All practice questions

8270 questions

All types8,270 Multiple choice4,249 Multiple select325 Numeric160 Matching1,849 Ordering1,687

Match each patient presenting with severe hypertension and distinct clinical features to the most appropriate initial targeted pharmacologic intervention.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Aortic dissection requires beta-blockade; Scleroderma renal crisis requires ACE inhibition; Pheochromocytoma requires alpha-blockade; Flash pulmonary edema requires venodilation and diuresis.

Each specific hypertensive emergency demands a precise pharmacological mechanism of action to counteract its pathophysiology. Using a generic approach for blood pressure lowering without addressing the specific underlying driver can lead to severe adverse outcomes.

Step-by-Step Solution

Analyze the clinical features of each patient to establish the underlying diagnosis causing the hypertensive emergency.

Identified diagnoses are acute aortic dissection, scleroderma renal crisis, pheochromocytoma crisis, and acute decompensated heart failure (flash pulmonary edema).

Accurate diagnosis is required because standard hypertensive emergency protocols vary drastically based on the target organ damage.

Identify the primary pathophysiological driver for each condition.

Drivers: shear stress (dissection), RAAS activation (scleroderma), catecholamine surge (pheochromocytoma), and high preload/afterload (flash pulmonary edema).

Understanding the mechanism allows for targeted pharmacotherapy rather than generic blood pressure reduction.

Match the diagnosis to the pharmacologic agent that specifically targets that pathophysiologic mechanism.

Matched esmolol to dissection, captopril to scleroderma, phentolamine to pheochromocytoma, and nitroglycerin/diuretics to heart failure.

This pairs the optimal intervention with the specific life-threatening condition while avoiding harmful contraindications.

Key Concept

Targeted pharmacotherapy for specific hypertensive emergencies based on underlying pathophysiology.

Estimated Time:1m 30s

Question 142Question →

An emergency medical services team brings a $62$ -year-old man to the hospital following $4$ days of profuse, nonbloody diarrhea. His past medical history is significant for severe chronic obstructive pulmonary disease (COPD) managed with a daily inhaled tiotropium. Upon arrival, he reports profound fatigue and lightheadedness.

Vital signs include a heart rate of $108/\text{min}$ , blood pressure of $105/65\text{ mm Hg}$ , respiratory rate of $24/\text{min}$ , and temperature of $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ). Physical examination reveals dry oral mucosa and diminished skin turgor. The lungs have diffuse expiratory wheezes bilaterally.

Initial laboratory investigations reveal the following:

Laboratory Test	Result
Sodium	$138\text{ mEq/L}$
Potassium	$3.4\text{ mEq/L}$
Chloride	$111\text{ mEq/L}$
Bicarbonate	$14\text{ mEq/L}$
Blood urea nitrogen	$32\text{ mg/dL}$
Creatinine	$1.4\text{ mg/dL}$

Arterial blood gas (on room air):

Arterial Blood Gas	Result
pH	$7.22$
$\text{pCO}_2$	$36\text{ mm Hg}$
$\text{pO}_2$	$62\text{ mm Hg}$

Based on the laboratory results, which of the following is the most accurate characterization of this patient's acid-base status?

Mixed metabolic acidosis and respiratory acidosis

Metabolic acidosis with appropriate respiratory compensation

Mixed metabolic acidosis and respiratory alkalosis

Primary respiratory acidosis with appropriate metabolic compensation

Uncompensated metabolic acidosis

Show answer & explanation

Answer: Mixed metabolic acidosis and respiratory acidosis

Answer

Mixed metabolic acidosis and respiratory acidosis

This patient has a low pH (

7.22

) and a low serum bicarbonate (

14\text{ mEq/L}

), which establishes the presence of a primary metabolic acidosis (non-anion gap, given the gap of

13

, which is consistent with severe diarrhea). To determine if the respiratory compensation is appropriate, Winter's formula must be applied: Expected

\text{pCO}_2 = (1.5 \times \text{HCO}_3^-) + 8 \pm 2

. For this patient, the expected

\text{pCO}_2

(1.5 \times 14) + 8 = 21 + 8 = 29 \pm 2

(range:

27-31\text{ mm Hg}

). The patient's actual

\text{pCO}_2

36\text{ mm Hg}

. Because the actual

\text{pCO}_2

is greater than the expected range, there is a concomitant primary respiratory acidosis. This is a common finding in patients with advanced COPD who cannot adequately increase their minute ventilation in response to acidemia.

Step-by-Step Solution

Identify the primary acid-base disorder by evaluating the pH and serum bicarbonate.

The pH is

7.22

(acidemia) and the bicarbonate is

14\text{ mEq/L}

(low). This indicates a primary metabolic acidosis.

The pH determines the primary direction of the derangement, and the concordant change in bicarbonate confirms a metabolic etiology.

Calculate the expected

\text{pCO}_2

using Winter's formula to assess for mixed disorders.

Expected

\text{pCO}_2 = (1.5 \times 14) + 8 = 29 \pm 2\text{ mm Hg}

(range

27-31\text{ mm Hg}

Winter's formula determines if the respiratory response (hyperventilation) to a metabolic acidosis is appropriate.

Compare the actual

\text{pCO}_2

to the expected

\text{pCO}_2

The actual

\text{pCO}_2

(

36\text{ mm Hg}

) is higher than the expected range (

27-31\text{ mm Hg}

A higher-than-expected

\text{pCO}_2

indicates inadequate ventilation, meaning a superimposed respiratory acidosis is present, likely secondary to the patient's severe COPD.

Key Concept

Patients with a primary metabolic acidosis must be evaluated with Winter's formula to determine if respiratory compensation is adequate; a pCO2 higher than expected indicates a concomitant respiratory acidosis.

Question 143Question →

A 15-month-old girl is brought to the clinic for a routine health maintenance visit. She lives with her parents and a 6-year-old brother who was diagnosed with acute lymphoblastic leukemia one month ago and is currently undergoing intensive induction chemotherapy. The parents express concern regarding the patient's development. They note that while she can say "mama" and "dada" specifically, she only has three other words in her vocabulary. Furthermore, she is unable to run or walk backward, though she walks independently without difficulty. She also scribbles spontaneously with crayons and drinks from a cup. Her immunizations are up to date through 6 months of age, but she missed her 12-month visit. The parents are reluctant to consent to any live-attenuated vaccines today, as they have read that these vaccines can shed and potentially cause severe infections in immunocompromised household members. Vital signs and physical examination are within normal limits. Which of the following is the most appropriate recommendation regarding this patient's management?

Reassure the parents regarding her development and administer all indicated inactivated and live-attenuated vaccines

Reassure the parents regarding her development, administer inactivated vaccines, and withhold live-attenuated vaccines

Refer the patient for early intervention evaluation and administer all indicated inactivated and live-attenuated vaccines

Refer the patient for early intervention evaluation, administer inactivated vaccines, and withhold live-attenuated vaccines

Reassure the parents regarding her development, administer all indicated vaccines, and advise separating the patient from her brother for 4 weeks

Show answer & explanation

Answer: Reassure the parents regarding her development and administer all indicated inactivated and live-attenuated vaccines

Answer

Reassure the parents regarding her development and administer all indicated inactivated and live-attenuated vaccines

The patient is demonstrating normal developmental milestones for a 15-month-old. She is walking independently (15 months), scribbling (15 months), using a cup (15 months), and has a vocabulary of 3-5 words (15 months). The lack of running and walking backward is appropriate, as these are 18-month milestones. Therefore, reassurance is indicated. Regarding her immunizations, she is due for catch-up vaccines, including the live-attenuated MMR and Varicella vaccines. According to CDC guidelines, healthy immunocompetent individuals who reside with an immunocompromised patient (such as a sibling undergoing chemotherapy) MUST receive all age-appropriate live vaccines. This creates a 'cocoon' of herd immunity around the vulnerable patient. Transmission of MMR vaccine virus does not occur, and transmission of Varicella vaccine virus is exceedingly rare. Routine isolation post-vaccination is not required unless the vaccinated child develops a vesicular rash.

Step-by-Step Solution

Evaluate the patient's developmental milestones for her age.

The patient's abilities (walking well, 3-5 words, scribbling, using a cup) match normal 15-month milestones. Her inability to run or walk backward is normal, as these emerge at 18 months.

