Fluid and electrolyte management Practice Questions

Q: A 58-year-old cirrhotic man with ascites undergoes large volume paracentesis (6 liters removed). Four hours later, he becomes hypotensive (BP 80/50 mmHg) and tachycardic (HR 115/min). Labs show: Cr 2.1 mg/dL (baseline 1.0), Na+ 128 mEq/L, Hct 38%. What is the most appropriate immediate management?

5% albumin 6-8 grams per liter of ascites removed. ***5% albumin 6-8 grams per liter of ascites removed*** - This patient is experiencing **post-paracentesis circulatory dysfunction (PPCD)**, characterized by hypotension and **acute kidney injury** (doubled creatinine) following a large volume paracentesis (>5L). - Administration of **intravenous albumin** is the gold standard treatement to expand the **effective arterial blood volume** and prevent further deterioration into hepatorenal syndrome. *Normal saline bolus 2 liters* - In cirrhotic patients, **crystalloids** are less effective as they rapidly redistribute into the **interstitial space** (third-spacing) and can worsen ascites/edema. - Saline does not provide the **oncotic pressure** required to counteract the splanchnic vasodilation typical of PPCD. *Octreotide and midodrine for hepatorenal syndrome* - While these agents are used for **Hepatorenal Syndrome (HRS)**, the immediate priority in post-procedure hypotension is **volume expansion** to correct the circulatory dysfunction. - These medications are typically reserved for patients who do not respond to **volume expansion with albumin** or meet specific criteria for type 1 HRS. *Vasopressors to maintain blood pressure* - Vasopressors like **norepinephrine** are generally considered after fluid resuscitation with **albumin** has failed to restore hemodynamic stability. - Using pressors alone ignores the underlying **intravascular volume deficit** caused by the fluid shift after paracentesis. *Re-infusion of filtered ascitic fluid* - This is not a standard or recommended clinical practice due to risks of **infection**, **coagulopathy**, and lack of evidence for efficacy. - The specific requirement in this pathology is **concentrated albumin** to maintain oncotic pressure, which ascitic fluid does not provide efficiently.

Q: A 42-year-old woman with prolonged vomiting from gastroparesis is admitted with weakness. Labs show: K+ 2.1 mEq/L, pH 7.51, HCO3- 42 mEq/L, Mg2+ 1.4 mg/dL. She receives 80 mEq of IV potassium chloride over 24 hours, but repeat K+ is 2.3 mEq/L. What explains the refractory hypokalemia?

Hypomagnesemia preventing potassium retention. ***Hypomagnesemia preventing potassium retention*** - Low **intracellular magnesium** inhibits **ROMK channels** in the renal collecting duct; without magnesium inhibition, these channels allow excessive **potassium secretion** into the urine. - **Magnesium** is also a necessary cofactor for the **Na+/K+-ATPase pump**, which is required to transport potassium into the cells and maintain serum levels. *Secondary hyperaldosteronism from volume depletion* - While **volume depletion** triggers the **Renin-Angiotensin-Aldosterone System (RAAS)**, leading to potassium loss, it does not typically cause absolute refraction to supplementation in the presence of adequate IV fluids. - Addressing the **volume status** alone will not fix the hypokalemia if the **magnesium deficiency** is still driving renal wasting. *Insufficient potassium replacement dose* - A dose of **80 mEq** over 24 hours is a significant amount of supplement for a patient who is hospitalized and being monitored. - Failure to increase serum potassium by more than 0.2 mEq/L despite high-dose IV replacement suggests an **active wasting mechanism** rather than just an under-correction. *Ongoing losses from continued vomiting* - Although vomiting causes loss of **hydrochloric acid** and induces **metabolic alkalosis**, the gastric fluid itself contains relatively low concentrations of potassium. - The primary cause of hypokalemia in vomiting is **renal loss** (due to alkalosis and RAAS) rather than direct loss of potassium from the stomach. *Metabolic alkalosis promoting intracellular potassium shift* - **Alkalosis** causes an intracellular shift of potassium as **hydrogen ions** exit cells to help buffer the serum pH. - While this contributes to the initial low lab value, it does not explain why **exogenous IV potassium** fails to raise the serum concentration over a 24-hour period.

