Pediatric fluid and electrolyte management US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Pediatric fluid and electrolyte management. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Pediatric fluid and electrolyte management US Medical PG Question 1: A 61-year-old female with congestive heart failure and type 2 diabetes is brought to the emergency room by her husband because of an altered mental status. He states he normally helps her be compliant with her medications, but he had been away for several days. On physical exam, her temperature is 37.2 C, BP 85/55, and HR 130. Serum glucose is 500 mg/dL. Which of the following is the first step in the management of this patient?
- A. IV ½ NS
- B. IV insulin
- C. Subcutaneous insulin injection
- D. IV NS (Correct Answer)
- E. IV D5W
Pediatric fluid and electrolyte management Explanation: ***IV NS***
- The patient presents with **hypotension (85/55 mmHg)** and **tachycardia (130 bpm)**, indicating significant **volume depletion** despite a history of congestive heart failure.
- **Isotonic intravenous fluids (e.g., normal saline)** are crucial in the initial management of **diabetic ketoacidosis (DKA)** or **hyperosmolar hyperglycemic state (HHS)** to restore intravascular volume and improve tissue perfusion.
*IV ½ NS*
- **Hypotonic solutions** such as IV ½ NS are typically used later in DKA/HHS management, once the patient's **hemodynamic stability** has been achieved and serum sodium levels are stable or elevated.
- Administering hypotonic fluids to an already **hypotensive and volume-depleted patient** could worsen hypotension and potentially lead to cerebral edema if not carefully monitored.
*IV insulin*
- While insulin is essential for correcting hyperglycemia, it is administered **after or concurrently with fluid resuscitation** to avoid worsening hypovolemia as it drives glucose and potassium into cells, potentially causing **hypokalemia** and further **hemoconcentration**.
- **Fluid resuscitation** should always precede or be initiated simultaneously with insulin therapy, especially in cases of hemodynamic instability.
*Subcutaneous insulin injection*
- **Subcutaneous insulin** is not appropriate for initial management in this critically ill patient due to its **slower onset of action** and potentially **erratic absorption** in hypotensive and poorly perfused states.
- **Intravenous insulin** is preferred in DKA/HHS for its rapid, titratable effect.
*IV D5W*
- **Dextrose 5% in water (D5W)** is a hypotonic solution primarily used when **blood glucose levels fall below 250 mg/dL** during DKA/HHS treatment to prevent hypoglycemia.
- Administering D5W in a patient with a **serum glucose of 500 mg/dL** would further elevate blood sugar and worsen the hyperosmolar state.
Pediatric fluid and electrolyte management US Medical PG Question 2: A 42-year-old man is brought to the emergency department by his wife because of a 1-day history of progressive confusion. He recently lost his job. He has a history of chronic alcoholism and has been drinking 14 beers daily for the past week. Before this time, he drank 6 beers daily. He appears lethargic. His vital signs are within normal limits. Serum studies show a sodium level of 111 mEq/L and a potassium level of 3.7 mEq/L. Urgent treatment for this patient's current condition increases his risk for which of the following adverse events?
- A. Wernicke encephalopathy
- B. Osmotic myelinolysis (Correct Answer)
- C. Cerebral edema
- D. Cardiac arrhythmia
- E. Hyperglycemia
Pediatric fluid and electrolyte management Explanation: ***Osmotic myelinolysis***
* **Rapid correction of severe hyponatremia** (serum sodium <120 mEq/L), especially when chronic, can cause **osmotic demyelination syndrome** (also known as central pontine myelinolysis).
* This condition results from a sudden shift in osmolality, causing water to leave brain cells, leading to neuronal damage and severe neurological deficits.
*Wernicke encephalopathy*
* **Wernicke encephalopathy** is caused by **thiamine deficiency**, common in chronic alcoholics.
* While he is at risk for Wernicke encephalopathy, the urgent treatment for his hyponatremia (rapid correction) is more likely to cause osmotic myelinolysis, not directly trigger Wernicke encephalopathy.
*Cerebral edema*
* **Cerebral edema** is a direct consequence of **severe, acute hyponatremia** (as fluid shifts into brain cells), not a risk of its *treatment*.
* The question asks about the risk of urgent treatment, which aims to *reduce* cerebral edema.
*Cardiac arrhythmia*
* While severe electrolyte imbalances can cause **cardiac arrhythmias**, the **rapid correction of hyponatremia** does not directly or primarily increase the risk of arrhythmias.
* The immediate risk associated with hyponatremia correction is neurological, related to osmotic shifts.
