Internal Medicine Alıştırma Soruları — USMLE Step 2 CK — Sayfa 94

Soru 1861Soru →

A 62-year-old man with a history of metastatic prostate cancer is brought to the emergency department due to three days of progressively worsening mid-back pain. Over the last 12 hours, he has developed bilateral lower extremity weakness and urinary retention. Vital signs are within normal limits. Neurologic examination reveals 3/5 motor strength in the lower extremities bilaterally, 3+ patellar reflexes, and decreased sensation to pinprick below the level of the umbilicus. Post-void residual volume is 600 mL.

Arrange the following steps in the most appropriate sequential order for the management of this patient's current condition.

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Cevap

The correct sequential order for managing suspected malignant epidural spinal cord compression with neurologic deficits is to first administer intravenous high-dose dexamethasone, followed by obtaining an urgent MRI of the spine, then consulting for definitive local therapy (surgery or radiation), and finally addressing long-term systemic therapy.

The patient's presentation of progressive back pain, lower extremity weakness, a distinct sensory level, and urinary retention in the setting of metastatic prostate cancer is highly suspicious for malignant epidural spinal cord compression (MESCC). When neurologic deficits are present, the absolute first step in management is the immediate administration of high-dose intravenous glucocorticoids (e.g., dexamethasone). Corticosteroids reduce vasogenic edema, relieve pressure on the spinal cord, and preserve neurologic function. They must not be delayed for imaging. Once steroids are given, an urgent whole-spine MRI is the gold standard to confirm the diagnosis and map the extent of the disease. Following MRI confirmation, patients require definitive local therapy with either surgical decompression (often preferred for spinal instability or radioresistant tumors) or radiation therapy. Finally, after the acute emergency is managed, modifications to the patient's systemic chemotherapy or hormonal therapy can be planned.

Adım Adım Çözüm

1

Identify the clinical emergency.

The patient's back pain, lower extremity weakness, sensory level, and urinary retention strongly indicate malignant epidural spinal cord compression (MESCC).

Recognizing the neurologic deficits dictates the urgency and appropriate sequence of management.

2

Administer high-dose corticosteroids.

Intravenous dexamethasone is given immediately as the very first step.

To decrease vasogenic edema surrounding the spinal cord and prevent irreversible ischemic injury and permanent paralysis.

3

Obtain diagnostic imaging.

Urgent MRI of the entire spine is performed.

To confirm the presence of epidural disease, determine the exact anatomical level of compression, and identify any asymptomatic lesions elsewhere in the spine.

4

Provide definitive local treatment.

Surgical decompression or radiation therapy is initiated.

To provide long-term relief of cord compression based on the MRI findings and tumor radiosensitivity.

Anahtar Kavram

In patients with suspected malignant epidural spinal cord compression who present with neurologic deficits, empiric high-dose corticosteroids must be administered immediately prior to confirmatory imaging.

Soru 1862Soru →

A 24-year-old primigravida at 24 weeks gestation comes to the clinic reporting frequent, unprovoked nosebleeds and a new rash on her lower extremities over the past two days. She feels fetal movement and has no other complaints. Temperature is $37.0^\circ\text{C}$ ( $98.6^\circ\text{F}$ ), blood pressure is $118/76 \text{ mmHg}$ , and heart rate is $82/\text{min}$ . Physical examination reveals scattered, non-blanching, pinpoint macules over her shins and ankles. The uterus is consistent in size with a 24-week gestation, and fetal heart rate is $145/\text{min}$ with normal variability.

Laboratory results are as follows:

Laboratory Test	Result
Hemoglobin	$11.4 \text{ g/dL}$
White blood cell count	$7,800/\mu\text{L}$
Platelet count	$14,000/\mu\text{L}$
Prothrombin time	$11 \text{ s}$
Partial thromboplastin time	$28 \text{ s}$
Creatinine	$0.7 \text{ mg/dL}$

A peripheral blood smear demonstrates a few enlarged platelets with normal morphology and a lack of schistocytes. Which of the following is the most appropriate next step in management?

Broad-spectrum intravenous antibiotics

Reassurance and routine prenatal care

Administration of systemic corticosteroids

Plasma exchange

Immediate induction of labor

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Cevap: Administration of systemic corticosteroids

Cevap

Administration of systemic corticosteroids

The correct answer is administration of systemic corticosteroids. This patient presents with isolated severe thrombocytopenia and mucocutaneous bleeding (epistaxis, petechiae) at 24 weeks gestation, which is characteristic of primary immune thrombocytopenic purpura (ITP). ITP is an autoimmune condition involving IgG antibodies against platelet membrane antigens (e.g., GpIIb/IIIa). In pregnancy, treatment for ITP is indicated when the platelet count is below

30,000/\mu\text{L}

or if there is clinically significant bleeding. Systemic corticosteroids (such as oral prednisone) or intravenous immune globulin (IVIG) are the safest and most effective first-line therapies.

Adım Adım Çözüm

1

Analyze the patient's symptoms and laboratory values.

The patient has isolated severe thrombocytopenia (platelets 14,000/μL) and mucocutaneous bleeding (epistaxis, petechiae) at 24 weeks gestation.

Identifying the primary derangement is required to formulate a differential diagnosis.

2

Evaluate the peripheral blood smear and coagulation profile.

Normal PT and PTT rule out consumptive coagulopathies like DIC. The absence of schistocytes rules out microangiopathic hemolytic anemias like TTP or HELLP syndrome.

Critical life-threatening causes of thrombocytopenia in pregnancy must be rapidly excluded.

3

Determine the most likely diagnosis and indications for treatment.

The diagnosis is primary immune thrombocytopenic purpura (ITP). Because the platelet count is below 30,000/μL and the patient is bleeding, active treatment is indicated.

Gestational thrombocytopenia does not cause severe bleeding or platelet counts < 70,000/μL, pointing to ITP which requires medical intervention.

4

Select the appropriate initial therapy.

Systemic corticosteroids (or IVIG) are selected as the safest and most effective first-line therapy in pregnancy.

Corticosteroids reduce immune-mediated platelet destruction and are safe in the second trimester.

Anahtar Kavram

Management of immune thrombocytopenic purpura (ITP) in pregnancy

Soru 1863Soru →

Emergency medical responders transport a $62$ -year-old woman to the emergency department due to progressive lethargy and a four-day history of a productive cough. Her past medical history is significant for severe chronic obstructive pulmonary disease. Upon arrival, her temperature is $38.8^\circ\text{C}$ ( $101.8^\circ\text{F}$ ), blood pressure is $88/54\text{ mm Hg}$ , pulse is $122/\text{min}$ , and respirations are $26/\text{min}$ . Oxygen saturation is $85\%$ on room air. Physical examination reveals a somnolent patient with prominent accessory muscle use, diffuse expiratory wheezing, and bilateral rhonchi. Laboratory results are as follows:

Parameter	Value
Serum sodium	$138\text{ mEq/L}$
Serum potassium	$4.2\text{ mEq/L}$
Serum chloride	$102\text{ mEq/L}$
Serum bicarbonate	$12\text{ mEq/L}$
Blood urea nitrogen	$42\text{ mg/dL}$
Serum creatinine	$1.8\text{ mg/dL}$
Serum lactate	$6.5\text{ mmol/L}$

Arterial blood gas analysis (on room air):

Parameter	Value
pH	$7.12$
$\text{PaO}_2$	$55\text{ mm Hg}$
$\text{PaCO}_2$	$38\text{ mm Hg}$

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

Normal anion gap metabolic acidosis and concurrent respiratory acidosis

High anion gap metabolic acidosis with appropriate respiratory compensation

High anion gap metabolic acidosis and concurrent respiratory acidosis

High anion gap metabolic acidosis and concurrent respiratory alkalosis

Normal anion gap metabolic acidosis with appropriate respiratory compensation

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Cevap: High anion gap metabolic acidosis and concurrent respiratory acidosis

Cevap

High anion gap metabolic acidosis and concurrent respiratory acidosis

The patient's laboratory results demonstrate a high anion gap metabolic acidosis with a concurrent primary respiratory acidosis. First, the severe acidemia (pH

7.12

) with a low bicarbonate (

12\text{ mEq/L}

) establishes a primary metabolic acidosis. Next, calculating the anion gap (

138 - [102 + 12] = 24\text{ mEq/L}

) confirms a high anion gap metabolic acidosis (HAGMA), which is driven by lactic acidosis from tissue hypoperfusion. Finally, Winter's formula must be applied to determine if the respiratory compensation is appropriate:

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

. For this patient, the expected

\text{PaCO}_2

is

(1.5 \times 12) + 8 = 26 \pm 2\text{ mm Hg}

. Because the measured

\text{PaCO}_2

of

38\text{ mm Hg}

is significantly higher than the expected range of

24-28\text{ mm Hg}

, there is an inadequate respiratory response. This indicates a superimposed primary respiratory acidosis, a life-threatening complication in COPD patients experiencing acute respiratory failure alongside shock.

