Dehydration Physiology — MCQs
A 4-year-old child is brought to the emergency department with severe dehydration due to diarrhea. What is the initial management for severe dehydration?
Which of the following is a sign of severe dehydration in a child?
Most reliable indicator of some dehydration?
Which of the following results in increased ADH activity?
Baby with diarrhea presents with restlessness, irritability, sunken eyes and baby is thirsty and drinks eagerly. What is the diagnosis of this child?
Normal amount of sodium in plasma is (in mEq/L)
Which of the following is the best method to assess the adequacy of fluid replacement?
In which of the following conditions is blood osmolality increased?
Newborns typically lose how much weight in the first week?
The normal range of serum osmolality (in mosm/L) is:
Dehydration Physiology Indian Medical PG Practice Questions and MCQs
Question 1: A 4-year-old child is brought to the emergency department with severe dehydration due to diarrhea. What is the initial management for severe dehydration?
- A. Oral rehydration therapy
- B. Intravenous fluids (Correct Answer)
- C. Antidiarrheal medication
- D. Antibiotics
Explanation: ***Intravenous fluids*** - For **severe dehydration**, rapid correction of fluid and electrolyte imbalances is critical, and **intravenous fluids** (normal saline or Ringer's lactate) are the **first-line treatment**. - As per **WHO and IAP guidelines**, children with severe dehydration require **IV fluid resuscitation** at 100 mL/kg over 3-6 hours (or 30 mL/kg bolus initially). - Signs of severe dehydration include **lethargy, sunken eyes, absent tears, very dry mucous membranes, poor skin turgor**, and inability to drink. - IV route ensures **rapid intravascular volume expansion** when oral intake is compromised or inadequate. *Oral rehydration therapy* - **ORT** is the treatment of choice for **mild to moderate dehydration only** (Plan B as per WHO). - In severe dehydration, children often have **altered consciousness, persistent vomiting**, or **circulatory compromise**, making oral intake ineffective or impossible. - ORT can be initiated once the child is alert and able to drink after initial IV resuscitation. *Antidiarrheal medication* - **Not recommended** in children with acute diarrhea, especially under 5 years. - Medications like loperamide can cause **ileus, drowsiness**, and may worsen outcomes. - They do **not address fluid and electrolyte deficits**, which is the immediate life-threatening concern. *Antibiotics* - Only indicated for **specific bacterial causes** (e.g., cholera, shigellosis with blood in stool, or proven invasive bacterial infection). - **Not part of initial management** for severe dehydration. - Indiscriminate use contributes to **antibiotic resistance** and delays critical rehydration.
Question 2: Which of the following is a sign of severe dehydration in a child?
- A. Sunken eyes (Correct Answer)
- B. Normal skin turgor
- C. Increased urine output
- D. Moist mucous membranes
Explanation: ***Sunken eyes*** - **Sunken eyes** are a classic sign of significant fluid loss, indicating a depletion of interstitial fluid around the eyes. - This finding is a strong indicator of **moderate to severe dehydration** in children, along with other signs like absent tears and dry mucous membranes. *Normal skin turgor* - **Normal skin turgor** means the skin returns quickly to its original position after being pinched, which is characteristic of adequate hydration. - In dehydration, skin turgor is usually **decreased**, meaning the skin will tent or recoil slowly. *Increased urine output* - **Increased urine output** is a sign of adequate hydration and proper kidney function, as the kidneys are able to excrete excess fluid. - In severe dehydration, the body conserves fluid, leading to significantly **decreased urine output** (oliguria) or no urine output (anuria). *Moist mucous membranes* - **Moist mucous membranes** (e.g., in the mouth or nose) indicate sufficient hydration, as the body can maintain secretions. - In dehydration, especially severe cases, mucous membranes become **dry and sticky** due to reduced fluid volume.
Question 3: Most reliable indicator of some dehydration?
- A. Lethargy
- B. Delayed skin pinch
- C. Thirst (Correct Answer)
- D. Sunken eyes
Explanation: Thirst - **Thirst** is a physiological response to even mild dehydration and is often the **earliest and most reliable indicator** that the body needs fluids [1], [2]. - It reflects an increase in **plasma osmolality**, signaling the brain to initiate fluid-seeking behaviors [1], [2]. *Lethargy* - **Lethargy** indicates more severe dehydration or other underlying conditions, making it a less specific and sensitive early indicator. - It suggests significant neurological impairment due to fluid and electrolyte imbalances, rather than just some dehydration. *Delayed skin pinch* - A **delayed skin pinch** (decreased skin turgor) is a sign of *significant* dehydration, indicating a substantial loss of interstitial fluid. - This sign is often less reliable in infants and the elderly due to differences in skin elasticity. *Sunken eyes* - **Sunken eyes** are a sign of more **moderate to severe dehydration**, reflecting significant fluid volume depletion, especially in infants. - It is not an early or subtle indicator of "some dehydration" but rather a late manifestation [3].
