Internal Medicine

An 82-year-old man with advanced Alzheimer dementia is brought to the emergency department from a skilled nursing facility due to progressive lethargy over the past 3 days. The facility staff report that he has been refusing meals and liquids. On examination, temperature is 37.1°C (98.8°F), blood pressure is 98/60 mm Hg, pulse is 112/min, and respiratory rate is 16/min. The patient appears cachectic with profoundly dry mucous membranes and poor skin turgor. His current weight is 60 kg (132 lb).

Laboratory studies show:
Serum sodium: 168 mEq/L
Serum potassium: 4.1 mEq/L
Serum chloride: 129 mEq/L
Serum bicarbonate: 24 mEq/L
Blood urea nitrogen: 56 mg/dL
Serum creatinine: 1.8 mg/dL

Based on an estimated total body water of 50% of his body weight, what is this patient's calculated free water deficit in liters?

A 65-year-old man with a history of chronic obstructive pulmonary disease (COPD) and type 2 diabetes mellitus is evaluated in the emergency department for progressive fatigue, shortness of breath, and lower extremity tingling over the past 4 weeks. He has not had fever, increased sputum production, or chest pain. Vital signs show a temperature of 37.0 C (98.6 F), blood pressure of 115/75 mmHg, pulse of 112/min, and respiratory rate of 22/min. Pulse oximetry is 94% on room air.

Physical examination reveals pale conjunctivae and a smooth, beefy red tongue. Neurologic examination shows decreased vibratory sensation in the lower extremities bilaterally. Lung auscultation is clear without wheezes or crackles. Heart exam reveals a 2/6 systolic ejection murmur at the left sternal border.

Laboratory results are as follows:

Arterial blood gas on room air shows pH 7.31, PaCO2 32 mmHg, and PaO2 75 mmHg. Peripheral blood smear reveals hypersegmented neutrophils and macro-ovalocytes. Blood cultures drawn 2 days ago in the outpatient clinic are negative.

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

Laboratory evaluation is performed during a routine follow-up visit for a 64-year-old man with a 15-year history of type 2 diabetes mellitus and hypertension. The patient reports feeling generally well and explicitly denies any recent nausea, vomiting, or diarrhea. His current medication regimen consists of metformin, lisinopril, amlodipine, and atorvastatin. Blood pressure is $134/82 \text{ mmHg}$ and pulse is $72/\text{min}$.

Laboratory results are as follows:

Urinalysis reveals a pH of $5.2$ and is negative for glucose, ketones, and cellular casts.

Which of the following pathophysiologic mechanisms best explains this patient's current laboratory findings?

Match each patient's clinical presentation with the most likely predominant finding on their peripheral blood smear.

A 72-year-old man is evaluated in the hospital for decreased urine output. He was admitted 3 days ago for an acute exacerbation of heart failure with reduced ejection fraction. His treatment regimen includes intravenous furosemide, lisinopril, carvedilol, and spironolactone. His weight has decreased by 4 kg (8.8 lb) since admission, and his peripheral edema has significantly improved. However, his urine output over the last 12 hours has been only 250 mL.

Vitals:
Blood pressure: 102/60 mm Hg
Heart rate: 94/min

Laboratory results from today:
Serum:
Sodium: 135 mEq/L
Potassium: 4.8 mEq/L
Chloride: 98 mEq/L
Bicarbonate: 28 mEq/L
Blood urea nitrogen: 80 mg/dL
Creatinine: 2.4 mg/dL

Urine:
Sodium: 75 mEq/L
Creatinine: 120 mg/dL
Urea nitrogen: 600 mg/dL

Based on the laboratory findings, what is this patient's calculated fractional excretion of urea (expressed as a percentage)?

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

Match each patient's clinical presentation with the most likely rheumatologic diagnosis.

A 54-year-old man is evaluated in the intensive care unit for a new-onset fever. He was admitted 6 days ago following a severe motor vehicle collision that resulted in multiple rib fractures and a pulmonary contusion. He required endotracheal intubation and mechanical ventilation on the day of admission. Over the past 24 hours, he has developed a temperature of $38.9^\circ\text{C}$ ($102.0^\circ\text{F}$) and requires an increasing fraction of inspired oxygen ($\text{FiO}_2$) and positive end-expiratory pressure. Endotracheal suctioning yields thick, purulent secretions. A chest radiograph reveals a new right lower lobe consolidation. His leukocyte count is $16,500/\text{mm}^3$. A bronchoalveolar lavage is performed, and he is started on empiric intravenous vancomycin and cefepime. Two days later, his oxygenation has stabilized. The bronchoalveolar lavage fluid cultures grow $> 10^4 \text{ CFU/mL}$ of *Pseudomonas aeruginosa*. The isolate is susceptible to cefepime, piperacillin-tazobactam, and meropenem. No other organisms are isolated. Which of the following is the most appropriate next step in the pharmacologic management of this patient?

An 81-year-old female resident of a skilled nursing facility is currently recovering in the intensive care unit after presenting three days prior with severe distributive shock secondary to a catheter-associated urinary tract infection. On admission, she was hypotensive and tachycardic, and empiric antimicrobial therapy was initiated with intravenous vancomycin and piperacillin-tazobactam. Today, she is hemodynamically stable, off vasopressor support, and her temperature has normalized to 37.1°C (98.8°F). The indwelling urinary catheter was removed on the first day. Both the admission urine and blood cultures have grown *Escherichia coli*. The susceptibility report for the bloodstream isolate is provided below:

Based on the culture results and the patient's current clinical status, which of the following is the most appropriate definitive pharmacotherapy?

