Internal Medicine

3151 questions

All types3,151 Multiple choice1,611 Multiple select73 Numeric81 Matching714 Ordering672

A 65-year-old man is evaluated in the hospital for a new, acutely swollen and painful right leg. He was admitted $7$ days ago for a massive pulmonary embolism and was started on a continuous intravenous infusion of unfractionated heparin. Over the past few days, his respiratory status has improved, and he currently requires no supplemental oxygen. His temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $132/82\text{ mmHg}$ , pulse is $88/\text{min}$ , and respirations are $14/\text{min}$ . Physical examination today reveals a swollen, tender right calf. Duplex ultrasonography demonstrates a new, noncompressible thrombus in the right popliteal vein. Laboratory studies on admission showed a platelet count of $240,000/\mu\text{L}$ . Today, his platelet count is $95,000/\mu\text{L}$ . Which of the following is the most appropriate next step in management?

Continue unfractionated heparin and transfuse platelets

Discontinue unfractionated heparin and start warfarin

Discontinue unfractionated heparin and start argatroban

Discontinue unfractionated heparin and start enoxaparin

Continue unfractionated heparin and start intravenous vancomycin and cefepime

Show answer & explanation

Answer: Discontinue unfractionated heparin and start argatroban

Answer

Discontinue unfractionated heparin and start argatroban

The correct answer is to discontinue unfractionated heparin and start argatroban. This patient's presentation is classic for Heparin-Induced Thrombocytopenia (HIT) type 2. HIT is a life-threatening, immune-mediated disorder caused by IgG autoantibodies directed against complexes of platelet factor 4 (PF4) and heparin. It typically presents

5

10

days after heparin initiation with a platelet count drop of

>50\%

and a paradoxical, significantly increased risk of arterial and venous thrombosis (e.g., the new popliteal deep vein thrombosis in this patient). The initial management of suspected HIT requires the immediate cessation of all heparin products and the initiation of a non-heparin anticoagulant. Direct thrombin inhibitors (e.g., argatroban, bivalirudin) or fondaparinux are the drugs of choice to prevent further thrombotic complications. Confirmatory testing (PF4-heparin antibody ELISA, followed by a Serotonin Release Assay) should be ordered, but treatment must not be delayed while awaiting these results.

Step-by-Step Solution

Calculate the 4T score for suspected Heparin-Induced Thrombocytopenia (HIT).

The score is high, driven by a >50% drop in platelets, occurrence between days 5-10 of heparin exposure, and a new proven thrombosis.

A high pretest probability (4T score) necessitates immediate clinical intervention prior to waiting for confirmatory laboratory testing.

Identify the appropriate first intervention for HIT.

All forms of heparin must be immediately discontinued.

Continued exposure to heparin will fuel the immune-mediated formation of prothrombotic platelet factor 4 (PF4)-heparin immune complexes.

Select a suitable alternative anticoagulant.

A direct thrombin inhibitor such as argatroban (or an indirect inhibitor like fondaparinux) is selected.

Patients with HIT are in a highly prothrombotic state (as evidenced by the new DVT) and require continuous anticoagulation with an agent that does not cross-react with circulating HIT antibodies.

Key Concept

Diagnosis and management of Heparin-Induced Thrombocytopenia (HIT) type 2

Question 1102Question →

A 45-year-old woman is receiving a packed red blood cell transfusion for symptomatic anemia. Fifteen minutes into the transfusion, she develops a fever, chills, tachycardia, and right flank pain. Her temperature is 38.8°C (101.8°F), blood pressure is 90/60 mmHg, and pulse is 115/min. Arrange the following management steps in the most appropriate chronological order.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence is: 1) Stop the red blood cell transfusion immediately, 2) Disconnect the blood tubing and attach new tubing with normal saline, 3) Verify the patient identification and blood product tags, 4) Send the remaining blood product and patient samples to the blood bank.

An acute hemolytic transfusion reaction typically presents within minutes of starting a transfusion with fever, chills, flank pain, and hemodynamic instability. The immediate management sequence prioritizes patient safety by stopping the exposure, maintaining hemodynamic support safely, identifying clerical errors, and finally confirming the diagnosis. Stopping the transfusion is always the first step. Next, the IV line must be maintained with normal saline through new tubing to prevent flushing incompatible blood. Bedside checks for clerical errors follow, and finally, samples are sent for definitive testing.

Step-by-Step Solution

Recognize the signs of an acute hemolytic transfusion reaction.

The patient's fever, chills, hypotension, tachycardia, and flank pain shortly after starting a transfusion highly suggest ABO incompatibility.

Immediate recognition is required to prevent fatal outcomes from ongoing hemolysis.

Halt the offending agent.

The red blood cell transfusion is stopped immediately.

Limiting the volume of incompatible blood administered is the most critical intervention to reduce morbidity and mortality.

Maintain supportive intravenous access safely.

Old tubing is disconnected and new tubing with normal saline is attached.

Intravenous fluids are needed to support blood pressure and maintain renal perfusion, but flushing the old line would push more incompatible blood into the patient.

Perform bedside investigation.

Patient identification and blood product tags are verified.

Clerical error is the most common cause of ABO-incompatible transfusions. A bedside check provides immediate clues to the etiology.

Obtain definitive laboratory confirmation.

The remaining blood unit and fresh patient blood and urine samples are sent to the blood bank.

The blood bank must perform a direct antiglobulin test (DAT), repeat crossmatch, and check for hemoglobinuria to confirm the diagnosis and ensure future transfusion safety.

Key Concept

Management of acute hemolytic transfusion reactions

Question 1103Question →

While recovering on postoperative day 6 following a coronary artery bypass graft, a 62-year-old male develops acute-onset right calf pain. His postoperative course had been previously uncomplicated, and he has been receiving subcutaneous unfractionated heparin for deep vein thrombosis prophylaxis.

Vital signs show a temperature of 37.1°C (98.8°F), heart rate of 94/min, blood pressure of 132/82 mm Hg, and respiratory rate of 16/min. Physical examination reveals a swollen, tender, and mildly erythematous right calf. The right calf circumference is 4 cm greater than the left.

Laboratory studies are obtained and reveal the following:

Laboratory Test	Result	Reference Range
Hemoglobin	11.4 g/dL	13.5-17.5 g/dL
Leukocytes	8,200/mm³	4,500-11,000/mm³
Platelets	85,000/mm³	150,000-400,000/mm³
Prothrombin time (PT)	12 sec	11-15 sec
Partial thromboplastin time (PTT)	28 sec	25-40 sec

A review of the patient's medical record shows a baseline platelet count of 220,000/mm³ on the day of admission.

Which of the following is the most appropriate next step in management of this patient?

Discontinue unfractionated heparin and initiate argatroban infusion

Discontinue unfractionated heparin and initiate oral warfarin

Continue unfractionated heparin and obtain a lower extremity venous duplex ultrasound

Discontinue unfractionated heparin and transfuse one unit of apheresis platelets

Continue unfractionated heparin and administer intravenous cefazolin

Show answer & explanation

Answer: Discontinue unfractionated heparin and initiate argatroban infusion

Answer

Discontinue unfractionated heparin and initiate argatroban infusion

The correct answer involves immediately discontinuing all heparin products and starting a non-heparin anticoagulant, such as a direct thrombin inhibitor (argatroban, bivalirudin) or fondaparinux. This patient presents with a classic picture of Heparin-Induced Thrombocytopenia (HIT) type 2. HIT is an immune-mediated disorder caused by IgG antibodies against platelet factor 4 (PF4) complexed with heparin. These antibodies activate platelets, leading to widespread thrombosis and consumptive thrombocytopenia. The '4Ts' score is used to assess clinical probability: Thrombocytopenia (platelet drop

>50\%

), Timing (typically

5

10

days after heparin exposure), Thrombosis (new DVT, PE, or arterial clot), and oTher causes of thrombocytopenia not evident. This patient has a platelet count that decreased from

220,000/mm^3

85,000/mm^3

(a drop of

\approx 61\%

), onset on day 6, and a new suspected DVT, yielding a high probability score. When the 4T score is intermediate or high, heparin must be stopped immediately, and a non-heparin anticoagulant must be started prior to waiting for laboratory confirmation (e.g., PF4-heparin ELISA or serotonin release assay).

