All practice questions

A 62-year-old man is admitted to the intensive care unit with septic shock secondary to severe pneumonia. He remains hypotensive despite adequate intravenous fluid resuscitation and requires vasopressor support. Laboratory studies are obtained to evaluate his acid-base status.

Based on the provided laboratory results, what is the patient's calculated serum anion gap?

To evaluate the efficacy of a novel sodium-glucose cotransporter-2 (SGLT2) inhibitor in preventing cardiovascular mortality, a multicenter, double-blind trial enrolls patients with chronic heart failure. Participants are randomly assigned to receive either the SGLT2 inhibitor or a placebo. After a median follow-up of three years, the data are analyzed. Among the $2,000$ patients in the intervention group, $240$ experienced a cardiovascular mortality event. In the control group, which also consisted of $2,000$ patients, $320$ experienced a cardiovascular mortality event. Based on these findings, what is the number needed to treat to prevent one cardiovascular mortality event over the study period?

A randomized, double-blind, placebo-controlled trial evaluates a new calcitonin gene-related peptide (CGRP) antagonist for the prevention of chronic migraines. A total of 1,000 adult patients with a history of chronic migraines are enrolled and randomized in a 1:1 ratio to receive either the CGRP antagonist or a matched placebo. The primary study endpoint is the proportion of patients achieving at least a 50% reduction in monthly migraine days over a 12-week period.

At the conclusion of the 12-week study, the following results are reported:
- Placebo group: 150 out of 500 patients met the primary endpoint.
- Treatment group (CGRP antagonist): 275 out of 500 patients met the primary endpoint.

The findings are determined to be statistically significant ($p < 0.01$). Based on these trial results, what is the number needed to treat (NNT) to achieve the primary endpoint in one additional patient? (Provide the exact whole number).

During a routine follow-up, a 28-year-old female patient complains of new-onset fatigue and profound muscle weakness. She has a notable past medical history of recurrent nephrolithiasis. Her vital signs are within normal limits.

Laboratory testing reveals the following values:

To help differentiate the cause of her normal anion gap metabolic acidosis, the attending physician requests calculation of the urine anion gap.

What is this patient's urine anion gap (in mEq/L)?

A $78$-year-old woman is evaluated in the hospital for worsening renal function. She was admitted $4$ days ago for acute decompensated heart failure and has been receiving aggressive intravenous bumetanide therapy. Over the past $24$ hours, her urine output has decreased to $300\text{ mL}$. On physical examination, her blood pressure is $105/65\text{ mmHg}$ and pulse is $92/\text{min}$. Jugular venous pressure is undetectable, and her lungs are clear to auscultation. Laboratory studies are obtained:

Based on the laboratory values, calculate the fractional excretion of urea ($FE_{Urea}$) as a percentage to help determine the etiology of her acute kidney injury.

A 24-year-old man is brought to the emergency department by paramedics after being found unresponsive in his garage. An open bottle of antifreeze was found nearby. His temperature is $36.5^\circ\text{C}$ ($97.7^\circ\text{F}$), blood pressure is $110/70\text{ mm Hg}$, pulse is $112\text{/min}$, and respirations are $28\text{/min}$ and deep. Physical examination reveals a comatose patient with no focal neurologic deficits.

Laboratory studies show the following:
Serum sodium: $138\text{ mEq/L}$
Serum potassium: $5.0\text{ mEq/L}$
Serum chloride: $104\text{ mEq/L}$
Serum bicarbonate: $10\text{ mEq/L}$
Blood urea nitrogen: $14\text{ mg/dL}$
Serum creatinine: $1.2\text{ mg/dL}$
Serum glucose: $90\text{ mg/dL}$
Measured serum osmolality: $315\text{ mOsm/kg H}_2\text{O}$

Arterial blood gas on room air:
pH: $7.20$
pCO $_2$: $24\text{ mm Hg}$
pO $_2$: $95\text{ mm Hg}$

What is this patient's serum osmolar gap? (Enter the value only)

A $72$-year-old woman is evaluated on hospital day $4$ for worsening renal function. She was admitted for acute decompensated heart failure and has been receiving intravenous furosemide. Over the past $48$ hours, her weight has decreased by $4.5\text{ kg}$, but her urine output has dropped to $300\text{ mL}$ over the last $12$ hours. Her blood pressure is $95/60\text{ mmHg}$ and heart rate is $102\text{/min}$. Laboratory studies show:

What is this patient's fractional excretion of urea ($FE_{Urea}$)? (Express the answer as a percentage).