Adım Adım Çözüm

1

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

The pH is

7.12

(acidemia) and the serum bicarbonate is

12\text{ mEq/L}

(markedly low), indicating a primary metabolic acidosis.

Establishing the primary direction of the pH derangement dictates which subsequent diagnostic formulas are required.

2

Calculate the serum anion gap to characterize the metabolic acidosis.

\text{Anion Gap} = \text{Na}^+ - (\text{Cl}^- + \text{HCO}_3^-) = 138 - (102 + 12) = 24\text{ mEq/L}

. This confirms a high anion gap metabolic acidosis (HAGMA).

Differentiation between high and normal anion gap acidosis is essential for uncovering the underlying etiology (in this case, lactic acidosis from sepsis).

3

Apply Winter's formula to assess the adequacy of the respiratory compensation.

\text{Expected PaCO}_2 = (1.5 \times \text{HCO}_3^-) + 8 \pm 2 = (1.5 \times 12) + 8 = 26 \pm 2\text{ mm Hg}

.

Metabolic acidosis stimulates central chemoreceptors to increase alveolar ventilation. Winter's formula predicts the physiologically appropriate

\text{PaCO}_2

for a given bicarbonate level.

4

Compare the measured PaCO2 to the expected PaCO2 range.

The measured

\text{PaCO}_2

is

38\text{ mm Hg}

, which is significantly higher than the maximum expected value of

28\text{ mm Hg}

.

Because the patient is retaining more

\text{CO}_2

than physiologically expected for her level of metabolic acidosis, a concurrent primary respiratory acidosis is present (consistent with her severe COPD exacerbation).

Anahtar Kavram

In patients with a primary metabolic acidosis, Winter's formula (

\text{Expected PaCO}_2 = [1.5 \times \text{HCO}_3^-] + 8 \pm 2

) must be used to evaluate if the respiratory compensation is adequate. A measured

\text{PaCO}_2

higher than the expected range indicates a superimposed primary respiratory acidosis.

Soru 1864Soru →

Match each clinical patient presentation with the most likely corresponding urinalysis sediment finding.

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The ischemic presentation matches with muddy brown granular casts; the post-infectious nephritic presentation matches with red blood cell casts; the medication-induced allergic presentation matches with white blood cell casts; and the diabetic nephrotic presentation matches with oval fat bodies.

Each correct pairing links a classic clinical presentation to its definitive microscopic urinary finding based on the compartment of the kidney affected. Ischemia affects the tubules (muddy brown casts), inflammation of the glomeruli allows RBC leakage (RBC casts), drug allergies inflame the interstitium (WBC casts), and severe podocyte damage causes massive lipiduria (fatty casts).

Adım Adım Çözüm

1

Analyze each clinical vignette to determine the underlying renal pathophysiology.

Identified the four mechanisms: ischemic acute tubular necrosis, nephritic syndrome (glomerulonephritis), acute interstitial nephritis, and nephrotic syndrome.

Accurate diagnosis of the underlying mechanism is required to predict the microscopic findings in the urine.

2

Correlate the identified pathophysiology with its pathognomonic urinalysis sediment finding.

Matched ATN to muddy brown casts, glomerulonephritis to RBC casts, AIN to WBC casts, and nephrotic syndrome to fatty casts.

Different compartments of the kidney (tubules, glomeruli, interstitium) slough specific cellular materials into the urine when injured.

Anahtar Kavram

Correlation of distinct acute kidney injury and glomerular disease mechanisms with their classic urinalysis sediment patterns.

Soru 1865Soru →

An emergency medical team brings a $68$ -year-old man to the acute care facility due to the sudden onset of severe respiratory distress that awoke him from sleep. Over the past month, he has noted progressive fatigue and a $4$ -kg ( $8.8$ -lb) weight gain. He has a $45$ -pack-year smoking history. He reports a mild, productive cough over the last week. A sputum culture collected at his primary care physician's office three days ago grew *Haemophilus influenzae* susceptible to amoxicillin.

Upon arrival, he is speaking in short phrases and appears anxious.
Temperature: $37.1^{\circ}\text{C}$ ( $98.8^{\circ}\text{F}$ )
Blood pressure: $172/96 \text{ mm Hg}$
Pulse: $115\text{ /min}$ , regular
Respirations: $26\text{ /min}$
Oxygen saturation: $88\%$ on ambient air

Physical examination reveals prominent distention of the external jugular veins when the patient is sitting upright. Cardiac auscultation demonstrates a normal S $1$ and S $2$ with an extra low-frequency diastolic sound. Pulmonary examination shows diffuse expiratory wheezing and bilateral inspiratory crackles extending to the mid-thoracic fields. The lower extremities exhibit $2+$ symmetric pitting edema.

Laboratory analysis reveals:
Thyroid-stimulating hormone (TSH): $1.4 \text{ }\mu\text{U/mL}$ (Normal: $0.5$ - $5.0$ )
Free thyroxine (T4): $0.6 \text{ ng/dL}$ (Normal: $0.9$ - $1.7$ )

Arterial blood gas analysis on ambient air:
pH: $7.46$
$\text{PaCO}_2$ : $32 \text{ mm Hg}$
$\text{PaO}_2$ : $56 \text{ mm Hg}$
$\text{HCO}_3^-$ : $22 \text{ mEq/L}$

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

Initiation of empiric vancomycin and piperacillin-tazobactam

Administration of nebulized albuterol and systemic glucocorticoids

Calculation of expected

\text{PaCO}_2

using Winter's formula

Intravenous administration of furosemide

Intravenous administration of levothyroxine

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Cevap: Intravenous administration of furosemide

Cevap

Intravenous administration of furosemide

The patient's presentation of paroxysmal nocturnal dyspnea, elevated jugular venous pressure, an S3 gallop, bibasilar crackles, and peripheral edema is highly specific for acute decompensated heart failure (ADHF) with pulmonary edema. The presence of wheezing, often termed 'cardiac asthma,' occurs due to peribronchial edema and can mimic primary airway disease. The most appropriate initial step in the management of volume-overloaded ADHF is the intravenous administration of a loop diuretic, such as furosemide, which provides both rapid venodilation (decreasing preload) and subsequent diuresis.

Adım Adım Çözüm

1

Analyze the clinical presentation and physical examination findings.

The combination of jugular venous distention, an S3 gallop, bilateral crackles, and peripheral edema in a patient with acute dyspnea indicates severe volume overload.

To differentiate between cardiogenic (heart failure) and pulmonary (COPD/asthma) causes of respiratory distress.

2

Evaluate the arterial blood gas and laboratory results.

The ABG shows hypoxemia with a respiratory alkalosis. Thyroid labs indicate euthyroid sick syndrome.

To rule out primary acid-base or endocrine emergencies driving the acute presentation.

3

Determine the most appropriate initial therapy.

Intravenous loop diuretics (e.g., furosemide) are indicated.