Step-by-Step Solution

Calculate the 4T score to determine the pretest probability of Heparin-Induced Thrombocytopenia (HIT).

The patient scores 6 points (High probability).

Thrombocytopenia (

>50\%

drop) gives 2 points, Timing (day 6) gives 2 points, and Thrombosis (suspected DVT) gives 2 points.

Determine the immediate management for high-probability HIT.

All heparin products must be stopped, and a non-heparin anticoagulant must be started.

HIT is a highly prothrombotic state. Continuing heparin worsens the condition, and simply stopping it without alternative anticoagulation leaves the patient at high risk for fatal thrombosis.

Key Concept

Heparin-Induced Thrombocytopenia (HIT) Management

Estimated Time:1m 30s

Question 1104Question →

A $72$ -year-old man is brought to the emergency department due to sudden-onset, severe shortness of breath that awoke him from sleep $2$ hours ago. The patient has a history of hypertension, coronary artery disease, and a $40$ -pack-year smoking history. He reports no recent fever, chills, or changes in sputum production. His blood pressure is $180/100$ mm Hg, pulse is $118$ /min, respirations are $28$ /min, and oxygen saturation is $86\%$ on room air. Physical examination reveals an upright, diaphoretic patient using accessory muscles of respiration. Jugular venous distention is present $9$ cm above the sternal angle. Lung auscultation demonstrates a prolonged expiratory phase with loud, diffuse bilateral wheezes and no distinct crackles. A third heart sound (S $3$ ) is heard at the apex. Bilateral $2+$ pitting edema is noted in the lower extremities. The patient is placed on noninvasive positive pressure ventilation, which improves his oxygen saturation to $94\%$ . Arterial blood gas analysis before positive pressure ventilation showed:

pH: $7.25$
PaCO $_2$ : $60$ mm Hg
PaO $_2$ : $52$ mm Hg
HCO $_3^-$ : $26$ mEq/L

Which of the following is the most appropriate next step in the management of this patient?

Administer intravenous furosemide

Administer inhaled albuterol and ipratropium

Administer intravenous piperacillin-tazobactam

Administer intravenous sodium bicarbonate

Administer intravenous metoprolol

Show answer & explanation

Answer: Administer intravenous furosemide

Answer

The most appropriate next step is to administer intravenous furosemide to treat the acute decompensated heart failure.

The correct answer is to administer intravenous furosemide. This patient is presenting with acute decompensated heart failure (ADHF), which can occasionally manifest with prominent wheezing known as 'cardiac asthma.' The wheezing occurs because elevated left-sided heart pressures lead to pulmonary venous congestion and peribronchial edema, which narrows the small airways. Although the patient has a significant smoking history making a COPD exacerbation a strong initial consideration, the sudden onset waking him from sleep (paroxysmal nocturnal dyspnea), severe hypertension, elevated jugular venous pressure, an S

3

gallop, and pitting edema are classic signs of ADHF. The primary medical treatment for ADHF with volume overload includes preload and afterload reduction, most commonly achieved with loop diuretics (e.g., intravenous furosemide) and vasodilators (e.g., nitroglycerin). Because he has already been placed on noninvasive positive pressure ventilation (NPPV) to support his acute respiratory acidosis and work of breathing, diuresis is the most appropriate next pharmacological step.

Step-by-Step Solution

Analyze the patient's presentation and vital signs.

The patient has sudden, severe dyspnea that awoke him from sleep (paroxysmal nocturnal dyspnea), marked hypertension (

180/100

mm Hg), and severe hypoxia.

To establish the acuity and potential etiologies of the respiratory distress.

Evaluate the physical examination findings.

The presence of jugular venous distention, an S

3

gallop, and bilateral pitting edema strongly indicate systemic and pulmonary venous congestion, despite the prominent wheezing (cardiac asthma).

To differentiate between acute decompensated heart failure and a primary COPD exacerbation.

Interpret the arterial blood gas (ABG).

The ABG shows an acute respiratory acidosis (pH

7.25

, PaCO

_2

60

mm Hg) due to respiratory muscle fatigue from severe pulmonary edema.

To assess the severity of the respiratory failure, which justified the initiation of noninvasive positive pressure ventilation.

Select the most appropriate pharmacological intervention.

Intravenous loop diuretics (furosemide) are indicated to rapidly decrease intravascular volume and relieve the pulmonary venous congestion.

Preload reduction is the cornerstone of medical management for acute decompensated heart failure.

Key Concept

Cardiac asthma is a presentation of acute decompensated heart failure characterized by wheezing due to peribronchial edema. It must be differentiated from COPD exacerbation by identifying clinical signs of volume overload (e.g., JVD, S3 gallop) and is treated with preload reduction (e.g., loop diuretics).

Alternative Method

While point-of-care ultrasound (POCUS) is not listed as an option, performing a bedside lung ultrasound that demonstrates diffuse B-lines (comet tails) would rapidly confirm the diagnosis of pulmonary edema over a COPD exacerbation (which would typically show A-lines).

Estimated Time:1m 30s

Question 1105Question →

A 48-year-old man comes to the clinic reporting severe, throbbing pain in his right big toe that awoke him from sleep last night. He states the pain is so intense that even the weight of a bedsheet is intolerable. He has no recent history of trauma or previous similar episodes. His medical history is notable for essential hypertension, for which he takes hydrochlorothiazide. Vital signs are within normal limits. Physical examination reveals a markedly swollen, erythematous, warm, and exquisitely tender right first metatarsophalangeal joint. Which of the following is the most appropriate initial medication for this patient's acute condition?

Oral indomethacin

Oral allopurinol

Intravenous ceftriaxone

Oral probenecid

Oral febuxostat

Show answer & explanation

Answer: Oral indomethacin

Answer

Oral indomethacin is the most appropriate initial medication for this acute gout flare.

The patient presents with podagra (acute inflammation of the first metatarsophalangeal joint), which is the classic manifestation of an acute gout flare. His use of a thiazide diuretic (hydrochlorothiazide) is a well-known risk factor because it decreases the renal excretion of uric acid. The most appropriate initial treatment for an acute gout flare is an anti-inflammatory medication. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin, naproxen, or ibuprofen are considered first-line therapy for patients without specific contraindications (like severe renal impairment or active peptic ulcer disease).

Step-by-Step Solution

Identify the clinical syndrome based on the patient's presentation.

The patient has sudden onset of severe monoarticular arthritis affecting the first metatarsophalangeal joint (podagra).

Recognizing podagra is key to suspecting acute gout, especially in a patient with risk factors such as thiazide diuretic use.

Determine the phase of the disease.

The patient is experiencing an acute inflammatory flare, rather than requiring chronic intercritical management.

Treatment strategies differ completely between acute flares (anti-inflammatory) and chronic management (urate-lowering).

Select the appropriate pharmacotherapy for the acute phase.

NSAIDs, colchicine, or glucocorticoids are indicated. Indomethacin is a commonly used and highly effective NSAID for this purpose.

The immediate goal of acute management is to reduce severe inflammation. Urate-lowering therapies are reserved for long-term prevention.

