Fluid and Electrolyte Management — MCQs
Best solution to be used in hypovolemic shock is:
Initial fluid of choice in treatment of hypovolemia in patients presenting after trauma is
Which electrolyte imbalance causes prolonged QT interval?
A 25-year-old male patient presents with ingestion of antifreeze solution. His arterial blood gas analysis report is as follows: pH = 7.20 Anion gap = 15 PCO2 = 25 HCO3 = 10 What is the most likely diagnosis?
Which of the following is true about ICF?
30-year-old male, weighing 70 kg , presents with a serum sodium level of $120 \mathrm{mEq} / \mathrm{L}$. Calculate the total sodium deficit.
Which fluid is ideally given for a patient experiencing dehydration?
A person with type 1 diabetes ran out of her prescription insulin and has not been able to inject insulin for the past 3 days. The patient is hyperventilating to compensate for her metabolic acidosis. Which of the following reactions explains this respiratory compensation for metabolic acidosis?
"Active core rewarming" refers to
In which condition does maximum sodium loss occur in a child?
Fluid and Electrolyte Management Indian Medical PG Practice Questions and MCQs
Question 1: Best solution to be used in hypovolemic shock is:
- A. Ringer's Lactate solution. (Correct Answer)
- B. Darrow's solution.
- C. 5% dextrose.
- D. 0.9% Nacl.
Explanation: ***Ringer's Lactate solution*** - This **isotonic crystalloid solution** is commonly used in hypovolemic shock because its electrolyte composition is similar to that of human plasma. [2] - The **lactate** component is metabolized by the liver to bicarbonate, which helps to buffer acidosis often associated with shock. [2] *Darrow's solution* - Darrow's solution is a **hypertonic solution** containing high concentrations of potassium, primarily used for severe dehydration and significant potassium deficits, not initial fluid resuscitation in hypovolemic shock. - Its high potassium content can be dangerous in patients with **renal impairment** or who are already hyperkalemic. *5% dextrose* - **5% dextrose in water (D5W)** is an initially isotonic solution, but the dextrose is quickly metabolized, making it effectively a hypotonic solution. [2] - It is primarily used to provide **free water** and is not effective for volume expansion in hypovolemic shock as it does not stay in the intravascular space. [2] *0.9% Nacl* - **0.9% normal saline** is an isotonic crystalloid often used for volume resuscitation but has a higher chloride content than plasma, which can lead to **hyperchloremic metabolic acidosis** with large volumes. [1], [2] - While it expands the intravascular space, Ringer's Lactate is often preferred in situations of significant blood loss or acidosis due to its more balanced electrolyte profile and buffering capacity. [2]
Question 2: Initial fluid of choice in treatment of hypovolemia in patients presenting after trauma is
- A. Blood
- B. Colloid
- C. Plasma expanders
- D. Crystalloid (Correct Answer)
Explanation: ***Crystalloid*** - **Crystalloids** such as normal saline or lactated Ringer's solution are the initial fluid of choice for **hypovolemia in trauma patients** due to their ready availability, low cost, and effectiveness in rapidly expanding the intravascular volume. - They freely distribute across the extracellular space, effectively compensating for fluid loss and supporting organ perfusion. *Blood* - While essential for significant **hemorrhage**, blood products are typically reserved for patients who do not respond to crystalloid resuscitation or have documented severe blood loss. - Transfusion carries risks such as **transfusion reactions**, and blood preparation and cross-matching take time, making them less suitable for initial, rapid fluid replacement. *Colloid* - **Colloids** (e.g., albumin, starches) are larger molecules that theoretically remain in the intravascular space longer, but their benefits over crystalloids in trauma are controversial and they are significantly more expensive. - Some colloids have been associated with adverse effects like **renal dysfunction** or **coagulopathy**, making crystalloids a safer initial option. *Plasma expanders* - **Plasma expanders** is a broad term that includes both colloids and some hypertonic crystalloid solutions, but it is not commonly used as a primary, specific category for initial fluid resuscitation. - The potential benefits of these agents are still debated, and they are typically not recommended as the first-line choice in the acute management of **traumatic hypovolemic shock**.
Question 3: Which electrolyte imbalance causes prolonged QT interval?
