Thirst and Fluid Balance Integration — MCQs

10 questions

Which of the following is most important in sodium and water retention ?

5 g mannitol was injected intravenously. 40% of mannitol is excreted. After equilibrium, plasma concentration of mannitol is 30 mg%. Calculate extracellular fluid volume.

Which of the following results in increased ADH activity?

Following surgery, a patient develops oliguria. You believe the patient is hypovolemic, but you seek corroborative data before increasing intravenous fluids. The best data is?

Increased aldosterone and ADH secretion following major trauma results in all the following except?

Positive Romberg test with eyes closed detects a defect in -

Third window effect is seen in

Resection of which part of intestine does not significantly affect fluid and electrolyte balance?

Dosage of intravenous fluid for 2 month old child in diarrhea with severe dehydration -

Q10

A 52-year-old man was referred to the clinic due to increased abdominal girth. He is diagnosed with ascites by the presence of a fluid thrill and shifting dullness on percussion. After administering diuretic therapy, which nursing action would be most effective in ensuring safe care for this patient?

Thirst and Fluid Balance Integration Indian Medical PG Practice Questions and MCQs

Question 1: Which of the following is most important in sodium and water retention ?

A. Renin angiotensin system (Correct Answer)
B. ANP
C. BNP
D. Vasopressin

Explanation: ***Renin angiotensin system*** - The **renin-angiotensin-aldosterone system (RAAS)** is the most important mechanism for **both sodium AND water retention**, which is what the question specifically asks about. - **Aldosterone** directly promotes **sodium reabsorption** in the principal cells of the collecting duct by increasing apical ENaC channels and basolateral Na-K-ATPase pumps. - **Angiotensin II** stimulates sodium reabsorption in the proximal tubule and also stimulates ADH release, contributing to water retention. - When sodium is retained, **water follows passively** due to the osmotic gradient, resulting in effective volume expansion. - RAAS is the primary system activated in states of volume depletion and is most important for combined sodium and water retention. *Vasopressin* - **Vasopressin (ADH)** primarily controls **water retention only** by increasing aquaporin-2 channels in the collecting duct. - While crucial for water balance, it has minimal direct effect on sodium reabsorption. - It causes retention of **free water**, which can actually dilute plasma sodium concentration. - ADH is the answer if the question asked about water retention alone, but not for combined sodium and water retention. *ANP* - **Atrial natriuretic peptide (ANP)** promotes **sodium and water excretion** (natriuresis and diuresis). - Released in response to atrial stretch from volume expansion. - Acts to *oppose* retention mechanisms, making it incorrect for this question. *BNP* - **Brain natriuretic peptide (BNP)** similarly promotes **natriuresis and diuresis**. - Released from ventricular myocytes in response to volume overload. - Like ANP, it acts to *excrete* sodium and water, not retain them.

Question 2: 5 g mannitol was injected intravenously. 40% of mannitol is excreted. After equilibrium, plasma concentration of mannitol is 30 mg%. Calculate extracellular fluid volume.

A. 18 L
B. 14 L
C. 10 L (Correct Answer)
D. 24 L

Explanation: ***10 L*** - The amount of mannitol retained in the body is 5 g - (40% of 5 g) = 5 g - 2 g = **3 g**. - Extracellular fluid volume (ECFV) is calculated by dividing the retained amount of substance by its plasma concentration: ECFV = 3000 mg / 30 mg/dL = **100 dL = 10 L**. *18 L* - This value would result if a different amount of retained mannitol or plasma concentration were used, not aligning with the given problem's parameters. - It implies either a miscalculation of the retained substance or an incorrect conversion during the volume calculation. *14 L* - This answer would imply a different calculation of the retained mannitol, potentially not accounting for the exact percentage excreted. - It is not consistent with the given dose, excretion percentage, and final plasma concentration. *24 L* - This volume is significantly larger than what would be expected, suggesting a substantial overestimation of the retained substance or an underestimation of the plasma concentration. - Such a large volume for extracellular fluid is physiologically improbable given the parameters.

Question 3: 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 4: Following surgery, a patient develops oliguria. You believe the patient is hypovolemic, but you seek corroborative data before increasing intravenous fluids. The best data is?