*Hyperglycemia*
* **Hyperglycemia** is a condition of high blood glucose and is not directly related to or caused by the **rapid correction of hyponatremia**.
* Although chronic alcohol abuse can affect glucose metabolism, hyperglycemia is not an acute adverse event of treating hyponatremia.
Pediatric fluid and electrolyte management US Medical PG Question 3: A 69-year-old male presents to the emergency department for slurred speech and an inability to use his right arm which occurred while he was eating dinner. The patient arrived at the emergency department within one hour. A CT scan was performed of the head and did not reveal any signs of hemorrhage. The patient is given thrombolytics and is then managed on the neurology floor. Three days later, the patient is recovering and is stable. He seems depressed but is doing well with his symptoms gradually improving as compared to his initial presentation. The patient complains of neck pain that has worsened slowly over the past few days for which he is being given ibuprofen. Laboratory values are ordered and return as indicated below:
Serum:
Na+: 130 mEq/L
K+: 3.7 mEq/L
Cl-: 100 mEq/L
HCO3-: 24 mEq/L
Urea nitrogen: 7 mg/dL
Glucose: 70 mg/dL
Creatinine: 0.9 mg/dL
Ca2+: 9.7 mg/dL
Urine:
Appearance: dark
Glucose: negative
WBC: 0/hpf
Bacterial: none
Na+: 320 mEq/L/24 hours
His temperature is 99.5°F (37.5°C), pulse is 95/min, blood pressure is 129/70 mmHg, respirations are 10/min, and oxygen saturation is 98% on room air. Which of the following is the best next step in management?
- A. Demeclocycline
- B. Fluid restriction (Correct Answer)
- C. Oral salt tablets
- D. Continue conservative management
- E. Conivaptan
Pediatric fluid and electrolyte management Explanation: ***Fluid restriction***
- The patient presents with **hyponatremia** (Na+ 130 mEq/L) and elevated urine sodium (320 mEq/L/24 hours) in the setting of recent stroke and possible SIADH (**Syndrome of Inappropriate Antidiuretic Hormone secretion**).
- **Fluid restriction** is the initial and most crucial step in managing euvolemic hyponatremia due to SIADH, reducing water intake to allow the kidney to excrete excess water and correct serum sodium.
*Demeclocycline*
- **Demeclocycline** is a tetracycline derivative that inhibits the action of ADH on renal tubules, used in chronic or refractory cases of SIADH.
- It is *not* the first-line treatment for acute, moderate hyponatremia, especially when fluid restriction has not yet been attempted.
*Oral salt tablets*
- **Oral salt tablets** would increase the solute load but would also draw water, potentially worsening hyponatremia if unrestricted fluid intake persists in SIADH.
- This intervention is generally not appropriate for **euvolemic hyponatremia** where the primary issue is excess free water.
*Continue conservative management*
- With a sodium level of 130 mEq/L, this is considered **mild to moderate hyponatremia** and requires active intervention to prevent potential neurological complications.
- Simply continuing conservative management without addressing the underlying **hyponatremia** or its cause would be inadequate and potentially harmful.
*Conivaptan*
- **Conivaptan** is an ADH receptor antagonist that can be used for persistent or significant hyponatremia in SIADH.
- It is typically reserved for more severe or refractory cases of hyponatremia and is usually administered intravenously, making it less suitable as a first-line outpatient management strategy.
Pediatric fluid and electrolyte management US Medical PG Question 4: An 11-year-old boy presents to his pediatrician with muscle cramps and fatigue that have progressively worsened over the past year. His mom says that he has always had occasional symptoms including abdominal pain, muscle weakness, and mild paresthesias; however, since starting middle school these symptoms have started interfering with his daily activities. In addition, the boy complains that he has been needing to use the restroom a lot, which is annoying since he has to ask for permission to leave class every time. Labs are obtained showing hypokalemia, hypochloremia, metabolic alkalosis, hypomagnesemia, and hypocalciuria. The most likely cause of this patient's symptoms involves a protein that binds which of the following drugs?
- A. Furosemide
- B. Mannitol
- C. Spironolactone
- D. Amiloride
- E. Hydrochlorothiazide (Correct Answer)
Pediatric fluid and electrolyte management Explanation: ***Hydrochlorothiazide***
- This patient's symptoms (muscle cramps, fatigue, polyuria, abdominal pain, muscle weakness) along with lab findings (hypokalemia, hypochloremia, metabolic alkalosis, hypomagnesemia, hypocalciuria) are classic for **Gitelman syndrome**.