- A. Hypernatremia
- B. Hyperkalemia
- C. Hypocalcemia (Correct Answer)
- D. Hyponatremia
Explanation: ***Hypocalcemia*** - **Hypocalcemia** prolongs the **repolarization phase** of the action potential in cardiac myocytes, leading to a lengthened **QT interval** on an electrocardiogram. - This increased duration of repolarization places the heart at higher risk for **Torsades de Pointes** and other life-threatening arrhythmias [2], [3]. *Hypernatremia* - **Hypernatremia** primarily affects neurological function and can cause symptoms like **confusion** and **seizures**. - It does not typically lead to a **prolonged QT interval**; instead, it can sometimes be associated with a shortened QT interval or other non-specific ECG changes. *Hyperkalemia* - **Hyperkalemia** primarily causes peaked T waves, a widened QRS complex, and eventually **bradycardia** and **asystole** [1]. - While it drastically alters cardiac conduction, it typically **shortens** rather than prolongs the QT interval. *Hyponatremia* - **Hyponatremia** is associated with cerebral edema and neurological symptoms such as **headaches**, **nausea**, and **altered mental status**. - It generally does not cause a **prolonged QT interval**; significant hyponatremia can sometimes be associated with non-specific ECG changes [1] but not a specific lengthening of the QT interval.
Question 4: A 25-year-old male patient presents with ingestion of antifreeze solution. His arterial blood gas analysis report is as follows: pH = 7.20 Anion gap = 15 PCO2 = 25 HCO3 = 10 What is the most likely diagnosis?
- A. None of the options
- B. Normal anion gap metabolic acidosis
- C. High anion gap metabolic acidosis (Correct Answer)
- D. Both
Explanation: ***High anion gap metabolic acidosis*** - The patient has a **low pH (7.20)**, indicating **acidosis**. The **bicarbonate (HCO3-) is low (10 mEq/L)**, which confirms it is a metabolic acidosis [1]. - The **anion gap is calculated as Na+ - (Cl- + HCO3-)**. With the given anion gap of 15, which is above the normal range (typically 8-12 mEq/L), it indicates a **high anion gap metabolic acidosis** [2]. This is consistent with **antifreeze (ethylene glycol) ingestion**, which produces acidic metabolites [2]. *Normal anion gap metabolic acidosis* - This type of acidosis occurs when the **anion gap remains within the normal range** (8-12 mEq/L), even though blood pH is low. - It usually results from a **loss of bicarbonate**, often through the gastrointestinal tract (e.g., severe diarrhea) or via the kidneys (e.g., renal tubular acidosis) [3], with a compensatory increase in chloride. *None of the options* - This option is incorrect as the presented clinical and lab findings clearly point to a specific type of acid-base disturbance. - The calculated anion gap and the pH/bicarbonate levels provide sufficient information for diagnosis. *Both* - This option is incorrect because the patient's lab values, specifically the **elevated anion gap**, distinctly categorize the condition as a high anion gap metabolic acidosis, ruling out a normal anion gap metabolic acidosis. - An acid-base disorder cannot simultaneously be both high and normal anion gap.
Question 5: Which of the following is true about ICF?
- A. 14 L
- B. 33% of body weight
- C. 20 % of body weight
- D. 28 L (Correct Answer)
Explanation: ***28 L*** - The **intracellular fluid (ICF)** volume is approximately two-thirds of the total body water, which for a 70 kg individual is around **28 liters**. - This fluid is found within the cells and is crucial for various cellular functions and metabolic processes. *14 L* - This value typically represents the **extracellular fluid (ECF)** volume, which is divided into interstitial fluid and plasma, not the ICF. - The ECF is approximately one-third of the total body water, or about 14 liters. *33% of body weight* - This percentage is **inaccurate for both ICF and ECF**. - ICF accounts for approximately **40% of body weight**, while ECF accounts for about 20% of body weight. - This option does not correctly represent any major fluid compartment. *20% of body weight* - While **20% of body weight** more closely represents the **extracellular fluid (ECF)** volume, it is an underestimate for the intracellular fluid (ICF) volume. - ICF makes up approximately **40% of body weight** in an adult, which is double this value.