A. Urine chloride of 15 meq/L
B. Fractional excretion of sodium less than 1 (Correct Answer)
C. Urine sodium of 28 meq/L
D. Urine/Serum creatinine ratio of 20

Explanation: ***Fractional excretion of sodium less than 1*** - A **fractional excretion of sodium (FENa) less than 1%** is a classic indicator of **prerenal azotemia** or hypovolemia, as the kidneys are avidly reabsorbing sodium and water to preserve circulating volume. - This indicates the kidneys are functioning appropriately in response to perceived hypoperfusion, attempting to conserve sodium and thus water. *Urine chloride of 15 meq/L* - While a **low urine chloride** can sometimes be seen in volume depletion, it is not as specific or reliable an indicator of hypovolemia as FENa. - Urine chloride is more helpful in differentiating causes of **metabolic alkalosis**, particularly saline-responsive versus saline-unresponsive. *Urine sodium of 28 meq/L* - A urine sodium concentration of **less than 20 mEq/L** is a more classic cutoff for prerenal azotemia/hypovolemia, indicating aggressive sodium reabsorption. - A value of 28 mEq/L, although relatively low, is less definitive than a low FENa in strongly supporting hypovolemia. *Urine/Serum creatinine ratio of 20* - A **urine/serum creatinine ratio greater than 20:1** is indicative of prerenal azotemia, suggesting the kidneys are concentrating urine in response to hypovolemia. - While supportive, FENa is often considered a more precise and widely accepted marker, especially in the absence of diuretic use or chronic kidney disease.

Question 5: Increased aldosterone and ADH secretion following major trauma results in all the following except?

A. Increased osmolarity of urine
B. Increased water excretion (Correct Answer)
C. Increased K+ excretion in urine
D. Decreased Na+ excretion in urine

Explanation: ***Increased water excretion*** - **ADH (antidiuretic hormone)** increases water reabsorption in the collecting ducts, leading to a *decrease* in water excretion, not an increase. - Increased aldosterone and ADH would promote fluid retention to maintain blood volume following trauma, thus reducing water loss via urine. *Decreased Na+ excretion in urine* - **Aldosterone** acts on the renal tubules to increase **sodium reabsorption** and potassium excretion. - This response is crucial in **conserving sodium** and thereby maintaining extracellular fluid volume after trauma. *Increased K+ excretion in urine* - **Aldosterone** directly stimulates **potassium secretion** into the urine in the principal cells of the collecting ducts. - This is a normal physiological consequence of increased aldosterone levels. *Increased osmolarity of urine* - **ADH** increases the permeability of the collecting ducts to water, leading to **more water reabsorption** back into the bloodstream. - This removal of water from the urine concentrates the solutes, resulting in a **more concentrated (higher osmolarity)** urine.

Question 6: Positive Romberg test with eyes closed detects a defect in -

A. Cerebellum
B. Peripheral nerve
C. Proprioceptive pathway (Correct Answer)
D. Spinothalamic tract

Explanation: Proprioceptive pathway - A positive Romberg test indicates a loss of proprioception, meaning the patient cannot maintain balance when visual cues are removed, relying solely on somatosensory input [2]. - This suggests damage to the dorsal columns of the spinal cord or peripheral nerves that transmit proprioceptive information to the brain [1], [3]. Cerebellum - While cerebellar dysfunction also causes ataxia and balance problems, it would typically present as difficulty maintaining balance even with eyes open, referred to as cerebellar ataxia [2]. - A Romberg test primarily assesses the integrity of the proprioceptive system, distinguishing it from cerebellar issues where balance problems are evident regardless of visual input [2]. Peripheral nerve - Peripheral neuropathy can indeed lead to a positive Romberg test if the sensory nerves responsible for proprioception are affected [1]. - However, "Proprioceptive pathway" is a more direct and encompassing answer, as peripheral nerves are a component of this pathway, which also includes spinal cord tracts [3]. Spinothalamic tract - The spinothalamic tract primarily transmits sensations of pain and temperature, not proprioception [3]. - Damage to this tract would result in deficits in these specific sensory modalities, rather than a positive Romberg test [1].

Question 7: Third window effect is seen in

A. Perforated tympanum
B. Round window
C. Dehiscent superior semicircular canal (Correct Answer)
D. Oval window

Explanation: ***Dehiscent superior semicircular canal*** - A **dehiscent superior semicircular canal (SSCC)** creates a "third window" in the inner ear, allowing sound energy to dissipate into the cranial cavity. - This abnormal opening leads to symptoms like **autophony**, **vertigo triggered by loud sounds (Tullio phenomenon)**, and **sound-evoked eye movements (nystagmus)**. *Perforated tympanum* - A **perforated tympanum** (eardrum) affects the sound transmission from the outer to the middle ear, causing **conductive hearing loss**. - It does not involve the inner ear fluid dynamics or symptom complex associated with a "third window" effect. *Round window* - The **round window** is one of the two normal openings to the inner ear, covered by a membrane, allowing fluid displacement within the cochlea during sound transmission. - It is a physiological structure essential for normal hearing and its function is different from an abnormal "third window." *Oval window* - The **oval window** is the other normal opening to the inner ear, where the stapes footplate transmits sound vibrations from the middle ear to the cochlear fluid. - It is a key component of normal auditory transduction and does not represent an abnormal "third window" allowing fluid leakage or pressure dissipation.