Accurate assessment of milestones dictates whether reassurance or a developmental referral is required.

Determine the safety and necessity of administering live-attenuated vaccines to a household contact of an immunocompromised patient.

Live-attenuated vaccines (such as MMR and Varicella) are highly recommended for healthy household contacts to establish herd immunity.

Vaccinating close contacts protects the severely immunocompromised patient (the brother) from life-threatening wild-type infections.

Synthesize the findings into a comprehensive management plan.

The correct course of action is to provide reassurance regarding her normal development and proceed with the administration of all age-appropriate vaccines, including MMR and Varicella.

This addresses both the parents' developmental concerns and appropriately manages the infectious risk to the sibling.

Key Concept

Healthy household contacts of immunocompromised patients should receive routine live-attenuated vaccines (MMR, Varicella) to provide herd immunity. Additionally, running and walking backward are 18-month gross motor milestones.

Question 144Question →

Correlate each distinct clinical vignette describing a cardiovascular emergency or structural abnormality with its exact pathophysiological mechanism or primary hemodynamic derangement.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The correct correlations are: The athlete with the Valsalva-responsive murmur matches with dynamic LVOT obstruction (HOCM). The irradiated patient with Kussmaul sign matches with rigid pericardium and ventricular interdependence (Constrictive Pericarditis). The post-MI shock patient matches with papillary muscle rupture and giant v-waves. The pregnant patient with hemoptysis matches with commissural fusion and trans-valvular pressure gradient (Mitral Stenosis).

Each clinical vignette provides highly specific diagnostic clues that uniquely map to a distinct pathophysiologic mechanism. The athlete's murmur is classic for HOCM, driven by SAM of the mitral valve. The radiation survivor exhibits constrictive pericarditis, characterized by a rigid pericardium. The post-MI patient has suffered a papillary muscle rupture causing acute MR and giant v-waves. The pregnant patient's findings are pathognomonic for rheumatic mitral stenosis caused by commissural fusion.

Step-by-Step Solution

Analyze the first vignette featuring a murmur that worsens with decreased preload (Valsalva).

Identified as Hypertrophic Obstructive Cardiomyopathy.

Decreasing preload narrows the LV outflow tract, worsening the dynamic obstruction.

Evaluate the second presentation involving remote radiation, ascites, Kussmaul sign, and a prominent y-descent.

Diagnosed as Constrictive Pericarditis.

Radiation causes pericardial scarring, leading to restricted filling and dissociation of intracardiac and intrathoracic pressures.

Assess the post-MI patient with a new holosystolic murmur, S3 gallop, and cardiogenic shock.

Identified as Acute Mitral Regurgitation secondary to papillary muscle rupture.

The posteromedial papillary muscle frequently ruptures 3-5 days after an inferior MI, causing massive retrograde flow and acute left atrial overload.

Examine the pregnant patient with hemoptysis, loud S1, and diastolic rumble.

Diagnosed as Rheumatic Mitral Stenosis.

Pregnancy increases cardiac output, exacerbating the pressure gradient across the fused commissures.

Key Concept

Differentiating structural and valvular cardiac pathologies based on specific hemodynamic responses, unique physical exam findings, and pathophysiologic mechanisms.

Question 145Question →

A 54-year-old man is brought to the emergency department by his wife due to lethargy, severe nausea, vomiting, and abdominal pain that began 24 hours ago. Over the past year, he has experienced progressive fatigue, cold intolerance, erectile dysfunction, and decreased libido. Two weeks ago, he was evaluated by a new primary care physician who obtained the following laboratory results:

Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	1.6 mIU/L	0.5 - 5.0 mIU/L
Free thyroxine (T4)	0.5 ng/dL	0.9 - 1.7 ng/dL

Based on these results, the physician diagnosed hypothyroidism and initiated levothyroxine therapy.

On presentation today, his temperature is 36.8°C (98.2°F), blood pressure is 78/50 mm Hg, heart rate is 115/min, and respiratory rate is 18/min. Physical examination reveals a lethargic man with pale skin and dry mucous membranes. There is no hyperpigmentation of the palmar creases or oral mucosa. Visual field testing by confrontation is normal.

Current laboratory results:

Test	Result
Sodium	128 mEq/L
Potassium	4.2 mEq/L
Chloride	95 mEq/L
Bicarbonate	22 mEq/L
Blood urea nitrogen	32 mg/dL
Creatinine	1.4 mg/dL
Glucose	52 mg/dL

Which of the following best explains the pathophysiologic mechanism of this patient's acute decompensation?

Accelerated hepatic clearance of endogenous glucocorticoids

Concurrent autoimmune destruction of the adrenal cortex

Inadequate renal synthesis of renin leading to aldosterone deficiency

Sudden hemorrhage and infarction of a preexisting pituitary macroadenoma

Excessive exogenous thyroxine causing high-output cardiac failure

Show answer & explanation

Answer: Accelerated hepatic clearance of endogenous glucocorticoids

Answer

Accelerated hepatic clearance of endogenous glucocorticoids

The correct answer is accelerated hepatic clearance of endogenous glucocorticoids. This patient's initial laboratory results (low free T4 with a normal TSH) indicate central (secondary) hypothyroidism. Combined with his history of erectile dysfunction and decreased libido, this points to broader panhypopituitarism, which frequently includes central adrenal insufficiency (ACTH deficiency). When levothyroxine is administered to a patient with untreated adrenal insufficiency, it increases the basal metabolic rate and upregulates hepatic enzymes responsible for cortisol metabolism. This accelerated clearance of the patient's already marginal endogenous cortisol stores rapidly precipitates an acute adrenal crisis, characterized by hypotension, hypoglycemia, and hyponatremia. For this reason, glucocorticoid replacement must always precede or accompany thyroid hormone replacement in patients with suspected panhypopituitarism.

Step-by-Step Solution

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

The patient has a low free T4 with an inappropriately normal TSH, indicating central (secondary) hypothyroidism, rather than primary hypothyroidism.

A properly functioning pituitary gland should produce an elevated TSH in response to low circulating free T4.

Correlate the central hypothyroidism with the patient's clinical symptoms.

The history of erectile dysfunction and decreased libido suggests concurrent hypogonadotropic hypogonadism. This points toward broader panhypopituitarism, which likely includes secondary adrenal insufficiency.

Multiple pituitary axis deficiencies often occur together, typically due to a pituitary mass or infiltrative disease.

Identify the etiology of the current acute presentation based on vital signs and metabolic derangements.

The patient is in distributive shock with hypoglycemia and hyponatremia (but normal potassium), which is a classic presentation of acute secondary adrenal crisis.

Glucocorticoid deficiency impairs vascular tone and hepatic gluconeogenesis. Normal potassium differentiates secondary from primary adrenal insufficiency.

Determine the pharmacological trigger for the acute crisis.

The initiation of levothyroxine increased his basal metabolic rate, accelerating the hepatic clearance of cortisol and tipping him into a severe acute cortisol deficit.

Thyroid hormone upregulates hepatic enzymes responsible for glucocorticoid metabolism. In patients with panhypopituitarism, glucocorticoid replacement must always precede thyroid hormone replacement.

Key Concept

Initiation of levothyroxine in a patient with undiagnosed panhypopituitarism (central hypothyroidism and central adrenal insufficiency) accelerates hepatic cortisol clearance and can precipitate a fatal acute adrenal crisis.

Estimated Time:2m 0s

Question 146Question →

A 42-year-old woman presents to the rheumatology clinic with a 4-month history of bilateral, symmetrical pain, swelling, and severe morning stiffness in her metacarpophalangeal and proximal interphalangeal joints. Arrange the following clinical actions in the correct chronological sequence for the long-term diagnostic workup and stepwise pharmacological management of this patient's condition, reflecting standard escalation of therapy.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence begins with diagnostic confirmation and baseline imaging, followed by initial methotrexate therapy. Upon failure of this initial therapy, infectious screening is performed before escalating to a TNF inhibitor. Finally, if the TNF inhibitor loses efficacy, the patient is transitioned to a biologic with a different mechanism of action.