To rapidly reduce left ventricular preload and alleviate pulmonary venous congestion in acute decompensated heart failure.

Anahtar Kavram

Acute decompensated heart failure can present with wheezing ('cardiac asthma') and must be distinguished from COPD exacerbations using clinical signs of volume overload (JVD, S3 gallop, edema) to guide appropriate diuretic therapy.

Tahmini Süre:1m 30s

Soru 1866Soru →

During an outpatient evaluation, a 28-year-old female patient reports experiencing profound anxiety, palpitations, and a $5$ -kg ( $11$ -lb) weight loss over the past two months. She states she recently began taking various unprescribed "fat-burner" dietary supplements purchased online to prepare for a fitness competition. She denies any neck pain, recent viral illnesses, or changes in her vision. Her temperature is $37.0^{\circ}$ C ( $98.6^{\circ}$ F), blood pressure is $135/75$ mm Hg, and pulse is $114$ /min. Physical examination reveals a fine resting tremor of the outstretched hands, warm and moist skin, and brisk deep tendon reflexes. Ophthalmic examination shows no proptosis, lid lag, or periorbital edema. The thyroid gland is not palpable, and there is no cervical lymphadenopathy. Laboratory studies reveal:

Thyroid-stimulating hormone (TSH): $< 0.02$ $\mu$ U/mL
Free thyroxine (T4): $3.2$ ng/dL

Which of the following additional findings is most likely present in this patient?

Decreased serum thyroglobulin concentration

Elevated serum thyroglobulin concentration

Diffusely increased radioactive iodine uptake

Increased color Doppler flow on thyroid ultrasound

Elevated thyroid-stimulating immunoglobulin levels

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Cevap: Decreased serum thyroglobulin concentration

Cevap

Decreased serum thyroglobulin concentration

This patient's presentation of thyrotoxicosis symptoms, suppressed TSH, elevated free T4, use of unprescribed weight-loss supplements, and a non-palpable thyroid gland is highly suggestive of factitious thyrotoxicosis (exogenous thyroid hormone ingestion). Many unregulated 'fat burners' contain animal thyroid extract or synthetic levothyroxine. In this condition, the exogenous hormone suppresses pituitary TSH secretion. The lack of TSH stimulation causes the endogenous thyroid gland to become inactive. Thyroglobulin is a protein precursor produced exclusively by the thyroid gland during the normal synthesis of endogenous thyroid hormones. Because the gland is inactive in exogenous thyrotoxicosis, serum thyroglobulin concentrations will be remarkably decreased. This key laboratory finding distinguishes exogenous thyrotoxicosis from destructive thyroiditis (e.g., subacute or silent thyroiditis), which also presents with low radioactive iodine uptake but features an elevated thyroglobulin level due to the release of preformed hormone and cellular debris from inflamed follicles.

Adım Adım Çözüm

1

Analyze the clinical presentation and initial laboratory results.

The patient has clinical thyrotoxicosis with a suppressed TSH and elevated free T4, confirming primary hyperthyroidism or exogenous thyroid hormone excess.

Establishing the biochemical presence of thyrotoxicosis is the first step in the diagnostic algorithm.

2

Evaluate the physical examination findings and history for etiology.

The patient lacks a palpable goiter, has no eye findings (proptosis), and is taking unregulated "fat-burner" supplements, pointing strongly toward exogenous thyroid hormone ingestion (factitious thyrotoxicosis).

Differentiating the cause of thyrotoxicosis dictates the expected ancillary test results.

3

Determine the expected thyroglobulin level based on the etiology.

Because the excess thyroid hormone is coming from an exogenous source, the endogenous thyroid gland is suppressed by the low TSH. Therefore, thyroglobulin (a byproduct of endogenous hormone synthesis) will be decreased.

Thyroglobulin levels differentiate exogenous thyrotoxicosis (low) from endogenous hyperthyroidism or destructive thyroiditis (both high).

Anahtar Kavram

Differentiation of thyrotoxicosis etiologies using serum thyroglobulin

Tahmini Süre:1m 0s

Soru 1867Soru →

A $32$ -year-old woman comes to the clinic reporting facial pressure and nasal congestion that began $5$ days ago. She states her symptoms started with a mild scratchy throat and clear rhinorrhea but have since progressed. Over the past two days, she has noticed thick, yellow-green nasal discharge and worsening pressure over her cheeks, which is exacerbated when leaning forward. She reports a subjective mild fever at home two days ago but has been afebrile since. Her medical history is unremarkable, and she takes no daily medications. Her temperature is $37.2^\circ\text{C}$ ( $99.0^\circ\text{F}$ ), blood pressure is $118/76\text{ mmHg}$ , and pulse is $78/\text{min}$ . Physical examination reveals erythematous, edematous nasal mucosa with purulent drainage in the bilateral middle meatus. There is mild tenderness to palpation over the maxillary sinuses. Which of the following is the most appropriate next step in management?

Reassurance and initiation of symptomatic therapy

Prescription for oral cefdinir

Prescription for oral clarithromycin

Prescription for oral doxycycline

Prescription for oral moxifloxacin

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Cevap: Reassurance and initiation of symptomatic therapy

Cevap

The most appropriate next step in management is reassurance and initiation of symptomatic therapy, as the patient's presentation is highly consistent with acute viral rhinosinusitis.

The correct approach is reassurance and symptomatic therapy. This patient presents with classic signs of acute rhinosinusitis (nasal congestion, purulent discharge, facial pain). Acute rhinosinusitis is overwhelmingly viral in etiology. According to current guidelines, acute bacterial rhinosinusitis is diagnosed clinically only if a patient meets at least one of three criteria: 1) symptoms lasting

\ge 10

days without clinical improvement, 2) severe symptoms at onset including a high fever (

\ge 39^\circ\text{C}

) and purulent nasal discharge for

\ge 3

consecutive days, or 3) 'double sickening' (worsening symptoms after initial improvement). Because this patient has only had symptoms for

5

days and lacks severe features or biphasic worsening, she has acute viral rhinosinusitis. Symptomatic management (e.g., intranasal saline irrigation, analgesics) is the standard of care.

Adım Adım Çözüm

1

Evaluate the duration and trajectory of the patient's symptoms.

The patient has had symptoms for 5 days without severe onset features (e.g., high fever) or a biphasic illness pattern (worsening after initial improvement).

Differentiating viral from bacterial rhinosinusitis relies entirely on clinical criteria, which dictates the need for antimicrobial therapy.

2

Determine the most appropriate intervention based on the diagnosis.

Observation and supportive care (e.g., intranasal saline, analgesics) are selected.

Antibiotics do not alter the clinical course of viral infections, and avoiding them adheres to core antibiotic stewardship principles.

Anahtar Kavram

Diagnosis of acute viral versus bacterial rhinosinusitis and application of antibiotic stewardship principles.

Tahmini Süre:1m 0s

Soru 1868Soru →

During a routine employment health screening, a $28$ -year-old man is found to have an incidental serum calcium level of $11.2$ mg/dL. The patient is entirely asymptomatic, reporting no fatigue, nephrolithiasis, bone pain, or abdominal discomfort. His family history is notable for mild, asymptomatic hypercalcemia in both his father and paternal aunt, neither of whom has undergone neck surgery. His renal function is normal. Arrange the following diagnostic and management steps in the correct chronological sequence to properly evaluate and manage this patient's condition.

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The correct chronological sequence is: Verify true hypercalcemia -> Differentiate etiology via PTH -> Calculate CCCR -> Confirm via genetic testing -> Provide conservative observation.

The evaluation of asymptomatic hypercalcemia follows a strict algorithmic pathway. After confirming true hypercalcemia, intact PTH is measured to isolate PTH-dependent causes. Because primary hyperparathyroidism and FHH both present with elevated or inappropriately normal PTH, the

24

-hour urine calcium-to-creatinine clearance ratio (CCCR) is the essential distinguishing test. Once a CCCR

< 0.01

points to FHH, genetic confirmation of the CaSR mutation ensures the correct diagnosis. Finally, because FHH is benign, the definitive management is observation, strictly avoiding parathyroidectomy.