Paramedics bring a 35-year-old male to the emergency department after he was rescued from a residential fire. The patient weighs 75 kg. According to the paramedics, the burn injury occurred exactly 2 hours prior to arrival. Physical examination reveals deep partial-thickness and full-thickness burns covering his entire posterior trunk and both of his entire upper extremities. The remainder of his skin is intact. Two large-bore intravenous lines are established.

Using the traditional Parkland formula ($4$ mL/kg/% total body surface area), what should be the intravenous fluid administration rate (in mL/hr) prescribed for the remaining time to complete the first 8-hour post-injury resuscitation goal?

Paramedics deliver a 68-year-old nursing home resident to the acute care bay after staff found him profoundly lethargic amid multiple episodes of bilious emesis over the preceding 48 hours. Medical history is significant for heart failure with preserved ejection fraction, severe osteoarthritis, and recently diagnosed type 2 diabetes mellitus. On initial assessment, he is obtunded but protects his airway.

Assuming a normal reference anion gap of 12 mEq/L and a normal reference serum bicarbonate of 24 mEq/L, what is this patient's delta ratio ($\Delta AG / \Delta HCO_3^-$)?

A 55-year-old man presents to the emergency department with a 4-day history of profuse watery diarrhea. He reports orthostatic dizziness, generalized weakness, and a significantly reduced urine output over the past 24 hours. He has no significant past medical history and takes no medications. Vital signs show a temperature of $37.1^\circ\text{C}$ ($98.8^\circ\text{F}$), blood pressure of $88/55\text{ mm Hg}$, and a heart rate of $122/\text{min}$. Physical examination reveals dry mucous membranes, decreased skin turgor, and flat jugular veins.

Laboratory studies are as follows:

Serum
Sodium: $140\text{ mEq/L}$
Potassium: $3.2\text{ mEq/L}$
Chloride: $110\text{ mEq/L}$
Bicarbonate: $18\text{ mEq/L}$
Blood urea nitrogen (BUN): $60\text{ mg/dL}$
Creatinine: $2.5\text{ mg/dL}$

Urine
Sodium: $14\text{ mEq/L}$
Creatinine: $50\text{ mg/dL}$

What is this patient's fractional excretion of sodium ($Fe_{Na}$) in percentage?

Paramedics bring a lethargic 45-year-old male patient to the acute care unit. According to his brother, the patient has consumed heavy amounts of alcohol daily for the past two weeks while completely abstaining from solid foods. Over the last 96 hours, he has suffered from intractable emesis. Physical examination reveals a deeply furrowed tongue, delayed capillary refill, and a loss of skin elasticity.

Laboratory evaluations reveal the following:

Urinalysis is strongly positive for ketones.

Assume a baseline normal serum anion gap of 12 mEq/L and a normal serum bicarbonate of 24 mEq/L. What is the calculated delta ratio ($\frac{\Delta AG}{\Delta HCO_3^-}$) for this patient?

A 42-year-old man is brought to the emergency department via helicopter following a structural fire. The injury occurred exactly 2 hours prior to arrival. He weighs $90 \text{ kg}$. Physical examination reveals deep partial-thickness and full-thickness burns involving his entire anterior trunk, his entire right arm, and the entire anterior surface of his right leg. The remainder of his skin is intact. During transport, paramedics administered $480 \text{ mL}$ of intravenous lactated Ringer solution. The trauma team initiates fluid resuscitation using the traditional Parkland formula ($4 \text{ mL} \times \text{weight in kg} \times \% \text{TBSA}$). At what rate (in $\text{mL/hr}$) should the lactated Ringer infusion be set for the remainder of the first 8-hour period following the injury?

A 54-year-old man is hospitalized for the management of severe pneumonia complicated by sepsis. On hospital day 3, his urine output drops to $200$ mL over a 12-hour period. To evaluate the etiology of his oliguric acute kidney injury, the following laboratory studies are obtained:

Serum sodium: $140$ mEq/L
Serum creatinine: $2.0$ mg/dL
Urine sodium: $56$ mEq/L
Urine creatinine: $40$ mg/dL

What is this patient's fractional excretion of sodium (FENa)? Give your answer as a percentage.

A 38-year-old mechanic presents to the urgent care clinic complaining of severe flank pain, nausea, and blurry vision that started earlier this morning. He admits to accidentally ingesting a few mouthfuls of a liquid from an unmarked container in his garage while working late last night. His temperature is 36.8°C (98.2°F), blood pressure is 142/88 mm Hg, pulse is 98/min, and respiratory rate is 22/min. Cardiopulmonary examination is unremarkable. Initial laboratory tests reveal the following:

* Serum sodium: $138 \text{ mEq/L}$
* Serum potassium: $4.5 \text{ mEq/L}$
* Serum chloride: $104 \text{ mEq/L}$
* Serum bicarbonate: $14 \text{ mEq/L}$
* Blood urea nitrogen (BUN): $28 \text{ mg/dL}$
* Serum glucose: $126 \text{ mg/dL}$
* Measured serum osmolality: $315 \text{ mOsm/kg H}_2\text{O}$

Based on these findings, what is the patient's calculated serum osmolar gap?