Question 6: 30-year-old male, weighing 70 kg , presents with a serum sodium level of $120 \mathrm{mEq} / \mathrm{L}$. Calculate the total sodium deficit.
- A. 630 mEq
- B. 280 mEq
- C. 420 mEq
- D. 840 mEq (Correct Answer)
- E. 1260 mEq
Explanation: ***840 mEq*** - The formula for calculating **total sodium deficit** is: **(Desired Na - Actual Na) × Total Body Water (TBW)**. - In a male, TBW is approximately **60% of body weight**. For a 70 kg male, **TBW = 0.6 × 70 kg = 42 L**. - With a desired sodium of **140 mEq/L** (normal) and actual sodium of **120 mEq/L**, the total deficit is: - **(140 - 120) × 42 = 20 × 42 = 840 mEq** - This represents the **complete calculated sodium deficit** needed to restore serum sodium to normal levels. - **Note:** In clinical practice, this entire deficit is NOT replaced rapidly. Typically, only **6-12 mEq/L increase per 24 hours** is recommended to prevent **osmotic demyelination syndrome**, but the question asks for the total calculated deficit. *630 mEq* - This value represents a **partial correction target**, corresponding to raising serum sodium to approximately **135 mEq/L** instead of 140 mEq/L: (135 - 120) × 42 = 630 mEq. - Alternatively, it equals about **75% of the total deficit** (840 × 0.75 = 630). - While this may reflect a practical clinical target, it does not answer the question which asks for the **total deficit**. *420 mEq* - This corresponds to raising serum sodium by **10 mEq/L** (10 × 42 = 420 mEq). - This represents the **maximum recommended increase in the first 24 hours** to prevent complications. - It is a safe initial correction amount but not the total calculated deficit. *280 mEq* - This represents an even smaller increment, roughly equivalent to raising serum sodium by **6-7 mEq/L**. - This would be an **ultra-conservative initial correction** for chronic hyponatremia. - It significantly underestimates the total sodium deficit. *1260 mEq* - This is an **overestimation** that might result from incorrectly using 100% body weight as TBW instead of 60%: (140 - 120) × 70 = 1400 mEq (close to this range). - Or from miscalculation using wrong formula components. - This exceeds the actual total sodium deficit.
Question 7: Which fluid is ideally given for a patient experiencing dehydration?
- A. Plasma
- B. Normal Saline (Correct Answer)
- C. Blood
- D. 5% dextrose
Explanation: ***Normal Saline*** - **Normal saline (0.9% sodium chloride)** is an **isotonic solution** that effectively increases **extracellular fluid volume**, making it ideal for treating **dehydration** and hypovolemia [1]. - It closely mimics the **osmolality of plasma** and stays predominantly in the intravascular space, helping to restore circulating volume [1]. *Plasma* - **Plasma** is primarily used for **coagulation factor deficiencies** or volume expansion in cases of severe **hypoproteinemia**, not routine dehydration. - It contains **proteins and clotting factors** that are not typically needed for simple dehydration and carries risks of **allergic reactions and transfusion-related acute lung injury (TRALI)**. *Blood* - **Blood transfusions** are indicated for patients with **significant anemia** or **acute blood loss**, not for generalized dehydration. - Using blood for dehydration would be inappropriate due to risks such as **transfusion reactions**, **infections**, and **iron overload**. *5% dextrose* - **5% dextrose in water (D5W)** is an **isotonic solution initially**, but once the dextrose is metabolized, it becomes **hypotonic**, causing free water to shift into the cells [1]. - While it provides some free water, it is not ideal for primary rehydration in cases of significant volume depletion due to its lack of electrolytes and potential for causing **hyponatremia** if given in large quantities [1].
Question 8: A person with type 1 diabetes ran out of her prescription insulin and has not been able to inject insulin for the past 3 days. The patient is hyperventilating to compensate for her metabolic acidosis. Which of the following reactions explains this respiratory compensation for metabolic acidosis?