Adım Adım Çözüm

1

Confirm the patient has true hypercalcemia.

Ionized calcium or albumin-corrected calcium is measured.

This rules out artifactual elevations (pseudohypercalcemia) before proceeding with an expensive and extensive algorithmic workup.

2

Determine if the hypercalcemia is driven by parathyroid hormone.

An intact PTH level is obtained.

This fundamentally branches the diagnostic algorithm, differentiating PTH-dependent causes (like FHH and primary hyperparathyroidism) from PTH-independent causes (like malignancy or granulomatous disease).

3

Differentiate Familial Hypocalciuric Hypercalcemia (FHH) from Primary Hyperparathyroidism.

A

24

-hour urine collection is utilized to calculate the calcium-to-creatinine clearance ratio (CCCR).

Patients with FHH have defective calcium-sensing receptors in the kidneys, leading to inappropriate renal calcium reabsorption (CCCR

< 0.01

). Primary hyperparathyroidism typically exhibits a CCCR

> 0.02

.

4

Confirm the underlying genetic etiology.

CaSR gene sequencing is performed.

Definitively confirms FHH, which is especially crucial when deciding to permanently withhold surgery in a young patient who clinically mimics primary hyperparathyroidism.

5

Initiate appropriate patient management.

The patient is managed with clinical observation and reassurance.

Because FHH is a benign, asymptomatic condition caused by a systemic receptor defect, parathyroidectomy does not correct the hypercalcemia and exposes the patient to surgical risks unnecessarily.

Anahtar Kavram

The diagnostic algorithm for asymptomatic hypercalcemia requires distinguishing primary hyperparathyroidism from familial hypocalciuric hypercalcemia (FHH) using a

24

-hour urine calcium-to-creatinine clearance ratio prior to considering any surgical intervention.

Soru 1869Soru →

Match each clinical presentation of a patient requiring initiation of antihypertensive therapy to the single most appropriate pharmacological class based on compelling indications and secondary clinical benefits.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

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Cevap

The correct matches align each patient's secondary comorbidity with the mechanistic benefit of specific antihypertensive classes: the patient with Raynaud phenomenon matches with a dihydropyridine calcium channel blocker; the patient with recurrent calcium oxalate stones matches with a thiazide diuretic; the patient with stable angina matches with a cardioselective beta-blocker; and the patient with diabetic nephropathy matches with an angiotensin-converting enzyme inhibitor.

Each correct pairing utilizes the pharmacological mechanism of an antihypertensive class to treat both the high blood pressure and a specific underlying condition. Dihydropyridine calcium channel blockers vasodilate peripheral vessels (benefiting Raynaud phenomenon). Thiazide diuretics enhance distal tubule calcium reabsorption (preventing calcium stones). Beta-blockers slow heart rate and contractility (relieving angina). ACE inhibitors dilate the efferent arteriole (protecting the kidneys in diabetes).

Adım Adım Çözüm

1

Diagnose the secondary comorbidity for each patient based on the clinical vignette.

Patient 1 has Raynaud phenomenon; Patient 2 has hypercalciuria/calcium stones; Patient 3 has stable angina pectoris; Patient 4 has diabetic nephropathy.

Identifying the underlying comorbidity is required before selecting a targeted antihypertensive medication that offers dual therapeutic benefits.

2

Select the optimal antihypertensive class that addresses both elevated blood pressure and the identified comorbidity.

Raynaud requires vasodilation (CCB); calcium stones require hypocalciuria (Thiazide); angina requires reduced myocardial oxygen demand (Beta-blocker); diabetic nephropathy requires reduced intraglomerular pressure (ACE inhibitor).

Clinical guidelines recommend prioritizing specific antihypertensive classes when compelling indications are present to optimize overall patient outcomes.

Anahtar Kavram

Selection of antihypertensive therapy must be individualized based on compelling patient comorbidities and the secondary physiologic mechanisms of the medication.

Soru 1870Soru →

A $58$ -year-old man is evaluated in the clinic for severe fatigue, nausea, and a mild headache that has progressively worsened over the past two weeks. His medical history is significant for metastatic melanoma, for which he began treatment with intravenous nivolumab $12$ weeks ago. His blood pressure is $90/60$ mmHg seated and $82/50$ mmHg upon standing. His pulse is $92$ /min seated and $110$ /min standing. Physical examination reveals no skin hyperpigmentation, rashes, or mucosal lesions. Visual fields are normal to confrontation. Laboratory results are as follows:

Test	Result	Reference Range
Serum sodium	$131$ mEq/L	$136$ - $145$ mEq/L
Serum potassium	$4.2$ mEq/L	$3.5$ - $5.0$ mEq/L
Thyroid-stimulating hormone (TSH)	$0.1$ $\mu$ U/mL	$0.4$ - $4.0$ $\mu$ U/mL
Free thyroxine (T4)	$0.4$ ng/dL	$0.9$ - $1.7$ ng/dL

Which of the following is the most likely additional laboratory finding in this patient?

Decreased early morning serum cortisol

Decreased serum aldosterone

Elevated serum potassium

Elevated serum prolactin greater than

200

ng/mL

Elevated serum thyroid peroxidase antibodies

Cevabı ve açıklamayı göster

Cevap: Decreased early morning serum cortisol

Cevap

The most likely additional finding is a decreased early morning serum cortisol level.

The correct answer identifies a decreased early morning serum cortisol level. This patient is presenting with symptoms of hypophysitis, a known immune-related adverse effect of checkpoint inhibitors like nivolumab. The laboratory findings of low TSH and proportionately low free T4 confirm central hypothyroidism. Inflammation of the pituitary gland typically leads to multiple anterior pituitary hormone deficiencies, most notably adrenocorticotropic hormone (ACTH), resulting in central adrenal insufficiency. A low early morning serum cortisol level is expected and explains the patient's orthostatic hypotension and hyponatremia (which occurs due to the loss of cortisol's suppressive effect on antidiuretic hormone release).

Adım Adım Çözüm

1

Interpret the patient's thyroid function tests in the context of his medical history.

The low TSH and low free T4 indicate central hypothyroidism. The recent use of nivolumab (a PD-1 inhibitor) suggests immune checkpoint inhibitor-induced hypophysitis as the etiology.

Accurate interpretation of the pituitary-thyroid axis is required to localize the lesion to the pituitary gland rather than the thyroid.

2

Determine the physiological consequences of pituitary inflammation (hypophysitis).

Hypophysitis causes multiple anterior pituitary hormone deficiencies (panhypopituitarism), including a decrease in adrenocorticotropic hormone (ACTH), leading to central adrenal insufficiency.

Understanding the widespread effects of hypophysitis allows prediction of concurrent endocrine deficits, such as low cortisol, which explains the patient's hypotension and hyponatremia.

3

Differentiate between central and primary adrenal insufficiency to predict mineralocorticoid levels.

Central adrenal insufficiency (low ACTH) results in low cortisol but spares aldosterone secretion, which is regulated independently by the renin-angiotensin-aldosterone system. Therefore, potassium and aldosterone levels remain normal.

This distinction eliminates distractors related to hyperkalemia and low aldosterone, which are hallmarks of primary adrenal insufficiency (Addison's disease).

Anahtar Kavram

Immune checkpoint inhibitors can cause hypophysitis, leading to central hypothyroidism and central adrenal insufficiency. In central adrenal insufficiency, cortisol is low, but aldosterone and potassium levels remain normal because the renin-angiotensin-aldosterone system is intact.

Soru 1871Soru →

A $68$ -year-old man comes to the office due to a $4$ -week history of progressive fatigue, tremors, and a $5$ -kg ( $11$ -lb) weight loss. His medical history is significant for ischemic cardiomyopathy with a left ventricular ejection fraction of $35\%$ and recurrent sustained ventricular tachycardia. His medications include amiodarone, metoprolol, lisinopril, and spironolactone. His pulse is $112$ /min and irregular, and blood pressure is $134/82$ mm Hg. Physical examination reveals a fine bilateral hand tremor and hyperreflexia. The thyroid gland is normal in size and non-tender on palpation. There is no proptosis or pretibial myxedema.