A 45-year-old man presents to the clinic with complaints of progressive enlargement of his hands and feet over the past two years, requiring him to buy larger shoes and a new wedding ring. He also reports excessive sweating and recently began snoring loudly at night. On physical examination, he has a prominent jaw, an enlarged nose, and macroglossia. You suspect a growth hormone-secreting pituitary adenoma. Arrange the following steps in the most appropriate chronological sequence for the diagnosis and initial management of this patient's condition.

Match each specific circulating autoantibody with the endocrine disorder it is most classically used to diagnose or evaluate.

Match each presentation of calcium, phosphorus, and parathyroid hormone (PTH) laboratory abnormalities with its most likely underlying pathophysiologic diagnosis.

Match each constellation of laboratory findings to the most likely underlying pathophysiologic diagnosis.

Match the following glomerular diseases with their classic renal biopsy or immunofluorescence findings.

A $35$-year-old man who recently emigrated from a country with high tuberculosis endemicity presents to the emergency department. He reports a $6$-week history of a persistent, blood-tinged cough, subjective fevers, drenching night sweats, and a $6$-kg ($13$-lb) weight loss. While in the crowded triage area, he is actively coughing. His vital signs show a temperature of $38.2^\circ\text{C}$ ($100.8^\circ\text{F}$). Arrange the following steps in the most appropriate chronological order for the optimal management of this patient.

A 45-year-old man with a history of intravenous drug use presents to the emergency department with a 1-week history of high fevers, chills, and profound fatigue. His temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, and heart rate is 115/min. Physical examination is notable for a new early diastolic murmur heard best at the left lower sternal border, and painless erythematous macules on the palms of his hands. Laboratory results show a leukocyte count of 18,000/mm³ with a left shift. Arrange the following diagnostic and therapeutic steps in the most appropriate chronological order for managing this patient's acute presentation.

A 68-year-old man is brought to the emergency department with 3 days of severe, watery diarrhea and poor oral intake. He reports feeling lightheaded upon standing. His temperature is $37.1^\circ$ C ($98.8^\circ$ F), blood pressure is $112/72$ mm Hg supine and $90/60$ mm Hg standing, and pulse is 92/min supine and 116/min standing. Physical examination reveals dry mucous membranes and delayed capillary refill.

Laboratory results are as follows:

Serum studies:
Sodium: $140$ mEq/L
Potassium: $3.5$ mEq/L
Chloride: $110$ mEq/L
Bicarbonate: $20$ mEq/L
Blood urea nitrogen: $42$ mg/dL
Creatinine: $1.4$ mg/dL

Urine studies:
Sodium: $20$ mEq/L
Creatinine: $40$ mg/dL

Based on these findings, what is the patient's fractional excretion of sodium?

A 71-year-old man is evaluated in the intensive care unit regarding his antimicrobial regimen. He was admitted 12 days ago for acute respiratory distress syndrome secondary to a severe viral pneumonitis and required endotracheal intubation. Five days ago, his clinical status deteriorated with the development of a fever up to 39.4°C (102.9°F), worsening hypoxia, and thick, purulent endotracheal secretions. A chest radiograph at that time demonstrated a new dense consolidation in the left lower lobe. Empiric intravenous therapy with piperacillin-tazobactam, tobramycin, and vancomycin was initiated.

Today, the patient is clinically improving; he is afebrile (37.1°C [98.8°F]), and his ventilator settings have been significantly weaned. The quantitative bronchoalveolar lavage culture obtained five days ago exhibits heavy growth ($10^5$ CFU/mL) of *Pseudomonas aeruginosa*. Antimicrobial susceptibility testing indicates the organism is susceptible to piperacillin-tazobactam, cefepime, and ciprofloxacin, but resistant to tobramycin. No other organisms, including methicillin-resistant *Staphylococcus aureus* (MRSA), have been isolated. Blood cultures show no growth.

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

A 58-year-old male is evaluated in the emergency department after his family noted progressive lethargy and confusion. According to his wife, he has experienced severe, nonbloody, bilious vomiting for the past five days. He has been unable to tolerate oral intake and has had minimal urine output for the past 24 hours. His medical history includes hypertension and untreated peptic ulcer disease. On physical examination, blood pressure is $88/54 \text{ mm Hg}$, and pulse is $118/\text{min}$. The patient appears lethargic. Mucous membranes are extremely dry, and skin turgor is significantly decreased.

Laboratory studies show the following:
Sodium: $140 \text{ mEq/L}$
Potassium: $3.2 \text{ mEq/L}$
Chloride: $90 \text{ mEq/L}$
Bicarbonate: $25 \text{ mEq/L}$
Blood urea nitrogen: $72 \text{ mg/dL}$
Creatinine: $3.4 \text{ mg/dL}$
Lactate: $6.2 \text{ mmol/L}$

Arterial blood gas (room air):
pH: $7.37$
$pCO_2$: $45 \text{ mm Hg}$
$pO_2$: $88 \text{ mm Hg}$

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

A 28-year-old woman, G1P0 at $30$ weeks gestation, comes to the clinic for a routine prenatal follow-up. She has a 5-year history of systemic lupus erythematosus (SLE) that has been quiescent on hydroxychloroquine. She reports mild, generalized fatigue and occasionally feeling "out of breath" when climbing stairs, but she explicitly denies joint pain, facial rashes, fevers, or chest pain. Her blood pressure is $112/70 \text{ mm Hg}$, and her pulse is $85/\text{min}$. Physical examination shows trace bilateral pedal edema but is otherwise unremarkable. Fetal heart tones are $145/\text{min}$.

Laboratory studies show the following:

Arterial blood gas analysis on room air reveals:

Urinalysis shows trace protein with no red blood cells or cellular casts. The patient is anxious and asks if her recent symptoms and laboratory abnormalities indicate that her autoimmune disease is worsening. Which of the following is the most appropriate next step in management?