Electrolytes and Body Fluids

Electrolytes and Body Fluids Indian Medical PG Question 1: A primigravida at 38 weeks pregnancy was put on oxytocin drip in view of slow labour at the rate of 30 mIU/min by the newly appointed registrar. She complains of confusion and starts throwing fits. What electrolyte imbalance is expected to have happened in this case?

• A. Hypokalemia
• B. Hyponatremia (Correct Answer)
• C. Hypocalcemia
• D. Hypernatremia

Electrolytes and Body Fluids Explanation: ***Hyponatremia*** - **Oxytocin** has an antidiuretic hormone (ADH)-like effect, leading to **water retention** and dilutional hyponatremia, especially when administered in large doses or with hypotonic solutions [1]. - Symptoms like **confusion** and **seizures (fits)** are classic signs of neurological impairment due to severe hyponatremia. *Hypokalemia* - While electrolyte imbalances can occur with oxytocin, **hypokalemia** is not typically associated with oxytocin's ADH-like actions or its direct effects on renal tubules. - Symptoms related to hypokalemia usually involve **muscle weakness** and cardiac arrhythmias, which are not the primary features here. *Hypocalcemia* - **Hypocalcemia** is more commonly associated with conditions like parathyroid dysfunction or vitamin D deficiency, not directly with oxytocin administration. - Symptoms would typically include **tetany**, muscle cramps, and paresthesias, not primarily confusion and seizures in this context. *Hypernatremia* - **Hypernatremia** would involve excess sodium or severe dehydration, which is contrary to the fluid retention effect of oxytocin and unlikely to cause seizures in this context. - Elevated sodium levels would typically present with symptoms of extreme thirst, lethargy, and dry mucous membranes.

Electrolytes and Body Fluids Indian Medical PG Question 2: A CKD patient develops serum K+ 7.2 mEq/L without ECG changes. Best initial management?

• A. Emergency dialysis
• B. Sodium polystyrene
• C. Insulin with glucose
• D. Calcium gluconate (Correct Answer)

Electrolytes and Body Fluids Explanation: **Calcium gluconate** - **Calcium gluconate** is the best initial management for severe hyperkalemia, particularly when the potassium level is very high (above 6.5 mEq/L) even without ECG changes [1]. It acts quickly to directly stabilize the cardiac membrane by **antagonizing the effects of potassium on myocardial excitability**, thereby preventing life-threatening arrhythmias [1]. - It provides immediate cardioprotection, buying time for other therapies to shift potassium into cells or remove it from the body. *Emergency dialysis* - While **dialysis** is the most effective way to remove potassium from the body, it is typically reserved for cases of severe, refractory hyperkalemia, or when other therapies have failed [3]. - It is not the *initial* management for immediate cardiac stabilization, especially if no ECG changes are present and calcium can be administered more rapidly. *Sodium polystyrene* - **Sodium polystyrene sulfonate (Kayexalate)** is a potassium-binding resin that works in the gastrointestinal tract to exchange sodium for potassium, thus removing potassium from the body. - Its onset of action is slow (hours to days), making it inappropriate for acute, severe hyperkalemia requiring immediate intervention. *Insulin with glucose* - **Insulin with glucose** therapy promotes the intracellular shift of potassium, temporarily lowering serum potassium levels [2]. - While effective, its onset of action is typically 15-30 minutes, and it functions as a temporary measure to redistribute potassium, not to acutely stabilize the cardiac membrane, which is the primary concern when potassium is severely elevated.

Electrolytes and Body Fluids Indian Medical PG Question 3: Which electrolyte disturbance is seen in primary hyperaldosteronism?

• A. Hyperkalemia
• B. Hyponatremia
• C. Hypercalcemia
• D. Hypokalemia (Correct Answer)

Electrolytes and Body Fluids Explanation: ***Hypokalemia*** - **Aldosterone** normally promotes sodium reabsorption and potassium excretion in the renal tubules [1]. - In primary hyperaldosteronism, excessive aldosterone production leads to increased potassium excretion, resulting in **hypokalemia** [1], [2]. *Hyperkalemia* - **Hyperkalemia** (high potassium) is the opposite of what occurs in primary hyperaldosteronism [1]. - Aldosterone's primary action is to increase potassium secretion, so excess aldosterone would not cause potassium retention. *Hyponatremia* - **Hyponatremia** (low sodium) is not typical in primary hyperaldosteronism; instead, **hypernatremia** or normal sodium levels may be observed due to increased sodium reabsorption. - The increased sodium reabsorption also leads to increased water reabsorption which can lead to **hypervolemia** but **normonatremia** [3]. *Hypercalcemia* - **Hypercalcemia** (high calcium) is not directly associated with primary hyperaldosteronism. - Calcium regulation is primarily controlled by parathyroid hormone and vitamin D, not aldosterone.