Key Concept

The first-line management of an acute gout flare involves anti-inflammatory agents such as NSAIDs, colchicine, or glucocorticoids. Urate-lowering therapy should not be initiated during an acute flare.

Estimated Time:45s

Question 1106Question →

A $44$ -year-old man is evaluated on the medical unit on the third day of hospitalization for a right thigh infection. He initially presented with an expanding, painful, fluctuant mass on his anterior thigh accompanied by a $10$ -cm area of surrounding erythema. Upon admission, he had a temperature of $38.4^\circ\text{C}$ ( $101.1^\circ\text{F}$ ) and a leukocyte count of $16,000/\text{mm}^3$ . An incision and drainage were performed, yielding $35\text{ mL}$ of purulent material. He was started on empiric intravenous vancomycin and piperacillin-tazobactam.

Today, the patient is afebrile, and his pain is well-controlled. The erythema has receded significantly, and his leukocyte count is $7,500/\text{mm}^3$ . The patient is tolerating a regular diet. The purulent fluid culture demonstrates heavy growth of *Staphylococcus aureus*. The isolate has the following susceptibility profile:

- Cefazolin: Susceptible
- Clindamycin: Susceptible
- Oxacillin: Susceptible
- Penicillin: Resistant
- Trimethoprim-sulfamethoxazole: Susceptible
- Vancomycin: Susceptible

Which of the following is the most appropriate next step in this patient's pharmacological management?

Transition to oral cephalexin

Transition to oral linezolid

Transition to oral ciprofloxacin

Maintain intravenous vancomycin and discontinue piperacillin-tazobactam

Maintain intravenous piperacillin-tazobactam and discontinue vancomycin

Show answer & explanation

Answer: Transition to oral cephalexin

Answer

Transition to oral cephalexin is the most appropriate management, as the patient has a methicillin-susceptible Staphylococcus aureus (MSSA) infection and is ready for oral step-down therapy.

The correct answer identifies that this patient has an infection caused by methicillin-susceptible Staphylococcus aureus (MSSA) based on the oxacillin susceptibility. Because he is clinically stable, afebrile, and tolerating oral intake, transitioning to an oral step-down agent is indicated. Oral cephalexin (a first-generation cephalosporin) or dicloxacillin are the preferred narrow-spectrum oral beta-lactams for MSSA. This choice appropriately targets the pathogen while adhering to antimicrobial stewardship principles.

Step-by-Step Solution

Interpret the culture and susceptibility results.

The culture shows Staphylococcus aureus that is susceptible to oxacillin.

Oxacillin susceptibility indicates that the organism is methicillin-susceptible Staphylococcus aureus (MSSA), which guides the choice of a targeted, narrow-spectrum antibiotic.

Evaluate the patient's clinical stability for step-down therapy.

The patient is afebrile, his erythema is receding, his leukocyte count has normalized, and he is tolerating a regular diet.

Clinical improvement and the ability to take oral medications indicate that the patient is ready to transition from intravenous to oral antibiotics.

Select the most appropriate targeted oral agent.

Cephalexin, a first-generation cephalosporin, is selected as the optimal step-down therapy.

Cephalexin provides excellent, narrow-spectrum coverage for MSSA, aligning with antimicrobial stewardship principles to minimize collateral damage and resistance.

Key Concept

Patients with methicillin-susceptible Staphylococcus aureus (MSSA) infections who are clinically improving and tolerating oral intake should be stepped down to a narrow-spectrum oral beta-lactam, such as cephalexin or dicloxacillin.

Question 1107Question →

A 71-year-old female resident of a long-term care facility was admitted to the hospital $4$ days ago with a temperature of $39.0^{\circ}\text{C}$ ( $102.2^{\circ}\text{F}$ ), rigors, and severe left-sided flank pain. Initial evaluation revealed marked left costovertebral angle tenderness. Laboratory testing demonstrated a leukocyte count of $15,200/\mu\text{L}$ with a left shift. Urinalysis was strongly positive for leukocyte esterase, nitrites, and numerous bacteria. The patient was started on empiric intravenous meropenem and intravenous fluids.

Today (hospital day 4), the patient is hemodynamically stable, has been afebrile for the past $48$ hours, and her flank pain has significantly improved. She is eating a normal diet and is eager to return to her facility. Blood cultures drawn on admission remain negative. The admission urine culture grew $>100,000$ colony-forming units/mL of *Escherichia coli*. Susceptibility testing results for the isolate are as follows:

Antimicrobial Agent	Susceptibility
Ampicillin	Resistant
Ceftriaxone	Resistant
Cefepime	Resistant
Ciprofloxacin	Resistant
Trimethoprim-sulfamethoxazole	Resistant
Nitrofurantoin	Susceptible
Fosfomycin	Susceptible
Ertapenem	Susceptible
Meropenem	Susceptible

Which of the following is the most appropriate next step in pharmacotherapy for this patient?

Transition to oral nitrofurantoin

Transition to oral fosfomycin

Transition to intravenous ertapenem and arrange for outpatient parenteral therapy

Continue intravenous meropenem and arrange for outpatient parenteral therapy

Transition to oral ciprofloxacin

Show answer & explanation

Answer: Transition to intravenous ertapenem and arrange for outpatient parenteral therapy

Answer

Transition to intravenous ertapenem and arrange for outpatient parenteral therapy.

The correct decision is to transition the patient to intravenous ertapenem. The patient has pyelonephritis caused by an ESBL-producing E. coli. Because ESBLs hydrolyze most beta-lactams and this isolate is resistant to fluoroquinolones and trimethoprim-sulfamethoxazole, a carbapenem is required. Ertapenem is the drug of choice for step-down therapy because it is the narrowest-spectrum carbapenem (sparing anti-pseudomonal coverage) and its once-daily dosing is ideal for outpatient parenteral antibiotic therapy (OPAT).

Step-by-Step Solution

Identify the clinical diagnosis based on the initial presentation.

The patient presented with high fever, rigors, and costovertebral angle tenderness, indicating acute pyelonephritis.

Differentiating between upper (pyelonephritis) and lower (cystitis) urinary tract infections is critical for selecting agents with appropriate tissue penetration.

Analyze the culture and susceptibility results.

The organism is an E. coli isolate resistant to penicillins, cephalosporins (including third- and fourth-generation), and fluoroquinolones, which is classic for an extended-spectrum beta-lactamase (ESBL) producer.

ESBL-producing organisms require specific targeted therapy, typically carbapenems, for invasive infections.

Determine the appropriate step-down therapy for pyelonephritis.

Oral agents like nitrofurantoin and fosfomycin, despite being susceptible in vitro, cannot be used due to poor renal tissue penetration. Intravenous carbapenems remain the standard of care.

Antibiotic selection must account for both organism susceptibility and the pharmacokinetic ability of the drug to reach the site of infection.

Apply principles of antibiotic stewardship to select the best parenteral agent.

Ertapenem is chosen over meropenem because it is a narrower-spectrum carbapenem (it lacks anti-pseudomonal activity) and its once-daily dosing profile is highly favorable for outpatient parenteral antibiotic therapy (OPAT).

De-escalating to the narrowest effective agent prevents the development of broader resistance, and prioritizing once-daily dosing facilitates safe discharge to a long-term care facility.

Key Concept

While nitrofurantoin and fosfomycin may show in vitro susceptibility against ESBL-producing organisms, they have poor renal tissue penetration and are strictly contraindicated for pyelonephritis. Ertapenem is the preferred step-down carbapenem due to its narrower spectrum and convenient once-daily dosing.

