Internal Medicine

3151 questions

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

An emergency medical services team brings a 67-year-old man to the hospital due to three days of progressive breathlessness. He reports a concurrent increase in cough frequency and a change in sputum from clear to thick, yellowish-green. His medical history is significant for ischemic cardiomyopathy with a left ventricular ejection fraction of $35\%$ , severe chronic obstructive pulmonary disease, and a 45-pack-year smoking history. Current vital signs reveal a temperature of $37.8^\circ\text{C}$ ( $100^\circ\text{F}$ ), heart rate of $108/\text{min}$ , blood pressure of $138/86\text{ mm Hg}$ , and respiratory rate of $24/\text{min}$ . Oxygen saturation is $88\%$ on room air. Physical examination demonstrates a barrel-shaped chest with the use of accessory muscles of respiration. Auscultation reveals a prolonged expiratory phase with diffuse wheezing bilaterally. There are no crackles, and the jugular veins are not distended. Trace bilateral pedal edema is present, which the patient states is unchanged from his baseline. Arterial blood gas analysis on room air shows:

pH: $7.31$
PaCO $_2$ : $62\text{ mm Hg}$
PaO $_2$ : $58\text{ mm Hg}$
HCO $_3^-$ : $30\text{ mEq/L}$

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

Administration of nebulized short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic

Administration of intravenous furosemide and initiation of non-invasive positive pressure ventilation

Administration of nebulized short-acting bronchodilators, oral glucocorticoids, and intravenous piperacillin-tazobactam

Intravenous administration of sodium bicarbonate and endotracheal intubation

Administration of an intravenous beta-blocker and urgent echocardiography

Show answer & explanation

Answer: Administration of nebulized short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic

Answer

Administration of nebulized short-acting bronchodilators, oral glucocorticoids, and an oral macrolide antibiotic

The patient presents with the three cardinal symptoms of an acute exacerbation of chronic obstructive pulmonary disease (COPD): increased dyspnea, increased sputum volume, and increased sputum purulence. Despite his history of ischemic cardiomyopathy, his physical examination (diffuse wheezing, lack of crackles, normal jugular venous pressure) strongly indicates a primary pulmonary etiology rather than acute decompensated heart failure. His arterial blood gas demonstrates an acute-on-chronic respiratory acidosis, evidenced by a high baseline bicarbonate with a superimposed acute drop in pH due to worsening hypercapnia. The standard of care for a severe COPD exacerbation with all three cardinal symptoms includes short-acting bronchodilators to relieve bronchospasm, systemic glucocorticoids to reduce airway inflammation, and a targeted antibiotic (such as a macrolide or respiratory fluoroquinolone) to cover typical respiratory pathogens like Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae.

Step-by-Step Solution

Analyze the patient's clinical presentation and physical exam.

The patient has increased dyspnea, sputum volume, and purulence alongside diffuse wheezing, with no evidence of fluid overload (no crackles, normal JVP).

To differentiate between an acute exacerbation of COPD and acute decompensated heart failure in a patient with a history of both.

Interpret the arterial blood gas values.

pH of 7.31, elevated PaCO2 (62 mm Hg), and elevated HCO3- (30 mEq/L) indicate an acute-on-chronic respiratory acidosis.

To accurately assess the patient's acid-base status and rule out primary metabolic derangements.

Determine the indications for antibiotic therapy in this scenario.

The patient has all three cardinal symptoms of a COPD exacerbation, which is a strong indication for targeted antibiotic therapy.

To apply antimicrobial stewardship principles by selecting an appropriate narrow-spectrum agent (e.g., macrolide) rather than an overly broad agent.

Select the most appropriate comprehensive management plan.

The correct plan includes bronchodilators (for bronchospasm), systemic steroids (to reduce inflammation), and a macrolide antibiotic (for likely bacterial triggers).

This combination addresses all pathophysiological components of the patient's acute COPD exacerbation.

Key Concept

Differentiating COPD exacerbation from acute decompensated heart failure and applying the standard triad of therapy (bronchodilators, glucocorticoids, targeted antibiotics) for COPD exacerbations.

Question 1362Question →

A 52-year-old man with newly diagnosed acute myeloid leukemia is evaluated on hospital day 10 of induction chemotherapy due to a new-onset fever. Over the past 4 hours, his temperature has risen to a maximum of 38.7°C (101.7°F). He reports mild generalized fatigue but denies cough, shortness of breath, dysuria, abdominal pain, or diarrhea. Vital signs show a blood pressure of 118/74 mmHg, pulse of 92/min, and respiratory rate of 16/min. He has an indwelling right internal jugular central venous catheter; examination of the insertion site reveals it to be clean and dry without any surrounding erythema, induration, or tenderness. Cardiopulmonary and abdominal examinations are unremarkable. There are no skin rashes or mucosal ulcerations. Laboratory studies reveal:

Test	Result
Hemoglobin	8.4 g/dL
Platelets	45,000 /mm³
Leukocytes	400 /mm³
Neutrophils	15%

Peripheral blood and catheter-drawn blood cultures have been obtained. Which of the following is the most appropriate empiric antimicrobial regimen for this patient?

Intravenous cefepime and vancomycin

Oral ciprofloxacin and amoxicillin-clavulanate

Intravenous cefepime

Intravenous vancomycin and ciprofloxacin

Intravenous meropenem, vancomycin, and caspofungin

Show answer & explanation

Answer: Intravenous cefepime

Answer

Intravenous cefepime

The correct approach for this patient is intravenous cefepime monotherapy. This patient has febrile neutropenia, defined as a single oral temperature

\geq

38.3°C (101°F) and an absolute neutrophil count (ANC)

< 500/mm^3

. Because he is undergoing induction chemotherapy for acute myeloid leukemia, he is at high risk for prolonged and profound neutropenia, necessitating immediate admission and empiric intravenous antibiotics. The standard of care for high-risk febrile neutropenia is monotherapy with an anti-pseudomonal beta-lactam (e.g., cefepime, meropenem, or piperacillin-tazobactam). Routine empiric addition of vancomycin is explicitly discouraged to prevent antimicrobial resistance and reduce toxicity, unless specific criteria are met (e.g., hemodynamic instability, severe mucositis, radiographic pneumonia, or a clinically infected catheter site).

Step-by-Step Solution

Calculate the Absolute Neutrophil Count (ANC) to diagnose febrile neutropenia.

ANC = 400 \times 0.15 = 60/mm^3

. Combined with a temperature

\geq

38.3°C, this confirms neutropenic fever.

Establishing the diagnosis and severity of neutropenia dictates the urgency and type of empiric therapy.

Risk-stratify the patient to determine the required setting and route of administration.

The patient has acute myeloid leukemia and is undergoing induction chemotherapy, predicting prolonged (>

7

days) and profound (

< 100/mm^3

) neutropenia. This classifies him as high-risk, requiring inpatient intravenous therapy.

Low-risk patients can sometimes be managed with oral antibiotics, but high-risk patients require immediate broad-spectrum IV coverage.

Select the appropriate empiric antibacterial coverage.

Guidelines recommend monotherapy with an anti-pseudomonal beta-lactam (e.g., cefepime, meropenem, or piperacillin-tazobactam) for high-risk patients.

Patients with severe neutropenia are highly susceptible to rapidly fatal Gram-negative sepsis, particularly from Pseudomonas aeruginosa.

Evaluate for specific indications to add MRSA coverage (vancomycin).

The patient is hemodynamically stable and has a clean, non-tender central venous catheter site without severe mucositis or pneumonia. Therefore, vancomycin is NOT indicated.

Antimicrobial stewardship guidelines specifically advise against the routine empiric addition of vancomycin for fever in neutropenic patients unless targeted risk factors are present.

Key Concept

Empiric management of high-risk febrile neutropenia requires anti-pseudomonal beta-lactam monotherapy; vancomycin is reserved for specific indications such as hemodynamic instability or overt catheter-site infections, and should not be added solely because a central line is present.

