Electrolytes and Acid-Base Balance Tests Indian Medical PG Practice Questions and MCQs
Practice Indian Medical PG questions for Electrolytes and Acid-Base Balance Tests. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 1: All of the following statements about acid-base disorders are true, EXCEPT:
- A. Metabolic acidosis is compensated by increasing Pco2 (Correct Answer)
- B. Buffering may be intra & extra cellular
- C. pH determined by Pco2 and HCO3
- D. Respiratory acidosis is compensated by HCO3
Electrolytes and Acid-Base Balance Tests Explanation: ***Metabolic acidosis is compensated by increasing Pco2***
- In **metabolic acidosis**, the primary problem is a decrease in **bicarbonate (HCO3-)**.
- The compensatory response is **respiratory**, involving an increase in **respiratory rate** and depth to **decrease Pco2**, thereby *raising* the pH back towards normal. Increasing Pco2 would worsen the acidosis.
*Buffering may be intra & extra cellular*
- **Buffering systems** operate both **intracellularly** (e.g., proteins, phosphates) and **extracellularly** (e.g., bicarbonate-carbonic acid system, hemoglobin).
- This dual buffering ensures a rapid and widespread response to changes in acid-base balance throughout the body.
*pH determined by Pco2 and HCO3*
- According to the **Henderson-Hasselbalch equation**, pH is directly proportional to the ratio of **bicarbonate (HCO3-)** to **Pco2**.
- This means that changes in either Pco2 (respiratory component) or HCO3- (metabolic component) will directly influence the overall pH of the blood.
*Respiratory acidosis is compensated by HCO3*
- In **respiratory acidosis**, the primary problem is an increase in **Pco2** due to hypoventilation.
- The compensatory response is **renal**, involving increased reabsorption of **bicarbonate (HCO3-)** and increased excretion of H+ ions to buffer the excess acid.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 2: A 24 year old male presents with altered sensorium and rapid shallow breathing. ABG shows:pH 7.2, sodium 140, bicarbonate 10 and chloride 98. Probable diagnosis is -
- A. Amphetamine toxicity
- B. DKA (Correct Answer)
- C. Renal tubular acidosis
- D. Ethylene glycol poisoning
Electrolytes and Acid-Base Balance Tests Explanation: ***DKA***
- The patient presents with **altered sensorium** and **rapid shallow breathing** (Kussmaul breathing), consistent with severe metabolic acidosis [1].
- The ABG results show **pH 7.2** (acidosis), **bicarbonate 10** (metabolic component), and an **elevated anion gap** (Na - (Cl + HCO3) = 140 - (98 + 10) = 32), which are characteristic findings in **diabetic ketoacidosis (DKA)** [1], [2].
*Amphetamine toxicity*
- Amphetamine toxicity typically causes **sympathomimetic effects** such as tachycardia, hypertension, hyperthermia, and agitation, rather than directly leading to a high anion gap metabolic acidosis of this severity.
- While it can cause some metabolic derangements, the primary acid-base disturbance is usually different or less pronounced in this manner compared to DKA.
*Renal tubular acidosis*
- Renal tubular acidosis (RTA) typically presents with a **normal anion gap metabolic acidosis** (hyperchloremic metabolic acidosis), where the anion gap would not be significantly elevated.
- The calculated anion gap of 32 in this patient rules out RTA as the primary cause of this severe acidosis.
*Ethylene glycol poisoning*
- Ethylene glycol poisoning also causes a **high anion gap metabolic acidosis** and altered mental status.
- However, it is typically associated with additional specific symptoms like **flank pain**, **oliguria**, and detection of **calcium oxalate crystals** in the urine, which are not mentioned in this case.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 3: Major ions in ECF are:
- A. Potassium and phosphate
- B. Sodium and phosphate
- C. Potassium and chloride
- D. Sodium and chloride (Correct Answer)
Electrolytes and Acid-Base Balance Tests Explanation: ***Sodium and chloride***
- **Sodium (Na+)** is the primary cation, and **chloride (Cl-)** is the primary anion in the extracellular fluid (ECF).
- These ions play crucial roles in maintaining **osmotic pressure**, **fluid balance**, and **nerve impulse transmission**.
*Potassium and phosphate*
- **Potassium (K+)** is the major intracellular cation, while **phosphate (PO43-)** is a major intracellular anion.
- While present in the ECF, their concentrations are significantly lower compared to sodium and chloride.
*Sodium and phosphate*
- **Sodium** is a major ECF cation, but **phosphate** is predominantly an intracellular anion.
- Therefore, phosphate is not considered one of the major extracellular ions.