Question 4: Which of the following results in increased ADH activity?
- A. Hypervolemia
- B. Hypertension
- C. Decrease osmolarity
- D. Hypovolemia (Correct Answer)
Explanation: ***Hypovolemia*** - **Hypovolemia** (decreased blood volume) is a potent stimulus for antidiuretic hormone (ADH) release, as the body attempts to conserve water and increase blood volume. - Reduced **stretch receptor activity** in the atria and great vessels due to decreased blood volume signals the posterior pituitary to release ADH. *Hypervolemia* - **Hypervolemia** (increased blood volume) would lead to a *decrease* in ADH activity, as the body tries to excrete excess water to normalize blood volume. - Increased stretch receptor activity in the atria inhibits ADH release. *Hypertension* - **Hypertension** (high blood pressure) generally *reduces* ADH secretion because the increased stretch on baroreceptors signals to decrease fluid volume. - This typically promotes diuresis rather than water retention. *Decrease osmolarity* - A **decrease in plasma osmolarity** (more dilute blood) inhibits ADH release, as the body aims to excrete excess water to bring osmolarity back to normal. - **Osmoreceptors** in the hypothalamus are sensitive to changes in plasma osmolarity and are the primary regulators of ADH secretion.
Question 5: Baby with diarrhea presents with restlessness, irritability, sunken eyes and baby is thirsty and drinks eagerly. What is the diagnosis of this child?
- A. Severe dehydration
- B. Very Severe dehydration
- C. Some dehydration (Correct Answer)
- D. No dehydration
Explanation: ***Some dehydration*** - The combination of **restlessness and irritability**, **sunken eyes**, and **drinking eagerly/thirsty** are classic signs indicating **some dehydration** according to WHO guidelines for assessing dehydration in children with diarrhea. - While significant, these signs do not meet the criteria for severe or very severe dehydration, which typically involve more profound signs like lethargy, inability to drink, or severe skin turgor loss. *Severe dehydration* - This typically presents with **two or more** of the following: **lethargy**, **unconsciousness**, **not able to drink**, or **skin pinch goes back very slowly** (more than 2 seconds). - The child in the scenario is restless and drinking eagerly, which contradicts the signs of severe dehydration. *Very Severe dehydration* - This is not a distinct classification in the primary WHO dehydration assessment for children with diarrhea; it usually falls under "severe dehydration" or implies shock. - The given symptoms, while indicative of dehydration, do not suggest the immediate life-threatening state implied by "very severe." *No dehydration* - A child with no dehydration would typically present as **alert**, with **normal eyes**, **not thirsty**, and a **normal skin pinch**. - The presence of restlessness, sunken eyes, and thirst clearly indicates that the child is experiencing some degree of fluid deficit.
Question 6: Normal amount of sodium in plasma is (in mEq/L)
- A. 95
- B. 143 (Correct Answer)
- C. 120
- D. 175
Explanation: ***Correct: 143 mEq/L*** - The normal physiological range for **sodium concentration in plasma** is typically between **135 and 145 mEq/L**. - Therefore, **143 mEq/L** falls right within the healthy range and represents a normal value. *Incorrect: 95 mEq/L* - A plasma sodium concentration of **95 mEq/L** would indicate severe **hyponatremia**. - This level is significantly below the normal range and would be associated with severe neurological symptoms such as **seizures or coma**. *Incorrect: 120 mEq/L* - A plasma sodium concentration of **120 mEq/L** would indicate **hyponatremia**. - While not as severe as 95 mEq/L, it is still below the normal range and could lead to symptoms like **nausea, malaise, and headache**. *Incorrect: 175 mEq/L* - A plasma sodium concentration of **175 mEq/L** would indicate severe **hypernatremia**. - This is significantly above the normal range and could cause symptoms such as **thirst, lethargy, seizures, or even brain damage**.
Question 7: Which of the following is the best method to assess the adequacy of fluid replacement?