The correct sequence strictly adheres to the standard guidelines for the management of Rheumatoid Arthritis (RA). The clinician must first confirm the diagnosis using autoantibodies and establish a structural baseline via radiographs. Methotrexate is then initiated as the mandatory first-line conventional synthetic DMARD. If the patient fails to achieve low disease activity after a 3 to 6-month trial, the next step is escalating to a biologic DMARD (e.g., TNF inhibitor); however, latent tuberculosis and viral hepatitis must be ruled out immediately prior to biologic initiation to prevent fatal reactivation. Finally, if the initial biologic loses efficacy over time (known as secondary failure, often due to anti-drug antibodies), the standard of care is to switch to a biologic with a distinctly different mechanism of action (e.g., IL-6 inhibitor, anti-CD20) rather than cycling through another drug of the same class.

Step-by-Step Solution

Establish diagnosis and structural baseline.

Confirmation of Rheumatoid Arthritis via serology and baseline radiographs.

Definitive diagnosis and structural staging are required before initiating potentially toxic immunosuppressive medications.

Initiate first-line pharmacotherapy.

Patient starts methotrexate and a short course of bridging glucocorticoids.

Methotrexate is the anchor drug and universally recommended first-line DMARD for Rheumatoid Arthritis.

Assess response and screen for latent infections.

Patient undergoes an interferon-gamma release assay (IGRA) and hepatitis serologies due to persistent synovitis.

Latent infections must be ruled out immediately before initiating biologic agents to prevent severe immune reactivation.

Escalate to combination therapy.

A TNF inhibitor is added to the methotrexate regimen.

This is the standard escalation algorithm for patients failing conventional synthetic DMARD monotherapy.

Manage secondary biologic failure.

Patient is switched to an IL-6 inhibitor or rituximab.

When a TNF inhibitor fails, switching to a non-TNF biologic mechanism is highly recommended over cycling within the same drug class.

Key Concept

Stepwise Management and Therapy Escalation in Rheumatoid Arthritis

Estimated Time:2m 0s

Question 147Question →

An $82$ -year-old man is evaluated in the preadmission clinic prior to a scheduled elective right total knee arthroplasty. His past medical history is significant for hypertension, type $2$ diabetes mellitus, and benign prostatic hyperplasia. He reports feeling well and specifically denies dysuria, urinary frequency, urgency, gross hematuria, or flank pain. Vital signs are temperature $37.1^\circ\text{C}$ ( $98.8^\circ\text{F}$ ), blood pressure $130/80\text{ mmHg}$ , pulse $72\text{/min}$ , and respirations $14\text{/min}$ . Physical examination is unremarkable, with no costovertebral angle tenderness or suprapubic pain. A routine preoperative urinalysis reveals trace leukocyte esterase, positive nitrites, and $15$ - $20$ white blood cells per high-power field. Which of the following is the most appropriate next step in management regarding this patient's urinary findings?

Proceed with the scheduled surgery without targeted antimicrobial therapy for the urinary findings

Prescribe a preoperative course of oral ciprofloxacin

Postpone the arthroplasty until a urine culture is finalized

Administer intravenous ceftriaxone specifically to sterilize the urinary tract

Prescribe oral nitrofurantoin to be taken for five days postoperatively

Show answer & explanation

Answer: Proceed with the scheduled surgery without targeted antimicrobial therapy for the urinary findings

Answer

Proceed with the scheduled surgery without targeted antimicrobial therapy for the urinary findings

The correct action is to proceed with the surgery without targeted therapy. This patient has asymptomatic bacteriuria (ASB), which is common in older men with benign prostatic hyperplasia and patients with diabetes mellitus. By definition, ASB is the presence of bacteria in the urine without accompanying signs or symptoms of a urinary tract infection (e.g., dysuria, frequency, urgency, fever, suprapubic pain). According to current infectious disease guidelines and antimicrobial stewardship principles, screening and treatment for ASB are strongly discouraged for the vast majority of patients. The only well-established indications for screening and treating ASB are in pregnant women, patients undergoing endoscopic urologic procedures associated with mucosal trauma (e.g., transurethral resection of the prostate), and in patients who have recently received a renal transplant. An elective orthopedic procedure, such as a total knee arthroplasty, is not an indication to treat ASB. Studies have consistently shown that treating ASB prior to joint arthroplasty does not reduce the risk of surgical site infections and only serves to promote antibiotic resistance and potential adverse drug effects.

Step-by-Step Solution

Identify the patient's clinical state based on symptoms and labs.

The patient is an elderly diabetic man with pyuria and positive nitrites on urinalysis, but he entirely lacks systemic or local genitourinary symptoms.

Differentiating between a symptomatic urinary tract infection (UTI) and asymptomatic bacteriuria (ASB) relies primarily on the presence or absence of clinical symptoms.

Diagnose the urinary condition.

The clinical picture is diagnostic of asymptomatic bacteriuria (ASB).

ASB is defined as the isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen from an individual without signs or symptoms of a UTI.

Recall the indications for treating asymptomatic bacteriuria.

Treatment is only indicated for pregnant women, patients undergoing invasive endoscopic urologic procedures associated with mucosal trauma, and recent renal transplant recipients.

Routine treatment in other populations does not improve outcomes and increases the risk of resistance.

Determine the appropriate management for this specific preoperative patient.

A total knee arthroplasty is a non-urologic orthopedic procedure, meaning the ASB does not require treatment or a delay of the surgery.

Treating ASB prior to joint replacement surgery does not reduce the incidence of prosthetic joint infections.

Key Concept

Management of asymptomatic bacteriuria in the preoperative setting

Question 148Question →

Paramedics bring a $34$ -year-old female to the emergency department due to profound weakness, recurrent vomiting, and confusion. Her husband notes that she had been experiencing worsening fatigue, anorexia, and a $5$ -kg ( $11$ -lb) weight loss over the past four months. Three weeks ago, she was evaluated by a primary care provider. At that time, laboratory studies showed a thyroid-stimulating hormone (TSH) level of $14.2$ $\mu$ U/mL (normal: $0.4$ – $4.2$ $\mu$ U/mL) and a free thyroxine (T4) level of $0.7$ ng/dL (normal: $0.9$ – $1.7$ ng/dL). Her daily levothyroxine dose, which she has taken for Hashimoto thyroiditis for six years, was subsequently increased from $75$ $\mu$ g to $125$ $\mu$ g.

Today, her temperature is $37.8^\circ\text{C}$ ( $100.0^\circ\text{F}$ ), blood pressure is $78/46$ mm Hg, heart rate is $118$ /min, and respiratory rate is $22$ /min. Physical examination reveals generalized darkening of the skin, most prominent over the palmar creases and buccal mucosa.

Laboratory evaluation in the emergency department shows:

Laboratory Parameter	Result	Reference Range
Serum sodium	$128$ mEq/L	$136$ – $145$ mEq/L
Serum potassium	$5.8$ mEq/L	$3.5$ – $5.0$ mEq/L
Serum chloride	$96$ mEq/L	$95$ – $105$ mEq/L
Serum bicarbonate	$16$ mEq/L	$22$ – $28$ mEq/L
Blood urea nitrogen	$32$ mg/dL	$7$ – $18$ mg/dL
Serum creatinine	$1.4$ mg/dL	$0.6$ – $1.2$ mg/dL
Serum glucose	$54$ mg/dL	$70$ – $110$ mg/dL

Which of the following pathophysiologic mechanisms most likely precipitated this patient's acute deterioration?

Enhanced hepatic clearance of endogenous glucocorticoids

Profound intracellular triiodothyronine depletion

Ischemic necrosis of the anterior pituitary gland

Acute bilateral hemorrhagic infarction of the adrenal glands

Severe tissue resistance to circulating mineralocorticoids

Show answer & explanation

Answer: Enhanced hepatic clearance of endogenous glucocorticoids

Answer

Enhanced hepatic clearance of endogenous glucocorticoids

The correct mechanism is enhanced hepatic clearance of endogenous glucocorticoids. This patient has Autoimmune Polyglandular Syndrome Type 2 (Hashimoto thyroiditis and Addison disease). Her insidious symptoms of weight loss and hyperpigmentation indicate chronic primary adrenal insufficiency. When her primary care provider carelessly increased her levothyroxine dose without evaluating for adrenal insufficiency, it precipitated an acute crisis. Thyroid hormone upregulates hepatic metabolism (specifically

11\beta

-hydroxysteroid dehydrogenase and ring-A reductases), which increases the clearance of cortisol. In an Addisonian patient whose adrenal glands cannot mount a compensatory increase in cortisol production, this rapid depletion of remaining cortisol stores leads to acute cardiovascular collapse, hyponatremia, hyperkalemia, and hypoglycemia.