Laboratory results are as follows:

Laboratory Test	Result	Reference Range
Thyroid-stimulating hormone (TSH)	$<0.01$ $\mu$ U/mL	$0.4-4.0$ $\mu$ U/mL
Free thyroxine (T4)	$4.2$ ng/dL	$0.7-1.9$ ng/dL
Free triiodothyronine (T3)	$6.8$ pg/mL	$2.0-4.4$ pg/mL

Color flow Doppler ultrasonography of the thyroid shows a structurally normal gland with markedly decreased vascularity. A $24$ -hour radioactive iodine uptake scan reveals $<1\%$ uptake.

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

Initiation of oral prednisone therapy

Initiation of methimazole therapy

Immediate discontinuation of amiodarone and observation

Administration of radioactive iodine 131

Initiation of levothyroxine therapy

Cevabı ve açıklamayı göster

Cevap: Initiation of oral prednisone therapy

Cevap

Initiation of oral prednisone therapy

This patient has amiodarone-induced thyrotoxicosis (AIT) Type 2. Amiodarone can cause thyrotoxicosis via two distinct mechanisms. Type 1 AIT occurs in patients with underlying autonomous thyroid tissue (e.g., nodular goiter) where the massive iodine load fuels excess hormone synthesis; this presents with normal or increased vascularity on Doppler ultrasound. In contrast, Type 2 AIT is a destructive thyroiditis occurring in normal thyroid glands, causing the release of preformed thyroid hormones. It is characterized by structurally normal glands with decreased or absent vascular flow on color Doppler. Because Type 2 is an inflammatory, destructive process, the first-line treatment is systemic glucocorticoids (e.g., prednisone) to reduce inflammation. Note that a

24

-hour radioactive iodine uptake scan is low (

<1\%

) in both types due to saturation of the iodine pool by amiodarone, making the Doppler ultrasound the critical distinguishing test.

Adım Adım Çözüm

1

Interpret the laboratory findings.

The patient has a suppressed TSH with elevated free T4 and free T3, confirming thyrotoxicosis.

Establishing the biochemical diagnosis is the first step in localizing the pathology.

2

Identify the underlying etiology based on medication history.

The patient is taking amiodarone, an iodine-rich antiarrhythmic drug that can cause amiodarone-induced thyrotoxicosis (AIT).

Amiodarone is a common trigger for thyroid dysfunction and alters standard diagnostic and treatment pathways.

3

Differentiate between AIT Type 1 and AIT Type 2 using imaging results.

Color flow Doppler ultrasound shows decreased vascularity, which confirms AIT Type 2 (destructive thyroiditis) rather than Type 1 (hyperthyroidism/increased vascularity).

Radioactive iodine uptake is low in both types due to the massive iodine load, making Doppler ultrasound the crucial distinguishing test.

4

Select the appropriate targeted therapy for AIT Type 2.

Glucocorticoids (such as prednisone) are indicated to treat the inflammatory destructive process.

Unlike Type 1 which requires antithyroid drugs to block synthesis, Type 2 is driven by preformed hormone release from tissue destruction, which responds to steroids.

Anahtar Kavram

Amiodarone-induced thyrotoxicosis (AIT) Type 2 is a destructive thyroiditis characterized by decreased vascularity on color Doppler ultrasound, and it is managed primarily with systemic glucocorticoids.

Tahmini Süre:1m 30s

Soru 1872Soru →

An emergency medical response team transports a young adult male to the hospital after he was discovered lethargic in his dormitory. The patient, a 22-year-old college student with a known psychiatric history, reportedly ingested a large, unknown quantity of over-the-counter pain relievers earlier in the day. Upon arrival at the triage desk, he is tachypneic and diaphoretic. Vital signs include a temperature of 38.1°C (100.6°F), blood pressure of 112/68 mm Hg, heart rate of 115/min, and respiratory rate of 28/min.

Laboratory evaluation is obtained immediately:

Sodium: $140$ mEq/L
Potassium: $4.2$ mEq/L
Chloride: $103$ mEq/L
Bicarbonate: $13$ mEq/L
Blood urea nitrogen: $18$ mg/dL
Creatinine: $1.0$ mg/dL

Arterial blood gas parameters on room air:
pH: $7.43$
PaCO2: $20$ mm Hg
PaO2: $98$ mm Hg

Based on the provided laboratory parameters, which of the following accurately characterizes the primary acid-base disturbance(s) in this patient?

High anion gap metabolic acidosis with adequate respiratory compensation

Mixed high anion gap metabolic acidosis and respiratory alkalosis

Mixed normal anion gap metabolic acidosis and respiratory alkalosis

Primary respiratory alkalosis with appropriate metabolic compensation

Mixed high anion gap metabolic acidosis and respiratory acidosis

Cevabı ve açıklamayı göster

Cevap: Mixed high anion gap metabolic acidosis and respiratory alkalosis

Cevap

Mixed high anion gap metabolic acidosis and respiratory alkalosis

This patient's clinical presentation (lethargy, tachypnea, ingestion of over-the-counter medication) and laboratory findings are highly characteristic of salicylate (aspirin) toxicity. Salicylates cause a classic mixed acid-base disorder: they directly stimulate the medullary respiratory center to cause a primary respiratory alkalosis, and they disrupt cellular metabolism by uncoupling oxidative phosphorylation, leading to organic acid accumulation and a primary high anion gap metabolic acidosis.

This can be proven mathematically:
1. The pH of

7.43

indicates alkalemia, meaning the dominant primary disorder is a respiratory alkalosis (driven by the PaCO2 of

20

mm Hg).
2. The expected acute metabolic compensation for a PaCO2 drop of

20

mm Hg (from the baseline of

40

) is a

4

mEq/L drop in

HCO_3^-

(

2

mEq/L per

10

mm Hg drop in PaCO2). The expected

HCO_3^-

is therefore

20

mEq/L.
3. The patient's actual

HCO_3^-

is

13

mEq/L, which is far lower than the compensatory

20

mEq/L. This signifies an additional, independent primary metabolic acidosis.
4. The anion gap is calculated as

Na^+ - (Cl^- + HCO_3^-) = 140 - (103 + 13) = 24

mEq/L. Since this is greater than the normal maximum of

12

mEq/L, the metabolic component is specifically a high anion gap metabolic acidosis.

Alternatively, applying Winter's formula to the metabolic acidosis:

Expected\ PaCO_2 = (1.5 \times 13) + 8 = 27.5 \pm 2

mm Hg. Because the measured PaCO2 (

20

mm Hg) is well below this range, a concurrent respiratory alkalosis is definitively present.

Adım Adım Çözüm

1

Determine the primary acid-base disorder based on the pH.

The pH is

7.43

, indicating alkalemia. The low PaCO2 (

20

mm Hg) aligns with this, establishing a primary respiratory alkalosis.

Identifying the primary disturbance directs the appropriate compensation formula to use.

2

Calculate the expected metabolic compensation for the primary respiratory alkalosis.

For acute respiratory alkalosis,

HCO_3^-

decreases by

2

mEq/L per

10

mm Hg drop in PaCO2. A drop from

40

to

20

mm Hg (a difference of

20

) should decrease

HCO_3^-

by

4

. Expected

HCO_3^-

is

24 - 4 = 20

mEq/L.

This determines if the low bicarbonate is solely compensatory or represents a concurrent primary metabolic acidosis.

3

Compare the measured bicarbonate to the expected compensatory value.

The measured

HCO_3^-

(

13

mEq/L) is significantly lower than the expected

20

mEq/L, confirming an additional primary metabolic acidosis.

A significant deviation from expected compensation indicates a mixed acid-base disorder.