Question 1363Question →

A 32-year-old woman presents to the clinic with a 6-month history of progressive exertional dyspnea, fatigue, and occasional exertional syncope. Physical examination reveals a right ventricular heave, a loud pulmonic component of the second heart sound (P2), and clear lung fields. A transthoracic echocardiogram demonstrates right atrial and ventricular enlargement with an estimated right ventricular systolic pressure of $65 \text{ mm Hg}$ . Left ventricular size and function are normal, with no left-sided valvular abnormalities. Arrange the following diagnostic and therapeutic steps in the most appropriate sequential order for the standard evaluation and definitive management of this patient's condition.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence for evaluating and managing unexplained pulmonary hypertension is: 1) V/Q scan, 2) Right heart catheterization, 3) Vasoreactivity testing, 4) Calcium channel blocker trial (if reactive), and 5) Escalation to advanced PAH therapies if efficacy wanes.

The evaluation of pulmonary hypertension follows a rigorous, stepwise algorithm. Following echocardiographic suspicion, the first mandatory step is a V/Q scan to rule out chronic thromboembolic pulmonary hypertension (CTEPH), which is potentially curable surgically. Once CTEPH and left-heart/lung diseases are excluded, a right heart catheterization (RHC) is performed to definitively diagnose pre-capillary pulmonary arterial hypertension (PAH). During the RHC, acute vasoreactivity testing is essential. Patients who demonstrate a reactive hemodynamic profile are initiated on high-dose calcium channel blockers. If a patient initially responds to CCBs but later deteriorates, or if they are non-reactive from the start, therapy is escalated to targeted PAH agents such as endothelin receptor antagonists or phosphodiesterase-5 inhibitors.

Step-by-Step Solution

Rule out Group 4 Pulmonary Hypertension (CTEPH)

Perform a V/Q scan to look for mismatched perfusion defects.

CTEPH is uniquely treatable with pulmonary thromboendarterectomy. It must be evaluated prior to invasive hemodynamics or medical therapy.

Confirm diagnosis hemodynamically

Perform right heart catheterization (RHC).

Echocardiography only estimates pressures. RHC is required to confirm pre-capillary pulmonary hypertension (

\text{mPAP} > 20 \text{ mm Hg}

\text{PCWP} \leq 15 \text{ mm Hg}

\text{PVR} \geq 2 \text{ WU}

Determine phenotype for medical therapy

Administer a short-acting vasodilator (e.g., inhaled nitric oxide) during the RHC.

Vasoreactivity testing identifies the minority of patients with idiopathic PAH who will respond favorably to calcium channel blockers.

Initiate first-line therapy for reactive patients

Start high-dose calcium channel blockers (CCBs).

Reactive patients have an excellent prognosis on CCBs and should be treated with them initially.

Manage treatment failure or disease progression

Escalate to targeted PAH therapies (e.g., ERAs, PDE-5 inhibitors, or prostacyclin analogs).

Patients who lose reactivity or clinically deteriorate on CCBs require advanced, pathway-specific pulmonary vasodilators.

Key Concept

The diagnostic algorithm for suspected pulmonary arterial hypertension requires non-invasive screening for CTEPH via a V/Q scan, followed by definitive hemodynamic confirmation via right heart catheterization with concurrent vasoreactivity testing to guide targeted pharmacotherapy.

Estimated Time:1m 30s

Question 1364Question →

A 54-year-old man with a known history of alcohol-associated cirrhosis presents to the emergency department after vomiting a large amount of bright red blood. On presentation, his blood pressure is 85/55 mm Hg, and his pulse is 120/min. He is lethargic but is maintaining his airway and oxygenating well on room air. Arrange the following management steps in the most appropriate chronological sequence.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence for managing acute variceal bleeding is to first ensure hemodynamic stability with intravenous access and fluids, followed by the administration of medical therapy (octreotide and prophylactic antibiotics), and finally performing definitive therapeutic endoscopy.

In any unstable patient with severe upper gastrointestinal bleeding, securing the ABCs (Airway, Breathing, Circulation) is paramount. Large-bore intravenous access and volume resuscitation must occur first. Following this, for suspected variceal bleeding, octreotide is given to decrease portal pressure, and prophylactic antibiotics (like ceftriaxone) are given to prevent infectious complications. Endoscopy is performed only after the patient is appropriately resuscitated to safely identify and treat the bleeding source.

Step-by-Step Solution

Prioritize Circulation (ABCs)

Placement of large-bore IVs and administration of fluids.

Prevention of cardiovascular collapse is the most urgent need in a hypotensive, bleeding patient.

Initiate directed medical therapy for suspected variceal hemorrhage

Administration of octreotide and antibiotics.

Octreotide causes splanchnic vasoconstriction to slow bleeding, while prophylactic antibiotics significantly reduce mortality and rebleeding rates in cirrhotic patients.

Proceed to definitive management

Perform esophagogastroduodenoscopy.

Once stabilized, endoscopy allows for visual identification of the bleeding source and therapeutic intervention such as variceal band ligation.

Key Concept

Sequential management of acute variceal hemorrhage focuses on initial hemodynamic resuscitation, followed by medical therapy (vasoactive agents and antibiotics), and lastly endoscopic intervention.

Question 1365Question →

A 69-year-old man is evaluated in the observation unit due to two days of worsening breathlessness, orthopnea, and a persistent cough producing pink-tinged sputum. His medical history includes long-standing essential hypertension, a myocardial infarction five years ago, and a 45 pack-year smoking history. Current medications include aspirin, lisinopril, and atorvastatin.

Vital signs are temperature 37.1°C (98.8°F), blood pressure 162/94 mm Hg, pulse 108/min, and respirations 24/min. Pulse oximetry displays 88% on room air.

Physical examination reveals a patient in moderate respiratory distress using accessory muscles of respiration. Auscultation of the lungs demonstrates a prolonged expiratory phase with high-pitched wheezes in all lung fields, accompanied by fine bibasilar crackles. Cardiac auscultation identifies a laterally displaced point of maximal impulse and a low-frequency diastolic sound immediately following S2. There is 2+ pitting edema extending to the mid-calves bilaterally.

An arterial blood gas analysis on room air shows:
pH: 7.50
PaCO2: 28 mm Hg
PaO2: 58 mm Hg
HCO3-: 21 mEq/L

Which of the following interventions is the most appropriate initial treatment for this patient's underlying condition?

Intravenous administration of a loop diuretic

Systemic administration of glucocorticoids

Empiric therapy with a broad-spectrum fluoroquinolone

Inhaled administration of a short-acting anticholinergic agent

Continuous infusion of isotonic sodium bicarbonate

Show answer & explanation

Answer: Intravenous administration of a loop diuretic

Answer

The most appropriate initial treatment is the intravenous administration of a loop diuretic to reduce preload and relieve pulmonary edema caused by acute decompensated heart failure.

The correct intervention is the intravenous administration of a loop diuretic. This patient's presentation of orthopnea, pink-tinged frothy sputum, bibasilar crackles, a laterally displaced point of maximal impulse (indicating cardiomegaly), and an S3 gallop (indicating rapid ventricular filling into a non-compliant or volume-overloaded ventricle) is highly specific for acute decompensated heart failure (ADHF) with pulmonary edema. Initial management of ADHF primarily involves reducing cardiac preload and optimizing volume status, which is rapidly achieved with intravenous loop diuretics (e.g., furosemide, bumetanide, torsemide).

Step-by-Step Solution

Analyze the patient's history and physical examination findings.

The patient has orthopnea, pink-tinged sputum, an S3 gallop (low-frequency diastolic sound after S2), laterally displaced PMI, bibasilar crackles, and peripheral edema.

These findings are classic for left ventricular dysfunction leading to acute pulmonary edema and subsequent right-sided volume overload.

Differentiate the cause of wheezing and dyspnea using the arterial blood gas and cardiac exam.

Despite the smoking history and wheezing, the S3 gallop and respiratory alkalosis (pH 7.50, low PaCO2) point to acute decompensated heart failure ('cardiac asthma') rather than a COPD exacerbation, which would typically present with a respiratory acidosis.

Hypoxia from pulmonary edema triggers hyperventilation, lowering PaCO2 and increasing pH in the early stages of ADHF.

Select the appropriate initial pharmacologic intervention.

Intravenous loop diuretics are chosen as the first-line therapy.

Loop diuretics rapidly decrease fluid volume and cause venodilation, significantly reducing cardiac preload and resolving the hydrostatic pulmonary edema.