Step-by-Step Solution

Analyze the patient's underlying chronic symptoms and physical exam.

The patient has a 4-month history of fatigue, weight loss, and hyperpigmentation in the context of known Hashimoto thyroiditis.

This constellation of findings strongly suggests underlying chronic primary adrenal insufficiency (Addison disease) as part of Autoimmune Polyglandular Syndrome Type 2 (Schmidt syndrome).

Interpret the emergency department presentation and laboratory values.

The patient presents with distributive shock (hypotension, tachycardia), hyponatremia, hyperkalemia, non-anion gap metabolic acidosis, and hypoglycemia.

These are the classic hallmarks of an acute adrenal crisis, confirming the decompensation of her primary adrenal insufficiency.

Identify the precipitating event that caused the transition from chronic Addison disease to acute crisis.

Three weeks prior, her levothyroxine dose was significantly increased.

Inquiring about recent medication changes is crucial for determining the trigger of an acute endocrine decompensation.

Determine the pathophysiologic link between levothyroxine administration and adrenal crisis.

Thyroid hormone increases the basal metabolic rate, which includes upregulating the hepatic enzymes responsible for cortisol metabolism and clearance.

In a patient with failing adrenal glands who cannot increase cortisol synthesis, the enhanced clearance of their remaining trace cortisol rapidly induces profound glucocorticoid deficiency and shock.

Key Concept

Initiating or increasing thyroid hormone replacement in a patient with untreated adrenal insufficiency accelerates hepatic cortisol clearance, precipitating an acute adrenal crisis.

Question 149Question →

A 26-year-old man comes to the clinic for a follow-up evaluation of chronic lower back pain. His symptoms began 2 years ago, are typically worse in the morning, and improve with exercise but not with rest. He often wakes up in the second half of the night due to the pain. Physical examination shows limited forward flexion of the lumbar spine with a modified Schober test of 2 cm. Magnetic resonance imaging of the sacroiliac joints demonstrates active osteitis indicative of bilateral sacroiliitis. Laboratory studies show a positive HLA-B27. A diagnosis of ankylosing spondylitis is established. The patient asks about the long-term therapeutic plan, understanding that initial treatments might not be fully effective over time.

Arrange the following interventions and clinical protocols in the correct chronological sequence for the escalation of therapy in this patient, assuming an inadequate clinical response to each prior step.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct chronological sequence of escalation is to first maximize NSAID therapy, then screen for latent infections upon NSAID failure, subsequently initiate a TNF alpha inhibitor, and finally switch to an IL-17 inhibitor if the TNF inhibitor is ineffective.

The management of ankylosing spondylitis follows a strict, evidence-based algorithm. It begins with continuous NSAIDs as the first-line therapy, which differs from rheumatoid arthritis where early DMARDs are initiated. If NSAIDs fail to control axial symptoms, the patient must be escalated to a biologic agent, bypassing conventional synthetic DMARDs (like methotrexate), which only work for peripheral joint involvement. Before any biologic agent is started, mandatory screening for latent tuberculosis (TB) and chronic hepatitis is required, as immunosuppression can lead to fatal reactivation. Once cleared, a TNF alpha inhibitor is the preferred initial biologic. Should the patient have an inadequate response or lose efficacy over time, guidelines recommend switching to an alternative biologic class, most commonly an IL-17 inhibitor.

Step-by-Step Solution

Identify the diagnosis and first-line therapy.

The patient has active axial ankylosing spondylitis. The first-line pharmacological treatment is continuous NSAID therapy combined with physical therapy.

NSAIDs are highly effective for symptom control in early axial disease and are the required first step before insurance or clinical guidelines permit biologic initiation.

Determine the necessary prerequisites for escalating therapy after NSAID failure.

Screening for latent tuberculosis (via interferon-gamma release assay) and viral hepatitis must be performed.

Because conventional synthetic DMARDs like methotrexate are ineffective for purely axial disease, the patient will need a biologic DMARD. Biologics significantly increase the risk of reactivating granulomatous and viral infections.

Select the appropriate second-line therapy.

Initiate a TNF alpha inhibitor (e.g., adalimumab, etanercept).

TNF inhibitors are the standard evidence-based second-line agents for axial spondyloarthritis in patients who have failed NSAIDs and have negative infectious screening.

Determine the next pharmacological step if the initial biologic fails.

Switch to an IL-17 inhibitor (e.g., secukinumab).

When a patient fails to respond to a TNF inhibitor, escalating to a different mechanistic class, such as an IL-17 inhibitor, is the recommended clinical pathway.

Key Concept

Pharmacological escalation and pre-biologic safety screening in the management of ankylosing spondylitis

Estimated Time:1m 15s

Question 150Question →

An 81-year-old man is brought to the emergency department by emergency medical services due to progressively worsening shortness of breath, altered mental status, and a high fever over the past two days. His past medical history is significant for severe chronic obstructive pulmonary disease (COPD). Upon arrival, he is lethargic and utilizing accessory muscles for respiration. Vital signs show a temperature of 38.9°C (102°F), heart rate of 122/min, blood pressure of 86/52 mmHg, and respiratory rate of 28/min. Oxygen saturation is 84% on room air.

Initial laboratory results are as follows:

Laboratory Test	Result	Reference Range
Sodium	140 mEq/L	136–145 mEq/L
Potassium	4.2 mEq/L	3.5–5.0 mEq/L
Chloride	98 mEq/L	98–106 mEq/L
Bicarbonate	12 mEq/L	22–28 mEq/L
Blood urea nitrogen	38 mg/dL	8–20 mg/dL
Creatinine	1.7 mg/dL	0.7–1.3 mg/dL
Lactate	7.1 mmol/L	0.5–1.0 mmol/L

Arterial blood gas on room air:

Parameter	Result	Reference Range
$pH$	7.12	7.35–7.45
$pCO_2$	38 mm Hg	35–45 mm Hg
$pO_2$	52 mm Hg	75–105 mm Hg

Based on the laboratory data provided, which of the following best describes this patient's acid-base status?

Mixed high anion gap metabolic acidosis and respiratory acidosis

Compensated high anion gap metabolic acidosis

Mixed high anion gap metabolic acidosis and respiratory alkalosis

Mixed normal anion gap metabolic acidosis and respiratory acidosis

Primary respiratory acidosis with appropriate metabolic compensation

Show answer & explanation

Answer: Mixed high anion gap metabolic acidosis and respiratory acidosis

Answer

Mixed high anion gap metabolic acidosis and respiratory acidosis

The correct answer accurately identifies two concurrent acid-base disturbances. First, the patient has a high anion gap metabolic acidosis (HAGMA) driven by lactic acidosis secondary to sepsis. The anion gap is calculated as

140 - (98 + 12) = 30

mEq/L. Next, respiratory compensation for a metabolic acidosis must be verified using Winter's formula: Expected

pCO_2 = 1.5 \times [HCO_3^-] + 8 \pm 2

. For this patient, the expected

pCO_2 = 1.5 \times 12 + 8 = 26 \pm 2

mm Hg. The patient's actual

pCO_2

is 38 mm Hg. Because the measured

pCO_2

is significantly higher than the expected compensated value, there is a concurrent respiratory acidosis. This commonly occurs when a patient with underlying COPD develops sepsis and respiratory muscle fatigue, rendering them unable to mount the massive minute ventilation required to compensate for a severe metabolic acidosis.

Step-by-Step Solution

Identify the primary acid-base disorder by looking at the

pH

and bicarbonate levels.

The patient is acidemic (

pH

= 7.12) with a low bicarbonate (

12

mEq/L), indicating a primary metabolic acidosis.

Both

pH

and

HCO_3^-

are shifted in the same direction (downward), which is the hallmark of a metabolic process.

Calculate the serum anion gap to determine the etiology of the metabolic acidosis.

Anion Gap =

Na^+ - (Cl^- + HCO_3^-) = 140 - (98 + 12) = 30

mEq/L.