Question 8: Resection of which part of intestine does not significantly affect fluid and electrolyte balance?

A. Ileum
B. Proximal jejunum
C. Distal jejunum (Correct Answer)
D. Colon

Explanation: ***Distal jejunum*** - The distal jejunum has significant **adaptive capacity** to take over the absorptive functions of other parts of the small intestine if they are resected. - Its resection typically has the **least impact** on fluid and electrolyte balance compared to other segments of the intestine, as critical absorption of most nutrients, water, and electrolytes occurs more proximally or distally. *Ileum* - The ileum is crucial for the absorption of **vitamin B12** and **bile salts**; its resection can lead to **malabsorption** and severe diarrhea. - Loss of bile salt absorption can result in **fat malabsorption** and lead to fluid and electrolyte disturbances. *Proximal jejunum* - The proximal jejunum is the primary site for the absorption of most **nutrients** (carbohydrates, proteins, fats), **water**, and **electrolytes**. - Its resection can lead to significant **malnutrition** and severe fluid and electrolyte imbalances due to widespread malabsorption. *Colon* - The colon is responsible for the final absorption of **water** and **electrolytes**, compacting stool for elimination. - Its resection can severely impair the body's ability to conserve water and electrolytes, leading to **dehydration** and electrolyte disturbances.

Question 9: Dosage of intravenous fluid for 2 month old child in diarrhea with severe dehydration -

A. 80 ml/Kg in 6 hour
B. 50 ml/Kg in 6 hour
C. 100 ml/Kg in 6 hour (Correct Answer)
D. 75 ml/Kg in 6 hour

Explanation: ***100 ml/Kg in 6 hour*** - For infants under 12 months with **severe dehydration** due to diarrhea, the standard recommendation for intravenous fluid resuscitation is to administer **100 ml/kg** over 6 hours. - This volume is divided, with 30 mL/kg given in the first hour, and the remaining 70 mL/kg given over the subsequent 5 hours, following the **WHO guidelines** for rehydration. *80 ml/Kg in 6 hour* - This dosage is **insufficient** for severe dehydration in infants, as it would not adequately replace the significant fluid and electrolyte deficits. - Undershooting the fluid requirements in severe dehydration can lead to persistent **hypovolemic shock** and worsen clinical outcomes. *50 ml/Kg in 6 hour* - This is a **critically low dose** for severe dehydration and would be entirely inadequate for effective rehydration in a 2-month-old. - Such a low fluid volume would fail to correct **circulatory compromise** and could lead to rapid clinical deterioration. *75 ml/Kg in 6 hour* - While closer to the recommended dose than other incorrect options, **75 ml/kg** is still generally considered insufficient for a 2-month-old with severe dehydration. - This dose may be appropriate for **less severe dehydration** or if fluid therapy is initiated too slowly, putting the infant at risk of incomplete rehydration.

Question 10: A 52-year-old man was referred to the clinic due to increased abdominal girth. He is diagnosed with ascites by the presence of a fluid thrill and shifting dullness on percussion. After administering diuretic therapy, which nursing action would be most effective in ensuring safe care for this patient?

A. Measuring serum potassium for hypokalemia
B. Assessing the client for hypovolemia
C. Measuring the client’s weight weekly
D. Documenting precise intake and output (Correct Answer)

Explanation: ***Documenting precise intake and output*** - **Accurate intake and output (I&O)** monitoring helps track fluid balance and the effectiveness of diuretic therapy in reducing ascites [1]. - This data is crucial for adjusting diuretic dosages and preventing complications like **dehydration** or **fluid overload** [2]. *Measuring serum potassium for hypokalemia* - While monitoring electrolytes is important, **hypokalemia** is a potential side effect of some diuretics, but not the *most effective* immediate nursing action for *safe care* post-diuretic administration for ascites [3]. - This is an important monitoring parameter, but not the primary action for overall safe care in this context. *Assessing the client for hypovolemia* - **Hypovolemia** is a risk with aggressive diuretic therapy, but frequently reassessing **I&O** provides more concrete data to *prevent* this complication rather than just *assessing* for it after it may have started [1]. - While important, focusing on the *outcome* rather than the *preventative measure* makes it less effective as a primary safe care action. *Measuring the client’s weight weekly* - **Weekly weight measurement** is a useful tool for tracking fluid shifts over time but is not immediate enough to ensure *safe care* after diuretic administration [3]. - **Daily weight measurements** or even more frequent monitoring might be warranted, but precise **I&O** provides real-time data for fluid balance decisions.

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