Electrolytes and Acid-Base Balance Tests — MCQs

10 questions

All of the following statements about acid-base disorders are true, EXCEPT:

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 -

Major ions in ECF are:

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 –

Which one of the following biochemical abnormalities can be produced by repeated vomiting?

Glutathione does all of the following except?

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

Positive Romberg test with eyes closed detects a defect in -

Which of the following tests is not used for detection of seminal stain?

Q10Medium

Which of the following conditions masks low serum haptoglobin in hemolysis?

Electrolytes and Acid-Base Balance Tests Indian Medical PG Practice Questions and MCQs

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

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.

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

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.

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)

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.

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

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].

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

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.

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

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.

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

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 8: 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 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)

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.

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

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.

Want unlimited practice?

Get full access to all questions, explanations, and performance tracking.

Start For Free