Question 1108Question →

A 31-year-old man with a known history of intravenous drug use presents to the emergency department complaining of high fever, severe chills, and generalized malaise for the past three days. Vital signs demonstrate a temperature of $39.0^\circ\text{C}$ ( $102.2^\circ\text{F}$ ), blood pressure of $112/68\text{ mmHg}$ , heart rate of $118/\text{min}$ , and respiratory rate of $20/\text{min}$ . Physical examination reveals a new blowing holosystolic murmur that is loudest at the left lower sternal border, along with pinpoint, non-tender, erythematous macules on his palms. Arrange the following management steps in the most appropriate chronological order for this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological order is to first obtain three sets of blood cultures, then administer empiric broad-spectrum intravenous antibiotics, and finally perform a transthoracic echocardiogram.

In cases of acutely ill patients presenting with suspected infective endocarditis, the standard of care requires obtaining three sets of blood cultures from separate venipuncture sites as the absolute first step. This ensures accurate pathogen isolation. Immediately following the blood draws, broad-spectrum empiric antibiotics must be started to control the severe infection. Finally, an echocardiogram (initially transthoracic, often followed by transesophageal) is performed to detect valvular vegetations and assess cardiac function; however, obtaining imaging should never delay the critical culture-and-treat sequence.

Step-by-Step Solution

Identify the suspected diagnosis based on the clinical presentation.

The patient's history of IV drug use, high fever, new right-sided murmur (tricuspid regurgitation), and Janeway lesions on the palms strongly suggest acute infective endocarditis.

Recognizing the severity and acute nature of the infection establishes the urgency of the subsequent management steps.

Determine the absolute first therapeutic step for a suspected severe bloodstream infection.

Obtain three sets of blood cultures from separate venipuncture sites.

Pathogen identification is crucial for targeted therapy, and antibiotics can cause false-negative cultures if given prior to the blood draw.

Determine the immediate subsequent step after cultures are secured.

Administer empiric broad-spectrum intravenous antibiotics.

Delaying treatment in acute right-sided endocarditis can lead to septic emboli and rapid clinical deterioration; treatment must follow immediately after cultures.

Determine the appropriate timing for diagnostic imaging.

Perform a transthoracic echocardiogram.

Once the patient is medically stabilized with cultures drawn and therapy initiated, imaging is needed to assess valve integrity and vegetation size.

Key Concept

In acute suspected infective endocarditis, multiple sets of blood cultures must be drawn prior to the initiation of empiric intravenous antibiotics to prevent sterilization of the cultures, followed subsequently by echocardiography to evaluate for valvular vegetations.

Question 1109Question →

Match each clinical presentation of an opportunistic infection in a patient with advanced HIV to its most appropriate first-line targeted antimicrobial therapy.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Pneumocystis pneumonia is treated with trimethoprim-sulfamethoxazole; Cryptococcal meningitis with amphotericin B and flucytosine; CMV retinitis with valganciclovir; and Toxoplasma encephalitis with sulfadiazine, pyrimethamine, and leucovorin.

Each opportunistic infection has a distinct clinical presentation linked to specific CD4 count thresholds and requires a corresponding optimal, evidence-based antimicrobial regimen.

Step-by-Step Solution

Identify the underlying opportunistic pathogen for each clinical vignette based on the patient's CD4 count and specific presenting symptoms or diagnostic findings.

The vignettes correspond to Pneumocystis jirovecii pneumonia, Cryptococcal meningitis, cytomegalovirus retinitis, and Toxoplasma encephalitis, respectively.

Accurate pathogen identification is a prerequisite for selecting the appropriate targeted antimicrobial therapy.

Determine the first-line treatment regimen for each identified opportunistic infection.

PCP requires trimethoprim-sulfamethoxazole. Cryptococcus requires amphotericin B and flucytosine. CMV requires valganciclovir. Toxoplasmosis requires sulfadiazine, pyrimethamine, and leucovorin.

Targeted therapy ensures maximal efficacy while reducing mortality and inappropriate use of broad-spectrum antimicrobials.

Key Concept

First-line treatment of opportunistic infections in HIV patients based on clinical presentation and CD4 count.

Question 1110Question →

Match each highly specific clinical scenario of an infectious disease with the most appropriate targeted pharmacologic management or intervention step, considering the patient's unique contraindications and risk factors.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Each clinical scenario requires matching the pathogen or exposure with a highly specific antimicrobial agent that safely navigates the patient's major contraindication (e.g., QTc prolongation, teratogenicity, nephrotoxicity, or drug-drug interactions).

The correct pairings require a synthesis of microbiology and pharmacology. The Aspergillus patient requires isavuconazole to avoid life-threatening arrhythmias. The pregnant syphilis patient requires penicillin desensitization as no safe alternatives exist. The Listeria patient requires trimethoprim-sulfamethoxazole to bypass penicillin anaphylaxis while maintaining efficacy. The CRAB patient requires cefiderocol to avoid polymyxin-induced renal failure. The meningococcal prophylaxis patient requires ceftriaxone to avoid contraceptive failure from rifampin and fatal arrhythmias from ciprofloxacin.

Step-by-Step Solution

Analyze the immunocompromised patient with the pulmonary halo sign and QTc of 560 ms.

Identify invasive aspergillosis. Recognize that voriconazole is contraindicated due to severe QTc prolongation. Select isavuconazonium sulfate.

Isavuconazole is a broad-spectrum triazole that uniquely shortens rather than prolongs the QTc interval.

Evaluate the pregnant patient with primary syphilis and penicillin anaphylaxis.

Identify that penicillin is absolutely required in pregnancy to prevent congenital syphilis. Select penicillin desensitization followed by benzathine penicillin G.

Alternative therapies are strictly contraindicated due to fetal harm or high resistance rates, necessitating the desensitization process despite the allergy.

Assess the post-transplant patient with Listeria meningitis and penicillin anaphylaxis.

Identify Listeria (Gram-positive rods with tumbling motility) and note the ampicillin allergy. Select trimethoprim-sulfamethoxazole.

Cephalosporins (including ceftriaxone and cefiderocol) do not cover Listeria. Trimethoprim-sulfamethoxazole is the drug of choice for Listeria in penicillin-allergic patients.

Review the ICU patient with carbapenem-resistant Acinetobacter baumannii (CRAB) and severe acute kidney injury.

Acknowledge the need for CRAB coverage while avoiding extreme nephrotoxins like polymyxins. Select cefiderocol.

Cefiderocol provides targeted therapy against CRAB via a novel siderophore mechanism, sparing the patient from the renal failure exacerbation seen with colistin.

Analyze the patient requiring meningococcal prophylaxis who takes oral contraceptives and has long QT syndrome.

Rule out rifampin (CYP450 induction ruins oral contraceptive efficacy) and ciprofloxacin (prolongs QTc). Select intramuscular ceftriaxone.

Ceftriaxone safely avoids both the drug-drug interaction and the cardiac electrophysiologic risk.

Key Concept

Advanced antimicrobial stewardship requires integrating microbiologic efficacy with patient-specific pharmacologic contraindications, including QTc interval prolongation, renal function, pregnancy status, and drug interactions.

Estimated Time:2m 30s

Question 1111Question →

A 28-year-old woman visits her primary care clinic due to a spreading rash on her right leg. She first noticed a small red bump four days ago, which has since expanded. The patient returned from a week-long camping trip in Connecticut ten days ago. She reports mild fatigue and muscle aches but denies fever, joint swelling, neck stiffness, or facial asymmetry. Her vital signs are within normal limits. Physical examination reveals a 9-cm erythematous annular plaque with central clearing on the right posterior calf. The lesion is flat, non-tender, and non-pruritic. Neurological and cardiovascular examinations are unremarkable. Which of the following is the most appropriate next step in management?