- A. H2O ⇌ H+ + OH-
- B. H+ + NH3 ⇌ NH4+
- C. CH3CHOHCH2COOH ⇌ CH3CHOHCH2COO- + H+
- D. CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3- (Correct Answer)
Explanation: ***CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3-*** - This reaction represents the **bicarbonate buffer system**, which is central to maintaining **pH balance** in the body. - In response to **metabolic acidosis**, the body hyperventilates to **decrease CO2** levels, shifting the equilibrium to the left and reducing H+ which compensates for the increased acidity. *H2O ⇌ H+ + OH-* - This reaction describes the **autoionization of water**, which is fundamental but does not directly explain the body's respiratory compensation mechanism for metabolic acidosis. - While it shows the presence of H+ ions, it doesn't illustrate how the respiratory system manipulates CO2 to influence pH. *H+ + NH3 ⇌ NH4+* - This reaction represents the **ammonia buffer system** primarily active in the **kidneys** for acid excretion. - It plays a role in renal compensation for pH imbalances, but it is not the mechanism for respiratory compensation. *CH3CHOHCH2COOH ⇌ CH3CHOHCH2COO- + H+* - This represents the **dissociation of beta-hydroxybutyric acid**, a **ketone body** produced in diabetic ketoacidosis (DKA). - While DKA is the cause of the metabolic acidosis in this patient, this specific reaction describes the *production* of H+ ions, not the *respiratory compensatory mechanism* to address it.
Question 9: "Active core rewarming" refers to
- A. Heated crystalloids (Correct Answer)
- B. Heated humidified O2
- C. Peritoneal dialysis
- D. All of the options
Explanation: ***Heated crystalloids*** - **Heated crystalloids** administered intravenously contribute to active core rewarming by directly introducing warm fluids into the circulatory system, raising the internal body temperature. - This method is particularly effective for **moderate to severe hypothermia** as it rapidly delivers heat to the body's core. *Heated humidified O2* - Administering **heated and humidified oxygen** helps prevent further heat loss from the respiratory tract and contributes to rewarming. - While beneficial, it is generally considered a less aggressive or primary method of **active core rewarming** compared to direct intravenous fluid administration because it does not directly warm the bloodstream. *Peritoneal dialysis* - **Peritoneal dialysis** involves introducing warm dialysate into the peritoneal cavity, allowing for heat exchange. - This is an invasive procedure primarily used when other rewarming methods are insufficient, and it is a specific type of active core rewarming, but not the only one or most common representation of the term itself. *All of the options* - While **heated humidified O2** and **peritoneal dialysis** are methods of active rewarming, the question asks for what "active core rewarming" refers to. - Each of these options represents a specific technique, and while all contribute to rewarming the core, **heated crystalloids** are a more general and common representation encompassed by the term "active core rewarming."
Question 10: In which condition does maximum sodium loss occur in a child?
- A. Gastric juice
- B. Non cholera Diarrhoea
- C. Ileal fluid
- D. Cholera (Correct Answer)
Explanation: ***Cholera*** - **Cholera** causes **massive losses of isotonic fluid** with stool volumes reaching up to **1 liter per hour** in severe cases - The **cholera toxin** activates intestinal epithelial cell secretion, producing characteristic "rice-water stool" with sodium concentration of **90-140 mEq/L** (nearly isotonic to plasma) - Results in severe losses of **sodium, chloride, bicarbonate, and potassium**, leading to profound dehydration and electrolyte imbalances - Represents the **maximum acute sodium loss** among all pediatric gastrointestinal conditions *Gastric juice* - Loss of gastric juice (e.g., from severe vomiting or pyloric stenosis) primarily depletes **hydrogen ions and chloride**, causing **metabolic alkalosis** - Gastric fluid has **relatively low sodium concentration** (~60 mEq/L), much less than cholera stool - While clinically significant, sodium loss is not the predominant electrolyte disturbance *Ileal fluid* - Ileal fluid has moderate sodium concentration (100-140 mEq/L), similar to cholera - However, **volume of loss is typically much less** than in acute cholera - Seen in conditions like high-output ileostomy or short bowel syndrome - Losses occur more **gradually** rather than the acute, massive depletion in cholera *Non cholera Diarrhoea* - Most non-cholera diarrheal illnesses (viral, bacterial) cause **less severe fluid losses** - The fluid is often more **hypotonic** (lower sodium concentration per unit volume) - Total sodium depletion is typically **less profound** than cholera, though still clinically significant
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