Q: A 50-year-old man is 5 days post-operative from a Whipple procedure. He has had high nasogastric output (1500 mL/day) and has been NPO. Labs show: Na+ 132 mEq/L, K+ 2.9 mEq/L, Cl- 88 mEq/L, HCO3- 38 mEq/L, pH 7.52. Urine chloride is 8 mEq/L. What is the appropriate management?

Normal saline with potassium chloride. ***Normal saline with potassium chloride*** - The patient has **hypochloremic, hypokalemic metabolic alkalosis** due to high-output gastric suctioning; a **urine chloride <10 mEq/L** confirms it is **chloride-responsive**. - Administering **Isotonic Saline (0.9% NaCl)** restores volume and provides the chloride needed to promote renal **bicarbonate excretion**, while **KCl** corrects the hypokalemia that maintains alkalosis. *Discontinue nasogastric suction only* - While suctioning is the source of acid loss, stopping it alone does not address the existing **volume depletion** or the severe **electrolyte imbalances** already present. - The kidneys require exogenous **chloride replacement** to effectively reverse the metabolic alkalosis and restore acid-base balance. *Acetazolamide to promote bicarbonate excretion* - This carbonic anhydrase inhibitor can lower bicarbonate but may worsen **hypokalemia** and contributes to further **volume depletion**. - It is generally reserved for patients with severe volume overload who cannot tolerate saline, which is not the case for this **hypovolemic** patient. *Half-normal saline with potassium supplementation* - **0.45% Saline** provides less sodium and chloride than required for rapid volume expansion and correction of **contraction alkalosis**. - **Isotonic 0.9% saline** is preferred to reliably expand the **extracellular fluid volume** and suppress the renin-angiotensin-aldosterone system. *Hydrochloric acid infusion* - This is an extreme measure reserved for life-threatening **metabolic alkalosis (pH >7.55-7.60)** that is refractory to standard saline and potassium replacement. - It requires **central venous access** due to its caustic nature and is not indicated as initial management for **chloride-responsive** states.

Q: A 28-year-old trauma patient received 8 units of packed RBCs, 6 units of FFP, and 2 units of platelets during damage control surgery. Two hours post-op, he develops: peaked T waves on EKG, K+ 6.8 mEq/L, Ca2+ 7.2 mg/dL, ionized calcium 0.9 mmol/L, pH 7.25. Which metabolic derangement is most responsible for his cardiac instability?

Combined hyperkalemia and hypocalcemia. ***Combined hyperkalemia and hypocalcemia*** - Massive transfusion protocols involve multiple blood products that synergistically cause **hyperkalemia** (due to potassium leakage from stored RBCs) and **hypocalcemia** (due to **citrate anticoagulants** binding ionized calcium). - These two derangements are most responsible for cardiac instability because **hypocalcemia** lowers the threshold for action potential while **hyperkalemia** increases membrane excitability, significantly increasing the risk of **fatal arrhythmias**. *Hypothermia-induced arrhythmia* - While massive transfusion can cause hypothermia if blood products aren't warmed, the primary markers here are **hyperkalemia** and **hypocalcemia**. - Hypothermia typically presents with **Osborn (J) waves** on EKG rather than the **peaked T waves** seen in this patient. *Hyperkalemia from massive transfusion* - Hyperkalemia alone explains the **peaked T waves** and elevated K+ of 6.8 mEq/L, but it ignores the significant **low ionized calcium (0.9 mmol/L)**. - Cardiac stabilization in this setting requires treating both electrolytes; addressing potassium without calcium is insufficient for **myocardial membrane stabilization**. *Hypocalcemia from citrate toxicity* - Citrate in FFP and PRBCs binds calcium, leading to the reported **ionized calcium** level, which can cause QT prolongation and reduced contractility. - This option is incomplete as it fails to account for the **life-threatening hyperkalemia** evidenced by the elevated serum potassium and EKG changes. *Metabolic acidosis alone* - The **pH of 7.25** indicates a metabolic acidosis which can shift K+ out of cells, but it is a contributing factor rather than the primary cause of instability in this 2-hour post-op window. - Acidosis primarily worsens the severity of **citrate toxicity** by decreasing the liver\'s ability to metabolize citrate, further exacerbating the hypocalcemia.