Prescribe oral doxycycline

Prescribe oral cephalexin

Prescribe intravenous ceftriaxone

Prescribe oral azithromycin

Prescribe topical clotrimazole

Show answer & explanation

Answer: Prescribe oral doxycycline

Answer

Prescribe oral doxycycline

The patient's clinical presentation of a large, expanding erythematous plaque with central clearing (erythema migrans) following outdoor activities in an endemic region (Connecticut) is pathognomonic for early localized Lyme disease. Caused by the spirochete Borrelia burgdorferi and transmitted by the Ixodes tick, early localized disease requires prompt empiric antibiotic therapy without waiting for serologic testing. Oral doxycycline is the treatment of choice for non-pregnant adults because it is highly effective and also treats potential coinfection with Anaplasma phagocytophilum.

Step-by-Step Solution

Identify the primary clinical finding and relevant patient history.

The patient has a large, expanding, flat annular rash with central clearing (erythema migrans) and recently camped in Connecticut (a highly endemic area for Lyme disease).

Recognizing the classic rash and endemic exposure establishes the clinical diagnosis of early localized Lyme disease.

Determine the need for diagnostic testing versus empiric treatment.

Erythema migrans is pathognomonic for early localized Lyme disease; serologic testing is not required and empiric treatment should be started immediately.

Antibody tests are often negative in the early stage of the disease, making clinical diagnosis paramount.

Select the most appropriate pharmacotherapy.

Oral doxycycline is the preferred first-line agent for non-pregnant adults.

Doxycycline effectively treats Borrelia burgdorferi and also provides coverage for Anaplasma phagocytophilum, a common coinfection transmitted by the same Ixodes tick.

Key Concept

Early localized Lyme disease is diagnosed clinically by the presence of erythema migrans in a patient with exposure to endemic areas, and it should be treated empirically with oral doxycycline.

Question 1112Question →

A $41$ -year-old woman comes to the clinic for evaluation of worsening fatigue, generalized weakness, and a $3$ -kg weight gain over the past $5$ months. She also reports increased sensitivity to cold and irregular menstrual cycles. She takes no daily medications. Her blood pressure is $110/70$ mm Hg, and her pulse is $58$ /min. Physical examination reveals dry skin and delayed relaxation of the deep tendon reflexes. Laboratory testing shows a thyroid-stimulating hormone (TSH) level of $0.15 \ \mu\text{U/mL}$ (normal: $0.4-4.0 \ \mu\text{U/mL}$ ) and a free thyroxine (T4) level of $0.6 \text{ ng/dL}$ (normal: $0.9-1.7 \text{ ng/dL}$ ). Which of the following is the most likely diagnosis?

Central hypothyroidism

Primary hypothyroidism

Subclinical hypothyroidism

Graves disease

Euthyroid sick syndrome

Show answer & explanation

Answer: Central hypothyroidism

Answer

Central hypothyroidism

The patient presents with classic clinical symptoms of hypothyroidism, including fatigue, weight gain, cold intolerance, bradycardia, and delayed relaxation of deep tendon reflexes. The laboratory findings show a low free T4 level, confirming a hypothyroid state. In a normally functioning hypothalamic-pituitary-thyroid axis, a low free T4 should stimulate the pituitary gland to increase TSH production. However, this patient's TSH is inappropriately low rather than elevated. The combination of low free T4 and low TSH indicates central (secondary) hypothyroidism, which is caused by a failure of the pituitary gland or hypothalamus to produce sufficient stimulating hormones.

Step-by-Step Solution

Evaluate the patient's clinical presentation and physical examination findings.

The presence of fatigue, weight gain, cold intolerance, bradycardia, and delayed relaxation of deep tendon reflexes indicates a clinical state of hypothyroidism.

To establish the primary clinical syndrome prior to interpreting the laboratory values.

Interpret the free T4 laboratory value.

The free T4 level is low at

0.6 \text{ ng/dL}

, which biochemically confirms the hypothyroid state.

To verify the clinical suspicion of hypothyroidism with objective data.

Assess the TSH level to determine the etiology of the hypothyroidism.

The TSH is low (

0.15 \ \mu\text{U/mL}

) instead of being elevated, indicating a failure of the hypothalamic-pituitary axis to respond to the low free T4.

To differentiate between primary (thyroid gland failure) and central (pituitary/hypothalamic failure) causes of hypothyroidism.

Key Concept

The diagnosis of central hypothyroidism requires the identification of a low free T4 level accompanied by a low or inappropriately normal TSH level, indicating a lack of appropriate pituitary stimulation.

Estimated Time:1m 0s

Question 1113Question →

A 65-year-old man is brought to the emergency department by his wife due to worsening confusion, weakness, and fatigue over the past 24 hours. He has a history of a nonfunctioning pituitary macroadenoma treated with transsphenoidal resection and radiation therapy 3 years ago, chronic obstructive pulmonary disease (COPD), and heart failure with preserved ejection fraction. Four days ago, he was diagnosed with a mild COPD exacerbation at an urgent care clinic and was prescribed a 5-day course of azithromycin. Today, his temperature is 36.1°C (97.0°F), blood pressure is 88/54 mm Hg, pulse is 110/min, and respirations are 24/min. Pulse oximetry is 93% on room air. Physical examination shows a lethargic man who follows simple commands. Jugular venous pressure is 6 cm $H_2O$ . Chest auscultation reveals distant breath sounds and scattered end-expiratory wheezes unchanged from his baseline. Heart sounds are normal. The extremities are cool without edema. Laboratory studies show:

Sodium: 131 mEq/L
Potassium: 3.9 mEq/L
Chloride: 98 mEq/L
Bicarbonate: 14 mEq/L
Blood urea nitrogen: 42 mg/dL
Creatinine: 1.8 mg/dL
Glucose: 62 mg/dL
Thyroid-stimulating hormone: 0.2 µU/mL (Normal: 0.4-4.0 µU/mL)
Free T4: 0.6 ng/dL (Normal: 0.9-1.7 ng/dL)

Arterial blood gas analysis on room air reveals:
pH: 7.31
PaCO2: 29 mm Hg
PaO2: 78 mm Hg

Which of the following is the most appropriate next step in management?

Initiate noninvasive positive-pressure ventilation

Switch azithromycin to intravenous piperacillin-tazobactam

Administer intravenous hydrocortisone

Administer intravenous levothyroxine

Administer intravenous furosemide

Show answer & explanation

Answer: Administer intravenous hydrocortisone

Answer

Administer intravenous hydrocortisone

The correct answer addresses the patient's acute adrenal crisis. The clinical presentation of hypotension, hypoglycemia, and lethargy in a patient with a history of pituitary irradiation is highly suspicious for panhypopituitarism. The laboratory findings of a low TSH and low free T4 confirm central hypothyroidism, which almost certainly means the patient has concurrent central adrenal insufficiency. In any patient with suspected secondary adrenal insufficiency and hypothyroidism, intravenous glucocorticoids (such as hydrocortisone) must be administered prior to thyroid hormone replacement. This is because thyroid hormone increases the basal metabolic rate and accelerates the hepatic clearance of cortisol. If levothyroxine is given first, it can rapidly deplete any remaining circulating cortisol, precipitating a life-threatening adrenal crisis.

Step-by-Step Solution

Evaluate the patient's hemodynamic status, metabolic panel, and arterial blood gas.

The patient is in distributive shock with hypoglycemia, hyponatremia, and a high anion gap metabolic acidosis (

AG = 19

). Winter's formula (

1.5 \times 14 + 8 = 29

) confirms perfect respiratory compensation.

To rule out uncompensated respiratory failure or cardiogenic shock, which would demand immediate ventilatory or diuretic support.

