **Inulin** is a polysaccharide primarily used to measure the **glomerular filtration rate (GFR)** because it is freely filtered by the glomeruli and neither reabsorbed nor secreted by the renal tubules. - It distributes into the **extracellular fluid compartment** and is not confined to the plasma, making it unsuitable for plasma volume measurement. *Mannitol* - **Mannitol** is an osmotic diuretic that distributes in the **extracellular fluid (ECF)**, it is generally used for its osmotic effects to reduce edema or intracranial pressure. - Due to its distribution beyond the plasma compartment, it is not used directly to measure **plasma volume**. *D20* - **D2O (deuterium oxide)**, or heavy water, is used to measure **total body water (TBW)** as it distributes throughout all fluid compartments of the body. - It does not selectively remain within the plasma compartment, making it unsuitable for measuring **plasma volume** alone.

Q: Normal range of serum osmolality is (mOsm/Kg)?

280 - 300. ***280 - 300*** - The normal range for **serum osmolality** is generally considered to be 280-300 mOsm/Kg. - This range reflects the appropriate balance of solutes (like sodium, glucose, and urea) in the blood, which is crucial for **fluid homeostasis**. *250 - 270* - A serum osmolality in this range would indicate **hypoosmolality**, suggesting a relative excess of water or a deficit of solutes in the blood. - This could be seen in conditions like **syndrome of inappropriate antidiuretic hormone (SIADH)** or primary polydipsia. *300 - 320* - This range suggests **hyperosmolality**, meaning there's a relative deficit of water or an excess of solutes. - Conditions such as **dehydration**, uncontrolled diabetes mellitus, or severe hypernatremia can lead to values in this range. *210 - 230* - Such a significantly low osmolality would represent severe **hypoosmolality**, usually associated with extreme overhydration or profound solute depletion. - This deviation is critically abnormal and would indicate severe electrolyte imbalance, potentially leading to **cerebral edema**.

Q: Insensible water loss per day is ?

1000 ml. ***1000 ml*** - **Insensible water loss** occurs through the skin (evaporation) and respiratory tract (exhalation) without conscious perception. - The typical daily insensible water loss in an adult is approximately **800-1000 ml/day**. - **Breakdown**: Skin evaporation (~400-500 ml) + Respiratory tract (~300-400 ml) = **~900-1000 ml total**. - **1000 ml** is the standard value cited in major physiology textbooks (Guyton & Hall, Ganong) and is the most commonly accepted answer for NEET PG examinations. *100 ml* - This value is significantly **lower** than the actual insensible water loss, which occurs continuously throughout the day. - Such a low volume would imply negligible evaporation and respiratory loss, which is not physiologically accurate. *300 ml* - While greater than 100 ml, 300 ml is still **far below** the typical range for daily insensible water loss. - This amount represents only about one-third of the actual insensible losses from the skin and respiratory system combined. *700 ml* - Although this value is sometimes mentioned in literature, it is at the **lower end** of the physiological range. - The more widely accepted standard value for insensible water loss in a healthy adult under normal conditions is **900-1000 ml/day**. - 700 ml would underestimate the normal daily insensible losses.

Question 1

Which of the following statements about total body water (TBW) is false?

Accepted Answer

In newborn TBW is 60% of body weight

Answer

In adults, TBW is 60% of body weight

Answer

ICF is 2/3rd of TBW

Answer

Premature newborns have more TBW

Question 2

Mannitol infusion causes increase in

Accepted Answer

Osmolarity

Answer

Blood viscosity

Answer

Intraocular pressure

Answer

Intracranial pressure

Question 3

What is the effect of infusion of hypotonic saline?

Accepted Answer

Increased in both ICF and ECF

Answer

Increased ICF only

Answer

Increased ECF only

Answer

Increased ICF and decreased ECF

Question 4

Tetany in muscle occurs in spite of normal serum Ca2+ level. Which ion is responsible?

Accepted Answer

Ionized Ca2+

Answer

Mg2+

Answer

K+

Answer

Na+

Question 5

What is the typical pH range of intracellular fluid (ICF) compared to extracellular fluid (ECF)?

Accepted Answer

Typically around 7.0, slightly less than ECF

Answer

Typically around 7.4, slightly more than ICF

Answer

Approximately equal to ECF

Answer

Significantly higher than ECF

Question 6

Result of liquorice ingestion

Accepted Answer

Hypokalemic alkalosis

Answer

Hyperkalemic alkalosis

Answer

Hypokalemic acidosis

Answer

Hypernatremic acidosis

Question 7

What is the average daily water loss in sweat during normal physical activities in temperate conditions?

Accepted Answer

500 - 700 ml

Answer

1000 - 1200 ml

Answer

50 - 100 ml

Answer

200 - 400 ml

Question 8

Plasma volume is measured by ?

Accepted Answer

Evans blue

Answer

Inulin

Answer

D2O

Answer

Mannitol

Question 9

Normal range of serum osmolality is (mOsm/Kg)?

Accepted Answer

280 - 300

Answer

250 - 270

Answer

300 - 320

Answer

210 - 230

Question 10

Insensible water loss per day is ?

Accepted Answer

1000 ml

Answer

100 ml

Answer

700 ml

Answer

300 ml

Electrolytes and Body Fluids — MCQs

Electrolytes and Body Fluids — MCQs

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