Key Concept

Acute decompensated heart failure often presents with wheezing ('cardiac asthma') that must be distinguished from COPD exacerbations using cardiac exam findings (S3 gallop, displaced PMI) and blood gas analysis (respiratory alkalosis vs acidosis) to ensure appropriate treatment with diuretics rather than bronchodilators/steroids.

Question 1366Question →

Paramedics transport a 30-year-old woman, gravida 2, para 1, at 34 weeks gestation to the emergency department for severe, acute-onset difficulty breathing. She has a history of moderate persistent asthma but stopped her inhaled medications weeks ago due to concerns about fetal safety. Over the past 90 minutes in the emergency department, she has been treated with continuous nebulized albuterol and ipratropium, as well as intravenous methylprednisolone. Despite these measures, her work of breathing remains highly labored. Vital signs are temperature $37.0^\circ C$ ( $98.6^\circ F$ ), blood pressure $128/78$ mm Hg, pulse $126$ /min, and respirations $32$ /min. Pulse oximetry is $91\%$ on a non-rebreather mask. Physical examination reveals a lethargic patient sitting in a tripod position, using accessory muscles of respiration. Auscultation shows notably decreased breath sounds bilaterally with only faint expiratory wheezes. There is no jugular venous distention or lower extremity edema. An arterial blood gas analysis on the current oxygen setting shows:

pH: $7.33$
$PaCO_2$ : $46$ mm Hg
$PaO_2$ : $64$ mm Hg
$HCO_3^-$ : $24$ mEq/L

Continuous fetal heart rate monitoring demonstrates a baseline of 150/min with minimal variability and recurrent late decelerations. Which of the following is the most appropriate next step in management?

Endotracheal intubation and mechanical ventilation

Initiation of a continuous bumetanide infusion

Infusion of sodium bicarbonate

Initiation of empiric piperacillin-tazobactam

Immediate cesarean delivery

Show answer & explanation

Answer: Endotracheal intubation and mechanical ventilation

Answer

Endotracheal intubation and mechanical ventilation

The correct intervention is endotracheal intubation and mechanical ventilation. This patient is in status asthmaticus and exhibiting classic signs of impending respiratory failure: she is lethargic, her wheezing has ceased due to critically low airflow ('silent chest'), and she is retaining carbon dioxide. In normal pregnancy, physiologic progesterone-driven hyperventilation creates a chronic respiratory alkalosis with a baseline

PaCO_2

of approximately 28 to 32 mm Hg. Therefore, a

PaCO_2

of 46 mm Hg in a pregnant woman represents severe, life-threatening hypercapnia. The recurrent late fetal decelerations are a direct consequence of maternal hypoxia and respiratory acidosis causing uteroplacental insufficiency. The most critical step in intrauterine resuscitation is definitive airway management to stabilize the mother.

Step-by-Step Solution

Interpret the clinical presentation and physical exam.

The patient has a severe asthma exacerbation with lethargy, accessory muscle use, and a 'silent chest'.

These findings are clinical markers of severe respiratory muscle fatigue and impending respiratory arrest.

Analyze the arterial blood gas (ABG) values in the context of pregnancy.

The pH is acidemic (7.33) with an elevated

PaCO_2

(46 mm Hg).

In normal pregnancy, physiologic hyperventilation lowers baseline

PaCO_2

to roughly 28-32 mm Hg. A

PaCO_2

of 46 mm Hg indicates severe carbon dioxide retention and complete failure of compensatory mechanisms.

Interpret the fetal heart rate tracing.

Recurrent late decelerations are present, indicating fetal hypoxia.

Maternal respiratory failure and resulting hypoxemia directly lead to uteroplacental insufficiency.

Determine the next best step in management.

Proceed with immediate maternal endotracheal intubation.

Maternal stabilization via definitive airway management (intrauterine resuscitation) must precede any obstetric intervention to improve both maternal and fetal outcomes.

Key Concept

Impending respiratory failure in severe asthma is indicated by an altered sensorium, silent chest, and a normal or elevated PaCO2, requiring immediate endotracheal intubation.

Estimated Time:1m 30s

Question 1367Question →

A $71$ -year-old man is evaluated in the intensive care unit for worsening shortness of breath and increasing somnolence. He was admitted $2$ days ago for an acute exacerbation of chronic obstructive pulmonary disease (COPD) and suspected pneumonia. His admission medications include intravenous piperacillin-tazobactam, vancomycin, methylprednisolone, and scheduled albuterol-ipratropium nebulizers. Medical history is significant for severe COPD (FEV $_1$ $45\%$ of predicted), ischemic cardiomyopathy (left ventricular ejection fraction $30\%$ ), and stage $3$ chronic kidney disease.

Temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), pulse is $112\text{/min}$ , blood pressure is $160/90\text{ mm Hg}$ , and respirations are $28\text{/min}$ . Oxygen saturation is $86\%$ on a $4\text{ L/min}$ nasal cannula. Physical examination reveals a lethargic but arousable patient in respiratory distress. Jugular venous pressure is estimated at $11\text{ cm H}_2\text{O}$ . Lung auscultation reveals bilateral basilar crackles and diffuse expiratory wheezes. Cardiac examination shows a regular, rapid rhythm with a prominent S $_3$ gallop. There is $2+$ bilateral pitting edema extending to the knees.

Laboratory results are as follows:

Test	Result
Leukocyte count	$11,000/\text{mm}^3$
$\text{Na}^+$	$136\text{ mEq/L}$
$\text{K}^+$	$4.2\text{ mEq/L}$
$\text{Cl}^-$	$102\text{ mEq/L}$
$\text{HCO}_3^-$	$15\text{ mEq/L}$
Blood urea nitrogen	$48\text{ mg/dL}$
Creatinine	$2.3\text{ mg/dL}$ (baseline $1.6$ )

An arterial blood gas on the current oxygen setting shows:
pH: $7.26$
PaO $_2$ : $56\text{ mm Hg}$
PaCO $_2$ : $36\text{ mm Hg}$
$\text{HCO}_3^-$ : $15\text{ mEq/L}$

A sputum culture obtained on admission has returned positive for Streptococcus pneumoniae that is susceptible to ceftriaxone, azithromycin, and levofloxacin.

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

Initiate noninvasive positive-pressure ventilation and intravenous furosemide

Administer intravenous sodium bicarbonate

Escalate systemic glucocorticoids and administer continuous nebulized bronchodilators

Continue empiric intravenous piperacillin-tazobactam and vancomycin

Administer a

1

-Liter intravenous normal saline bolus

Show answer & explanation

Answer: Initiate noninvasive positive-pressure ventilation and intravenous furosemide

Answer

Initiate noninvasive positive-pressure ventilation and intravenous furosemide

The correct action is to initiate noninvasive positive-pressure ventilation (NIPPV) and intravenous furosemide. This patient is experiencing acute decompensated heart failure (ADHF), evidenced by an S3 gallop, elevated jugular venous pressure, basilar crackles, and peripheral edema. The diffuse wheezing is secondary to peribronchial edema ('cardiac asthma'). Furthermore, the patient has a severe primary metabolic acidosis (pH

7.26

, HCO

_3^-

15\text{ mEq/L}

). According to Winter's formula (Expected PaCO

_2

1.5 \times \text{HCO}_3^- + 8

), the patient's expected PaCO

_2

30.5 \pm 2\text{ mm Hg}

. The actual PaCO

_2

36\text{ mm Hg}

is higher than the expected range, diagnosing a superimposed respiratory acidosis. This indicates that the patient's respiratory drive is fatiguing and failing to compensate for the metabolic demand. NIPPV is indicated to reduce the work of breathing and improve oxygenation, while furosemide is required to offload the severe hypervolemia.

Step-by-Step Solution

Analyze the physical examination and clinical presentation.

Identifies clear signs of volume overload and left-sided heart failure: orthopnea, elevated jugular venous pressure, S3 gallop, crackles, and peripheral edema.

Differentiates primary acute decompensated heart failure (ADHF) from a pure COPD exacerbation, recognizing that wheezing in this context represents 'cardiac asthma'.

Interpret the arterial blood gas utilizing Winter's formula.