Analyze the thyroid function tests in the context of the patient's past medical history.

Low TSH and low free T4 indicate central hypothyroidism, which, combined with the history of pituitary irradiation, strongly suggests panhypopituitarism.

To identify the underlying etiology of the distributive shock and hypoglycemia, which points to an acute adrenal crisis.

Determine the appropriate pharmacological sequencing for treating central hypothyroidism and concurrent adrenal insufficiency.

Intravenous hydrocortisone must be administered before levothyroxine.

Administering thyroid hormone first accelerates hepatic metabolism of cortisol, which can precipitate or fatally worsen an adrenal crisis.

Key Concept

In patients with suspected panhypopituitarism presenting with concurrent central adrenal insufficiency and central hypothyroidism, glucocorticoids must be administered before thyroid hormone replacement to prevent precipitating a fatal adrenal crisis.

Estimated Time:2m 0s

Question 1114Question →

During a January night shift, emergency medical services transport a 64-year-old woman to the resuscitation bay due to a progressive decline in consciousness over the past two days. According to her daughter, the patient recently had a mild upper respiratory tract infection but has not been febrile. Her medical history includes diet-controlled type 2 diabetes mellitus and a hospitalization one year ago for 'fluid in the lungs.'

Vital signs reveal a temperature of 34.5°C (94.1°F), blood pressure of 90/60 mm Hg, heart rate of 48/min, and respiratory rate of 10/min. Pulse oximetry shows 89% on room air.

Physical examination demonstrates a somnolent patient with generalized non-pitting edema, a puffy face, and macroglossia. Deep tendon reflexes exhibit markedly delayed relaxation. Auscultation reveals diminished breath sounds at both lung bases without wheezes or crackles.

Laboratory analysis:
Sodium: 128 mEq/L
Potassium: 4.1 mEq/L
Chloride: 98 mEq/L
Bicarbonate: 28 mEq/L
Blood urea nitrogen: 25 mg/dL
Creatinine: 1.1 mg/dL
Thyroid-stimulating hormone (TSH): 1.1 µU/mL (normal: 0.5–5.0 µU/mL)
Free thyroxine (T4): 0.3 ng/dL (normal: 0.9–1.7 ng/dL)

Arterial blood gas (room air):
pH: 7.31
pCO2: 56 mm Hg
pO2: 58 mm Hg

An electrocardiogram shows sinus bradycardia with low voltage complexes. Chest radiography reveals mild cardiomegaly and small bilateral pleural effusions without focal consolidation.

Which of the following is the most appropriate initial management for this patient?

Intravenous levothyroxine and hydrocortisone

Intravenous levothyroxine monotherapy

Intravenous furosemide and non-invasive positive pressure ventilation

Broad-spectrum antibiotics and rapid intravenous fluid resuscitation

Intravenous sodium bicarbonate infusion

Show answer & explanation

Answer: Intravenous levothyroxine and hydrocortisone

Answer

The correct intervention is the combined administration of intravenous levothyroxine and hydrocortisone.

The correct answer addresses the immediate need for thyroid hormone replacement while safely mitigating the risk of adrenal crisis. This patient's presentation of hypothermia, bradycardia, hypoventilation, and somnolence is classic for myxedema coma. The profoundly low free T4 combined with an inappropriately normal TSH indicates central (secondary) hypothyroidism, which carries a high probability of concurrent central adrenal insufficiency. Administering exogenous thyroid hormone accelerates the hepatic metabolism and clearance of cortisol. If given without glucocorticoid coverage, this rapid metabolic shift can precipitate a fatal acute adrenal crisis. Therefore, empiric intravenous hydrocortisone is mandatory prior to or alongside levothyroxine administration.

Step-by-Step Solution

Diagnose the clinical syndrome based on the physical examination and vital signs.

The patient is experiencing myxedema coma.

Hypothermia, severe bradycardia, hypoventilation, altered mental status, and delayed relaxation of deep tendon reflexes are pathognomonic for this life-threatening manifestation of severe hypothyroidism.

Interpret the thyroid function tests to determine the etiology of the hypothyroidism.

The patient has central (secondary) hypothyroidism.

The free T4 is profoundly low, but the TSH is inappropriately normal rather than elevated, indicating a failure of the pituitary-hypothalamic axis rather than a primary thyroid gland issue.

Determine the therapeutic implications of central hypothyroidism in a critical care setting.

Glucocorticoids must be administered alongside thyroid hormone replacement.

Central hypothyroidism strongly suggests panhypopituitarism and concurrent central adrenal insufficiency. Administering levothyroxine alone accelerates the metabolic clearance of cortisol, which can precipitate a fatal acute adrenal crisis.

Key Concept

In patients with myxedema coma, especially those with laboratory evidence of central hypothyroidism, intravenous glucocorticoids (e.g., hydrocortisone) must be administered concurrently with levothyroxine to prevent precipitating an acute adrenal crisis.

Estimated Time:2m 0s

Question 1115Question →

A hematology consultation service is reviewing the clinical data and coagulation profiles of five distinct adult patients. Based on the patterns of standard coagulation testing (PT, aPTT), mixing studies, and clinical presentation, match each patient's profile to the most accurate underlying diagnosis.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Profile 1 matches Factor XIII deficiency; Profile 2 matches Early vitamin K deficiency; Profile 3 matches Acquired hemophilia A; Profile 4 matches Antiphospholipid syndrome; Profile 5 matches Systemic AL amyloidosis.

The correct pairings require synthesis of clinical signs and advanced hematologic testing. Factor XIII deficiency selectively fails the 5M urea clot solubility test because fibrin is not cross-linked, causing delayed bleeding. Early vitamin K deficiency rapidly depletes Factor VII (shortest half-life), prolonging the PT, which corrects on a standard mixing study. Acquired hemophilia A (Factor VIII inhibitor) is classically time- and temperature-dependent, showing initial correction followed by prolongation. Lupus anticoagulant immediately binds phospholipids, causing immediate non-correction of the aPTT without bleeding, instead driving thrombosis. Systemic AL amyloidosis uniquely causes isolated Factor X deficiency due to direct fibril binding, presenting alongside macroglossia and nephropathy.

Step-by-Step Solution

Analyze standard coagulation tests (PT and aPTT) to determine the affected pathways.

Isolated PT prolongation points to the extrinsic pathway; isolated aPTT points to the intrinsic pathway; combined points to the common pathway; entirely normal tests with delayed bleeding suggest structural fibrin cross-linking issues.

Basic coagulation cascade interpretation sets the foundation for diagnosing hemostatic disorders.

Evaluate mixing study results for the profiles with prolonged tests.

Immediate correction suggests a simple factor deficiency (e.g., Vitamin K deficiency). Immediate non-correction suggests an immediate inhibitor (Lupus anticoagulant). Time-dependent non-correction suggests a slow-acting inhibitor (Factor VIII autoantibody).

Mixing studies differentiate between missing factors and the presence of acquired neutralizing antibodies or phospholipid inhibitors.

Incorporate specific clinical syndromes and unique laboratory phenomena.

The 5M urea test specifically identifies Factor XIII. The triad of macroglossia, periorbital purpura, and nephropathy points to AL amyloidosis, which exhibits unique Factor X binding. Broad-spectrum antibiotics and malnutrition point to Vitamin K depletion.

Advanced diagnosis requires integrating abstract laboratory phenomena with systemic physical exam findings.

Key Concept

Advanced integration of coagulation cascade abnormalities, mixing studies, and systemic disease associations.

