Tüm alıştırma soruları

A hospital ward team is evaluating a 74-year-old female who was admitted three days ago for an acute exacerbation of chronic systolic heart failure. Since admission, she has received continuous intravenous bumetanide. Over the past 24 hours, her urine output has significantly decreased, and routine morning laboratory studies reveal an acute rise in her serum creatinine from a baseline of $1.1 \text{ mg/dL}$.

The following laboratory values are obtained:

Due to the confounding effect of ongoing loop diuretic therapy, the standard fractional excretion of sodium (FENa) may be misleading. The attending physician asks for the calculation of the most appropriate alternative diagnostic index to differentiate between prerenal azotemia and intrinsic acute tubular necrosis in this specific clinical context.

What is the value of this alternative index (expressed as a percentage)?

A $58$-year-old man with a history of decompensated alcoholic cirrhosis presents to the emergency department with diffuse abdominal pain and a low-grade fever over the past $24$ hours. Vital signs are temperature $37.9^\circ C$ ($100.2^\circ F$), blood pressure $105/65$ mmHg, heart rate $98$/min, and respiratory rate $18$/min. Physical examination reveals scleral icterus and a distended, diffusely tender abdomen with a positive fluid wave. To evaluate for spontaneous bacterial peritonitis, a diagnostic paracentesis is performed. The procedure is complicated by a traumatic tap, yielding noticeably bloody fluid. The ascitic fluid laboratory analysis reveals the following:

Ascitic fluid red blood cell (RBC) count: $62,500/\mu L$
Ascitic fluid white blood cell (WBC) count: $1,250/\mu L$
Ascitic fluid differential: $50\%$ neutrophils, $30\%$ lymphocytes, $20\%$ macrophages

Based on these results, what is the corrected ascitic fluid absolute neutrophil count (in cells/$\mu L$) that should be used to evaluate the patient for spontaneous bacterial peritonitis?

A 42-year-old woman presents to the emergency department complaining of sudden-onset shortness of breath and right-sided pleuritic chest pain. She recently returned from a 14-hour international flight. She has no significant past medical history and takes no medications other than oral contraceptives.

Vital signs:
Temperature: 37.1°C (98.8°F)
Blood pressure: 128/78 mm Hg
Heart rate: 115/min
Respiratory rate: 26/min
Oxygen saturation: 88% on room air

Arterial blood gas analysis on room air reveals:
pH: 7.48
$PaCO_2$: 28 mm Hg
$PaO_2$: 55 mm Hg
$HCO_3^-$: 20 mEq/L

Assume the inspired partial pressure of oxygen ($P_IO_2$) is 150 mm Hg and the respiratory quotient ($R$) is 0.8.

What is this patient's alveolar-arterial ($A-a$) oxygen gradient in mm Hg?

A 72-year-old man is admitted to the hospital with a 3-day history of severe diarrhea and decreased oral intake. His past medical history is significant for heart failure with preserved ejection fraction, for which he takes furosemide and lisinopril daily. On physical examination, his blood pressure is $90/60\text{ mm Hg}$ and heart rate is $112/\text{min}$. Mucous membranes are dry, and capillary refill time is prolonged.

Initial laboratory studies are obtained:

The patient's baseline serum creatinine is $1.0\text{ mg/dL}$. The physician suspects prerenal acute kidney injury secondary to volume depletion. Given the patient's active loop diuretic use, the fractional excretion of sodium (FENa) may be artifactually elevated and unreliable.

What is the calculated value (expressed as a percentage) of the alternative fractional excretion index that should be used to confirm the etiology of his kidney injury?

A 39-year-old previously healthy woman is brought to the emergency department after her roommates found her lethargic and confused. Empty bottles of an unknown liquid were found in her room. On arrival, she is difficult to rouse and responds poorly to stimuli. Vital signs show a temperature of $36.8^\circ\text{C}$ ($98.2^\circ\text{F}$), blood pressure of $115/75\text{ mm Hg}$, pulse of $110/\text{min}$, and respiratory rate of $28/\text{min}$ with deep, rapid breaths. Laboratory studies report the following:

Additional laboratory analysis:
* Measured serum osmolality: $340\text{ mOsm/kg } H_2O$
* Arterial blood gas (room air) pH: $7.15$
* Arterial PaCO2: $20\text{ mm Hg}$

Based on these laboratory results, what is this patient's osmolar gap? (Express the result in $\text{mOsm/kg } H_2O$.)

A 32-year-old woman with a history of type 1 diabetes mellitus is brought to the emergency department by her husband due to altered mental status and 3 days of severe nausea, recurrent vomiting, and generalized abdominal pain. She has been unable to retain any oral intake and missed her last three doses of insulin.