A 58-year-old man with a history of chronic alcohol use disorder is brought to the emergency department due to profound weakness and a four-day history of intractable vomiting. He reports being unable to keep any food or fluids down. On physical examination, he appears lethargic and has dry mucous membranes with decreased skin turgor.

Laboratory studies reveal the following:

Serum:
Sodium: 140 mEq/L
Potassium: 3.1 mEq/L
Chloride: 88 mEq/L
Bicarbonate: 14 mEq/L
Blood urea nitrogen: 35 mg/dL
Creatinine: 1.6 mg/dL

Arterial blood gas on room air reveals a pH of 7.32 and a $pCO_2$ of 29 mm Hg. The physician suspects a complex mixed acid-base disorder driven by alcoholic ketoacidosis and protracted emesis.

Assuming a baseline normal anion gap of 12 mEq/L and a baseline normal serum bicarbonate of 24 mEq/L, what is the calculated delta-delta ratio ($\Delta AG / \Delta HCO_3^-$) for this patient?

A 54-year-old man with a history of severe alcohol use disorder is admitted to the intensive care unit with acute necrotizing pancreatitis. Over the past 72 hours, he has experienced intractable vomiting and an inability to tolerate any oral intake. On physical examination, the patient is lethargic. Mucous membranes are extremely dry, and skin turgor is poor. Vital signs show a blood pressure of 88/50 mmHg, a pulse of 118/min, and a respiratory rate of 22/min.

Laboratory studies reveal the following:

The physician evaluates the patient's acid-base status. Assuming a baseline normal anion gap of 12 mEq/L and a normal serum bicarbonate of 24 mEq/L, what is the patient's calculated delta ratio ($\Delta\text{AG}/\Delta\text{HCO}_3^-$) after appropriately correcting the anion gap for his hypoalbuminemia?

A 52-year-old man is brought to the emergency department by ambulance after being found obtunded in his garage. His medical history is significant for major depressive disorder and alcohol use disorder. He is unresponsive to verbal stimuli but localizes to pain. Vital signs are within normal limits except for a respiratory rate of $24/\text{min}$. Laboratory evaluation reveals the following:

Arterial blood gas on room air shows a pH of $7.22$, $PCO_2$ of $26 \text{ mm Hg}$, and $PO_2$ of $92 \text{ mm Hg}$.

Based on these laboratory results, what is the patient's calculated serum osmolar gap?

A $34$-year-old woman with a history of type $1$ diabetes mellitus is brought to the emergency department due to severe nausea, diffuse abdominal pain, and intractable vomiting for the past $48$ hours. She reports missing her last three doses of insulin because she was unable to tolerate any oral intake. On physical examination, her blood pressure is $98/60\text{ mm Hg}$, heart rate is $118\text{ /min}$, and respiratory rate is $22\text{ /min}$. Her mucous membranes are remarkably dry, and skin turgor is decreased.

Laboratory testing reveals:

Assuming a normal serum anion gap of $12\text{ mEq/L}$ and a normal serum bicarbonate of $24\text{ mEq/L}$, calculate the patient's delta ratio ($\frac{\Delta\text{AG}}{\Delta\text{HCO}_3^-}$) to evaluate for the presence of a mixed acid-base disorder.

A 22-year-old man with type 1 diabetes mellitus presents to the emergency department with abdominal pain, nausea, and persistent vomiting for the past 2 days. He reports missing his last several doses of insulin. His vital signs include a heart rate of 118/min and a blood pressure of 90/60 mm Hg. Laboratory studies show the following:

Assuming a normal reference serum anion gap of 12 mEq/L and a normal serum bicarbonate of 24 mEq/L, what is the patient's delta ratio (calculated as the change in anion gap divided by the change in serum bicarbonate)? (Provide the exact calculated decimal value).

Emergency medical services transport a 30-year-old factory worker to the regional trauma center after an industrial flash fire. The primary survey confirms a patent airway, symmetric breath sounds, and stable hemodynamics. Secondary evaluation of the patient's integumentary system reveals partial-thickness and full-thickness burns covering the entire anterior aspect of his trunk as well as the entire anterior aspect of his left leg. The genital region, head, posterior torso, arms, right leg, and posterior left leg are completely spared. Based on the standard adult Rule of Nines, what is the estimated percentage of total body surface area affected by these burns?