Q: A 38-year-old woman develops severe diarrhea after small bowel resection for Crohn's disease. Over 3 days, she has lost 6 kg. Labs show: Na+ 148 mEq/L, K+ 2.8 mEq/L, Cl- 118 mEq/L, HCO3- 15 mEq/L, BUN 45 mg/dL, Cr 1.8 mg/dL (baseline 0.9). Urine sodium is 8 mEq/L. What fluid should be administered?

Lactated Ringer's solution with potassium supplementation. ***Lactated Ringer's solution with potassium supplementation*** - **Lactated Ringer's (LR)** is the ideal crystalloid for volume resuscitation in this patient as the **lactate** is metabolized to bicarbonate, helping to correct her **hyperchloremic metabolic acidosis**. - Compared to Normal Saline, LR has a **lower sodium content** (130 mEq/L) which helps address the **hypernatremia**, while potassium supplementation is vital to treat the severe **hypokalemia** (2.8 mEq/L). *3% hypertonic saline* - This solution is used for treating severe **hyponatremia** or cerebral edema, whereas this patient is already **hypernatremic** (Na+ 148 mEq/L). - Administration would dangerously worsen the hyperosmolar state and aggravate **cellular dehydration**. *0.9% normal saline with 40 mEq/L potassium chloride* - **Normal Saline (0.9% NaCl)** contains 154 mEq/L of chloride, which can exacerbate the patient's existing **hyperchloremia** and metabolic acidosis. - It is less physiologic than LR in this scenario of **bicarbonate loss** typically seen in small bowel diarrhea. *0.45% normal saline with 20 mEq/L potassium chloride* - **0.45% NaCl (Half-normal saline)** is a hypotonic solution unsuitable for initial **resuscitation** in a patient with 6 kg of acute weight loss and signs of **prerenal azotemia**. - It lacks sufficient volume expansion capacity and does not provide an **alkalinizing agent** to treat the systemic acidosis correctly. *D5W with potassium phosphate* - **D5W** is essentially free water and is contraindicated as an initial resuscitation fluid in **hypovolemic shock** as it will not stay in the intravascular space. - While it provides water for hypernatremia, it fails to restore the **effective circulating volume** needed to correct the elevated **creatinine** and BUN.

Q: A 55-year-old man with a history of alcoholism presents with acute pancreatitis. His calcium level is 6.8 mg/dL, albumin is 2.5 g/dL, and he is symptomatic with perioral numbness and carpopedal spasm. After correcting for albumin, his corrected calcium is 7.6 mg/dL. What is the most appropriate initial treatment?