Question 1116Question →

A 68-year-old man is evaluated in the hospital for sudden-onset, severe right knee pain. He is currently on postoperative day 6 following an uncomplicated robotic-assisted prostatectomy for prostate cancer. He reports that the pain began abruptly overnight and is so severe that he cannot tolerate the weight of his bedsheet on his leg. His medical history is significant for hypertension, type 2 diabetes mellitus, and chronic kidney disease stage 3. His temperature is $38.4^\circ\text{C}$ ( $101.1^\circ\text{F}$ ), blood pressure is $138/85\text{ mmHg}$ , and pulse is $98/\text{min}$ . Physical examination reveals a markedly swollen, erythematous, and warm right knee. There is a palpable effusion, and both active and passive range of motion are severely limited by pain. The surgical incisions in the abdomen are clean, dry, and intact with no surrounding erythema. Which of the following is the most appropriate next step in management of this patient's joint pain?

Arthrocentesis and synovial fluid analysis

Administration of intravenous vancomycin and ceftriaxone

Lower extremity venous Doppler ultrasound

Measurement of serum uric acid concentration

Magnetic resonance imaging of the right knee

Show answer & explanation

Answer: Arthrocentesis and synovial fluid analysis

Answer

The most appropriate next step in management is arthrocentesis and synovial fluid analysis.

The correct response is arthrocentesis and synovial fluid analysis. An acute, hot, swollen, and exquisitely tender joint with restricted range of motion is a rheumatologic emergency. In a postoperative patient, surgical stress often triggers acute crystal arthropathies (gout or pseudogout), but septic arthritis must be definitively ruled out due to its potential to rapidly destroy joint cartilage and cause systemic sepsis. Synovial fluid analysis (checking for leukocyte count, crystal presence under polarized light, Gram stain, and culture) is the gold standard diagnostic step. It must be performed before the administration of antibiotics, as early antibiotics can quickly render synovial fluid cultures negative, severely complicating long-term management.

Step-by-Step Solution

Identify the primary clinical problem from the vignette.

The patient has an acute, atraumatic, inflammatory monoarthritis of the knee with systemic fever occurring in the postoperative period.

Recognizing the 'hot, swollen joint' is critical for prioritizing life- or limb-threatening conditions.

Formulate a differential diagnosis based on the timeline and physical exam.

The primary differentials are septic arthritis (which can rapidly destroy the joint) and acute crystal arthropathies like gout or pseudogout (which can mimic infection and cause fever, especially triggered by surgical stress).

Both conditions present identically on physical examination and require fluid analysis to distinguish.

Select the intervention that provides a definitive diagnosis without compromising future treatment.

Arthrocentesis to obtain synovial fluid for cell count, Gram stain, culture, and crystal analysis is chosen.

It definitively distinguishes between crystals and bacteria. Starting antibiotics beforehand or relying on indirect markers (like serum uric acid or imaging) will compromise patient care.

Key Concept

The initial evaluation of a single, acutely inflamed joint (monoarthritis) must prioritize ruling out septic arthritis via arthrocentesis and synovial fluid analysis before initiating empiric antibiotic therapy.

Question 1117Question →

Evaluate the following four patient presentations encountered in the acute internal medicine setting. Match each clinical vignette describing a toxicological emergency with the most appropriate definitive pharmacologic intervention.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct pairings are: the post-endoscopy hypoxia patient with intravenous methylene blue; the obtunded patient with crystalluria with intravenous fomepizole; the refractory bradycardic patient with intravenous glucagon; and the nitroprusside toxicity patient with intravenous hydroxocobalamin.

Each specific toxicological emergency relies on identifying unique clinical markers: a saturation gap for methemoglobinemia (treated with methylene blue); osmolar gap with crystalluria for ethylene glycol (treated with fomepizole); refractory bradycardic shock for beta-blocker overdose (treated with glucagon); and lactic acidosis with high mixed venous oxygen post-nitroprusside for cyanide toxicity (treated with hydroxocobalamin).

Step-by-Step Solution

Analyze the first clinical vignette for specific physiological discrepancies.

Identify a saturation gap (low pulse oximetry, normal arterial

PaO_2

) and dark blood following topical anesthetic use, diagnostic of methemoglobinemia.

Topical anesthetics are classic oxidizing agents. Methylene blue is the specific antidote to reduce oxidized iron in hemoglobin.

Analyze the laboratory findings in the second clinical vignette.

Identify an elevated osmolar gap, severe metabolic acidosis, and calcium oxalate crystals without elevated lactate, indicative of ethylene glycol ingestion.

Ethylene glycol requires immediate blockade of alcohol dehydrogenase with fomepizole to prevent renal failure and severe systemic toxicity.

Evaluate the third clinical vignette's hemodynamic profile.

Identify refractory cardiogenic shock (bradycardia and hypotension) unresponsive to standard vasopressors and atropine, classic for severe beta-blocker toxicity.

Definitive management requires an alternative pathway to increase intracellular

cAMP

, which is achieved by administering intravenous glucagon.

Assess the iatrogenic complication in the fourth clinical vignette.

Identify cyanide toxicity secondary to prolonged sodium nitroprusside infusion, evidenced by lactic acidosis and impaired cellular oxygen extraction (high mixed venous oxygen).

Cyanide binds mitochondrial cytochrome oxidase. Hydroxocobalamin acts as a direct cyanide scavenger, forming non-toxic cyanocobalamin.

Key Concept

Diagnosis of acute toxicological emergencies based on pathognomonic clinical and laboratory findings, and the subsequent selection of definitive targeted antidotes.

Question 1118Question →

A 45-year-old man is hospitalized for the treatment of acute promyelocytic leukemia. Eight days ago, he was started on induction therapy with all-trans retinoic acid and arsenic trioxide, along with empiric intravenous cefepime for neutropenic fever. Over the last $24$ hours, his temperature is $38.6^\circ\text{C}$ ( $101.5^\circ\text{F}$ ), blood pressure is $110/70\text{ mm Hg}$ , pulse is $112/\text{min}$ , and respirations are $24/\text{min}$ . Oxygen saturation is $89\%$ on room air. He reports progressive shortness of breath and a nonproductive cough. Physical examination reveals bilateral basilar crackles, $2+$ bilateral lower extremity edema, and elevated jugular venous pressure. Laboratory studies show a leukocyte count of $28,000/\text{mm}^3$ (up from $4,000/\text{mm}^3$ on admission). Chest radiography demonstrates bilateral diffuse interstitial opacities and small bilateral pleural effusions. Which of the following is the most specific and critical next step in the management of this patient's acute respiratory decompensation?

Intravenous dexamethasone

Intravenous furosemide

Addition of intravenous vancomycin

Discontinuation of all-trans retinoic acid and arsenic trioxide

Immediate leukapheresis

Show answer & explanation

Answer: Intravenous dexamethasone

Answer

Intravenous dexamethasone

The correct answer is the immediate administration of intravenous dexamethasone. This patient is presenting with Differentiation Syndrome (formerly known as retinoic acid syndrome), a life-threatening complication of induction therapy with all-trans retinoic acid (ATRA) and arsenic trioxide for acute promyelocytic leukemia (APL). As the malignant promyelocytes are forced to differentiate into mature neutrophils, they release massive amounts of inflammatory cytokines. This results in a systemic inflammatory response syndrome characterized by fever, peripheral edema, weight gain, hypotension, and profound capillary leak leading to pulmonary infiltrates, pleural effusions, and pericardial effusions. The diagnostic hallmark often includes a rapidly rising leukocyte count. The definitive, life-saving therapy is the immediate initiation of high-dose corticosteroids, specifically intravenous dexamethasone, which rapidly blunts the cytokine storm. Importantly, ATRA is typically continued during moderate differentiation syndrome; temporary discontinuation is reserved only for severe cases (e.g., acute respiratory distress syndrome requiring intubation or acute renal failure).