Expected PaCO2 =

1.5 \times 15 + 8 = 30.5 \pm 2\text{ mm Hg}

. The actual PaCO2 of

36\text{ mm Hg}

is significantly higher than expected.

Diagnoses a combined metabolic acidosis and superimposed respiratory acidosis, which signifies respiratory muscle fatigue and impending ventilatory failure.

Determine the most appropriate immediate intervention.

Selects noninvasive positive-pressure ventilation (NIPPV) and intravenous furosemide.

NIPPV provides vital respiratory support to decrease the work of breathing, while furosemide reduces preload to treat the underlying cardiogenic pulmonary edema.

Key Concept

Identifying acute decompensated heart failure presenting as 'cardiac asthma' and utilizing Winter's formula to uncover impending respiratory failure in mixed acid-base disorders.

Question 1368Question →

A 52-year-old male presents to the outpatient clinic reporting a 6-month history of worsening fatigue, decreased libido, and erectile dysfunction. He also notes chronic constipation and feeling unusually sluggish. His medical history is unremarkable, and he takes no medications. Vital signs show a blood pressure of $110/70 \text{ mmHg}$ and a heart rate of $56/\text{min}$ . Physical examination reveals pale, dry skin and a delay in the relaxation phase of the deep tendon reflexes. Visual fields are full to confrontation.

Laboratory results are as follows:

Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	$1.2 \text{ mIU/L}$	$0.5-5.0 \text{ mIU/L}$
Free thyroxine (T4)	$0.5 \text{ ng/dL}$	$0.9-1.7 \text{ ng/dL}$
Total testosterone	$140 \text{ ng/dL}$	$300-1000 \text{ ng/dL}$
Luteinizing hormone (LH)	$1.5 \text{ mIU/mL}$	$1.5-9.3 \text{ mIU/mL}$

Which of the following is the most likely underlying mechanism for this patient's presentation?

Compression of anterior pituitary tissue by a benign sellar mass

Autoimmune lymphocytic infiltration of the thyroid gland

Fibrotic replacement of the testicular interstitium

Activating mutation of the thyrotropin receptor

Target organ resistance to circulating thyroid hormone

Show answer & explanation

Answer: Compression of anterior pituitary tissue by a benign sellar mass

Answer

Compression of anterior pituitary tissue by a benign sellar mass

This patient's laboratory findings reveal concurrent central hypothyroidism (low free T4 with inappropriately normal TSH) and central hypogonadism (low testosterone with inappropriately normal LH). When multiple anterior pituitary axes fail simultaneously, it typically indicates a destructive or compressive lesion in the sella turcica. The most common cause of panhypopituitarism in adults is a nonfunctioning pituitary adenoma, which compresses the normal anterior pituitary tissue and impairs its ability to secrete trophic hormones.

Step-by-Step Solution

Analyze the thyroid laboratory values.

The patient has low free T4 (

0.5 \text{ ng/dL}

) with an inappropriately normal TSH (

1.2 \text{ mIU/L}

This pattern indicates secondary (central) hypothyroidism. In primary hypothyroidism, the normal pituitary would secrete high levels of TSH in response to low T4.

Analyze the gonadal laboratory values.

The patient has low total testosterone (

140 \text{ ng/dL}

) with an inappropriately normal LH (

1.5 \text{ mIU/mL}

This pattern indicates secondary (central) hypogonadism. In primary testicular failure, the LH would be elevated.

Synthesize the laboratory findings to identify the site of pathology.

Deficiencies in multiple anterior pituitary axes (panhypopituitarism) point to a central structural lesion.

The most common cause of acquired combined anterior pituitary hormone deficiencies in an adult male is compression of the glandular tissue by a pituitary adenoma (mass effect).

Key Concept

Central (Secondary) Endocrine Deficiencies

Question 1369Question →

On her sixth day of recovery following an open partial colectomy for recurrent diverticulitis, a 65-year-old woman develops severe, sudden-onset abdominal pain associated with bilious vomiting. Although she had previously tolerated clear liquids and passed flatus on postoperative day 3, she has not passed gas or had a bowel movement in the last 24 hours. Vital signs show a temperature of 38.9°C (102.0°F), blood pressure of 86/54 mm Hg, and heart rate of 122/min. Abdominal examination reveals severe distension, absent bowel sounds, and diffuse rigidity with rebound tenderness. Laboratory evaluation is notable for a leukocyte count of 19,500/mm³ (with 12% band forms) and a serum lactate concentration of 4.8 mmol/L. Upright abdominal radiography displays prominent, dilated loops of small intestine with multiple air-fluid levels. Which of the following is the most appropriate next step in management?

Insertion of a nasogastric tube and intravenous fluid resuscitation

Computed tomography of the abdomen and pelvis with intravenous contrast

Immediate exploratory laparotomy

Blood cultures and initiation of empiric intravenous antifungal therapy

Administration of an intravenous sodium bicarbonate infusion

Show answer & explanation

Answer: Immediate exploratory laparotomy

Answer

Immediate exploratory laparotomy is the correct management for a patient with signs of a strangulated small bowel obstruction.

The correct answer is immediate exploratory laparotomy. This patient presents with a classic picture of a strangulated small bowel obstruction (SBO), characterized by bowel dilation with air-fluid levels, absence of flatus, and severe clinical deterioration. The presence of fever, tachycardia, hypotension, severe abdominal rigidity (peritonitis), leukocytosis with a left shift, and lactic acidosis all point to ischemic or necrotic bowel. When signs of strangulation or peritonitis are present, or when the patient is hemodynamically unstable, immediate surgical intervention is mandated. Delaying surgery for further imaging or attempting conservative management greatly increases mortality.

Step-by-Step Solution

Identify the primary diagnosis from the clinical presentation and radiographic findings.

The patient has a small bowel obstruction, indicated by vomiting, inability to pass flatus, and dilated small bowel loops with air-fluid levels on X-ray.

Recognizing the underlying pathology is necessary before determining the treatment algorithm.

Assess for signs of complications, specifically bowel ischemia or peritonitis.

The patient has fever, hypotension, tachycardia, abdominal rigidity, rebound tenderness, leukocytosis, and elevated lactate.

The presence of these 'red flag' symptoms shifts the management from conservative to emergent surgical intervention.

Determine the most appropriate next step in management based on patient stability.

Immediate exploratory laparotomy is selected.

Hemodynamically unstable patients with an acute surgical abdomen require immediate operative intervention without delay for further imaging.

Key Concept

Management of complicated small bowel obstruction

Question 1370Question →

An inpatient medical emergency team is activated for a 68-year-old male who develops abrupt-onset respiratory distress and profound agitation. He was admitted four days prior for an inferior ST-elevation myocardial infarction but declined coronary angiography. He has a 45-pack-year smoking history.

Upon arrival, the patient is diaphoretic with cool, mottled extremities. Vital signs show a temperature of 37.1°C (98.8°F), blood pressure of 76/46 mm Hg, heart rate of 128/min, and respiratory rate of 32/min. Pulse oximetry is 84% on room air. Jugular venous pulsation is estimated at $12 \text{ cm H}_2\text{O}$ .

Pulmonary examination reveals diffuse expiratory wheezes and prominent bibasilar crackles. Cardiac auscultation reveals a regular, rapid rhythm with a soft, early-to-mid systolic murmur heard best at the apex. No thrill is palpated.

Laboratory evaluation reveals a leukocyte count of $14,500/\text{mm}^3$ and a serum lactate of $5.2 \text{ mmol/L}$ . An arterial blood gas shows a pH of 7.24, $\text{PaCO}_2$ of 58 mm Hg, and $\text{PaO}_2$ of 52 mm Hg.

