Internal Medicine

During morning rounds, the healthcare team reviews the laboratory results of a 58-year-old woman admitted to the intensive care unit three days ago for severe community-acquired pneumonia and sepsis. Her respiratory status has significantly improved following the administration of appropriate intravenous antibiotics and supportive care. Vital signs today show a temperature of $37.1^\circ\text{C}$ ($98.8^\circ\text{F}$), blood pressure of $118/76\text{ mm Hg}$, heart rate of $88\text{/min}$, and respiratory rate of $16\text{/min}$. As part of a broad laboratory panel ordered on admission, her thyroid studies return with the following values:

Thyroid-stimulating hormone (TSH): $0.3\text{ }\mu\text{U/mL}$ (Normal: $0.4-4.0\text{ }\mu\text{U/mL}$)
Free T4: $0.7\text{ ng/dL}$ (Normal: $0.9-2.4\text{ ng/dL}$)
Total T3: $45\text{ ng/dL}$ (Normal: $80-200\text{ ng/dL}$)

The patient has no history of thyroid disease and takes no home medications. Physical examination reveals a normal-sized thyroid gland without nodules, normal deep tendon reflexes, and no tremors. Which of the following is the most appropriate next step in the management of this patient's thyroid laboratory findings?

A $54$-year-old woman is evaluated in the emergency department for a fever that started $6$ hours ago. She is currently hospitalized and undergoing induction chemotherapy for acute myeloid leukemia (AML). She reports mild generalized fatigue but denies cough, shortness of breath, dysuria, abdominal pain, or diarrhea. Her temperature is $38.6^\circ\text{C}$ ($101.5^\circ\text{F}$), blood pressure is $112/72 \text{ mm Hg}$, pulse is $108/\text{min}$, and respiratory rate is $16/\text{min}$. Physical examination reveals a clean and intact right internal jugular central venous catheter site with no surrounding erythema, induration, or tenderness. The lungs are clear to auscultation bilaterally. There are no oral ulcers or skin rashes.

Laboratory studies show:

Blood and urine cultures have been obtained. Which of the following is the most appropriate next step in management?

Following an emergency exploratory laparotomy for ischemic colitis, a $68$-year-old patient remains mechanically ventilated in the surgical intensive care unit. Over the past $48$ hours, continuous nasogastric suctioning has yielded $2.5$ liters of fluid. The patient is currently receiving continuous intravenous infusions of fentanyl and propofol. Current vital signs include a temperature of $38.9^\circ C$ ($102.0^\circ F$), pulse of $118$/min, and blood pressure of $88/54$ mm Hg. The ventilator is set to synchronized intermittent mandatory ventilation mode, and the patient is triggering very few spontaneous breaths.

Laboratory evaluation demonstrates:

What is the complete characterization of this patient's acid-base status?

Match each patient's clinical presentation with the classic renal biopsy finding most likely to be seen in their condition.

A $54$-year-old woman is evaluated in the intensive care unit on day $14$ of an admission for severe acute respiratory distress syndrome (ARDS) secondary to viral pneumonia. She was treated with a $10$-day course of intravenous dexamethasone, which was completed two days ago. The patient remains on mechanical ventilation, but her oxygen requirements are slowly decreasing. While attempting to wean sedation, the patient appears profoundly lethargic and unresponsive to verbal stimuli. Her temperature is $36.2^\circ\text{C}$ ($97.2^\circ\text{F}$), pulse is $92/\text{min}$, and blood pressure is $110/68\text{ mmHg}$. Physical examination reveals trace bilateral pedal edema and delayed relaxation of deep tendon reflexes. A thyroid panel is obtained to evaluate her delayed awakening:

Based on these findings, which of the following is the most appropriate next step in the management of this patient's thyroid function?

Review the four distinct patient laboratory profiles concerning calcium and bone metabolism. Reference ranges: Calcium 8.4-10.2 mg/dL; Phosphorus 2.5-4.5 mg/dL; Intact PTH 15-65 pg/mL; 25-hydroxyvitamin D 20-50 ng/mL; 1,25-dihydroxyvitamin D 18-72 pg/mL. Assign each laboratory profile to the most accurate underlying pathophysiologic etiology.