Magnesium sulfate 2 grams IV followed by calcium. ***Magnesium sulfate 2 grams IV followed by calcium*** - In patients with a history of **alcoholism** and **acute pancreatitis**, hypocalcemia is frequently driven by concurrent **hypomagnesemia**. - Magnesium is a necessary cofactor for **PTH secretion** and end-organ responsiveness; failure to correct magnesium first will result in **refractory hypocalcemia**. *Oral calcium carbonate 1000 mg three times daily* - Oral supplementation is inappropriate for **acute, symptomatic hypocalcemia** (perioral numbness, carpopedal spasm) which requires immediate IV intervention. - Patients with acute pancreatitis often have **impaired absorption** and high metabolic demand, making the oral route insufficient. *Intravenous calcium gluconate 1-2 grams over 10 minutes* - While IV calcium gluconate is used for symptomatic hypocalcemia, it will be **ineffective** if the underlying **hypomagnesemia** is not addressed first. - Magnesium deficiency causes a functional **hypoparathyroidism**, preventing the body from maintaining calcium levels even after IV administration. *Intravenous calcium chloride bolus* - Calcium chloride is significantly more **caustic to peripheral veins** and is generally reserved for emergency situations like **cardiac arrest** or severe hyperkalemia. - Giving a bolus without addressing the **magnesium deficit** in an alcoholic patient fails to treat the root cause of the electrolyte disturbance. *Vitamin D supplementation only* - Vitamin D takes **days to weeks** to increase serum calcium levels via intestinal absorption and bone resorption, which is too slow for acute management. - It does not address the immediate life-threatening potential of **neuromuscular irritability** or the secondary effects of pancreatitis-related **saponification**.

Q: A 62-year-old woman develops postoperative hyponatremia (sodium 118 mEq/L) on day 2 after a total colectomy. She is confused and lethargic. Her urine sodium is 45 mEq/L, urine osmolality is 520 mOsm/kg, and serum osmolality is 245 mOsm/kg. She has been receiving D5W at 125 mL/hr. What is the most likely cause of her hyponatremia?

Syndrome of inappropriate ADH secretion (SIADH). ***Syndrome of inappropriate ADH secretion (SIADH)*** - This patient demonstrates **hypotonic hyponatremia** with **high urine sodium (>40 mEq/L)** and inappropriately concentrated urine, which are the diagnostic hallmarks of **SIADH**. - Postoperative **pain, stress, and nausea** are potent triggers for ADH release, and the administration of **hypotonic fluids (D5W)** further worsens the water retention and hyponatremia. *Diuretic use* - Although diuretics can cause hyponatremia and high urine sodium, they usually lead to **hypovolemia** and elevated **blood urea nitrogen (BUN)** levels, which are not described here. - Thiazide diuretics are a more common cause of hyponatremia than loop diuretics, but there is no history of medication use in this patient. *Cerebral salt wasting* - This condition occurs primarily in patients with **central nervous system pathology** (e.g., subarachnoid hemorrhage) and results in massive **renal sodium wasting**. - It is distinguished from SIADH by the presence of true **hypovolemia** and clinical signs of dehydration, whereas SIADH patients are usually **euvolemic**. *Primary polydipsia* - In primary polydipsia, the excess intake of water leads to maximal suppression of ADH, resulting in **dilute urine** (osmolality <100 mOsm/kg). - This patient has a **high urine osmolality (520 mOsm/kg)**, which directly contradicts a diagnosis of primary polydipsia. *Adrenal insufficiency* - Acute adrenal insufficiency can cause hyponatremia due to lack of mineralocorticoids but is typically associated with **hyperkalemia** and **hypotension**. - The clinical context of recent surgery and the specific labs provided (euvolemic hyponatremia) more strongly favor **SIADH** over adrenal failure.

Q: A 45-year-old man undergoes emergent exploratory laparotomy for a gunshot wound to the abdomen. Intraoperatively, 2 liters of blood are lost. His blood pressure is 85/50 mmHg, heart rate is 125/min, and urine output is 15 mL/hr. The anesthesiologist has administered 3 liters of lactated Ringer's solution. What is the most appropriate next step in fluid resuscitation?

