All practice questions

A 24-year-old woman with a history of type 1 diabetes mellitus presents to the emergency department with nausea, vomiting, and diffuse abdominal pain. She reports missing her insulin doses for the past two days due to illness. On physical examination, she appears lethargic. Her blood pressure is 105/65 mm Hg, heart rate is 118/min, and respiratory rate is 26/min with deep, rapid breaths. Laboratory studies show the following:

What is the patient's calculated serum anion gap? (Provide the numerical value in mEq/L).

A 68-year-old man is evaluated in the intensive care unit for decreased urine output. Three days ago, he was admitted with septic shock secondary to a perforated appendix and underwent an emergent exploratory laparotomy. Since admission, he has received broad-spectrum antibiotics and aggressive intravenous fluid resuscitation. Over the past 24 hours, his total urine output has been $300$ mL. His blood pressure is $108/64$ mmHg and his heart rate is $92$/min. The patient appears euvolemic on physical examination.

Laboratory studies are as follows:

Serum studies
Sodium: $140$ mEq/L
Potassium: $5.0$ mEq/L
Chloride: $104$ mEq/L
Bicarbonate: $18$ mEq/L
Blood urea nitrogen: $72$ mg/dL
Creatinine: $3.5$ mg/dL (baseline: $1.0$ mg/dL)

Spot urine studies
Sodium: $60$ mEq/L
Creatinine: $50$ mg/dL

Urinalysis reveals muddy brown granular casts.

What is this patient's calculated fractional excretion of sodium ($FE_{Na}$) expressed as a percentage?

A 42-year-old man presents to the emergency department with a 3-day history of severe nausea, nonbilious vomiting, and diffuse abdominal pain. He has a history of poorly controlled type 1 diabetes mellitus. His temperature is $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$), blood pressure is $90/60\text{ mm Hg}$, pulse is $118/\text{min}$, and respirations are $26/\text{min}$. Physical examination reveals dry mucous membranes, decreased skin turgor, and a diffusely tender abdomen without rebound or guarding.

Laboratory studies show the following:
Serum sodium: $142\text{ mEq/L}$
Serum potassium: $3.2\text{ mEq/L}$
Serum chloride: $92\text{ mEq/L}$
Serum bicarbonate: $14\text{ mEq/L}$
Blood glucose: $550\text{ mg/dL}$
Serum blood urea nitrogen: $45\text{ mg/dL}$
Serum creatinine: $1.8\text{ mg/dL}$

Assuming a normal serum anion gap of $12\text{ mEq/L}$ and a normal serum bicarbonate of $24\text{ mEq/L}$, what is this patient's delta-delta ratio ($\Delta\text{AG} / \Delta\text{HCO}_3^-$)?

A 54-year-old man is evaluated in the hospital for decreased urine output. He was admitted 7 days ago for infective endocarditis and has been receiving intravenous vancomycin and gentamicin. Over the past 24 hours, his urine output has dropped to 300 mL. His vital signs are within normal limits and he appears euvolemic on examination. Laboratory studies show the following:

Microscopic urinalysis reveals muddy brown granular casts.

Based on the provided laboratory findings, what is this patient's fractional excretion of sodium ($Fe_{Na}$)? (Express your answer as a percentage)

A 35-year-old automobile mechanic is evaluated in the emergency department for altered mental status. His spouse reports finding him confused and stumbling in their unventilated garage. Vital signs show a blood pressure of 132/82 mm Hg, a pulse of 98/min, and a respiratory rate of 26/min. He appears lethargic and is oriented only to person.

Laboratory studies reveal the following:

The patient's measured serum osmolality is 330 mOsm/kg H₂O.

What is this patient's calculated serum osmolar gap (in mOsm/kg H₂O)?

A 30-year-old male electrician is brought to the emergency department after sustaining a high-voltage electrical injury at a construction site. The accident occurred exactly 2 hours prior to his arrival. On physical examination, the patient is awake and alert. Vital signs show a heart rate of 115/min and blood pressure of 105/65 mm Hg. He has deep partial-thickness and full-thickness burns involving his entire right arm and his entire anterior trunk (chest and abdomen). No other areas of the body are burned. His body weight is 75 kg. Two large-bore peripheral intravenous lines are established, and a Foley catheter is placed.

Based on current Advanced Trauma Life Support (ATLS) guidelines for high-voltage electrical burns, what should be the continuous intravenous fluid infusion rate (in mL/hr) of lactated Ringer solution for this patient over the next 6 hours?