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

Perform bedside echocardiography and obtain an emergent cardiothoracic surgery consultation

Administer systemic corticosteroids and inhaled bronchodilators

Transport the patient to radiology for a computed tomography angiography of the chest

Initiate empiric intravenous broad-spectrum antibiotics and a rapid fluid bolus

Administer an intravenous sodium bicarbonate infusion to correct the acidemia

Show answer & explanation

Answer: Perform bedside echocardiography and obtain an emergent cardiothoracic surgery consultation

Answer

Perform bedside echocardiography and obtain an emergent cardiothoracic surgery consultation

The correct action is to perform bedside echocardiography and urgently consult cardiothoracic surgery. This patient is presenting with acute cardiogenic shock and florid pulmonary edema four days after an inferior STEMI, which is the classic presentation for posteromedial papillary muscle rupture. The resulting acute severe mitral regurgitation pushes massive volume into a normal-sized, non-compliant left atrium. The rapid rise in left atrial pressure during systole quickly equalizes with left ventricular pressure, causing the murmur to be deceptively soft and isolated to early-to-mid systole. Bedside echocardiography rapidly confirms the diagnosis without moving an unstable patient, and surgical intervention is the only definitive treatment.

Step-by-Step Solution

Analyze the patient's hemodynamic status and timeline.

The patient is in cardiogenic shock (hypotension, lactic acidosis, cool extremities) on day 4 following a medically managed inferior STEMI.

Days 3 to 5 post-MI represent the peak risk window for catastrophic mechanical complications, such as ventricular septal rupture, free wall rupture, or papillary muscle rupture.

Interpret the physical examination findings.

Diffuse wheezing and crackles indicate acute pulmonary edema. The soft, early-to-mid systolic apical murmur points to acute mitral regurgitation.

Posteromedial papillary muscle rupture commonly follows inferior MI (supplied solely by the RCA/PDA). In acute severe MR, the murmur is often soft and early systolic, NOT holosystolic, because rapid pressure equalization between the LV and the non-compliant LA terminates the pressure gradient early in systole.

Determine the next best diagnostic and therapeutic steps.

Bedside transthoracic echocardiography is required immediately to confirm the mechanical complication, accompanied by emergent surgical consultation.

Definitive management requires surgical valve repair or replacement; medical stabilization (e.g., intra-aortic balloon pump) serves only as a bridge.

Key Concept

Acute papillary muscle rupture classically presents 3-5 days after an inferior STEMI with cardiogenic shock, pulmonary edema (which may manifest with wheezing, or 'cardiac asthma'), and a deceptively soft, early systolic apical murmur due to rapid LA-LV pressure equalization.

Estimated Time:2m 0s

Question 1371Question →

A 72-year-old man is admitted to the hospital due to fatigue, dark stools, and symptomatic anemia. His medical history includes hypertension and chronic kidney disease. Laboratory studies on admission show a hemoglobin level of $6.2 \text{ g/dL}$ . A transfusion of packed red blood cells is initiated. One hour into the transfusion, the patient reports the sudden onset of shortness of breath and a dry cough. The transfusion is immediately stopped. Temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure is $172/96 \text{ mm Hg}$ , pulse is $112/\text{min}$ , and respirations are $24/\text{min}$ . Pulse oximetry shows an oxygen saturation of $89\%$ on room air. Physical examination reveals elevated jugular venous pressure. Pulmonary auscultation reveals bilateral basilar crackles. Cardiac auscultation reveals an S3 gallop. There is no rash, wheezing, or stridor. Which of the following is the most appropriate next step in management?

Administer intravenous furosemide

Analyze donor plasma for anti-leukocyte antibodies

Administer intravenous diphenhydramine and hydrocortisone

Obtain blood cultures and administer broad-spectrum antibiotics

Administer oral acetaminophen and resume the transfusion at a slower rate

Show answer & explanation

Answer: Administer intravenous furosemide

Answer

Administer intravenous furosemide

The correct next step is to administer intravenous furosemide. This patient is experiencing Transfusion-Associated Circulatory Overload (TACO). TACO occurs when a blood product is transfused rapidly or in a large volume, leading to volume overload and cardiogenic pulmonary edema. It is characterized by acute dyspnea, hypoxia, hypertension, tachycardia, and physical exam findings of fluid overload, such as elevated jugular venous pressure (JVP), an S3 gallop, and bilateral basilar lung crackles. The first step in management is always to stop the transfusion. Subsequent management involves respiratory support (oxygen, positive pressure ventilation if necessary) and aggressive diuresis with loop diuretics (e.g., intravenous furosemide) to reduce intravascular volume.

Step-by-Step Solution

Analyze the patient's symptoms and vital signs that developed during the blood transfusion.

The patient developed acute dyspnea, hypoxia, hypertension (

172/96 \text{ mm Hg}

), elevated jugular venous pressure, basilar crackles, and an S3 gallop.

Identifying the specific symptom cluster and hemodynamic status is necessary to differentiate between the various types of acute transfusion reactions.

Differentiate between Transfusion-Associated Circulatory Overload (TACO) and Transfusion-Related Acute Lung Injury (TRALI).

The presence of hypertension, elevated JVP, and an S3 gallop strongly points to cardiogenic pulmonary edema due to volume overload (TACO), rather than noncardiogenic pulmonary edema (TRALI), which would typically present with hypotension.

Both TACO and TRALI cause respiratory distress during or shortly after transfusion, but their pathophysiology and definitive management differ completely.

Determine the most appropriate management for TACO.

Management includes stopping the transfusion, providing supplemental oxygen, and administering loop diuretics like intravenous furosemide.

Loop diuretics rapidly reduce intravascular volume, alleviating the hydrostatic pressure that causes cardiogenic pulmonary edema.

Key Concept

Transfusion-associated circulatory overload (TACO) presents with respiratory distress, hypertension, and signs of volume overload (elevated JVP, S3 gallop, crackles) during or within 6 hours of a blood transfusion. Management includes respiratory support and diuresis.

Question 1372Question →

A 74-year-old man is evaluated on postoperative day 3 following an elective open inguinal hernia repair due to new-onset right knee pain and swelling. The pain began overnight and has become so severe that he cannot bear weight on his right leg. His medical history is significant for hypertension, chronic kidney disease stage 3b (baseline creatinine $2.1$ mg/dL), and a history of a bleeding gastric ulcer $2$ years ago. His temperature is $38.1$ °C ( $100.6$ °F), blood pressure is $142/86$ mm Hg, and pulse is $98$ /min. Physical examination of the right knee reveals marked effusion, erythema, and warmth. The joint is exquisitely tender to palpation, and range of motion is severely limited by pain. Arthrocentesis is performed, yielding $15$ mL of cloudy yellow fluid. Synovial fluid analysis shows a leukocyte count of $32,000/\mu L$ with $85\%$ neutrophils. Polarized light microscopy reveals numerous rhomboid-shaped crystals that exhibit weak positive birefringence. Gram stain shows no organisms. Which of the following is the most appropriate next step in management?

Intra-articular triamcinolone injection

Intravenous vancomycin and ceftriaxone

Arthroscopic joint irrigation and debridement

Initiation of oral allopurinol

Administration of oral indomethacin

Show answer & explanation

Answer: Intra-articular triamcinolone injection

Answer

Intra-articular triamcinolone injection

The correct step is to perform an intra-articular glucocorticoid injection. This patient is experiencing an acute flare of calcium pyrophosphate deposition (CPPD) disease, commonly known as pseudogout. This condition frequently manifests in the setting of physical stress, such as acute medical illness or surgery (e.g., postoperative day 3). The diagnosis is confirmed by the presence of rhomboid-shaped, weakly positively birefringent crystals in the synovial fluid. Standard first-line therapies for acute pseudogout flares include NSAIDs, oral colchicine, or intra-articular glucocorticoids. However, this patient's chronic kidney disease (CKD stage 3b) and history of a bleeding gastric ulcer are strong contraindications to NSAIDs. Additionally, colchicine must be used with extreme caution or avoided in advanced CKD due to the risk of severe neuromyotoxicity and bone marrow suppression. For monoarticular involvement in a patient with these comorbidities, intra-articular glucocorticoid injection (e.g., triamcinolone) is the safest and most effective therapy.

Step-by-Step Solution

Evaluate the clinical presentation and synovial fluid analysis.

The synovial fluid shows rhomboid-shaped, weakly positively birefringent crystals and a leukocyte count of

32,000/\mu L

This establishes a definitive diagnosis of acute calcium pyrophosphate dihydrate (CPPD) crystal arthritis (pseudogout) and makes septic arthritis highly unlikely.

Review the patient's medical history for contraindications to standard therapies.

The patient has chronic kidney disease stage 3b and a history of a bleeding gastric ulcer.