- Gitelman syndrome is caused by a defect in the **thiazide-sensitive NaCl co-transporter (NCC)** in the distal convoluted tubule, which is the target of **thiazide diuretics** like hydrochlorothiazide.
*Furosemide*
- Furosemide is a **loop diuretic** that acts on the **Na-K-2Cl co-transporter (NKCC2)** in the thick ascending limb of the loop of Henle.
- While loop diuretics can cause similar electrolyte imbalances, Gitelman syndrome presents with **hypocalciuria**, whereas loop diuretics typically cause **hypercalciuria**.
*Spironolactone*
- Spironolactone is a **potassium-sparing diuretic** that acts as an **aldosterone antagonist** in the collecting duct.
- It would typically lead to hyperkalemia, not the hypokalemia seen in this patient.
*Amiloride*
- Amiloride is a **potassium-sparing diuretic** that inhibits the **epithelial sodium channel (ENaC)** in the collecting duct.
- Like spironolactone, it is associated with **hyperkalemia**, which contradicts the patient's presentation of hypokalemia.
*Mannitol*
- Mannitol is an **osmotic diuretic** that works in the renal tubule, particularly the proximal tubule and descending limb of the loop of Henle, where it is not reabsorbed.
- It primarily increases urinary output to reduce intracranial or intraocular pressure and does not typically cause the specific electrolyte abnormalities seen in Gitelman syndrome.
Pediatric fluid and electrolyte management US Medical PG Question 5: An 8-year old boy is brought to the emergency department because he has been lethargic and has had several episodes of nausea and vomiting for the past day. He has also had increased thirst over the past two months. He has lost 5.4 kg (11.9 lbs) during this time. He is otherwise healthy and has no history of serious illness. His temperature is 37.5 °C (99.5 °F), blood pressure is 95/68 mm Hg, pulse is 110/min, and respirations are 30/min. He is somnolent and slightly confused. His mucous membranes are dry. Laboratory studies show:
Hemoglobin 16.2 g/dL
Leukocyte count 9,500/mm3
Platelet count 380,000/mm3
Serum
Na+ 130 mEq/L
K+ 5.5 mEq/L
Cl- 99 mEq/L
HCO3- 16 mEq/L
Creatinine 1.2 mg/dL
Glucose 570 mg/dL
Ketones positive
Blood gases, arterial
pH 7.25
pCO2 21 mm Hg
Which of the following is the most appropriate next step in management?
- A. Intravenous hydration with 0.45% normal saline and insulin
- B. Intravenous hydration with 5% dextrose solution and 0.45% normal saline
- C. Intravenous sodium bicarbonate
- D. Intravenous hydration with 0.9% normal saline and insulin (Correct Answer)
- E. Intravenous hydration with 0.9% normal saline and potassium chloride
Pediatric fluid and electrolyte management Explanation: ***Intravenous hydration with 0.9% normal saline and insulin***
- This patient presents with **diabetic ketoacidosis (DKA)**, characterized by hyperglycemia (glucose 570 mg/dL), metabolic acidosis (pH 7.25, HCO3- 16 mEq/L, ketones positive), and dehydration (dry mucous membranes, increased thirst, weight loss).
- Initial management of DKA involves aggressive **volume expansion** with **0.9% normal saline** to restore perfusion and reduce hyperglycemia; subsequently, **insulin infusion** is started to correct hyperglycemia and halt ketogenesis.
*Intravenous hydration with 0.45% normal saline and insulin*
- While insulin is crucial, **0.45% normal saline (hypotonic saline)** is generally not the initial fluid of choice for DKA due to the risk of exacerbating cerebral edema, especially in children.
- **Isotonic saline (0.9% normal saline)** is preferred for initial resuscitation to rapidly restore extracellular fluid volume.
*Intravenous hydration with 5% dextrose solution and 0.45% normal saline*
- **5% dextrose solution** should only be added to intravenous fluids when the blood glucose level falls to around 200-250 mg/dL, to prevent hypoglycemia while continuing insulin to resolve ketosis.
- Administering dextrose initially would worsen the existing severe hyperglycemia.
*Intravenous sodium bicarbonate*
- **Sodium bicarbonate** is generally not recommended for mild to moderate DKA due to potential risks like cerebral edema and metabolic alkalosis, and potential paradoxical worsening of CNS acidosis.
- Bicarbonate therapy is reserved for **severe acidosis (pH < 6.9 or 7.0)** with hemodynamic instability or impaired cardiac contractility, which is not the case here.