*Potassium and chloride*
- **Potassium** is primarily an intracellular ion, not a major ECF cation.
- While **chloride** is a major ECF anion, its pairing with potassium does not represent the two major ions in the ECF.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 4: Renal tubular acidosis with ABG value pH = 7.24 PO2=80; PaCO2= 36 Na = 131; HCO3 = 14 Cl= 90; BE = -13 Glucose = 135 the above ABG picture suggests –
- A. Metabolic acidosis (Correct Answer)
- B. Respiratory alkalosis
- C. Metabolic alkalosis
- D. Respiratory acidosis
Electrolytes and Acid-Base Balance Tests Explanation: The ABG shows a pH of 7.24, indicating **acidemia** [1]. The HCO3 is 14 mEq/L, which is significantly **low**, and the base excess (BE) is -13 [1]. The PaCO2 of 36 mmHg is within the normal range, indicating no significant primary respiratory derangement [2]. The overall picture is consistent with an uncompensated or partially compensated **metabolic acidosis** [1][2].
***Metabolic acidosis***
- The **low pH (acidemia)**, **low bicarbonate (HCO3)**, and **negative base excess (BE)** are direct indicators of metabolic acidosis [1].
- The **PaCO2 within normal limits** or slightly decreased suggests either no respiratory compensation or insufficient compensation for the metabolic derangement [1][2].
*Respiratory acidosis*
- This would present with a **low pH** and an **elevated PaCO2** as the primary defect, which is not seen here (PaCO2 is normal) [1].
- Bicarbonate would typically be normal or elevated if compensated, not significantly decreased.
*Respiratory alkalosis*
- This would be characterized by an **elevated pH** and a **low PaCO2**, which is the opposite of the findings in this ABG [1].
- HCO3 would be normal or low if compensated.
*Metabolic alkalosis*
- This would present with an **elevated pH** and an **elevated HCO3**, which contradicts the given ABG values (low pH and low HCO3) [2].
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 5: Which one of the following biochemical abnormalities can be produced by repeated vomiting?
- A. Metabolic acidosis
- B. Metabolic alkalosis (Correct Answer)
- C. Ketosis
- D. Uraemia
Electrolytes and Acid-Base Balance Tests Explanation: ***Metabolic alkalosis***
- Repeated vomiting leads to the loss of **hydrochloric acid (HCl)** from the stomach, causing **hypochloremic metabolic alkalosis** with an increase in serum **bicarbonate (HCO3-)** and a rise in blood pH.
- The loss of H+ and Cl- ions results in **compensatory hypokalemia** as the kidneys exchange K+ for H+ to maintain electroneutrality.
- **Volume depletion** from vomiting triggers aldosterone secretion, which further promotes K+ loss and H+ excretion, perpetuating the alkalosis (contraction alkalosis).
- This is one of the most common causes of metabolic alkalosis in clinical practice.
*Metabolic acidosis*
- This condition is characterized by a decrease in **serum pH** and **bicarbonate levels**, typically due to excess acid production or bicarbonate loss from diarrhea or renal tubular acidosis.
- Vomiting does not directly cause metabolic acidosis; rather, it leads to the opposite effect by removing acidic gastric contents.
*Ketosis*
- **Ketosis** occurs when the body metabolizes fat for energy, producing **ketone bodies**, common in conditions like uncontrolled diabetes or prolonged starvation.
- While severe, prolonged vomiting with reduced oral intake can indirectly lead to starvation ketosis, the primary and most characteristic biochemical abnormality of repeated vomiting is metabolic alkalosis, not ketosis.
*Uraemia*
- **Uraemia** is a syndrome caused by the accumulation of **nitrogenous waste products** (urea, creatinine) in the blood, primarily due to kidney failure.
- Vomiting may be a *symptom* of uraemia, but it does not *cause* uraemia. Kidney function is the primary determinant of urea levels.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 6: Glutathione does all of the following except?
- A. Scavenge peroxides
- B. Decreases the stability of erythrocyte membranes (Correct Answer)
- C. Form conjugates with some drugs to increase water solubility
- D. Participates in the transport of amino acids across some cell membranes
Electrolytes and Acid-Base Balance Tests Explanation: ***Decreases the stability of erythrocyte membranes***
- Glutathione actually **increases** the stability of erythrocyte membranes by protecting them from oxidative damage, particularly through its role in reducing **hydrogen peroxide** and organic hydroperoxides.
- A deficiency in glutathione or the enzymes that reduce it (like **G6PD**) leads to increased oxidative stress, which **destabilizes** erythrocyte membranes and can cause **hemolysis**.