On physical examination, her temperature is 37.1°C (98.8°F), blood pressure is 98/60 mm Hg, pulse is 122/min, and respirations are 24/min and deep. Her mucous membranes are remarkably dry, and skin turgor is decreased. Her breath has a fruity odor.

Laboratory studies show:
Serum sodium: $140 \text{ mEq/L}$
Serum potassium: $4.1 \text{ mEq/L}$
Serum chloride: $92 \text{ mEq/L}$
Serum bicarbonate: $14 \text{ mEq/L}$
Serum glucose: $540 \text{ mg/dL}$
Serum BUN: $45 \text{ mg/dL}$
Serum creatinine: $1.9 \text{ mg/dL}$
Serum ketones: Positive

Arterial blood gas on room air:
pH: 7.28
$\text{PaCO}_2$: $29 \text{ mmHg}$
$\text{PaO}_2$: $98 \text{ mmHg}$

Assuming a normal reference serum anion gap of $12 \text{ mEq/L}$ and a normal reference serum bicarbonate of $24 \text{ mEq/L}$, what is the calculated delta ratio ($\Delta\text{AG} / \Delta\text{HCO}_3^-$) for this patient?

A 62-year-old woman with a history of severe protein-calorie malnutrition and chronic diarrhea is admitted to the hospital with generalized weakness and lethargy. Vital signs are within normal limits. An arterial blood gas analysis reveals a $pH$ of $7.31$ and a $PaCO_2$ of $32\text{ mmHg}$.

Serum laboratory studies report the following:

What is the patient's albumin-corrected serum anion gap in $\text{mEq/L}$? (Assume a standard reference serum albumin concentration of $4.0\text{ g/dL}$).

A 72-year-old woman is evaluated in the hospital for acute kidney injury. She was admitted 6 days ago for urosepsis and has been treated with intravenous ampicillin, gentamicin, and intravenous fluids. Over the past 24 hours, her urine output has decreased to 400 mL. Her blood pressure is 122/76 mm Hg, and heart rate is 84/min. She appears euvolemic, and her mucous membranes are moist. Laboratory studies show:

Based on these laboratory results, what is the patient's fractional excretion of sodium (FENa) in percent?

A 41-year-old man is brought to the emergency department by ambulance after being found obtunded in an alleyway. Medical records indicate a history of severe alcohol use disorder and major depressive disorder. Vital signs are temperature 36.1°C (97.0°F), blood pressure 105/65 mm Hg, pulse 112/min, and respirations 24/min. Physical examination shows a somnolent man who arouses only to painful stimuli. Pupils are equal and reactive. Cardiopulmonary examination is unremarkable.

Laboratory results are as follows:

Arterial blood gas analysis on room air reveals:
pH: 7.23
PaCO2: 28 mm Hg
PaO2: 96 mm Hg

Based on the laboratory results provided, calculate the patient's osmolar gap.

A 42-year-old man with known nephrotic syndrome is brought to the emergency department due to altered mental status and fever. His family reports he developed a spreading, painful, erythematous rash on his right lower extremity over the past three days. Vital signs reveal a temperature of $39.1^\circ\text{C}$ ($102.4^\circ\text{F}$), heart rate of $118/\text{min}$, blood pressure of $88/54\text{ mmHg}$, and respiratory rate of $26/\text{min}$.

Initial laboratory studies show:

What is the patient's albumin-corrected serum anion gap in mEq/L? (Assume a normal serum albumin concentration of $4.0\text{ g/dL}$).

A tertiary care transplant center is validating a new rapid biomarker assay to detect an invasive opportunistic fungal infection in post-operative patients. According to internal hospital data, the baseline prevalence of this fungal infection among their solid organ transplant recipients is $25\%$. During the validation phase, the rapid assay correctly identified $90\%$ of patients who had biopsy-proven fungal tissue invasion. The assay also correctly returned a negative result in $90\%$ of transplant recipients who were proven to be free of the infection. A 58-year-old man who recently received a renal allograft is tested as part of a routine post-operative monitoring protocol, and his biomarker assay returns a positive result. Based on the test's performance characteristics in this population, what is the probability (expressed as a percentage) that he actually has the invasive fungal infection?

An international research consortium recently published the findings of a large-scale, phase III, double-blind trial. The study assessed a novel oral small-molecule immunosuppressant against a placebo for maintaining clinical remission in adults with severe ulcerative colitis.

A total of $6,000$ participants were enrolled and randomly assigned in a $1:1$ ratio to receive either the novel drug or the placebo. All participants were followed for a $52$-week maintenance phase. By the end of the study, clinical disease relapse occurred in $435$ patients in the placebo group and $312$ patients in the intervention group.