*Intravenous hydration with 0.9% normal saline and potassium chloride*
- While **0.9% normal saline** is appropriate, this option lacks **insulin therapy**, which is essential for treating DKA by halting ketogenesis and correcting hyperglycemia.
- Although potassium supplementation will be necessary during DKA treatment (as insulin drives K+ into cells and can cause hypokalemia), the most appropriate **next step** is to initiate both fluid resuscitation and insulin therapy together.
- The patient's current potassium level of 5.5 mEq/L is at the upper limit of normal, but reflects total body potassium depletion; potassium should be added to maintenance fluids once adequate urine output is established.
Pediatric fluid and electrolyte management US Medical PG Question 6: A 65-year-old woman is brought to the emergency department by her husband who found her lying unconscious at home. He says that the patient has been complaining of progressively worsening weakness and confusion for the past week. Her past medical history is significant for hypertension, systemic lupus erythematosus, and trigeminal neuralgia. Her medications include metoprolol, valsartan, prednisone, and carbamazepine. On admission, blood pressure is 130/70 mm Hg, pulse rate is 100 /min, respiratory rate is 17/min, and temperature is 36.5°C (97.7ºF). She regained consciousness while on the way to the hospital but is still drowsy and disoriented. Physical examination is normal. Finger-stick glucose level is 110 mg/dl. Other laboratory studies show:
Na+ 120 mEq/L (136—145 mEq/L)
K+ 3.5 mEq/L (3.5—5.0 mEq/L)
CI- 107 mEq/L (95—105 mEq/L)
Creatinine 0.8 mg/dL (0.6—1.2 mg/dL)
Serum osmolality 250 mOsm/kg (275—295 mOsm/kg)
Urine Na+ 70 mEq/L
Urine osmolality 350 mOsm/kg
She is admitted to the hospital for further management. Which of the following is the next best step in the management of this patient's condition?
- A. Rapid resuscitation with hypertonic saline (Correct Answer)
- B. Fluid restriction
- C. Tolvaptan
- D. Lithium
- E. Desmopressin
Pediatric fluid and electrolyte management Explanation: **Rapid resuscitation with hypertonic saline**
- The patient presents with **severe hyponatremia** (120 mEq/L) and neurological symptoms (drowsiness, disorientation, history of unconsciousness), indicating a need for **urgent correction** to prevent cerebral edema.
- **Hypertonic saline** (e.g., 3%) is indicated for severe symptomatic hyponatremia to rapidly increase serum sodium levels and reduce brain swelling.
*Fluid restriction*
- **Fluid restriction** is a conservative measure appropriate for **mild to moderate asymptomatic hyponatremia** or as an adjunct in SIADH management once severe symptoms are controlled.
- It would be too slow to address the patient's acute neurological symptoms and severe hyponatremia, potentially delaying critical treatment.
*Tolvaptan*
- **Tolvaptan** is a **vasopressin receptor antagonist** used in the treatment of **euvolemic or hypervolemic hyponatremia**, often in the context of SIADH.
- Its use is generally reserved for patients who have not responded to fluid restriction and is **contraindicated** in patients with severe symptoms or to rapidly correct severe hyponatremia due to the risk of overly rapid correction and osmotic demyelination syndrome.
*Lithium*
- **Lithium** is primarily used as a **mood stabilizer** in psychiatric conditions, particularly bipolar disorder.
- It can cause **nephrogenic diabetes insipidus** as a side effect and is not a treatment for hyponatremia.
*Desmopressin*
- **Desmopressin** is a synthetic analog of **antidiuretic hormone (ADH)** and is used to treat **diabetes insipidus** or nocturnal enuresis.
- Administering desmopressin would **worsen hyponatremia** by promoting water reabsorption, making it an inappropriate choice for this patient.
Pediatric fluid and electrolyte management US Medical PG Question 7: An 8-year-old boy is shifted to a post-surgical floor following neck surgery. The surgeon has restricted his oral intake for the next 24 hours. He does not have diarrhea, vomiting, or dehydration. His calculated fluid requirement is 1500 mL/day. However, he receives 2000 mL of intravenous isotonic fluids over 24 hours. Which of the following physiological parameters in the boy’s circulatory system is most likely to be increased?