Administer packed red blood cells. ***Administer packed red blood cells*** - The patient exhibits **hemorrhagic shock** (Class III/IV) with significant blood loss and persistent **hypotension** and **tachycardia** despite initial crystalloid resuscitation. - **Packed red blood cells (PRBCs)** are essential to restore **oxygen-carrying capacity** and volume in patients who do not stabilize after early crystalloid infusion. *Give fresh frozen plasma only* - **Fresh frozen plasma (FFP)** is used to replace clotting factors and is typically given alongside PRBCs in a **massive transfusion protocol**. - Using FFP alone does not address the critical need for **hemoglobin** and oxygen delivery in acute traumatic hemorrhage. *Continue crystalloid resuscitation with normal saline* - Excessive **crystalloid administration** can lead to **hemodilution**, coagulopathy, and "the lethal triad" in trauma patients. - This patient has already received 3 liters of fluid; continuing with only crystalloids fails to address the **2-liter blood loss** effectively. *Give 5% albumin solution* - **Albumin** is a colloid that may be used for volume expansion but has no advantage over blood products in **acute trauma** management. - Colloid solutions like albumin do not provide the **erythrocytes** needed to treat the profound anemia associated with a 2-liter hemorrhage. *Administer hypertonic saline* - **Hypertonic saline** is primarily used to manage **intracranial pressure** in head trauma rather than as a primary resuscitation fluid for hemorrhagic shock. - It provides rapid but transient volume expansion and does not replace the **red cell mass** lost during surgery.

Question 1

A 58-year-old cirrhotic man with ascites undergoes large volume paracentesis (6 liters removed). Four hours later, he becomes hypotensive (BP 80/50 mmHg) and tachycardic (HR 115/min). Labs show: Cr 2.1 mg/dL (baseline 1.0), Na+ 128 mEq/L, Hct 38%. What is the most appropriate immediate management?

Accepted Answer

5% albumin 6-8 grams per liter of ascites removed

Answer

Normal saline bolus 2 liters

Answer

Octreotide and midodrine for hepatorenal syndrome

Answer

Vasopressors to maintain blood pressure

Answer

Re-infusion of filtered ascitic fluid

Question 2

A 42-year-old woman with prolonged vomiting from gastroparesis is admitted with weakness. Labs show: K+ 2.1 mEq/L, pH 7.51, HCO3- 42 mEq/L, Mg2+ 1.4 mg/dL. She receives 80 mEq of IV potassium chloride over 24 hours, but repeat K+ is 2.3 mEq/L. What explains the refractory hypokalemia?

Accepted Answer

Hypomagnesemia preventing potassium retention

Answer

Secondary hyperaldosteronism from volume depletion

Answer

Insufficient potassium replacement dose

Answer

Ongoing losses from continued vomiting

Answer

Metabolic alkalosis promoting intracellular potassium shift

Question 3

A 65-year-old diabetic man with TURP syndrome presents with confusion, nausea, and seizures 2 hours post-operatively. Labs show: Na+ 115 mEq/L, serum osmolality 240 mOsm/kg. He weighs 70 kg. What is the target sodium correction rate and fluid management strategy?

Accepted Answer

3% saline to increase sodium by 4-6 mEq/L in first 2-4 hours, then slower correction

Answer

Conivaptan infusion for water diuresis

Answer

Normal saline infusion with fluid restriction

Answer

Rapid correction to 135 mEq/L with 3% hypertonic saline over 4 hours

Answer

Increase sodium by 6-8 mEq/L in first 24 hours with 3% saline boluses

Question 4

A 50-year-old man is 5 days post-operative from a Whipple procedure. He has had high nasogastric output (1500 mL/day) and has been NPO. Labs show: Na+ 132 mEq/L, K+ 2.9 mEq/L, Cl- 88 mEq/L, HCO3- 38 mEq/L, pH 7.52. Urine chloride is 8 mEq/L. What is the appropriate management?

Accepted Answer

Normal saline with potassium chloride

Answer

Discontinue nasogastric suction only

Answer

Acetazolamide to promote bicarbonate excretion

Answer

Half-normal saline with potassium supplementation

Answer

Hydrochloric acid infusion

Question 5

A 28-year-old trauma patient received 8 units of packed RBCs, 6 units of FFP, and 2 units of platelets during damage control surgery. Two hours post-op, he develops: peaked T waves on EKG, K+ 6.8 mEq/L, Ca2+ 7.2 mg/dL, ionized calcium 0.9 mmol/L, pH 7.25. Which metabolic derangement is most responsible for his cardiac instability?