4

Calculate the anion gap to classify the metabolic acidosis.

Anion Gap =

Na^+ - (Cl^- + HCO_3^-) = 140 - (103 + 13) = 24

mEq/L. Since

24 > 12

, it is a high anion gap metabolic acidosis.

Metabolic acidosis must always be classified as normal or high anion gap to narrow the differential diagnosis.

Anahtar Kavram

Salicylate toxicity classically causes a mixed acid-base disorder: a primary respiratory alkalosis due to direct medullary respiratory center stimulation, and a primary high anion gap metabolic acidosis due to uncoupling of oxidative phosphorylation.

Tahmini Süre:1m 30s

Soru 1873Soru →

A 45-year-old woman is receiving a packed red blood cell transfusion for symptomatic anemia. Thirty minutes into the infusion, she develops sudden-onset chills, severe flank pain, and dyspnea. Her temperature is $39.2^\circ\text{C}$ ( $102.6^\circ\text{F}$ ), blood pressure is $85/50\text{ mmHg}$ , and heart rate is $122/\text{min}$ . Her urine in the Foley catheter tubing has acutely become dark red. Arrange the following steps in the most appropriate chronological order for managing this patient's suspected acute hemolytic transfusion reaction.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct sequence is: 1) Stop the transfusion, 2) Maintain IV access with fresh tubing and saline, 3) Perform a clerical check, 4) Send samples and the blood bag to the blood bank, 5) Administer aggressive intravenous fluids.

An acute hemolytic transfusion reaction (AHTR) is a life-threatening medical emergency caused by ABO incompatibility. The chronological priority is immediately halting the offending agent (stopping the transfusion). Because the patient is hypotensive, IV access is critical; however, the line must be disconnected and replaced with fresh tubing and normal saline to avoid pushing residual incompatible blood into the patient. A bedside clerical check is then performed because misidentification is the leading cause of AHTR. Subsequently, the blood bank must receive new samples and the donor bag to investigate the etiology (Coombs test, hemolysis labs). Finally, definitive supportive care, including aggressive IV fluids, is initiated to maintain urine output and flush hemoglobin from the renal tubules, thereby preventing acute tubular necrosis.

Adım Adım Çözüm

1

Stop the blood transfusion immediately.

Further infusion of incompatible blood is halted.

Minimizes the load of incompatible red blood cells and limits the severity of the immune response.

2

Disconnect the blood tubing and maintain IV access with normal saline using fresh tubing.

Hemodynamic support pathway is secured without flushing remaining blood.

Crucial for impending shock management. Flushing the existing line would inadvertently administer more incompatible blood.

3

Perform a bedside clerical check.

Identifies if the wrong blood was hung.

Clerical errors (wrong patient, wrong unit) account for the vast majority of acute hemolytic transfusion reactions.

4

Send post-transfusion blood and urine samples, along with the blood bag, to the blood bank.

Initiates laboratory confirmation.

Allows for repeat crossmatching, direct Coombs testing, and visual inspection for free hemoglobin.

5

Administer aggressive intravenous fluid hydration.

Maintains high urine output and renal perfusion.

Free hemoglobin from massive intravascular hemolysis precipitates in the renal tubules, causing acute kidney injury. Aggressive hydration mitigates this risk.

Anahtar Kavram

The management of an acute hemolytic transfusion reaction requires immediately stopping the transfusion, securing IV access without flushing the blood tubing, checking for clerical errors, sending diagnostic samples, and providing aggressive hydration to prevent acute kidney injury.

Soru 1874Soru →

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

Initial laboratory studies reveal the following:

Laboratory Parameter	Value
Sodium	$138\text{ mEq/L}$
Potassium	$4.2\text{ mEq/L}$
Chloride	$104\text{ mEq/L}$
Bicarbonate	$22\text{ mEq/L}$
Blood urea nitrogen (BUN)	$28\text{ mg/dL}$
Creatinine	$1.1\text{ mg/dL}$
Glucose	$126\text{ mg/dL}$
Ethanol	$92\text{ mg/dL}$
Measured serum osmolality	$340\text{ mOsm/kg H}_2\text{O}$

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

Cevabı ve açıklamayı göster

Cevap: 27

Cevap

27

The serum osmolar gap is defined as the difference between the measured serum osmolality and the calculated serum osmolality. The standard formula for calculated serum osmolality in the United States (using

\text{mg/dL}

for glucose and BUN) is

2 \times [\text{Na}^+] + \frac{[\text{Glucose}]}{18} + \frac{[\text{BUN}]}{2.8}

. However, when ethanol is present and measured, its contribution must also be subtracted to isolate the gap caused by other unidentified toxic alcohols (e.g., methanol, ethylene glycol). The conversion factor for ethanol is

4.6

. Therefore, the complete calculation for this patient is

2 \times 138 + \frac{126}{18} + \frac{28}{2.8} + \frac{92}{4.6} = 276 + 7 + 10 + 20 = 313 \text{ mOsm/kg H}_2\text{O}

. Subtracting this from the measured osmolality of

340 \text{ mOsm/kg H}_2\text{O}

gives a gap of

27 \text{ mOsm/kg H}_2\text{O}

.

Adım Adım Çözüm

1

Identify the need to calculate the serum osmolar gap.

The patient has altered mental status and a measured serum osmolality of

340 \text{ mOsm/kg H}_2\text{O}

, indicating a potential toxic alcohol ingestion.

Calculating the osmolar gap is essential to unmask the presence of unmeasured osmotically active substances (like methanol, ethylene glycol, or isopropyl alcohol) not accounted for by standard chemistry panels.

2

Calculate the expected (calculated) serum osmolality.

Using the expanded formula:

2 \times 138 + \frac{126}{18} + \frac{28}{2.8} + \frac{92}{4.6} = 276 + 7 + 10 + 20 = 313 \text{ mOsm/kg H}_2\text{O}

.

Because ethanol is present in the patient's blood, its osmotic contribution must be included in the calculation. Failure to include it will result in an artificially elevated osmolar gap.

3

Determine the osmolar gap.

340 \text{ (Measured)} - 313 \text{ (Calculated)} = 27 \text{ mOsm/kg H}_2\text{O}

.

The osmolar gap is the difference between the measured and calculated osmolality. A normal gap is typically less than

10\text{-}15 \text{ mOsm/kg H}_2\text{O}

. A gap of

27

is elevated, suggesting ingestion of an additional toxic alcohol.

Anahtar Kavram

Calculation of the serum osmolar gap, including the proper osmotic contribution of ethanol.

Soru 1875Soru →

Match each clinical presentation of an opportunistic infection in a patient with advanced HIV to the most appropriate first-line induction or targeted pharmacological therapy.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

Cryptococcal meningitis pairs with amphotericin B and flucytosine. Toxoplasmic encephalitis pairs with sulfadiazine, pyrimethamine, and leucovorin. CMV retinitis pairs with valganciclovir. Disseminated MAC pairs with clarithromycin and ethambutol.

Each clinical scenario presents a classic manifestation of a specific opportunistic infection in a patient with HIV, which dictates a highly specific first-line antimicrobial regimen according to current clinical guidelines.

Adım Adım Çözüm

1

Identify the underlying opportunistic pathogen described in each clinical vignette based on CD4 count, presentation, and diagnostic findings.

Pathogens identified: Cryptococcus neoformans, Toxoplasma gondii, Cytomegalovirus (CMV), and Mycobacterium avium complex (MAC).

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

2

Determine the first-line treatment regimen for each identified pathogen.

Cryptococcus requires amphotericin B/flucytosine; Toxoplasma requires sulfadiazine/pyrimethamine; CMV requires valganciclovir; MAC requires a macrolide/ethambutol.

Different classes of pathogens (fungal, parasitic, viral, bacterial) require distinctly different pharmacological interventions.

3

Match the clinical vignette to its corresponding pharmacological regimen.

The appropriate pairs are successfully established.