*Scavenge peroxides*
- Glutathione, in its reduced form (GSH), serves as a crucial **antioxidant** by **scavenging peroxides** through the action of **glutathione peroxidase**.
- This reaction converts harmful **hydrogen peroxide** into water, protecting cellular components from oxidative damage.
*Form conjugates with some drugs to increase water solubility.*
- Glutathione plays a vital role in phase II detoxification reactions, where it forms **conjugates** with various xenobiotics and drugs.
- This **conjugation** typically increases the **water solubility** of these compounds, facilitating their excretion from the body.
*Participates in the transport of amino acids across some cell membranes*
- Glutathione is involved in the **gamma-glutamyl cycle**, which is a mechanism for the **transport of amino acids** into cells, particularly in the kidney.
- In this cycle, glutathione donates its **gamma-glutamyl group** to an amino acid, forming a gamma-glutamyl amino acid that is then transported across the membrane.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 7: 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
Electrolytes and Acid-Base Balance Tests 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.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 8: Positive Romberg test with eyes closed detects a defect in -
- A. Cerebellum
- B. Peripheral nerve
- C. Proprioceptive pathway (Correct Answer)
- D. Spinothalamic tract
Electrolytes and Acid-Base Balance Tests 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].
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 9: Which of the following tests is not used for detection of seminal stain?
- A. Acid Phosphatase test
- B. Florence test
- C. Barbeiros test
- D. Phadebas Test (Correct Answer)
Electrolytes and Acid-Base Balance Tests Explanation: ***Phadebas Test***
- The Phadebas test is primarily used for the detection and quantification of **alpha-amylase**, an enzyme found in high concentrations in saliva.
- While amylase can be present in other bodily fluids, including semen, the Phadebas test is not a specific or primary method for detecting seminal stains due to its low specificity for semen compared to other methods.
*Acid Phosphatase test*
- The **acid phosphatase (AP) test** is a widely used presumptive test for seminal fluid due to the high concentration of **prostatic acid phosphatase** in semen.
- A positive result, usually indicated by a color change, suggests the probable presence of semen, although false positives can occur.
*Florence test*
- The Florence test is a **confirmatory test** for the presence of **choline** in semen, which reacts with potassium iodide to form characteristic dark brown, rhombic crystals.
- While historically significant, it is a less sensitive and specific test compared to modern methods.
*Barbeiros test*
- The Barbeiros test (or Barberio's test) is another **confirmatory chemical test** for the presence of **spermine** in semen.
- Spermine reacts with picric acid to form characteristic needle-like crystals, further indicating the presence of seminal fluid.
Electrolytes and Acid-Base Balance Tests Indian Medical PG Question 10: Which of the following conditions masks low serum haptoglobin in hemolysis?
- A. Bile duct obstruction (Correct Answer)
- B. Liver disease
- C. Malnutrition
- D. Pregnancy
Electrolytes and Acid-Base Balance Tests Explanation: **Explanation:**
The primary clinical utility of **Haptoglobin** is as a marker for **intravascular hemolysis**. Haptoglobin is an acute-phase reactant synthesized by the liver that binds free hemoglobin. During hemolysis, haptoglobin levels drop significantly as it is cleared by the reticuloendothelial system.
**Why Bile Duct Obstruction is correct:**
Haptoglobin is a **positive acute-phase reactant**. In conditions like **bile duct obstruction (obstructive jaundice)**, inflammation or biliary stasis triggers an increase in the hepatic synthesis of haptoglobin. This elevation can artificially "mask" or normalize the low levels typically seen in hemolysis, leading to a false-negative result for hemolytic anemia.
**Analysis of Incorrect Options:**
* **Liver Disease:** Since haptoglobin is synthesized in the liver, severe liver disease (e.g., cirrhosis) leads to **decreased** production. This would mimic or exacerbate low levels rather than masking them.
* **Malnutrition:** Protein-energy malnutrition leads to a generalized decrease in plasma protein synthesis, including haptoglobin, resulting in **low** levels.
* **Pregnancy:** Pregnancy is associated with a physiological decrease in haptoglobin levels (estrogen effect), which would not mask a hemolytic state.
**NEET-PG High-Yield Pearls:**
* **Gold Standard for Hemolysis:** A **decreased** serum haptoglobin level is one of the most sensitive markers for confirming hemolysis.
* **Acute Phase Reactants:** Remember that haptoglobin levels rise in infection, trauma, and malignancy, which can confound the diagnosis of co-existing hemolysis.
* **Neonate Fact:** Haptoglobin levels are naturally very low or absent in newborns (physiologic ahaptoglobinemia) and reach adult levels by 6 months of age.
More Electrolytes and Acid-Base Balance Tests Indian Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