An anion gap > 12 mEq/L confirms the presence of a high anion gap metabolic acidosis (HAGMA), consistent with this patient's elevated lactate from septic shock.

Calculate the expected respiratory compensation using Winter's formula.

Expected

pCO_2 = 1.5 \times [HCO_3^-] + 8 = 1.5 \times 12 + 8 = 18 + 8 = 26 \pm 2

mm Hg.

Winter's formula determines if the lungs are appropriately blowing off

CO_2

to compensate for the metabolic acidemia.

Compare the expected

pCO_2

with the patient's actual

pCO_2

The actual

pCO_2

is 38 mm Hg, which is significantly greater than the expected range of 24-28 mm Hg.

Because the actual

CO_2

is higher than expected, the patient is retaining

CO_2

. This establishes the presence of a second, concurrent disorder: a respiratory acidosis.

Key Concept

Acid-base disorders with calculation of anion gap and respiratory compensation using Winter's formula.

Alternative Method

Once HAGMA is established, you can optionally calculate the Delta-Delta ratio (

\Delta

Anion Gap /

\Delta HCO_3^-

) to check for a third disorder. Here,

\Delta

AG =

30 - 12 = 18

, and

\Delta HCO_3^-

24 - 12 = 12

. The ratio is

18 / 12 = 1.5

. A ratio between 1.0 and 2.0 suggests an uncomplicated HAGMA without an underlying concurrent normal AG metabolic acidosis or metabolic alkalosis.

Estimated Time:1m 0s

Question 151Question →

A 62-year-old man is admitted to the hospital with a 3-week history of low-grade fevers, fatigue, and progressive shortness of breath. His medical history is significant for mitral valve prolapse with severe regurgitation. Temperature is $38.4^{\circ}\text{C}$ ( $101.1^{\circ}\text{F}$ ), pulse is $102/\text{min}$ , and blood pressure is $110/65 \text{ mmHg}$ . Cardiac examination reveals a grade 3/6 holosystolic murmur at the apex. Small, painless, erythematous macules are noted on the palms.

Laboratory studies show:
- Leukocyte count: $14,200/\text{mm}^3$
- Hemoglobin: $10.4 \text{ g/dL}$
- Serum creatinine: $2.6 \text{ mg/dL}$ (baseline $0.9 \text{ mg/dL}$ three months ago)

Urinalysis reveals 2+ protein, 15-20 red blood cells/hpf, and the presence of red blood cell casts.

Three sets of blood cultures are drawn, and empiric intravenous vancomycin and cefepime are initiated. Transesophageal echocardiography reveals a $1.4\text{-cm}$ oscillating vegetation on the posterior mitral leaflet.

On hospital day 3, all blood culture bottles grow *Enterococcus faecalis*. Antimicrobial susceptibility testing reveals the following minimum inhibitory concentrations (MIC):
- Ampicillin: $\leq 1 \ \mu\text{g/mL}$ (Susceptible)
- Vancomycin: $1 \ \mu\text{g/mL}$ (Susceptible)
- Gentamicin (high-level testing): Susceptible

The laboratory report includes a standard comment: 'Enterococci are intrinsically resistant to cephalosporins, antistaphylococcal penicillins, and clindamycin in vitro.'

The patient's serum creatinine remains elevated at $2.7 \text{ mg/dL}$ .

Which of the following is the most appropriate definitive pharmacotherapy for this patient?

Intravenous ampicillin and gentamicin

Intravenous vancomycin and gentamicin

Intravenous ampicillin and ceftriaxone

Intravenous ampicillin monotherapy

Intravenous daptomycin monotherapy

Show answer & explanation

Answer: Intravenous ampicillin and ceftriaxone

Answer

Intravenous ampicillin and ceftriaxone

The most appropriate definitive pharmacotherapy is intravenous ampicillin and ceftriaxone. Enterococcus faecalis infective endocarditis requires a bactericidal antimicrobial regimen, as monotherapy with ampicillin is only bacteriostatic against enterococci. Historically, bactericidal synergy was achieved by combining ampicillin with an aminoglycoside (e.g., gentamicin). However, this patient has developed severe acute kidney injury (creatinine 2.7 mg/dL) secondary to immune complex glomerulonephritis, rendering aminoglycosides highly contraindicated due to their significant nephrotoxicity. The combination of ampicillin and ceftriaxone has emerged as a first-line, nephron-sparing alternative. Although enterococci are intrinsically resistant to cephalosporins in vitro (as noted on the lab report), the combination is highly synergistic in vivo. Ampicillin saturates Penicillin-Binding Proteins 4 and 5 (PBP4/PBP5), while ceftriaxone saturates PBP2 and PBP3. This dual PBP saturation leads to highly effective bactericidal cell wall breakdown.

Step-by-Step Solution

Analyze the clinical and echocardiographic findings.

The patient has native valve infective endocarditis based on fever, new murmur, Janeway lesions, and a large vegetation on the mitral valve.

Establishes the diagnosis and the requirement for a prolonged bactericidal antimicrobial regimen.

Evaluate laboratory results, specifically renal function and urinalysis.

Identification of acute kidney injury (creatinine elevated to 2.7 mg/dL) with RBC casts, indicating immune complex glomerulonephritis.

Recognizing severe renal impairment is critical as it determines the contraindication of nephrotoxic agents like aminoglycosides.

Interpret microbiological culture and susceptibility data.

The pathogen is Enterococcus faecalis. It is susceptible to ampicillin, vancomycin, and high-level gentamicin.

Guides the transition from broad-spectrum empiric therapy to pathogen-directed definitive therapy.

Select the optimal bactericidal regimen that balances efficacy and safety.

Selection of ampicillin plus ceftriaxone.

This combination provides the necessary bactericidal synergy against E. faecalis while avoiding the nephrotoxicity of gentamicin, overcoming the noted in vitro cephalosporin resistance.

Key Concept

The treatment of Enterococcus faecalis infective endocarditis in patients with significant renal impairment requires synergistic dual beta-lactam therapy (ampicillin plus ceftriaxone) to achieve bactericidal activity while avoiding the nephrotoxicity associated with aminoglycosides.

Question 152Question →

An emergency medical services team transports a $68$ -year-old retired teacher to the emergency department due to rapidly progressive breathlessness that awoke her from sleep. She has a medical history significant for a myocardial infarction three years ago and moderate chronic obstructive pulmonary disease, for which she uses an as-needed albuterol inhaler. Over the past $12$ hours, her inhaler has provided no relief. Her home medications include aspirin, metoprolol, and lisinopril.

On arrival, her temperature is $37.0^\circ \text{C}$ ( $98.6^\circ \text{F}$ ), blood pressure is $178/104 \text{ mm Hg}$ , pulse is $112/\text{min}$ , and respiratory rate is $28/\text{min}$ . Oxygen saturation is $86\%$ on room air. The patient appears highly anxious and is sitting upright on the stretcher. Physical examination reveals distended jugular veins when sitting at a $45^\circ$ angle. Pulmonary auscultation reveals diffuse expiratory wheezing with a prolonged expiratory phase, as well as bilateral bibasilar crackles. Cardiac examination demonstrates a regular tachycardia with a prominent early diastolic extra heart sound.

Arterial blood gas analysis on room air shows:
- pH: $7.28$
- $\text{PaCO}_2$ : $56 \text{ mm Hg}$
- $\text{PaO}_2$ : $54 \text{ mm Hg}$
- $\text{HCO}_3^-$ : $25 \text{ mEq/L}$

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

Intravenous furosemide

Intravenous methylprednisolone

Continuous albuterol nebulization

Intravenous ceftriaxone and azithromycin

Intravenous sodium bicarbonate

Show answer & explanation

Answer: Intravenous furosemide

Answer

Intravenous furosemide is the most appropriate initial management to reduce preload and treat acute decompensated heart failure.

The correct answer provides a medication that rapidly reduces cardiac preload. The patient is experiencing acute decompensated heart failure (ADHF) manifesting as flash pulmonary edema. This is evidenced by her acute dyspnea, hypertension, hypoxemia, jugular venous distention, crackles, and an S3 gallop (an early diastolic extra heart sound strongly associated with elevated left ventricular end-diastolic pressure). The diffuse wheezing is 'cardiac asthma', a condition where peribronchial edema causes airway narrowing that mimics primary lung disease. Initial management for ADHF relies on intravenous loop diuretics (like furosemide) and/or vasodilators to relieve pulmonary congestion.