Synthesizing the diagnosis with the standard-of-care guidelines yields the correct matching.

Anahtar Kavram

Targeted pharmacological treatment regimens for major opportunistic infections in advanced HIV.

Tahmini Süre:1m 30s

Soru 1876Soru →

A $24$ -year-old woman with a history of type 1 diabetes mellitus is brought to the emergency department due to altered mental status, nausea, and vomiting that has progressively worsened over the past $24$ hours. She recently had a urinary tract infection and missed several doses of her basal insulin. Her temperature is $37.4^\circ\text{C}$ ( $99.3^\circ\text{F}$ ), blood pressure is $90/60$ mmHg, pulse is $122$ /min, and respirations are $28$ /min (deep and rapid). Physical examination reveals dry mucous membranes and delayed capillary refill. Laboratory results are as follows:

Test	Result
Serum glucose	$580$ mg/dL
Arterial pH	$7.05$
Serum bicarbonate	$9$ mEq/L
Serum potassium	$2.8$ mEq/L
Serum sodium	$132$ mEq/L
Serum creatinine	$1.6$ mg/dL
Serum ketones	Positive

Arrange the following steps in the correct sequential order for the most appropriate acute management of this patient's condition.

Öğeleri doğru sıraya koymak için sürükleyin

Cevabı ve açıklamayı göster

Cevap

The correct sequence is: (1) Administer rapid intravenous fluid resuscitation with

0.9\%

normal saline, (2) Administer intravenous potassium chloride and withhold insulin, (3) Initiate a continuous intravenous regular insulin infusion, (4) Add

5\%

dextrose to the intravenous fluid regimen, (5) Transition to a subcutaneous basal-bolus insulin regimen.

The management of diabetic ketoacidosis (DKA) requires a rigorous, stepwise approach. First, profound fluid deficits must be addressed with isotonic saline to restore perfusion. Second, electrolyte derangements must be evaluated. In DKA, total body potassium is depleted due to osmotic diuresis and vomiting. Even if initial serum potassium is normal or high, it will rapidly fall with insulin administration. If the initial potassium is

<3.3

mEq/L (as seen in this patient with

2.8

mEq/L), insulin MUST be strictly withheld while aggressive intravenous potassium is administered to prevent arrhythmias. Once potassium is

\geq 3.3

mEq/L, a continuous intravenous insulin infusion is started to halt ketogenesis. When glucose falls to

\leq 200

mg/dL, dextrose is added to the fluids to prevent hypoglycemia while continuing the insulin required to close the anion gap. Finally, once the anion gap closes and the patient can eat, a transition to subcutaneous insulin is performed.

Adım Adım Çözüm

1

Evaluate hemodynamic status and initiate volume resuscitation.

Rapid intravenous fluid administration with

0.9\%

normal saline is initiated.

Severe osmotic diuresis leads to profound dehydration in diabetic ketoacidosis, making volume expansion the most critical first step.

2

Evaluate serum potassium prior to insulin administration.

Potassium chloride is administered and insulin is held.

The patient has severe hypokalemia (

2.8

mEq/L). Giving insulin immediately would drive potassium into cells, risking fatal cardiac arrhythmias. Potassium must be replenished to

\geq 3.3

mEq/L first.

3

Start intravenous insulin therapy once potassium levels are safe.

Continuous intravenous regular insulin is initiated.

Insulin is required to suppress ketogenesis and resolve the high anion gap metabolic acidosis.

4

Monitor blood glucose and adjust maintenance fluids.

5\%

dextrose is added to the fluids when glucose reaches

\leq 200

mg/dL.

Insulin must be continued until the anion gap closes, but adding dextrose prevents hypoglycemia as serum glucose typically falls faster than ketones clear.

5

Transition to maintenance therapy once the crisis resolves.

Subcutaneous insulin is started.

After the acidosis resolves and the patient can tolerate oral intake, intravenous insulin is switched to a long-term subcutaneous regimen.

Anahtar Kavram

Stepwise management of Diabetic Ketoacidosis (DKA) in the setting of severe hypokalemia

Soru 1877Soru →

Match each clinical vignette describing a renal or electrolyte complication of pharmacotherapy with the most likely responsible mechanism or drug effect.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

The correct pairings match the anti-pseudomonal therapy complication to aminoglycoside-induced ATN, the encephalitis treatment complication to intratubular acyclovir precipitation, the bipolar treatment complication to lithium-induced nephrogenic diabetes insipidus, and the pneumonia prophylaxis complication to trimethoprim-induced channel blockade.

Each medication causes a unique and predictable pattern of renal impairment. Aminoglycosides directly damage proximal tubular cells causing ATN. Acyclovir is relatively insoluble in urine and precipitates in the tubules. Lithium impairs aquaporin insertion in the collecting duct. Trimethoprim acts on specific transporters without damaging the glomerulus itself.

Adım Adım Çözüm

1

Analyze the first vignette featuring a delayed, gradual rise in creatinine and pigmented granular casts during anti-pseudomonal therapy.

Identified as acute tubular necrosis.

Aminoglycosides are classically associated with delayed-onset, non-oliguric ATN characterized by muddy brown casts.

2

Evaluate the second vignette detailing rapid oliguric acute kidney injury and needle-shaped crystals during treatment for viral encephalitis.

Identified as acyclovir crystal nephropathy.

Intravenous acyclovir is notorious for precipitating in the renal tubules, forming birefringent crystals and causing obstructive nephropathy.

3

Assess the third vignette describing polyuria, hypernatremia, and desmopressin-resistant dilute urine in a patient with a psychiatric history.

Identified as lithium-induced nephrogenic diabetes insipidus.

Lithium is a primary cause of acquired nephrogenic diabetes insipidus, which presents with ADH resistance at the collecting duct.

4

Examine the fourth vignette showing isolated hyperkalemia and elevated creatinine without true GFR decline during opportunistic pneumonia prophylaxis.

Identified as trimethoprim effect.

Trimethoprim blocks ENaC in the distal nephron (causing hyperkalemia) and inhibits creatinine secretion (elevating serum creatinine artificially).

Anahtar Kavram

Recognizing the distinct clinical presentations, timing, and urinary findings of medication-induced nephrotoxicity and electrolyte derangements.

Tahmini Süre:1m 30s

Soru 1878Soru →

A 27-year-old woman is brought to the emergency department by her roommate due to severe weakness and four days of intractable vomiting. The patient has type 1 diabetes mellitus but has not administered her insulin for the past two days because she has been unable to tolerate oral intake. On physical examination, she appears lethargic. Her temperature is 37.1°C (98.8°F), blood pressure is 92/58 mm Hg, pulse is 122/min, and respirations are 16/min. Her mucous membranes are notably dry and skin turgor is decreased. Laboratory studies show the following:

Laboratory Test	Result
Sodium	$142 \text{ mEq/L}$
Potassium	$3.8 \text{ mEq/L}$
Chloride	$94 \text{ mEq/L}$
Bicarbonate	$20 \text{ mEq/L}$
Blood urea nitrogen	$35 \text{ mg/dL}$
Creatinine	$1.4 \text{ mg/dL}$
Glucose	$512 \text{ mg/dL}$

An arterial blood gas on room air reveals:

Test	Result
pH	$7.34$
$PaCO_2$	$38 \text{ mm Hg}$
$PaO_2$	$94 \text{ mm Hg}$

Which of the following best describes this patient's acid-base status?

High anion gap metabolic acidosis and metabolic alkalosis

High anion gap metabolic acidosis with appropriate respiratory compensation

High anion gap metabolic acidosis and respiratory acidosis

High anion gap metabolic acidosis and normal anion gap metabolic acidosis

Normal anion gap metabolic acidosis and metabolic alkalosis

Cevabı ve açıklamayı göster

Cevap: High anion gap metabolic acidosis and metabolic alkalosis

Cevap

The patient has a mixed acid-base disorder consisting of a high anion gap metabolic acidosis (due to diabetic ketoacidosis) and a concurrent metabolic alkalosis (due to severe vomiting).