Electrolytes and Body Fluids Indian Medical PG Question 4: Which of the following drugs is not used for the emergency (immediate) management of hyperkalaemia?

• A. 10% calcium gluconate over 10 min
• B. Insulin-dextrose
• C. Injection MgSO4 (Correct Answer)
• D. Salbutamol nebulisation

Electrolytes and Body Fluids Explanation: ***Injection MgSO4*** - Magnesium sulfate is not a direct treatment for hyperkalaemia; its primary use is for conditions like **eclampsia**, **asthma exacerbations**, or **torsades de pointes**. - It does not directly affect potassium levels or cardiac membrane stability in the context of hyperkalaemia. *10% calcium gluconate over 10 min* - **Calcium gluconate** is used for immediate cardioprotection in hyperkalaemia by stabilizing the **cardiac membrane**, thereby reducing the risk of arrhythmias. - It does not lower serum potassium levels but mitigates the dangerous cardiac effects. *Insulin-dextrose* - This combination is an effective treatment for hyperkalaemia as **insulin** drives potassium from the extracellular to the intracellular space. - **Dextrose** is administered concurrently to prevent hypoglycaemia induced by insulin. *Salbutamol nebulisation* - **Beta-2 agonists** like salbutamol promote the uptake of potassium into cells, thus lowering serum potassium levels. - While effective, its action is generally less rapid and potent than insulin-dextrose or calcium gluconate in severe cases.

Electrolytes and Body Fluids Indian Medical PG Question 5: Hyperkalemia and metabolic acidosis are commonly associated with which type of renal tubular acidosis?

• A. Type II renal tubular acidosis
• B. Type I renal tubular acidosis
• C. Type IV renal tubular acidosis (Correct Answer)
• D. Type III renal tubular acidosis

Electrolytes and Body Fluids Explanation: ***Type IV renal tubular acidosis*** - This type is characterized by **hypoaldosteronism** or **aldosterone resistance**, leading to impaired potassium excretion and bicarbonate reabsorption [2]. - The resulting **hyperkalemia** inhibits ammonium excretion, contributing to a **non-anion gap metabolic acidosis** [1]. *Type I renal tubular acidosis* - This is a **distal RTA** caused by a defect in acid secretion in the collecting duct, leading to an inability to acidify urine [1]. - It typically presents with **hypokalemia**, **nephrolithiasis** (kidney stones), and an alkaline urine pH. *Type II renal tubular acidosis* - This is a **proximal RTA** due to impaired bicarbonate reabsorption in the proximal tubule. - It is typically associated with **hypokalemia**, and the urine can be acidified when systemic acidosis is severe. *Type III renal tubular acidosis* - This is a rare, historically used term, sometimes referring to a combination of features from Type I and Type II RTA. - It is not routinely used in current classification systems and does not specifically or primarily feature hyperkalemia and metabolic acidosis as its defining characteristics.

Electrolytes and Body Fluids Flashcard 1 of 5

Question: _____ in serum Mg2+ concentration cause increased PTH secretion

Answer: Mild decreases

Electrolytes and Body Fluids Flashcard 2 of 5

Question: Extracellular fluid is divided into _____ (75% of ECF) and plasma (25% of ECF)

Answer: interstitial fluid

Electrolytes and Body Fluids Flashcard 3 of 5

Question: The major cation of _____ fluid is Na+

Answer: extracellular

Electrolytes and Body Fluids Flashcard 4 of 5

Question: The movement of which molecule across the membrane is affected most by osmotic pressure?_____

Answer: Water

Electrolytes and Body Fluids Flashcard 5 of 5

Question: On average, _____ fluid is 40% of body weight

Answer: intracellular