These comorbidities represent absolute or strong relative contraindications to nonsteroidal anti-inflammatory drugs (NSAIDs) and systemic colchicine.

Select the most appropriate, safe intervention for an acute monoarticular flare.

Intra-articular triamcinolone injection is chosen.

Intra-articular glucocorticoids provide rapid local relief without the systemic risks associated with NSAIDs, colchicine, or oral corticosteroids in this high-risk patient.

Key Concept

Management of acute calcium pyrophosphate deposition (CPPD) disease (pseudogout) in a patient with contraindications to NSAIDs and colchicine.

Estimated Time:1m 0s

Question 1373Question →

Match each patient scheduled for an elective surgical or endoscopic procedure with the most appropriate perioperative medication management strategy.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct matches align each patient's specific preoperative risk profile (thromboembolic, bleeding, infectious, and metabolic) with the appropriate medication modification: low-risk mechanical valves do not require bridging; DOACs are held without bridging; biologic DMARDs are held while methotrexate is continued; and SGLT2 inhibitors are held 3-4 days preoperatively while basal insulin is reduced.

Each management strategy is supported by current clinical guidelines aimed at minimizing both surgical complications (bleeding, infection) and exacerbations of the patient's underlying chronic conditions.

Step-by-Step Solution

Evaluate the thromboembolic risk for the patient with a mechanical aortic valve to determine the need for bridging anticoagulation.

The patient is determined to be at low thromboembolic risk.

Bridging anticoagulation is not indicated for low-risk patients, so warfarin is simply stopped 5 days prior to surgery.

Assess the pharmacokinetics and bridging requirements for apixaban in a patient with atrial fibrillation.

Apixaban is held 48-72 hours prior to the procedure.

DOACs have rapid offset and short half-lives; bridging with heparin increases bleeding risk without any proven benefit and is contraindicated.

Differentiate the perioperative management of biologic versus non-biologic DMARDs.

Infliximab is withheld, while methotrexate is continued.

Biologics significantly increase postoperative infection risk and must be held. Conversely, holding methotrexate increases the risk of debilitating RA flares without significantly altering infection risk.

Formulate a fasting management plan for a patient's diabetes medications.

Empagliflozin is held 3-4 days prior, and glargine insulin is administered at a reduced dose.

SGLT2 inhibitors can cause perioperative euglycemic DKA. Basal insulin prevents DKA and severe hyperglycemia but must be reduced to avoid fasting hypoglycemia on the morning of surgery.

Key Concept

Perioperative medication management requires balancing the risks of disease exacerbation (e.g., thrombosis, RA flare, DKA) against surgical complications (e.g., bleeding, infection, hypoglycemia).

Estimated Time:2m 0s

Question 1374Question →

Match each clinical and laboratory presentation with the most likely underlying pathophysiologic mechanism.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct matches are: the patient with nephrolithiasis and alkaline urine corresponds to impaired alpha-intercalated cell hydrogen ion secretion; the diabetic patient with hyperkalemia corresponds to aldosterone deficiency or resistance; the normotensive patient with hypocalciuria corresponds to a defect in the distal convoluted tubule sodium-chloride cotransporter; and the hypertensive patient with low renin/aldosterone corresponds to constitutive activation of the collecting duct epithelial sodium channel.

Each presentation aligns with a distinct tubular defect. Distal H+ secretion failure causes Type 1 RTA. Aldosterone deficiency causes Type 4 RTA. Na-Cl cotransporter defects cause Gitelman syndrome. ENaC overactivity causes Liddle syndrome.

Step-by-Step Solution

Analyze the acid-base and potassium status for each patient to categorize the broad pathophysiologic mechanism.

Two patients have metabolic acidosis with differing potassium levels (one low, one high), and two have metabolic alkalosis with hypokalemia.

Acid-base and potassium abnormalities act as the primary branching points for diagnosing renal tubular defects.

Differentiate the two patients with metabolic acidosis.

The hypokalemic patient with alkaline urine and kidney stones has distal (Type 1) RTA, caused by impaired H+ secretion. The hyperkalemic patient with acidic urine has Type 4 RTA, caused by aldosterone deficiency/resistance.

Urine pH and serum potassium are essential keys to distinguishing subtypes of normal anion gap metabolic acidosis.

Differentiate the two patients with metabolic alkalosis.

The normotensive patient with hypocalciuria has Gitelman syndrome (Na-Cl cotransporter defect). The severely hypertensive patient with suppressed renin and aldosterone has Liddle syndrome (ENaC overactivity).

Blood pressure and urine calcium levels distinguish between different causes of hypokalemic metabolic alkalosis.

Key Concept

Pathophysiology and clinical differentiation of renal tubular acidosis (RTA) and hereditary tubulopathies.

Question 1375Question →

A 28-year-old man with a history of intravenous drug use presents to the emergency department with a 2-day history of high fever, chills, and severe fatigue. Temperature is 39.4°C (102.9°F), blood pressure is 105/65 mm Hg, and pulse is 118/min. Physical examination reveals a new holosystolic murmur at the left lower sternal border and pinpoint petechiae on the conjunctivae. Arrange the following management steps in the most appropriate sequential order for this patient.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence of management for acute infective endocarditis is to first obtain multiple blood cultures, then initiate empiric broad-spectrum antibiotics, followed by an echocardiogram, and finally narrow the antibiotic therapy based on culture results.

The correct sequence prioritizes microbiologic diagnosis by drawing blood cultures first, followed immediately by empiric antibiotics to treat the severe infection. Echocardiography is then performed for definitive diagnosis, and finally, therapy is narrowed based on culture results to adhere to antimicrobial stewardship principles.

Step-by-Step Solution

Recognize the clinical presentation of acute infective endocarditis.

The patient has a high fever, new murmur, peripheral stigmata (petechiae), and a history of intravenous drug use, highly suggestive of acute right-sided infective endocarditis.

Establishing the presumptive diagnosis dictates the urgency and sequence of the subsequent interventions.

Determine the first priority in a potentially bacteremic patient.

Blood cultures must be drawn.

Drawing cultures before giving antibiotics is essential to prevent sterile cultures, which would severely complicate definitive, targeted therapy later.

Determine the next immediate step after drawing cultures.

Start empiric broad-spectrum antibiotics.

The patient is acutely ill; delaying antibiotics for imaging can lead to rapid clinical deterioration and increased mortality.

Select the appropriate diagnostic imaging modality.

Perform a transthoracic echocardiogram (TTE).

TTE is the initial imaging modality of choice to visualize vegetations and assess valvular function, completing the diagnostic workup.

Determine the final step in the therapeutic pathway.

Narrow the antibiotic therapy.

Once the organism is identified and susceptibilities are known, transitioning to narrow-spectrum therapy improves efficacy, reduces toxicity, and prevents antimicrobial resistance.

Key Concept

In patients with acute, severe suspected infective endocarditis, blood cultures must be drawn prior to the immediate initiation of empiric antibiotics, followed by echocardiography and subsequent tailoring of antibiotics once sensitivities are available.

Estimated Time:1m 0s

Question 1376Question →

A 78-year-old woman is evaluated in a skilled nursing facility for abnormal urine characteristics. She was transferred to the facility two weeks ago for rehabilitation following an ischemic stroke. She has a chronic indwelling urethral catheter due to persistent neurogenic bladder. Today, the nursing staff noticed her urine is cloudy and has a strongly offensive odor. The patient is alert, conversant, and oriented to person and place, which represents her baseline cognitive status since the stroke. She denies suprapubic pain, flank pain, nausea, or chills. Her temperature is 37.0°C (98.6°F), blood pressure is 128/78 mm Hg, pulse is 76/min, and respirations are 14/min. Physical examination reveals a soft, non-tender abdomen and no costovertebral angle tenderness. Urinalysis shows a pH of 7.5, positive leukocyte esterase, positive nitrites, and >100 WBCs/hpf. A urine culture grows >10^5 CFU/mL of Proteus mirabilis that is sensitive to amoxicillin, ciprofloxacin, ceftriaxone, and trimethoprim-sulfamethoxazole. Which of the following is the most appropriate next step in management?