- A. Interstitial oncotic pressure
- B. Interstitial hydrostatic pressure
- C. Capillary wall permeability
- D. Capillary oncotic pressure
- E. Capillary hydrostatic pressure (Correct Answer)
Pediatric fluid and electrolyte management Explanation: ***Capillary hydrostatic pressure***
- Giving 2000 mL of intravenous isotonic fluids when the calculated requirement is 1500 mL/day leads to a **positive fluid balance** and **fluid overload**.
- This excess fluid directly increases the **intravascular volume**, thereby raising the **capillary hydrostatic pressure**, which pushes fluid out of the capillaries.
*Interstitial oncotic pressure*
- This pressure is primarily determined by the **protein concentration** in the interstitial fluid.
- While fluid overload can dilute interstitial proteins, it generally does not directly increase interstitial oncotic pressure; rather, it might decrease it due to fluid movement.
*Interstitial hydrostatic pressure*
- As fluid moves out of the capillaries due to increased capillary hydrostatic pressure, the **interstitial hydrostatic pressure** will also increase.
- However, the primary driving force for this change, and thus the most direct consequence of fluid overload, is the increase in capillary hydrostatic pressure.
*Capillary wall permeability*
- This parameter refers to the ease with which substances, including fluid and proteins, can cross the capillary wall.
- Fluid overload does not typically affect **capillary wall permeability** unless there is an underlying condition causing inflammation or damage to the capillary endothelium.
*Capillary oncotic pressure*
- This pressure is mainly determined by the **protein concentration** within the capillaries.
- In a state of fluid overload with isotonic fluids, the plasma proteins are diluted, leading to a **decrease** in capillary oncotic pressure, not an increase.
Pediatric fluid and electrolyte management US Medical PG Question 8: A 4-day-old male newborn is brought to the physician for a well-child examination. His mother is concerned that he is losing weight. He was born at 40 weeks' gestation and weighed 2980g (6-lb 9-oz); he currently weighs 2830g (6-lb 4-oz). Pregnancy was uncomplicated. He passed stool and urine 8 and 10 hours after delivery. He has been exclusively breast fed since birth and feeds 11–12 times daily. His mother says she changes 5–6 heavy diapers daily. Examination shows an open and firm anterior fontanelle. Mucous membranes are moist. Capillary refill time is less than 2 seconds. Cardiopulmonary examination shows no abnormalities. Which of the following is the most appropriate next best step in management?
- A. Continue breastfeeding (Correct Answer)
- B. Add rice based cereal
- C. Add cow milk based formula
- D. Serum creatinine and urea nitrogen
- E. Switch to soy-based formula
Pediatric fluid and electrolyte management Explanation: ***Continue breastfeeding***
- A 4-day-old newborn losing less than 7% of birth weight, with good feeding frequency, adequate wet diapers, and normal physical examination findings, is considered typical for **physiological weight loss** in breastfed infants.
- The infant's current weight of 2830g is within the expected range, as healthy full-term newborns may lose up to 7-10% of their birth weight in the first few days, and his weight loss is only about 5%.
*Add rice based cereal*
- **Solid foods**, including rice cereal, should not be introduced before 4-6 months of age due to the immaturity of the infant's digestive system and potential for choking.
- Introducing solids too early can interfere with nutrient absorption from breast milk and increase the risk of allergies.
*Add cow milk based formula*
- Supplementing with formula is unnecessary in a healthy, breastfed infant exhibiting normal physiological weight loss and adequate feeding cues.
- Early introduction of formula can interfere with **successful breastfeeding establishment** and alter the infant's gut microbiome.
*Serum creatinine and urea nitrogen*
- These tests are used to assess **renal function** and are not indicated here, as the infant shows no signs of renal impairment (e.g., adequate urine output, moist mucous membranes).
- The physical examination findings and feeding pattern suggest a healthy newborn, not one requiring investigation for kidney issues.
*Switch to soy-based formula*
- Switching to any formula is unwarranted given the normal weight loss and breastfeeding progress, and specifically, soy-based formula is not routinely recommended for healthy infants.
- Soy formula is often reserved for infants with **cow's milk protein allergy** or **galactosemia**, neither of which is suggested by this clinical picture.
Pediatric fluid and electrolyte management US Medical PG Question 9: A 35-year-old man is brought to the emergency department 40 minutes after spilling hot oil over himself in a kitchen accident. Examination shows multiple tense blisters over the abdomen, anterior chest, and right upper extremity. On deroofing the blisters, the skin over the right upper extremity is tender, pink, and blanches with pressure. The skin over the abdomen and anterior chest is tender, mottled, and does not blanch with pressure. The left thigh shows erythema only, is tender, and shows quick capillary refill after blanching with pressure. Which of the following most closely approximates the body surface area affected by 2nd-degree burns in this patient?