Step-by-Step Solution

Analyze the patient's history and vital signs.

The patient has a history of ischemic heart disease and COPD. She is presenting with severe acute hypoxemia, tachypnea, and significant hypertension (

178/104 \text{ mm Hg}

Identifying the baseline risk factors and hemodynamic status helps narrow the differential diagnosis for acute respiratory distress.

Synthesize the physical examination findings.

The exam shows jugular venous distention, bibasilar crackles, an S3 gallop (early diastolic extra sound), and diffuse wheezing.

An S3 gallop and elevated jugular venous pressure are highly specific for left and right-sided heart failure. The wheezing represents 'cardiac asthma' resulting from peribronchial edema, not a primary bronchospastic event.

Interpret the arterial blood gas (ABG) results.

The ABG reveals pH

7.28

\text{PaCO}_2

56 \text{ mm Hg}

, and

\text{HCO}_3^-

25 \text{ mEq/L}

, indicating acute respiratory acidosis secondary to poor ventilation from pulmonary edema.

Correctly identifying the acid-base disorder prevents the inappropriate administration of alkalizing agents like bicarbonate.

Determine the next best step in management.

The diagnosis is acute decompensated heart failure (ADHF) presenting as flash pulmonary edema. The standard initial therapy is intravenous loop diuretics (e.g., furosemide) or vasodilators (e.g., nitroglycerin).

These agents rapidly decrease central venous pressure and pulmonary capillary wedge pressure, immediately improving pulmonary congestion and gas exchange.

Key Concept

Patients with acute decompensated heart failure may present with wheezing (cardiac asthma) that mimics a COPD exacerbation; the presence of an S3 gallop, jugular venous distention, and bibasilar crackles confirms a cardiogenic etiology requiring diuresis or vasodilation.

Question 153Question →

A 54-year-old woman with a history of hormone receptor-positive metastatic breast cancer presents to the emergency department with a 2-day history of progressively worsening mid-back pain. Over the past 12 hours, she has developed difficulty walking due to bilateral leg weakness and reports a new onset of urinary incontinence. Physical examination reveals 3/5 muscle strength in the lower extremities bilaterally, exaggerated patellar and Achilles deep tendon reflexes, and decreased sensation to pinprick below the level of the nipples. Vital signs are within normal limits. Arrange the following steps in the most appropriate sequential order for the immediate evaluation and management of this patient's current condition.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is: Administration of high-dose intravenous dexamethasone, followed by Magnetic resonance imaging (MRI) of the entire spine, then Consultation with neurosurgery or radiation oncology, and finally Initiation of targeted decompressive therapy.

Malignant spinal cord compression is an oncologic emergency. The immediate priority is preserving neurologic function by reducing vasogenic edema with high-dose intravenous corticosteroids (e.g., dexamethasone). This must be done empirically as soon as the condition is suspected, even before diagnostic imaging. After steroids are given, an MRI of the entire spine is obtained to confirm the diagnosis and assess the extent of the disease. Following imaging, surgical and/or radiation oncology consultation is obtained to plan and initiate definitive decompressive therapy.

Step-by-Step Solution

Administer high-dose intravenous dexamethasone.

Decreases peritumoral vasogenic edema and relieves pressure on the spinal cord.

Neurologic deficits in malignant spinal cord compression can become irreversible quickly. Steroids are the most critical initial step and must be given before waiting for imaging.

Perform an MRI of the entire spine.

Visualizes the epidural metastasis and determines the level of compression.

MRI is the imaging modality of choice to confirm the diagnosis and delineate the extent of the disease.

Consult specialized services (neurosurgery or radiation oncology).

Establishes a definitive treatment plan based on imaging findings.

Expert evaluation is necessary to weigh the benefits of surgery versus radiation based on spinal stability, tumor radiosensitivity, and overall prognosis.

Initiate definitive decompressive therapy.

Provides long-term relief of cord compression and local tumor control.

This is the final intervention in the acute management pathway to prevent permanent paralysis.

Key Concept

In patients with suspected malignant spinal cord compression presenting with neurologic deficits, intravenous corticosteroids must be administered immediately prior to diagnostic imaging to prevent irreversible neurologic damage.

Estimated Time:1m 30s

Question 154Question →

An intensive care unit team is evaluating a $68$ -year-old man who remains ventilator-dependent $18$ days after an emergency exploratory laparotomy and bowel resection for acute mesenteric ischemia. His prolonged hospitalization has been complicated by septic shock and ventilator-associated pneumonia. He is currently hemodynamically stable and off vasopressor support, but repeated attempts to wean him from mechanical ventilation have failed. His temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), blood pressure is $118/76\text{ mm Hg}$ , and pulse is $88\text{/min}$ . Physical examination reveals generalized muscle wasting and diffuse anasarca. The thyroid gland is not palpable. As part of a comprehensive evaluation for the failure to wean, the following laboratory results are obtained:

Laboratory Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	$0.15\text{ mIU/L}$	$0.4 - 4.0\text{ mIU/L}$
Free T4	$0.6\text{ ng/dL}$	$0.9 - 1.7\text{ ng/dL}$
Total T3	$42\text{ ng/dL}$	$80 - 200\text{ ng/dL}$
Morning serum cortisol	$32\text{ \mu g/dL}$	$5 - 23\text{ \mu g/dL}$

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

Continue current supportive care without thyroid hormone supplementation

Initiate enteral levothyroxine replacement therapy

Initiate enteral methimazole therapy

Perform a radioactive iodine uptake scan

Measure serum thyroid peroxidase antibodies

Show answer & explanation

Answer: Continue current supportive care without thyroid hormone supplementation

Answer

Continue current supportive care without thyroid hormone supplementation

The correct answer is to continue current supportive care without thyroid hormone supplementation. This patient's laboratory profile (low T3, low free T4, and low TSH) in the setting of severe, prolonged critical illness is classic for euthyroid sick syndrome (also known as nonthyroidal illness syndrome). This condition represents an adaptive physiologic response to severe systemic stress, characterized primarily by decreased peripheral conversion of T4 to active T3 (due to decreased 5'-deiodinase activity) and altered central TRH/TSH regulation. Thyroid hormone supplementation (such as levothyroxine or liothyronine) has not been shown to improve clinical outcomes, weaning from mechanical ventilation, or survival in these patients, and it may be harmful. The appropriate management is to treat the underlying illness; thyroid function typically normalizes upon recovery.

Step-by-Step Solution

Evaluate the patient's clinical status and context.

The patient is in a state of severe, prolonged critical illness (postoperative shock, prolonged mechanical ventilation, generalized wasting).

Establishing the severity and acuity of the illness is critical for interpreting endocrine adaptations versus true pathology.

Analyze the thyroid laboratory panel in conjunction with the clinical context.

The panel shows low TSH, low free T4, and profoundly low total T3.

This specific pattern (especially the low T3 with variable T4 and TSH) is the hallmark of euthyroid sick syndrome, not primary or secondary hypothyroidism.

Evaluate the adrenal axis to rule out panhypopituitarism.

Morning serum cortisol is appropriately elevated (

32\text{ \mu g/dL}

) in the setting of severe stress.

A robust cortisol response effectively rules out central adrenal insufficiency, making true panhypopituitarism highly unlikely and confirming the thyroid labs are a standalone systemic adaptation.

Determine the evidence-based management strategy.

The plan should be observation and supportive care without exogenous thyroid hormones.

Clinical trials have consistently shown that supplementing thyroid hormone in euthyroid sick syndrome provides no benefit and may cause harm.

Key Concept

Euthyroid Sick Syndrome (Nonthyroidal Illness Syndrome)

Question 155Question →

Evaluate the following clinical vignettes detailing neonates with suspected congenital infections. Match each clinical presentation to the most likely etiologic agent based on the distinctive physical and radiographic findings.

Click a left item, then click its matching right item

Show answer & explanation

Answer

The presentations match as follows: Periventricular calcifications with Cytomegalovirus; Diffuse cortical calcifications and hydrocephalus with Toxoplasma gondii; Desquamating palmar rash and snuffles with Treponema pallidum; and Cataracts with a continuous murmur with Rubella virus.