Oral amoxicillin

Observation without antibiotic therapy

Oral ciprofloxacin

Intravenous ceftriaxone

Daily prophylactic trimethoprim-sulfamethoxazole

Show answer & explanation

Answer: Observation without antibiotic therapy

Answer

Observation without antibiotic therapy

The correct approach is observation without antibiotic therapy. This patient has asymptomatic bacteriuria (ASB), which is defined as the presence of bacteria in the urine without signs or symptoms of a urinary tract infection. In patients with chronic indwelling urinary catheters, colonization of the bladder and the development of a catheter biofilm are universal and inevitable within weeks of placement. Clinical manifestations such as cloudy, foul-smelling urine, as well as the presence of pyuria (white blood cells) and positive leukocyte esterase on urinalysis, are expected baseline findings in these patients and do NOT independently indicate a symptomatic tissue infection. Because the patient is at her baseline mental status and lacks systemic symptoms (e.g., fever, chills, hemodynamic instability) or localizing signs (e.g., flank pain, suprapubic tenderness), antibiotic therapy is strictly contraindicated. Treating ASB in this population does not decrease the incidence of future symptomatic UTIs or improve mortality. Instead, it actively contributes to the development of multidrug-resistant organisms and exposes the patient to adverse drug effects, including Clostridioides difficile infection.

Step-by-Step Solution

Analyze the patient's symptoms and vital signs in the context of her chronic catheter.

The patient is afebrile, hemodynamically stable, at her neurological baseline, and lacks any localizing signs of infection (e.g., flank pain, suprapubic tenderness).

Distinguishing between asymptomatic bacteriuria (ASB) and a symptomatic urinary tract infection (UTI) relies entirely on clinical presentation, not laboratory values.

Evaluate the urinalysis and culture findings.

There is pyuria, malodorous urine, and >10^5 CFU/mL of bacteria, which are expected, inevitable findings due to chronic colonization of the bladder and catheter biofilm.

In chronically catheterized patients, cloudy, foul-smelling urine and pyuria do not independently diagnose an active infection and should not prompt treatment.

Determine the most appropriate management strategy based on infectious disease guidelines.

Observation without antibiotic therapy is indicated.

Treating ASB provides no clinical benefit, fails to permanently eradicate the bacteriuria, and actively increases the risk of multidrug-resistant organisms and Clostridioides difficile infection.

Key Concept

Asymptomatic bacteriuria (ASB) is universal in patients with chronic indwelling catheters and should not be treated with antibiotics, regardless of pyuria, malodorous urine, or positive cultures, unless systemic or localizing signs of infection are present.

Question 1377Question →

A 32-year-old woman is brought to the clinic by her husband due to profound fatigue, lightheadedness, and a $4\text{-kg}$ ( $8.8\text{-lb}$ ) weight loss over the past 3 months. She also reports amenorrhea since the birth of her second child 14 months ago. Her delivery was complicated by severe postpartum hemorrhage requiring emergency blood transfusions and an intensive care unit admission. Following the delivery, she was unable to produce milk to breastfeed her infant. Vital signs show a blood pressure of $88/56\text{ mm Hg}$ and a heart rate of $92\text{/min}$ . Physical examination reveals delayed relaxation of deep tendon reflexes and a complete absence of pubic and axillary hair. Laboratory results are as follows:

Thyroid-stimulating hormone (TSH): $1.2\text{ \mu U/mL}$ (Normal: $0.5 - 5.0\text{ \mu U/mL}$ )
Free thyroxine (T4): $0.4\text{ ng/dL}$ (Normal: $0.9 - 1.7\text{ ng/dL}$ )
Prolactin: $2\text{ ng/mL}$ (Normal: $4 - 23\text{ ng/mL}$ )

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

Initiate levothyroxine therapy

Measure serum thyroid peroxidase antibodies

Magnetic resonance imaging of the brain

Measure 8 AM serum cortisol level

Initiate fludrocortisone therapy

Show answer & explanation

Answer: Measure 8 AM serum cortisol level

Answer

The most appropriate next step is to measure the 8 AM serum cortisol level.

The correct action is to measure the 8 AM serum cortisol level. This patient's history of postpartum hemorrhage followed by agalactia, amenorrhea, and loss of pubic hair is highly characteristic of Sheehan syndrome (ischemic necrosis of the pituitary). Her laboratory tests confirm central hypothyroidism (low free T4 with inappropriately normal TSH). In any patient with suspected hypopituitarism, it is an absolute rule to evaluate and treat the adrenal axis (ACTH/cortisol deficiency) before initiating thyroid hormone replacement. Levothyroxine increases basal metabolic rate and hepatic clearance of cortisol; administering it to a patient with untreated adrenal insufficiency can precipitate a lethal acute adrenal crisis.

Step-by-Step Solution

Analyze the patient's history and symptoms.

The patient has a history of severe postpartum hemorrhage followed by failure to lactate, amenorrhea, profound fatigue, and loss of pubic hair.

These findings are classic for Sheehan syndrome (postpartum ischemic necrosis of the anterior pituitary gland).

Interpret the laboratory findings.

A low free T4 with an inappropriately normal TSH indicates central (secondary) hypothyroidism. The low prolactin confirms anterior pituitary failure.

In primary hypothyroidism, TSH would be significantly elevated. The normal TSH here confirms a central defect.

Determine the necessary management sequence for panhypopituitarism.

The patient likely has concurrent central adrenal insufficiency (ACTH deficiency), which is a life-threatening condition.

Thyroid hormone replacement increases the basal metabolic rate and enhances the hepatic clearance of cortisol. If levothyroxine is given before ensuring adequate cortisol levels, it can precipitate an acute adrenal crisis.

Select the most appropriate immediate intervention.

Measure the 8 AM serum cortisol level to evaluate the adrenal axis.

Biochemical confirmation of the adrenal axis must be completed (and glucocorticoids initiated if low) before starting levothyroxine.

Key Concept

In patients with panhypopituitarism (e.g., Sheehan syndrome), evaluation and treatment of the adrenal axis (glucocorticoids) must always precede thyroid hormone replacement to avoid precipitating an acute adrenal crisis.

Estimated Time:1m 30s

Question 1378Question →

A 19-year-old college student is brought to the emergency department by her roommate due to agitation, nausea, and ringing in her ears for the past several hours. The roommate states she found several empty bottles of over-the-counter pain relievers on the patient's desk. The patient is breathing rapidly.

Her temperature is $38.1^\circ\text{C}$ ( $100.6^\circ\text{F}$ ), blood pressure is $112/70$ mm Hg, pulse is $118$ /min, and respirations are $28$ /min. Physical examination shows a diaphoretic, anxious young woman. Her lungs are clear to auscultation.

Laboratory studies show:

Laboratory Test	Result
Serum sodium	$142$ mEq/L
Serum potassium	$3.8$ mEq/L
Serum chloride	$105$ mEq/L
Serum bicarbonate	$14$ mEq/L
Arterial pH	$7.42$
Arterial PaO $_2$	$98$ mm Hg
Arterial PaCO $_2$	$21$ mm Hg

Which of the following best characterizes this patient's current acid-base disturbance?

Mixed increased anion gap metabolic acidosis and primary respiratory alkalosis

Primary increased anion gap metabolic acidosis with adequate respiratory compensation

Primary respiratory alkalosis with adequate metabolic compensation

Mixed increased anion gap metabolic acidosis and primary metabolic alkalosis

Primary non-anion gap metabolic acidosis with adequate respiratory compensation

Show answer & explanation

Answer: Mixed increased anion gap metabolic acidosis and primary respiratory alkalosis

Answer

Mixed increased anion gap metabolic acidosis and primary respiratory alkalosis

The patient's laboratory results demonstrate an elevated anion gap of

23

mEq/L (

142 - (105 + 14)

), which confirms the presence of a primary increased anion gap metabolic acidosis. By applying Winter's formula (

1.5 \times [HCO_3^-] + 8 \pm 2

), the expected PaCO

_2

for maximal respiratory compensation is

29 \pm 2

mm Hg. The patient's actual PaCO

_2

21

mm Hg. Because the measured PaCO

_2

is lower than the expected compensatory value, there is a concurrent primary respiratory alkalosis. This mixed acid-base disorder is the classic presentation of salicylate (aspirin) toxicity, which both directly stimulates the medullary respiratory center (causing respiratory alkalosis) and uncouples oxidative phosphorylation (causing an accumulation of organic acids and a subsequent metabolic acidosis).