Based on these trial results, what is the number needed to treat (NNT) to prevent one disease relapse over the $52$-week period? (Calculate the exact value and apply the standard biostatistical rounding rule for NNT).

A randomized, double-blind, placebo-controlled trial is conducted to evaluate the efficacy of a novel glucagon-like peptide-1 (GLP-1) receptor agonist for the secondary prevention of major adverse cardiovascular events (MACE). The study enrolls patients with type 2 diabetes mellitus and established cardiovascular disease. Participants are randomized in a 1:1 ratio to receive either the GLP-1 receptor agonist or a placebo, in addition to standard of care.

Over a 3-year follow-up period, the investigators report the following outcomes:

Based on the study results, what is the number needed to treat (NNT) with the novel GLP-1 receptor agonist to prevent one major adverse cardiovascular event over the 3-year follow-up period?

A clinical research organization is finalizing the methodology for a randomized, placebo-controlled trial evaluating a novel pharmacologic agent for generalized anxiety disorder. The investigators stipulate that they are willing to accept a 5% risk of concluding the agent is effective when it is truly no different from placebo. Furthermore, formal sample size calculations reveal a 0.14 probability of concluding that the drug has no effect when it actually provides a clinically meaningful benefit to patients.

Based on these parameters, what is the planned statistical power of this trial, expressed as a percentage?

An elderly man is admitted due to a two-week history of worsening dyspnea, orthopnea, and increasing lower extremity edema. His past medical history is significant for ischemic cardiomyopathy with a left ventricular ejection fraction of $30\%$. To manage his fluid overload at home, he recently doubled his daily dose of oral torsemide independently.

Upon admission, his blood pressure is $92/58\text{ mmHg}$, pulse is $108/\text{min}$, and respiratory rate is $22/\text{min}$. Jugular venous pressure is visibly elevated. Lung auscultation reveals bilateral basilar crackles, and a third heart sound (S3) is present on cardiac exam.

Laboratory evaluation yields the following results:
Serum chemistry:
Sodium: $132\text{ mEq/L}$
Potassium: $3.1\text{ mEq/L}$
Chloride: $94\text{ mEq/L}$
Bicarbonate: $29\text{ mEq/L}$
Blood urea nitrogen (BUN): $75\text{ mg/dL}$
Creatinine: $2.5\text{ mg/dL}$ (baseline $1.2\text{ mg/dL}$)

Spot urine chemistry:
Sodium: $66\text{ mEq/L}$
Urea nitrogen: $450\text{ mg/dL}$
Creatinine: $60\text{ mg/dL}$

To evaluate the etiology of the acute kidney injury in the setting of recent loop diuretic use, the medical team decides to calculate a specific fractional excretion index that is less confounded by his medication regimen than sodium excretion.

What is the calculated value of this preferred index, expressed as a percentage?

A $36$-year-old man is brought to the emergency department by emergency medical services after being found obtunded in his garage. Beside him were several unlabeled containers of antifreeze and an empty bottle of vodka. 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 $22/\text{min}$. The patient is responsive only to deep pain.

Laboratory evaluation yields the following results:

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

(Enter your answer as a whole number).

A 22-year-old man with a history of type 1 diabetes mellitus is brought to the emergency department due to altered mental status, nausea, and diffuse abdominal pain. He has not taken his insulin for the past two days. Vital signs show a heart rate of $118/\text{min}$, blood pressure of $105/65\text{ mmHg}$, and respiratory rate of $28/\text{min}$ with deep, rapid breaths.

Laboratory results are as follows:

Serum sodium: $142\text{ mEq/L}$
Serum potassium: $4.8\text{ mEq/L}$
Serum chloride: $98\text{ mEq/L}$
Serum bicarbonate: $14\text{ mEq/L}$
Blood urea nitrogen: $32\text{ mg/dL}$
Serum creatinine: $1.4\text{ mg/dL}$
Serum glucose: $520\text{ mg/dL}$

Arterial blood gas (room air):
pH: $7.21$
$pCO_2$: $24\text{ mmHg}$
$pO_2$: $98\text{ mmHg}$

Using Winter's formula, what is the mean expected $pCO_2$ (in mmHg) to determine if this patient has an appropriately compensated primary metabolic acidosis?

A 27-year-old man with a history of type 1 diabetes mellitus is brought to the emergency department due to altered mental status. His roommate reports that the patient has been suffering from a severe gastrointestinal illness for the past three days, characterized by profuse, intractable vomiting, and has been unable to tolerate food, fluids, or his scheduled insulin doses. On physical examination, the patient is lethargic and tachycardic, with deep, labored respirations. His mucous membranes are markedly parched, and skin turgor is poor.

Laboratory results are as follows:

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