Each congenital infection presents with a distinct, defining constellation of clinical and radiographic findings. Congenital CMV is distinguished by periventricular calcifications; Toxoplasmosis by diffuse cortical calcifications and severe hydrocephalus; Syphilis by snuffles, palmar/plantar desquamation, and metaphyseal osteochondritis; and Rubella by cataracts and a patent ductus arteriosus.

Step-by-Step Solution

Analyze the pattern of intracranial calcifications in the neuroimaging vignettes.

Subependymal/periventricular calcifications isolate Cytomegalovirus, whereas diffuse parenchymal/cortical calcifications with hydrocephalus isolate Toxoplasma gondii.

CMV has a predilection for the germinal matrix lining the ventricles, while Toxoplasma causes widespread tissue necrosis and subsequent calcification throughout the brain parenchyma.

Evaluate the constellation of cardiac and ophthalmologic findings.

The presence of an absent red reflex (cataracts) and a continuous machine-like murmur (patent ductus arteriosus) identifies the Rubella virus vignette.

These specific developmental disruptions occurring during the first trimester are the pathognomonic triad of congenital Rubella syndrome.

Assess the mucocutaneous and skeletal abnormalities.

The combination of severe serosanguineous rhinitis, palmar/plantar desquamation, and metaphyseal lucencies identifies the Treponema pallidum vignette.

These findings represent the early inflammatory manifestations (osteochondritis and mucocutaneous lesions) specific to early congenital syphilis.

Key Concept

Clinical differentiation of congenital (TORCH) infections based on unique physical examination triads and neuroimaging calcification patterns.

Estimated Time:2m 0s

Question 156Question →

Match the following serum calcium and intact parathyroid hormone (PTH) laboratory profiles to their most likely underlying pathophysiologic diagnosis.

Click a left item, then click its matching right item

Show answer & explanation

Answer

Elevated Ca/Elevated PTH matches Primary hyperparathyroidism. Decreased Ca/Elevated PTH matches Vitamin D deficiency. Elevated Ca/Suppressed PTH matches Humoral hypercalcemia of malignancy. Decreased Ca/Suppressed PTH matches Iatrogenic parathyroidectomy.

The parathyroid glands maintain calcium homeostasis through a direct negative feedback loop. Normal physiology dictates an inverse relationship: high calcium suppresses PTH, and low calcium stimulates PTH (secondary disorders). A direct relationship (both high or both low) indicates a primary parathyroid disorder.

Step-by-Step Solution

Evaluate the serum calcium level in the provided profile.

Determines whether the clinical state is characterized by hypercalcemia or hypocalcemia.

Calcium is the primary regulated variable in this endocrine loop, driving the downstream hormonal response.

Evaluate the intact PTH level in the context of the calcium abnormality.

Identifies if the PTH response is appropriate (compensatory) or inappropriate (primary pathology).

An intact negative feedback loop will show PTH moving in the opposite direction of calcium. If PTH moves in the same direction, the parathyroid gland is the source of the pathology.

Key Concept

Calcium and Parathyroid Hormone (PTH) Homeostasis and Feedback Loop

Question 157Question →

A full-term female infant is examined in the newborn nursery at $48\text{ hours}$ after birth due to the sudden appearance of a widespread skin eruption. She was born at $40\text{ weeks}$ of gestation via uncomplicated vaginal delivery to a $26\text{-year-old}$ primigravid mother. Maternal prenatal laboratory testing was unremarkable, and group B \textit{Streptococcus} screening was negative. Birth weight was $3,450\text{ g}$ . Apgar scores were $7$ and $9$ at $1$ and $5\text{ minutes}$ , respectively. The infant has been breastfeeding well every $2$ to $3\text{ hours}$ and has passed meconium and urine normally.

Vital signs are temperature $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), heart rate $135/\text{min}$ , and respiratory rate $42/\text{min}$ . Physical examination reveals an active, alert neonate. There is a disseminated rash characterized by multiple $1$ to $3\text{ mm}$ pale-yellow pustules surrounded by broad erythematous macules. The lesions are prominent on the trunk, face, and proximal extremities, but completely spare the palms and soles. The remainder of the physical examination, including neurologic reflexes, is within normal limits.

A complete blood count and microscopic evaluation of the pustular fluid are obtained. The results are as follows:

Parameter	Result	Reference Range
Leukocytes	$14,500/\mu\text{L}$	$9,000-30,000/\mu\text{L}$
Neutrophils	$48\%$	$40-60\%$
Lymphocytes	$35\%$	$20-40\%$
Eosinophils	$12\%$	$1-3\%$
Pustule Wright-Giemsa stain	Predominance of bilobed granular leukocytes; no microorganisms seen	-

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

Reassurance and continued routine newborn care

Blood, urine, and cerebrospinal fluid cultures followed by intravenous ampicillin and gentamicin

Empirical administration of intravenous acyclovir and surface swabbing for polymerase chain reaction

Application of topical mupirocin ointment to the affected skin areas

Skin scraping for potassium hydroxide preparation and empirical topical nystatin

Show answer & explanation

Answer: Reassurance and continued routine newborn care

Answer

Reassurance and continued routine newborn care

The correct answer is reassurance and continued routine newborn care. This neonate presents with classic findings of erythema toxicum neonatorum (ETN), which is one of the most common benign rashes in healthy term newborns. It typically appears within the first 24 to 72 hours of life. The rash is characterized by firm, 1 to 3 mm pale-yellow or white papules and pustules surrounded by a prominent erythematous base (often described as having a 'flea-bitten' appearance). The lesions frequently appear on the trunk and proximal extremities but characteristically spare the palms and soles. The underlying pathophysiology involves a sterile, localized accumulation of eosinophils. This is definitively demonstrated in this vignette by the peripheral eosinophilia (12%) and the Wright-Giemsa stain of the pustule contents, which reveals bilobed granular leukocytes (eosinophils) and lacks microorganisms. Because ETN is an entirely benign condition that spontaneously resolves without scarring over 1 to 2 weeks, no laboratory evaluation or pharmacological intervention is required. The most appropriate management is to reassure the parents and continue routine newborn care.

Step-by-Step Solution

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

The patient is a healthy, full-term neonate at 48 hours of life with normal vital signs and a rash composed of pustules on an erythematous base that spares the palms and soles.

Identifying the timing, morphology, and distribution of the rash alongside the patient's systemic stability is essential to differentiate between benign newborn rashes and life-threatening congenital or neonatal infections.

Interpret the laboratory and cytological data.

The peripheral blood shows eosinophilia (12%), and the Wright-Giemsa stain of the pustule reveals bilobed granular leukocytes (eosinophils) without any bacteria or viral cytopathic effects.

Cytology provides the definitive pathophysiologic mechanism for the rash, ruling out bacterial or viral etiologies.

Synthesize the findings to establish a diagnosis.

The combination of a 'flea-bitten' pustular rash sparing the palms/soles in a healthy neonate, coupled with eosinophils in the pustules and blood, is diagnostic of erythema toxicum neonatorum (ETN).

ETN is a common, self-limited, immune-mediated condition characterized by localized eosinophilic infiltration.

Determine the appropriate management plan based on the diagnosis.

Because ETN is entirely benign and resolves spontaneously within 1 to 2 weeks, the correct step is reassurance and observation.

Recognizing benign conditions prevents unnecessary, painful, and potentially harmful invasive procedures and antibiotic use.

Key Concept

Erythema toxicum neonatorum is a benign, self-limited rash appearing in the first few days of life, characterized by erythematous macules with central pustules containing eosinophils, requiring only reassurance.

Estimated Time:1m 30s

Question 158Question →

A 32-year-old woman is evaluated in the emergency department for severe, watery diarrhea occurring over the past 5 days after returning from a trip abroad. She reports weakness and dry mouth. Vital signs show a blood pressure of 100/60 mm Hg and a heart rate of 110/min.

Laboratory studies show:
Serum sodium: $140 \text{ mEq/L}$
Serum chloride: $115 \text{ mEq/L}$
Serum bicarbonate: $16 \text{ mEq/L}$
Serum potassium: $3.2 \text{ mEq/L}$

Arterial blood gas analysis on room air shows a pH of 7.30.