Step-by-Step Solution

Identify the primary diagnosis and current treatment.

The patient has acute promyelocytic leukemia (APL) and is receiving induction therapy with all-trans retinoic acid (ATRA) and arsenic trioxide.

Establishing the current therapeutic context is essential for identifying treatment-specific complications.

Analyze the new clinical presentation and timeline.

Eight days after starting ATRA, the patient developed fever, dyspnea, hypoxemia, weight gain (edema), a rising leukocyte count, and bilateral pulmonary opacities.

This timeline and symptom cluster (fever, pulmonary infiltrates, effusions, expected leukocytosis) are the hallmark signs of a specific adverse drug reaction.

Formulate a diagnosis for the acute decompensation.

The clinical picture perfectly matches Differentiation Syndrome (formerly retinoic acid syndrome), caused by differentiating promyelocytes releasing inflammatory cytokines.

Recognizing the capillary leak nature of this syndrome prevents misdiagnosing it as isolated heart failure or pneumonia.

Select the definitive management for the complication.

The treatment of choice is immediate high-dose intravenous dexamethasone.

Steroids are required to suppress the life-threatening cytokine storm. ATRA is generally continued unless the syndrome is severe (e.g., renal failure, need for intubation).

Key Concept

Differentiation Syndrome in APL

Question 1119Question →

Match each patient's clinical presentation and laboratory profile with the most likely corresponding peripheral blood smear finding.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The sulfonamide-induced hemolysis matches Heinz bodies and bite cells; the home renovator with wrist drop matches basophilic stippling; the sickle cell patient matches Howell-Jolly bodies; and the lupus patient with a positive direct antiglobulin test matches spherocytes.

Each vignette represents a classic hematologic presentation where the peripheral blood smear serves as a critical diagnostic tool, reflecting the exact underlying mechanism of erythrocyte damage, abnormal maturation, or failed splenic clearance.

Step-by-Step Solution

Analyze each clinical vignette to establish the primary pathophysiologic diagnosis.

Diagnoses identified: 1 is G6PD deficiency, 2 is lead poisoning, 3 is sickle cell disease with autosplenectomy, and 4 is warm autoimmune hemolytic anemia.

Correctly identifying the underlying disease process is a prerequisite to anticipating its microscopic cellular features.

Correlate the identified diagnoses with classic peripheral blood smear morphological changes.

G6PD deficiency links to Heinz bodies/bite cells. Lead poisoning links to basophilic stippling. Autosplenectomy links to Howell-Jolly bodies. Warm AIHA links to spherocytes.

Specific pathophysiological mechanisms directly dictate the morphological alterations of erythrocytes visible on a peripheral smear.

Key Concept

Correlating clinical presentations of hematologic disorders with their characteristic pathophysiological peripheral blood smear findings.

Question 1120Question →

A 52-year-old woman with a history of primary Sjögren syndrome, characterized by severe keratoconjunctivitis sicca, xerostomia, and positive anti-Ro/SSA antibodies, is brought to the emergency department by her husband due to sudden, profound generalized muscle weakness that started this morning. She reports feeling so weak she could not get out of bed. She also complains of new-onset shortness of breath and difficulty taking a deep breath. She currently takes no medications.

Temperature is 37.1°C (98.8°F), blood pressure is 115/75 mm Hg, pulse is 95/min, and respiratory rate is 24/min with shallow breathing. Pulse oximetry is 94% on room air.

Physical examination reveals 2/5 motor strength in the proximal muscles of the upper and lower extremities. Deep tendon reflexes are 1+ bilaterally. Chest auscultation reveals clear lungs bilaterally.

Laboratory studies show:

Serum Analyte	Value	Reference Range
Sodium ( $Na^+$ )	140 mEq/L	136-145 mEq/L
Potassium ( $K^+$ )	1.8 mEq/L	3.5-5.0 mEq/L
Chloride ( $Cl^-$ )	118 mEq/L	98-106 mEq/L
Bicarbonate ( $HCO_3^-$ )	12 mEq/L	22-28 mEq/L
Blood urea nitrogen	15 mg/dL	8-20 mg/dL
Creatinine	0.9 mg/dL	0.7-1.3 mg/dL

Urine Analyte	Value
pH	6.5
Sodium ( $Na^+$ )	35 mEq/L
Potassium ( $K^+$ )	20 mEq/L
Chloride ( $Cl^-$ )	20 mEq/L

Which of the following is the most appropriate next step in the management of this patient?

Intravenous administration of potassium chloride

Intravenous administration of sodium bicarbonate to correct a high anion gap acidosis

Initiation of furosemide and positive pressure ventilation for an acute cardiopulmonary exacerbation

Initiation of broad-spectrum antibiotics to empirically treat a suspected systemic infection

Measurement of thyroid-stimulating hormone levels to evaluate for a concomitant autoimmune endocrinopathy

Show answer & explanation

Answer: Intravenous administration of potassium chloride

Answer

Intravenous administration of potassium chloride

The correct answer addresses the most immediate, life-threatening derangement: severe hypokalemia (

K^+ = 1.8

mEq/L). This patient's presentation of profound weakness, respiratory distress (due to respiratory muscle paralysis), and a normal anion gap metabolic acidosis with a positive urine anion gap (+35) and a urine pH > 5.5 is the classic presentation of distal (Type 1) renal tubular acidosis (RTA). Type 1 RTA is a well-documented extraglandular complication of Sjögren syndrome, caused by autoimmune-mediated destruction of the

\alpha

-intercalated cells in the collecting duct. This prevents

H^+

secretion, leading to systemic acidosis, and secondarily impairs

K^+

reabsorption, leading to severe hypokalemia. The most critical step in management is intravenous potassium replacement. Administering alkali (sodium bicarbonate) to correct the acidosis before replacing potassium is strictly contraindicated, as raising the blood pH shifts potassium into the intracellular space, which can precipitate fatal cardiac arrhythmias.

Step-by-Step Solution

Calculate the serum anion gap to classify the metabolic acidosis.

The anion gap is normal (10 mEq/L).

AG = Na^+ - (Cl^- + HCO_3^-) = 140 - (118 + 12) = 10

. This indicates a normal anion gap metabolic acidosis (NAGMA).

Calculate the urine anion gap (UAG) to determine the source of the NAGMA.

The UAG is positive (+35 mEq/L).

UAG = Na^+ + K^+ - Cl^- = 35 + 20 - 20 = +35

. A positive UAG in NAGMA suggests impaired renal

NH_4^+

excretion, confirming a renal tubular acidosis (RTA).

Integrate laboratory findings with the patient's rheumatologic history.

The patient has distal (Type 1) RTA secondary to Sjögren syndrome.

Sjögren syndrome frequently causes autoantibody-mediated damage to the

\alpha

-intercalated cells of the distal tubule, leading to failure of

H^+

secretion (urine pH > 5.5) and severe hypokalemia (

1.8

mEq/L).

Identify the most critical and immediate step in management.

Intravenous potassium chloride must be administered immediately.

The profound weakness and shallow breathing are due to severe hypokalemia. Administering alkali (like bicarbonate) to correct the acidosis before replacing potassium would drive

K^+

into cells, exacerbating the hypokalemia and risking fatal arrhythmias.

Key Concept

Extraglandular manifestations of primary Sjögren syndrome include distal (Type 1) renal tubular acidosis, characterized by a normal anion gap metabolic acidosis, a positive urine anion gap, high urine pH, and severe hypokalemia. In the management of Type 1 RTA, potassium must be repleted before initiating alkali therapy.

Estimated Time:2m 30s

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