An ambulatory care physician evaluates a 33-year-old woman who reports a one-month history of persistent fatigue and severe muscle weakness. She denies any recent illnesses, diarrhea, vomiting, or medication use. Her vital signs are within normal limits. Physical examination reveals diffusely decreased muscle strength in all extremities with diminished deep tendon reflexes.

Laboratory studies reveal the following:

Based on the laboratory data provided, what is this patient's urine anion gap (in mEq/L)?

A patient in the surgical intensive care unit develops oliguria on the second day following an elective partial colectomy. Over the past 8 hours, the urinary catheter has drained only 150 mL of highly concentrated urine. The patient has been receiving maintenance intravenous fluids at a conservative rate due to a known history of heart failure with preserved ejection fraction.

Vital signs show a temperature of 37.2°C (99.0°F), heart rate of 105/min, and blood pressure of 102/65 mmHg. Physical examination reveals dry oral mucosa and flat jugular veins.

Laboratory studies are obtained:

Based on the provided laboratory values, calculate the patient's fractional excretion of sodium (FENa). (Enter your answer as a percentage.)

A 48-year-old man with a history of severe alcohol use disorder is brought to the emergency department by paramedics after being found obtunded in a park. His temperature is $36.2^\circ\text{C}$ ($97.2^\circ\text{F}$), blood pressure is $110/70\text{ mmHg}$, pulse is $105/\text{min}$, and respiratory rate is $18/\text{min}$. The patient is unarousable and responds only to painful stimuli.

Initial laboratory studies reveal the following:

Based on the provided laboratory results, what is this patient's serum osmolar gap in $\text{mOsm/kg H}_2\text{O}$?

A 34-year-old female is brought to the emergency department via helicopter after being rescued from a residential house fire. The burn injury occurred at 14:00, and she arrives at the trauma bay at 17:00. Her weight is $90 \text{ kg}$. Physical examination reveals deep partial-thickness and full-thickness burns involving her entire anterior trunk (chest and abdomen), her entire right arm (circumferential), and the anterior surface of her left leg. The remainder of her skin is uninjured. En route to the hospital, paramedics successfully intubated her for airway protection and administered $740 \text{ mL}$ of lactated Ringer solution intravenously. According to current Advanced Trauma Life Support (ATLS) guidelines ($2 \text{ mL/kg/\%TBSA}$ for adult thermal burns), what should be the intravenous fluid infusion rate in $\text{mL/hr}$ for the remainder of the first 8-hour post-injury period?

Emergency medical services bring a 47-year-old mechanic to the hospital after he was found deeply lethargic in his workshop. His coworkers report that he had been working alone on a vehicle's cooling system and seemed disoriented before collapsing. On presentation, his temperature is $36.8^\circ C$ ($98.2^\circ F$), blood pressure is $105/65$ mmHg, pulse is $112$/min, and respiratory rate is $24$/min. Physical examination reveals an unarousable patient with deep, rapid breathing. Arterial blood gas analysis on room air shows a pH of 7.21, $PaCO_2$ of 24 mmHg, and $PaO_2$ of 95 mmHg.

Based on the provided laboratory results, what is the patient's calculated serum osmolar gap in mOsm/kg $H_2O$?

A 68-year-old man is evaluated in the hospital for decreased urine output. He was admitted 3 days ago for severe community-acquired pneumonia and has been receiving intravenous antibiotics. His blood pressure is 98/60 mm Hg and heart rate is 102/min. Physical examination shows dry mucous membranes and flat jugular veins. Laboratory studies are obtained to evaluate his acute kidney injury:

What is the patient's fractional excretion of sodium (FeNa) expressed as a percentage?

A 64-year-old woman is brought to the emergency department by her family due to profound weakness and confusion. She has had 5 days of severe, voluminous watery diarrhea. Her medical history includes type 2 diabetes mellitus and hypertension. On examination, blood pressure is 82/50 mm Hg, heart rate is 118/min, and respiratory rate is 24/min. She has dry mucous membranes, flat neck veins, and delayed capillary refill.

Laboratory studies show:
Serum $Na^+$: 140 mEq/L
Serum $K^+$: 3.2 mEq/L
Serum $Cl^-$: 112 mEq/L
Serum $HCO_3^-$: 8 mEq/L
Blood urea nitrogen: 54 mg/dL
Serum creatinine: 2.8 mg/dL (baseline 0.9 mg/dL)
Serum lactate: 5.2 mmol/L (Normal: 0.5-1.0 mmol/L)
Serum albumin: 4.0 g/dL

Assuming a reference anion gap of 12 mEq/L and a normal serum bicarbonate of 24 mEq/L, what is this patient's calculated delta ratio (also known as the $\Delta/\Delta$ ratio)?