- A. Blood pressure
- B. Decrease in thirst
- C. Increased PaO2
- D. Increase in urine output (Correct Answer)
Explanation: ***Increase in urine output*** - An **increasing urine output** (typically above 0.5-1 mL/kg/hr in adults) is a reliable indicator that **renal perfusion** is improving and the body's fluid status is normalizing, especially in hypovolemic states. - This reflects restored **circulating volume** and adequate **organ perfusion**, which is the primary goal of fluid replacement. *Blood pressure* - While an increase in **blood pressure** can indicate improved fluid status, it is a relatively late and often conserved compensatory mechanism; the body can maintain blood pressure even with significant fluid deficits. - Blood pressure can be influenced by many factors other than fluid status, such as **vasoactive medications** or underlying cardiac conditions, making it less specific than urine output. *Decrease in thirst* - A decrease in thirst might indicate subjective improvement, but it is a **subjective symptom** and not an objective, quantifiable measure of adequate fluid replacement or organ perfusion [1]. - Thirst can be influenced by psychological factors and may not accurately reflect the body's true **hydration status** or the adequacy of fluid resuscitation, especially in critically ill patients [2]. *Increased PaO2* - An increase in **PaO2 (partial pressure of oxygen in arterial blood)** primarily reflects improved oxygenation and ventilation, not necessarily the adequacy of fluid replacement. - While severe hypovolemia can compromise tissue oxygen delivery, an increase in PaO2 alone is not a direct or primary indicator of successful volume resuscitation; it's more specific to **respiratory function**.
Question 8: In which of the following conditions is blood osmolality increased?
- A. SIADH
- B. Psychogenic polydipsia
- C. Diarrhea (Correct Answer)
- D. Cerebral toxoplasmosis
Explanation: ***Diarrhea*** - Diarrhea leads to a significant loss of **water and electrolytes** from the body, primarily from the extracellular fluid compartment. - This imbalance causes **hemoconcentration** and an increase in the concentration of solutes in the blood, thereby raising blood osmolality. *SIADH* - **Syndrome of Inappropriate Antidiuretic Hormone (SIADH)** is characterized by excessive secretion of ADH, leading to **dilutional hyponatremia**. - The excess water retention dilutes the blood, resulting in **decreased serum osmolality**. *Psychogenic polydipsia* - This condition involves excessive water intake due to psychological factors, which causes **dilution of body fluids**. - The increased water volume without a proportional increase in solutes leads to **decreased plasma osmolality**. *Cerebral toxoplasmosis* - **Cerebral toxoplasmosis** is an opportunistic infection of the brain, typically seen in immunocompromised individuals. - It primarily causes neurological symptoms and **does not directly impact blood osmolality** unless complicated by other factors like dehydration or SIADH (which is not a primary effect).
Question 9: Newborns typically lose how much weight in the first week?
- A. 5-10% (Correct Answer)
- B. 1-2%
- C. 11-15%
- D. 15-20%
Explanation: ***5-10%*** - **Physiologic weight loss** of 5-10% of birth weight is normal in newborns during the first week of life. - This loss is primarily due to the **mobilization of extracellular fluid** and delayed onset of full milk production (lactogenesis). - Most infants regain their birth weight by **10-14 days** of age. *1-2%* - A weight loss of only 1-2% in the first week would be **less than expected** and might suggest the infant is retaining excess fluid. - While not necessarily pathological, it's at the **lower end of the normal range** and less typical than the 5-10% range. *11-15%* - A weight loss greater than **10%** is generally considered **excessive** and indicates inadequate feeding or possible dehydration. - Weight loss of 11-15% typically requires **closer monitoring**, feeding assessment, and possible lactation support or supplementation. *15-20%* - A weight loss of 15-20% is significantly **above the normal physiological range** and represents a serious concern for **severe dehydration** or inadequate nutritional intake. - This degree of weight loss would warrant **immediate medical evaluation** and intervention, including possible hospitalization.
Question 10: The normal range of serum osmolality (in mosm/L) is:
- A. 200 to 250
- B. 280 to 295 (Correct Answer)
- C. 300 to 320
- D. 350 to 375
Explanation: ***280 to 295*** - This range represents the **physiological concentration** of solutes in the blood, primarily determined by sodium, glucose, and urea. - Maintaining osmolality within this **narrow range** is crucial for proper cellular function and fluid balance. *200 to 250* - A serum osmolality in this range would indicate **hypotonicity**, leading to water movement into cells and potential **cellular swelling**. - Values this low are typically seen in conditions like **severe hyponatremia** or excessive water intake. *300 to 320* - While slightly above the normal range, this might be seen in cases of **mild dehydration** or conditions like uncontrolled diabetes where blood glucose is elevated. - Sustained levels in this range indicate increased solute concentration, which can lead to **cellular dehydration**. *350 to 375* - This range represents significantly elevated serum osmolality, indicating **hypertonic states** such as severe dehydration, **hyperglycemic hyperosmolar state (HHS)**, or severe hypernatremia. - Such high osmolality would result in substantial **cellular shrinkage** and can be life-threatening.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free