Accepted Answer

Combined hyperkalemia and hypocalcemia

Answer

Hypothermia-induced arrhythmia

Answer

Hyperkalemia from massive transfusion

Answer

Hypocalcemia from citrate toxicity

Answer

Metabolic acidosis alone

Question 6

A 38-year-old woman develops severe diarrhea after small bowel resection for Crohn's disease. Over 3 days, she has lost 6 kg. Labs show: Na+ 148 mEq/L, K+ 2.8 mEq/L, Cl- 118 mEq/L, HCO3- 15 mEq/L, BUN 45 mg/dL, Cr 1.8 mg/dL (baseline 0.9). Urine sodium is 8 mEq/L. What fluid should be administered?

Accepted Answer

Lactated Ringer's solution with potassium supplementation

Answer

3% hypertonic saline

Answer

0.9% normal saline with 40 mEq/L potassium chloride

Answer

0.45% normal saline with 20 mEq/L potassium chloride

Answer

D5W with potassium phosphate

Question 7

A 70-year-old man with small bowel obstruction has been receiving aggressive IV fluid resuscitation with normal saline for 48 hours (total 12 liters). His nasogastric tube has drained 3 liters. Labs show: Na+ 138 mEq/L, K+ 3.2 mEq/L, Cl- 112 mEq/L, HCO3- 18 mEq/L, pH 7.30. What acid-base disturbance is present?

Accepted Answer

Mixed metabolic acidosis: high anion gap and normal anion gap

Answer

Metabolic alkalosis with paradoxical aciduria

Answer

Metabolic acidosis with appropriate respiratory compensation

Answer

Normal anion gap metabolic acidosis from saline administration

Answer

High anion gap metabolic acidosis from bowel ischemia

Question 8

A 55-year-old man with a history of alcoholism presents with acute pancreatitis. His calcium level is 6.8 mg/dL, albumin is 2.5 g/dL, and he is symptomatic with perioral numbness and carpopedal spasm. After correcting for albumin, his corrected calcium is 7.6 mg/dL. What is the most appropriate initial treatment?

Accepted Answer

Magnesium sulfate 2 grams IV followed by calcium

Answer

Oral calcium carbonate 1000 mg three times daily

Answer

Intravenous calcium gluconate 1-2 grams over 10 minutes

Answer

Intravenous calcium chloride bolus

Answer

Vitamin D supplementation only

Question 9

A 62-year-old woman develops postoperative hyponatremia (sodium 118 mEq/L) on day 2 after a total colectomy. She is confused and lethargic. Her urine sodium is 45 mEq/L, urine osmolality is 520 mOsm/kg, and serum osmolality is 245 mOsm/kg. She has been receiving D5W at 125 mL/hr. What is the most likely cause of her hyponatremia?

Accepted Answer

Syndrome of inappropriate ADH secretion (SIADH)

Answer

Diuretic use

Answer

Cerebral salt wasting

Answer

Primary polydipsia

Answer

Adrenal insufficiency

Question 10

A 45-year-old man undergoes emergent exploratory laparotomy for a gunshot wound to the abdomen. Intraoperatively, 2 liters of blood are lost. His blood pressure is 85/50 mmHg, heart rate is 125/min, and urine output is 15 mL/hr. The anesthesiologist has administered 3 liters of lactated Ringer's solution. What is the most appropriate next step in fluid resuscitation?

Accepted Answer

Administer packed red blood cells

Answer

Give fresh frozen plasma only

Answer

Continue crystalloid resuscitation with normal saline

Answer

Give 5% albumin solution

Answer

Administer hypertonic saline

Fluid and electrolyte management — MCQs

Fluid and electrolyte management — MCQs

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