A 28-year-old woman with a history of Sjögren syndrome is evaluated in the clinic for progressive muscle weakness over the past week. She reports no vomiting, diarrhea, or recent illnesses. Her vital signs are within normal limits. Physical examination reveals 3/5 strength in the proximal muscles of her lower extremities. Laboratory studies show:

Serum:
Na $^+$: 139 mEq/L
K $^+$: 2.8 mEq/L
Cl $^-$: 114 mEq/L
HCO $_3^-$: 14 mEq/L

Arterial blood gas (room air):
pH: 7.28
pCO $_2$: 32 mm Hg

Urine:
Na $^+$: 62 mEq/L
K $^+$: 30 mEq/L
Cl $^-$: 55 mEq/L
pH: 6.0

What is the calculated urine anion gap for this patient in mEq/L?

A 68-year-old man is admitted to the hospital with acute decompensated heart failure. He is started on an intravenous bumetanide infusion. On hospital day 3, his urine output decreases to 300 mL over the last 24 hours. Physical examination shows jugular venous distention, bibasilar crackles, and bilateral lower extremity pitting edema.

Laboratory studies are obtained:
Serum sodium: $140 \text{ mEq/L}$
Serum potassium: $3.5 \text{ mEq/L}$
Serum chloride: $98 \text{ mEq/L}$
Serum bicarbonate: $26 \text{ mEq/L}$
Serum blood urea nitrogen (BUN): $60 \text{ mg/dL}$
Serum creatinine: $2.0 \text{ mg/dL}$

A spot urine sample is analyzed:
Urine sodium: $105 \text{ mEq/L}$
Urine blood urea nitrogen (BUN): $600 \text{ mg/dL}$
Urine creatinine: $100 \text{ mg/dL}$

Based on these findings, what is the patient's fractional excretion of urea nitrogen (expressed as a percentage)?

Paramedics transport a 45-year-old male to the hospital after his wife discovered him confused and stumbling inside their garage. The patient reports severe bilateral flank pain and appears visibly intoxicated, though his wife states he has not consumed alcohol. Vital signs include a temperature of 37.1°C (98.8°F), blood pressure of 145/90 mm Hg, heart rate of 98/min, and respiratory rate of 22/min.

Based on the provided laboratory data, determine this patient's serum osmolar gap in mOsm/kg H₂O.

A 52-year-old woman is evaluated in the emergency department for severe, watery diarrhea over the past five days. She reports feeling profoundly weak. She has no significant past medical history. Her blood pressure is 105/65 mm Hg, pulse is 112/min, and respiratory rate is 22/min. Physical examination shows dry mucous membranes and delayed capillary refill.

Laboratory results:
- Serum sodium: 138 mEq/L
- Serum potassium: 3.2 mEq/L
- Serum chloride: 114 mEq/L
- Serum bicarbonate: 12 mEq/L
- Arterial blood gas (room air): pH 7.24, PaCO2 24 mm Hg, PaO2 96 mm Hg

Using Winter's formula, calculate the patient's expected PaCO2. (Provide the exact median numerical value in mm Hg, excluding the ±2 range)

A 52-year-old woman with a history of type 1 diabetes mellitus is brought to the emergency department after $3$ days of intractable vomiting and generalized abdominal pain. She ran out of her prescribed insulin $4$ days ago. On physical examination, she appears lethargic with dry mucous membranes and decreased skin turgor. Temperature is $37.2^\circ$ C ($99.0^\circ$ F), blood pressure is $95/60$ mm Hg, pulse is $118$/min, and respirations are $26$/min and deep.

Laboratory studies reveal:

Assume a normal anion gap of $12$ mEq/L and a normal serum bicarbonate of $24$ mEq/L.

What is the patient's calculated delta ratio (also known as the $\Delta$ AG / $\Delta$ HCO $_3^-$ ratio)?

A 45-year-old male is evaluated in the surgical intensive care unit on postoperative day 3 following an extensive small bowel resection for mesenteric ischemia. Over the last 12 hours, the nursing staff reports that his urine output has decreased to $15 \text{ mL/hr}$. He has been receiving maintenance intravenous fluids but has had large volumes of nasogastric tube output. His temperature is $37.2^\circ\text{C}$ ($99.0^\circ\text{F}$), blood pressure is $90/55 \text{ mmHg}$, and pulse is $118/\text{min}$. Physical examination reveals flat jugular veins, delayed capillary refill, and dry mucous membranes.

Laboratory studies are obtained:

Based on the provided laboratory values, what is this patient's fractional excretion of sodium (FENa)? (Provide your answer as a numerical percentage, e.g., if the calculated value is 1.2%, enter 1.2)