Assuming appropriate respiratory compensation has occurred, which of the following is the expected arterial partial pressure of carbon dioxide (PaCO2) in this patient?

16 \text{ mm Hg}

24 \text{ mm Hg}

32 \text{ mm Hg}

40 \text{ mm Hg}

48 \text{ mm Hg}

Show answer & explanation

Answer: $32 \text{ mm Hg}$

Answer

32 \text{ mm Hg}

This patient presents with a primary metabolic acidosis due to gastrointestinal bicarbonate losses (severe diarrhea). In the presence of metabolic acidosis, the physiological respiratory compensation is hyperventilation, which decreases the carbon dioxide level. The exact expected PaCO2 can be calculated using Winter's formula:

\text{Expected } PaCO_2 = (1.5 \times [HCO_3^-]) + 8 \pm 2

. Using the patient's bicarbonate of

16 \text{ mEq/L}

, the calculation is

(1.5 \times 16) + 8 = 24 + 8 = 32 \text{ mm Hg}

Step-by-Step Solution

Identify the primary acid-base disorder based on the provided laboratory values.

The patient has a low pH (7.30) and low bicarbonate (

16 \text{ mEq/L}

), indicating a primary metabolic acidosis.

Severe diarrhea causes loss of bicarbonate in the stool, leading to a normal anion gap metabolic acidosis.

Select the appropriate formula to calculate respiratory compensation for metabolic acidosis.

Use Winter's formula:

\text{Expected } PaCO_2 = (1.5 \times [HCO_3^-]) + 8 \pm 2

Winter's formula is the standard physiological calculation to determine if respiratory compensation for metabolic acidosis is adequate.

Perform the calculation using the patient's serum bicarbonate level.

(1.5 \times 16) + 8 = 24 + 8 = 32 \text{ mm Hg}

Inserting the given bicarbonate value of

16 \text{ mEq/L}

yields the precise expected target for PaCO2.

Key Concept

Respiratory compensation in primary metabolic acidosis (Winter's formula)

Question 159Question →

A 4-day-old term male neonate is brought to the emergency department due to repeated episodes of dark green vomiting over the past 4 hours. The infant has been exclusively breastfed and previously tolerated feeds without difficulty. Vital signs reveal a heart rate of 170/min, respiratory rate of 48/min, and blood pressure of 65/40 mm Hg. Physical examination shows a fussy neonate with a mildly distended abdomen and dry mucous membranes. Arrange the following steps in the most appropriate chronological order for the evaluation and management of this patient's condition.

Drag items to arrange them in the correct order

Show answer & explanation

Answer

The correct sequence is to first initiate intravenous fluid resuscitation and nasogastric decompression, followed by obtaining a plain abdominal radiograph, then performing an upper gastrointestinal contrast series, and finally proceeding with an emergent exploratory laparotomy.

The evaluation of neonatal bilious emesis follows a strict algorithmic approach to rapidly identify surgical emergencies while minimizing harm. The neonate must first be hemodynamically stabilized (intravenous fluids) and decompressed (nasogastric tube) to prevent aspiration. Following stabilization, a plain abdominal radiograph is mandatory to rule out a perforated bowel. Because the plain film in malrotation is often non-diagnostic (showing a normal or gasless abdomen), an upper gastrointestinal contrast series is then required to definitively diagnose the condition by identifying an abnormally placed duodenojejunal junction. Once the diagnosis of malrotation with volvulus is established, emergent surgical intervention via the Ladd procedure is the definitive treatment to restore bowel perfusion.

Step-by-Step Solution

Hemodynamic stabilization and bowel decompression

The patient's intravascular volume is restored and the stomach is decompressed to prevent aspiration.

Bilious emesis is a sign of intestinal obstruction. Dehydration and potential shock must be addressed first before sending the infant for diagnostic imaging.

Plain abdominal radiography

Assesses the abdomen for pneumoperitoneum or the classic 'double bubble' sign.

It is critical to rule out a perforated viscus before administering contrast. If free air is present, contrast studies are strictly contraindicated.

Upper gastrointestinal contrast series

Visualizes the anatomy of the upper GI tract, specifically looking for an abnormally placed ligament of Treitz or a 'corkscrew' appearance.

This is the most sensitive and specific study to diagnose malrotation and midgut volvulus when the plain film does not show free air.

Surgical intervention (Ladd procedure)

Definitive treatment via exploratory laparotomy to resolve the obstruction.

Emergent surgery is required to untwist the volvulus, divide the Ladd bands, and broaden the mesenteric base to prevent recurrent ischemia and bowel necrosis.

Key Concept

Algorithm for the evaluation and management of neonatal bilious emesis

Question 160Question →

A 68-year-old man is brought to the emergency department by his son because he has been acting confused since yesterday morning. For the past three days, he has also experienced subjective fevers, chills, and a cough productive of yellowish sputum. His medical history includes hypertension, benign prostatic hyperplasia, and osteoarthritis. He does not use tobacco, alcohol, or illicit substances. His temperature is $38.7^\circ\text{C}$ ( $101.7^\circ\text{F}$ ), pulse is $102/\text{min}$ , blood pressure is $115/70\text{ mmHg}$ , and respiratory rate is $24/\text{min}$ . Pulse oximetry indicates an oxygen saturation of $92\%$ on room air. He appears acutely ill and is oriented only to person. Pulmonary auscultation reveals crackles and bronchial breath sounds over the left lower lung fields. Laboratory evaluation is notable for a leukocyte count of $15,500/\text{mm}^3$ and a blood urea nitrogen (BUN) level of $24\text{ mg/dL}$ . Chest radiography demonstrates a dense left lower lobe consolidation. The patient is admitted to the general medical ward. Which of the following is the most appropriate empiric pharmacotherapy for this patient?

Intravenous ceftriaxone and azithromycin

Oral amoxicillin-clavulanate and azithromycin

Intravenous piperacillin-tazobactam and vancomycin

Intravenous ciprofloxacin

Oral amoxicillin

Show answer & explanation

Answer: Intravenous ceftriaxone and azithromycin

Answer

Intravenous ceftriaxone and azithromycin

The correct answer is intravenous ceftriaxone and azithromycin. This patient presents with community-acquired pneumonia (CAP) and signs of significant severity, including confusion and an elevated blood urea nitrogen (BUN). Utilizing the CURB-65 scoring system, he scores 3 points (Confusion, BUN > 19 mg/dL, Age > 65), which mandates inpatient admission to a medical ward. Current guidelines recommend that non-ICU inpatients with CAP be treated empirically with a beta-lactam (such as intravenous ceftriaxone, cefotaxime, or ampicillin-sulbactam) combined with a macrolide (such as azithromycin). Alternatively, monotherapy with a respiratory fluoroquinolone (like levofloxacin or moxifloxacin) can be used. This beta-lactam plus macrolide combination effectively targets the most common typical organisms (e.g., Streptococcus pneumoniae, Haemophilus influenzae) as well as atypical organisms (e.g., Mycoplasma pneumoniae, Legionella pneumophila).

Step-by-Step Solution

Calculate the patient's severity using a validated scoring system such as CURB-65.

The patient scores 3 points (Confusion = 1, BUN > 19 mg/dL = 1, Age > 65 = 1).

Determines the appropriate site of care (outpatient vs. inpatient ward vs. ICU).

Determine the appropriate setting for treatment based on the severity score.

A CURB-65 score of 3 indicates severe community-acquired pneumonia warranting inpatient hospital admission.

Patients with scores 0-1 can typically be treated as outpatients, a score of 2 requires consideration for admission, and 3-5 require hospital admission.

Select the guideline-concordant empiric antibiotic regimen for inpatient (non-ICU) community-acquired pneumonia.

The standard of care is an intravenous beta-lactam (e.g., ceftriaxone) plus a macrolide (e.g., azithromycin), or monotherapy with a respiratory fluoroquinolone.

This regimen covers the most common typical and atypical respiratory pathogens without unnecessarily broadening the spectrum.

Key Concept

Empiric antibiotic selection for inpatient community-acquired pneumonia

PreviousPage 8 / 414Next

All practice questions

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Alternative Method

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Answer

Step-by-Step Solution