- A. 45%
- B. 18%
- C. 54%
- D. 9% (Correct Answer)
- E. 36%
Pediatric fluid and electrolyte management Explanation: ***9%***
- **2nd-degree (partial-thickness) burns** are characterized by blistering with an intact dermis that remains **painful and blanches with pressure**.
- In this patient, the **right upper extremity** shows tense blisters that, when deroofed, reveal tender, pink skin that **blanches with pressure** - this is consistent with **superficial to mid-partial-thickness (2nd-degree) burns**.
- Using the **Rule of Nines**: the entire upper extremity (arm) = **9%**.
- The abdomen and anterior chest show **mottled, non-blanching skin**, which indicates **full-thickness (3rd-degree) burns**, NOT 2nd-degree.
- The left thigh shows only **erythema with blanching**, consistent with **1st-degree (superficial) burns**.
*18%*
- This would represent two full segments using the Rule of Nines (e.g., both upper extremities or anterior trunk).
- The described 2nd-degree burns affect only the right upper extremity (9%), not two segments.
*36%*
- This would represent the anterior chest (9%) + abdomen (9%) + both upper extremities (18%).
- However, the abdomen and anterior chest show **non-blanching, mottled skin**, indicating **3rd-degree burns**, not 2nd-degree.
*45%*
- This represents approximately half the body surface area.
- Far exceeds the single upper extremity affected by 2nd-degree burns in this patient.
*54%*
- This represents more than half the total body surface area.
- Significantly overestimates the 2nd-degree burn involvement, which is limited to one upper extremity.
Pediatric fluid and electrolyte management US Medical PG Question 10: Three hours after undergoing open proctocolectomy for ulcerative colitis, a 42-year-old male complains of abdominal pain. The pain is localized to the periumbilical and hypogastric regions. A total of 20 mL of urine has drained from his urinary catheter since the end of the procedure. Temperature is 37.2°C (98.9°F), pulse is 92/min, respirations are 12/min, and blood pressure is 110/72 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 99%. Physical examination shows a 20 cm vertical midline incision and an ileostomy in the right lower quadrant. There is no fluid drainage from the surgical wounds. The urinary catheter flushes easily and is without obstruction. Cardiopulmonary examination shows no abnormalities. Serum studies show a blood urea nitrogen of 30 mg/dL and a creatinine of 1.3 mg/dL. Which of the following is the most appropriate next step in management?
- A. Administer tamsulosin
- B. Administer intravenous furosemide
- C. Obtain an abdominal CT
- D. Start ciprofloxacin
- E. Administer intravenous fluids (Correct Answer)
Pediatric fluid and electrolyte management Explanation: ***Administer intravenous fluids***
- The patient's **oliguria** (20 mL urine over 3 hours, ~7 mL/hour) post-surgery, elevated **BUN (30 mg/dL)**, and **creatinine (1.3 mg/dL)** with a **BUN:Cr ratio >20:1** suggest **prerenal acute kidney injury** due to **hypovolemia**.
- Post-operative fluid losses from **third-spacing**, blood loss, and insensible losses commonly cause hypovolemia after major abdominal surgery.
- **Intravenous fluids** are the most appropriate initial step to restore intravascular volume and improve renal perfusion.
*Administer tamsulosin*
- **Tamsulosin** is an alpha-blocker used to relax smooth muscle in the prostate and bladder neck, primarily for **urinary retention** due to benign prostatic hyperplasia.
- This patient's oliguria is due to **prerenal azotemia** from hypovolemia, not prostatic obstruction, and the catheter flushes easily without obstruction.
*Administer intravenous furosemide*
- **Furosemide** is a loop diuretic that increases urine output, but administering it in the context of **prerenal acute kidney injury** can worsen hypovolemia and further compromise renal function.
- Diuretics are generally contraindicated in oliguria due to hypovolemia and should only be considered after volume resuscitation.
*Obtain an abdominal CT*
- While an abdominal CT can diagnose surgical complications, there are no immediate signs of a surgical emergency like **anastomotic leak** or **bowel obstruction**.
- Addressing the likely **hypovolemia** is more urgent and should precede further imaging in this scenario.
*Start ciprofloxacin*
- The patient does not show signs of infection, such as fever or localized signs of bacterial peritonitis, making **antibiotics** like ciprofloxacin inappropriate as the initial management step.
- The elevated BUN and creatinine are more indicative of volume depletion than infection.
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