Step-by-Step Solution

Calculate the anion gap to check for the presence of a metabolic acidosis.

Anion Gap =

Na^+ - (Cl^- + HCO_3^-)

142 - (105 + 14) = 23

mEq/L.

An elevated anion gap (

>12

mEq/L) definitively establishes the presence of an increased anion gap metabolic acidosis, regardless of the overall pH.

Calculate the expected respiratory compensation using Winter's formula.

Expected PaCO

_2

1.5 \times 14 + 8 = 29 \pm 2

mm Hg.

This determines if the respiratory response is appropriate or if there is a superimposed primary respiratory disorder.

Compare the expected PaCO

_2

to the measured PaCO

_2

The measured PaCO

_2

(

21

mm Hg) is significantly lower than the expected range (

27-31

mm Hg).

A measured PaCO

_2

that is lower than expected indicates an additional primary respiratory alkalosis.

Calculate the delta gap to rule out a third acid-base disorder.

Delta AG =

23 - 12 = 11

. Expected HCO

_3^-

24 - 11 = 13

mEq/L. This is very close to the measured

14

mEq/L.

Because the expected and measured bicarbonate values are similar, there is no concurrent metabolic alkalosis or non-anion gap metabolic acidosis.

Key Concept

Salicylate toxicity typically presents with a mixed increased anion gap metabolic acidosis and primary respiratory alkalosis.

Question 1379Question →

Match each patient's clinical presentation with their most likely expected serum and urine laboratory profile.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct pairings match Sjogren syndrome to Type 1 RTA (severe hypokalemia, urine pH > 5.5), multiple myeloma to Type 2 RTA (normoglycemic glycosuria, intact distal acidification), diabetic nephropathy on ACE inhibitor to Type 4 RTA (hyperkalemia), bulimia to metabolic alkalosis (low urine chloride), and lithium use to nephrogenic diabetes insipidus (hypernatremia, very dilute urine).

Each systemic condition targets a specific segment or function of the nephron. Sjogren syndrome destroys distal intercalated cells (Type 1 RTA). Multiple myeloma light chains poison the proximal tubule (Type 2 RTA with Fanconi). Diabetic nephropathy and ACE inhibitors eliminate the aldosterone axis (Type 4 RTA). Vomiting depletes volume and chloride, stimulating profound proximal and distal reabsorption (hypochloremic alkalosis). Lithium blocks ADH action in the collecting duct (nephrogenic DI).

Step-by-Step Solution

Analyze the clinical vignettes to identify the primary systemic disease or toxic exposure.

Identified Sjogren syndrome, multiple myeloma, diabetic nephropathy with ACEi use, bulimia nervosa, and lithium toxicity.

Each of these conditions has a highly specific effect on renal tubular function and acid-base/electrolyte homeostasis.

Determine the expected acid-base and potassium derangements for each condition.

Sjogren (distal RTA 1) = hypokalemia/acidosis; Myeloma (proximal RTA 2) = hypokalemia/acidosis; Diabetes+ACEi (RTA 4) = hyperkalemia/acidosis; Bulimia = hypokalemia/alkalosis; Lithium = normal acid-base, hypernatremia.

Potassium levels and blood pH immediately differentiate RTA 4 (hyperkalemic), vomiting (alkalosis), and nephrogenic DI (pure water loss) from RTA 1 and 2.

Use specific urine chemistries to differentiate the remaining similar disorders (Type 1 vs. Type 2 RTA).

Type 1 RTA has a strict urine pH > 5.5 due to distal acidification failure. Type 2 RTA has a urine pH < 5.5 during steady state and presents with proximal tubule defects like glycosuria.

Urine pH and the presence of Fanconi syndrome components precisely distinguish the mechanisms of normal anion gap metabolic acidosis.

Key Concept

Integration of systemic disease pathophysiology with specific renal tubular defects, focusing on the differentiation of Renal Tubular Acidoses (RTAs), metabolic alkalosis generation, and renal concentrating defects.

Estimated Time:3m 0s

Question 1380Question →

A 17-year-old girl is brought to the physician by her mother for evaluation of primary amenorrhea. She has never had a menstrual period. The patient has no significant past medical history and takes no medications. Her blood pressure is $162/100\text{ mmHg}$ and pulse is $78/\text{min}$ . Physical examination shows a tall, thin adolescent with Tanner stage 1 breast development and absent pubic and axillary hair. A pelvic ultrasound reveals a small, prepubertal uterus and bilateral ovaries. Laboratory studies show a serum sodium of $145\text{ mEq/L}$ , potassium of $2.8\text{ mEq/L}$ , and bicarbonate of $32\text{ mEq/L}$ . Which of the following additional laboratory findings is most likely present in this patient?

Decreased serum aldosterone and elevated serum corticosterone

Elevated serum testosterone and elevated 11-deoxycortisol

Decreased serum luteinizing hormone and decreased serum follicle-stimulating hormone

Elevated serum aldosterone and decreased plasma renin activity

Elevated 17-hydroxyprogesterone and elevated plasma renin activity

Show answer & explanation

Answer: Decreased serum aldosterone and elevated serum corticosterone

Answer

The correct answer is decreased serum aldosterone and elevated serum corticosterone.

This patient's presentation is pathognomonic for

17\alpha

-hydroxylase deficiency, a rare form of Congenital Adrenal Hyperplasia. The enzyme

17\alpha

-hydroxylase is required to convert pregnenolone and progesterone into

17

-hydroxypregnenolone and

17

-hydroxyprogesterone, respectively. A deficiency completely blocks the synthesis of both glucocorticoids (cortisol) and sex steroids (androgens and estrogens). The lack of estrogen causes primary amenorrhea and absent breast development, while the lack of androgens causes absent pubic and axillary hair. Because cortisol synthesis is impaired, loss of negative feedback increases ACTH, which continuously drives the only unblocked adrenal pathway: mineralocorticoid synthesis. This results in massive overproduction of 11-deoxycorticosterone (DOC) and corticosterone. DOC is a potent mineralocorticoid that causes sodium retention (hypertension) and potassium/hydrogen excretion (hypokalemic metabolic alkalosis). Crucially, this intravascular volume expansion suppresses the juxtaglomerular apparatus, leading to low plasma renin activity. The low renin subsequently fails to stimulate aldosterone synthase, resulting in paradoxical decreased true serum aldosterone levels despite the profound mineralocorticoid effect.

Step-by-Step Solution

Analyze the clinical triad.

The patient has primary amenorrhea with sexual infantilism (Tanner stage 1 breasts, absent pubic hair), severe hypertension, and hypokalemic metabolic alkalosis.

Identifying these three distinct physiological abnormalities is required to localize a single unifying enzymatic defect.

Differentiate the causes of Congenital Adrenal Hyperplasia (CAH).

The combination of hypertension and sexual infantilism points specifically to

17\alpha

-hydroxylase deficiency.

Other CAH forms cause virilization (

11\beta

-hydroxylase,

21

-hydroxylase) or hypotension (

21

-hydroxylase).

Trace the biochemical consequences of a

17\alpha

-hydroxylase block.

The block prevents conversion of progesterone to

17

-hydroxyprogesterone, halting the synthesis of cortisol and sex steroids (estrogens/androgens), while shunting all precursors into the mineralocorticoid pathway.

Understanding the steroidogenesis pathway predicts the exact serum hormone levels.

Determine the downstream effects on the renin-angiotensin-aldosterone system.

Excess 11-deoxycorticosterone (DOC) and corticosterone act as potent mineralocorticoids, causing sodium retention, hypertension, and hypokalemia. This volume expansion suppresses renin release, which in turn leads to decreased synthesis of true aldosterone.

This explains the paradoxical finding of high mineralocorticoid effect with low actual serum aldosterone.

Key Concept

Congenital Adrenal Hyperplasia (

17\alpha

-hydroxylase deficiency)

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Internal Medicine

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Key Concept

Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Common Mistakes

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Key Concept

Common Mistakes

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Key Concept

Common Mistakes

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Key Concept