This patient presents with a high anion gap metabolic acidosis (HAGMA) driven by diabetic ketoacidosis, evidenced by an anion gap of 28 (normal ~12). Despite the severe HAGMA, her bicarbonate is only mildly depressed at 20 mEq/L. To fully evaluate a HAGMA, the delta gap must be calculated to look for mixed metabolic disorders. The delta gap here is 16 (28 - 12). If HAGMA were the sole disorder, the bicarbonate should drop by an amount equal to the delta gap, resulting in an expected bicarbonate of 8 mEq/L (24 - 16 = 8). Because the patient's actual measured bicarbonate (20 mEq/L) is much higher than 8 mEq/L, there must be a second disorder independently raising the bicarbonate. In this clinical scenario, prolonged vomiting leads to substantial hydrogen ion and chloride loss, generating a concurrent metabolic alkalosis. Finally, Winter's formula calculation (

1.5 \times 20 + 8 = 38

) perfectly matches the patient's measured PaCO2, confirming appropriate respiratory compensation and ruling out any superimposed respiratory disorder.

Adım Adım Çözüm

1

Calculate the primary anion gap to determine the core metabolic disorder.

AG = 142 - (94 + 20) = 28

.

An anion gap greater than 12 indicates the presence of a high anion gap metabolic acidosis (HAGMA), which in this patient is due to diabetic ketoacidosis.

2

Calculate the expected respiratory compensation using Winter's formula.

Expected

PaCO_2 = (1.5 \times 20) + 8 = 38 \pm 2 \text{ mm Hg}

. The measured

PaCO_2

is exactly

38 \text{ mm Hg}

.

Because the measured

PaCO_2

falls precisely within the expected range, there is no concurrent respiratory acidosis or alkalosis.

3

Calculate the delta gap (delta-delta) to identify hidden secondary metabolic disorders.

\Delta AG = 28 - 12 = 16

. The expected normal

HCO_3^-

if only HAGMA were present is

24 - 16 = 8 \text{ mEq/L}

. The measured

HCO_3^-

is

20 \text{ mEq/L}

.

Because the measured bicarbonate (

20 \text{ mEq/L}

) is significantly higher than the expected compensated bicarbonate (

8 \text{ mEq/L}

), a second disorder that independently raises bicarbonate must be present—specifically, a metabolic alkalosis.

Anahtar Kavram

In a patient with a high anion gap metabolic acidosis, calculating the delta gap is essential to identify hidden concurrent metabolic disorders. If the measured bicarbonate is significantly higher than the expected bicarbonate (calculated as 24 minus the delta gap), a concurrent metabolic alkalosis is present.

Soru 1879Soru →

Match the following classic auscultatory findings with their most likely underlying valvular pathology.

Soldaki öğeye tıklayın, sonra eşleşen sağdaki öğeye tıklayın

Cevabı ve açıklamayı göster

Cevap

The auscultatory findings map to their respective valvular pathologies: the opening snap with diastolic rumble indicates mitral stenosis; the harsh systolic crescendo-decrescendo murmur indicates aortic stenosis; the holosystolic apical murmur indicates mitral regurgitation; and the early diastolic decrescendo murmur indicates aortic regurgitation.

Each auscultatory description contains pathognomonic features for the matched valvular disorder based on foundational hemodynamic principles of timing, optimal location, anatomical radiation, and sound quality.

Adım Adım Çözüm

1

Identify the timing of the murmur relative to the cardiac cycle (systole vs. diastole).

Determines whether the pathology involves forward flow through a stenotic valve or backward flow through an incompetent valve.

Timing is the most critical initial step in classifying heart murmurs.

2

Evaluate the location of maximal murmur intensity and its pattern of radiation.

Localizes the specific valve involved (e.g., apex for mitral lesions, right upper sternal border for aortic lesions).

Anatomic position and blood flow direction dictate where specific murmurs are auscultated best on the chest wall.

3

Assess for specific acoustic characteristics.

Identifies classic diagnostic features such as an opening snap for mitral stenosis or a crescendo-decrescendo shape for aortic stenosis.

Specific structural valve lesions produce unique flow dynamics and characteristic cardiac sounds.

Anahtar Kavram

Clinical recognition of primary valvular heart diseases via cardiac auscultation

Soru 1880Soru →

Emergency medical services bring a male patient, aged 62, to the acute care unit due to rapidly worsening breathlessness and near-syncope over the last 48 hours. His past medical history includes severe chronic obstructive pulmonary disease (COPD) and a recently diagnosed advanced non-small cell lung carcinoma. The patient's daughter, who accompanies him, notes he has been entirely unable to lie flat and feels as though he might pass out when standing upright.

Initial vital signs demonstrate a blood pressure of 86/54 mm Hg, a heart rate of 122/min, and a respiratory rate of 24/min. Pulse oximetry indicates 92% saturation on 2 L/min of supplemental oxygen via nasal cannula.

On examination, he is sitting upright in obvious respiratory distress. Inspection of the neck reveals markedly engorged jugular veins. Auscultation of the thorax demonstrates symmetrically diminished breath sounds without any wheezing or crackles. The cardiac examination is notable for distinctly muffled heart sounds. Peripheral pulses are rapid and thready, with a noticeable decline in radial pulse amplitude during spontaneous inspiration.

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

Perform bedside echocardiography

Initiate noninvasive positive pressure ventilation and administer intravenous furosemide

Provide nebulized albuterol and administer intravenous methylprednisolone

Transfer the patient for computed tomography angiography of the chest

Record a right-sided electrocardiogram

Cevabı ve açıklamayı göster

Cevap: Perform bedside echocardiography

Cevap

Perform bedside echocardiography

The correct answer is to perform bedside echocardiography. This patient's presentation of hypotension, jugular venous distention, and distant heart sounds constitutes Beck's triad. Combined with pulsus paradoxus (a drop in systolic blood pressure >10 mm Hg during inspiration, manifested here as a noticeably weakening radial pulse) and a history of advanced lung cancer, this clinical picture is classic for cardiac tamponade due to a malignant pericardial effusion. In cardiac tamponade, the accumulation of fluid in the pericardial space increases intrapericardial pressure, leading to impaired diastolic filling of the right and left ventricles and a subsequent drop in cardiac output (obstructive shock). Bedside echocardiography is the most appropriate initial diagnostic step because it is rapid, noninvasive, and can be performed without moving the hemodynamically unstable patient. It will demonstrate the pericardial effusion and classic signs of tamponade, such as right atrial systolic collapse and right ventricular diastolic collapse, thereby guiding definitive treatment with pericardiocentesis.

Adım Adım Çözüm

1

Analyze the patient's vital signs and physical examination findings.

The patient exhibits hypotension, tachycardia, jugular venous distention, muffled heart sounds, and a significant decrease in pulse amplitude during inspiration (pulsus paradoxus).

Identifying this specific cluster of findings (Beck's triad plus pulsus paradoxus) is critical for pinpointing the etiology of the patient's shock.

2

Correlate the physical findings with the patient's medical history.

The combination of these hemodynamic findings in a patient with advanced non-small cell lung cancer strongly indicates cardiac tamponade secondary to a malignant pericardial effusion.

Malignancy frequently causes pericardial effusions, which can accumulate and compress the cardiac chambers, severely impairing right and left ventricular diastolic filling.

3

Determine the most appropriate diagnostic intervention for this unstable presentation.

A bedside echocardiogram should be performed immediately to confirm the presence of the effusion and signs of tamponade, guiding urgent pericardiocentesis.

Bedside imaging rapidly confirms the diagnosis in a hemodynamically unstable patient without the risks associated with transporting them out of the resuscitation area.

Anahtar Kavram

Cardiac tamponade should be strongly suspected in patients with malignancy presenting with Beck's triad (hypotension, jugular venous distention, muffled heart sounds) and pulsus paradoxus. The immediate next step in an unstable patient is bedside echocardiography.

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