Match each clinical vignette describing a patient's presentation to the autoantibody profile most closely associated with their underlying condition.

Systemic vasculitides often present with a wide spectrum of overlapping clinical manifestations, but specific patterns of organ involvement, histological features, and autoantibody associations can help differentiate them. Match each of the following vasculitis diagnoses with its classic clinical presentation and associated laboratory findings.

A 68-year-old man with a history of type 2 diabetes mellitus is brought to the emergency department due to progressively worsening confusion and profound weakness over the past 4 days. He recently recovered from a mild upper respiratory illness. On examination, he is lethargic but arousable. Vital signs show a blood pressure of $92/58\text{ mm Hg}$, a heart rate of $118/\text{min}$, and a respiratory rate of $16/\text{min}$. His mucous membranes are parched, and skin turgor is significantly decreased.

Initial laboratory evaluation reveals:
Serum sodium: $129\text{ mEq/L}$
Serum potassium: $4.4\text{ mEq/L}$
Serum chloride: $95\text{ mEq/L}$
Serum bicarbonate: $22\text{ mEq/L}$
Blood urea nitrogen: $48\text{ mg/dL}$
Serum creatinine: $1.9\text{ mg/dL}$
Serum glucose: $600\text{ mg/dL}$

In order to properly select the composition of intravenous fluids for resuscitation, the patient's true sodium status must be evaluated.

What is the patient's corrected serum sodium concentration in $\text{mEq/L}$? (Assume a correction factor of $1.6\text{ mEq/L}$ for each $100\text{ mg/dL}$ increase in glucose above $100\text{ mg/dL}$).

A 22-year-old man comes to the clinic due to worsening bilateral lower extremity swelling over the past 3 weeks. He reports that his urine has become very frothy. He has no other chronic medical conditions but has experienced recurrent, self-limited episodes of fever and severe, diffuse abdominal pain since childhood. During these episodes, which occur 2 to 3 times a year and last 48 to 72 hours, he also occasionally develops right ankle swelling and pain. He recently moved to the United States from Turkey and has not had a primary care provider in several years. His parents are first cousins. Vital signs are within normal limits. Physical examination reveals moderate ascites and 3+ pitting edema up to the knees.

Laboratory results are as follows:

A renal biopsy demonstrates amorphous deposits in the mesangium and capillary walls. When stained with Congo red and viewed under polarized light, the deposits exhibit apple-green birefringence. Long-term adherence to which of the following medications would have most effectively prevented this patient's current renal complication?

An 68-year-old woman is brought to the emergency department by her daughter due to progressive confusion, agitation, and nausea over the past 24 hours. The daughter notes that the patient has had a mild upper respiratory illness for the last few days and has been taking an over-the-counter remedy frequently. The patient has a medical history of severe osteoarthritis and hypertension. Current home medications include lisinopril and multiple daily doses of an over-the-counter pain reliever.

Temperature is 37.8°C (100.0°F), blood pressure is 110/65 mm Hg, pulse is 114/min, and respirations are 28/min. Pulse oximetry shows 98% on ambient air. Physical examination reveals a diaphoretic, agitated woman who is oriented only to person. She occasionally complains of a "ringing" sound in her ears. The lungs are clear to auscultation bilaterally. Cardiac examination shows tachycardia with a regular rhythm. There is mild, diffuse epigastric tenderness.

Laboratory studies show the following:

Serum chemistry:
Sodium: 140 mEq/L
Potassium: 3.6 mEq/L
Chloride: 104 mEq/L
Bicarbonate: 14 mEq/L
Blood urea nitrogen: 24 mg/dL
Creatinine: 1.3 mg/dL
Glucose: 112 mg/dL

Complete blood count:
Leukocyte count: 14,500/mm³

Arterial blood gas analysis (room air):
pH: 7.42
PaCO2: 21 mm Hg
PaO2: 96 mm Hg

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

A 72-year-old man is brought to the emergency department by his family due to confusion and severe weakness. He has a history of severe chronic obstructive pulmonary disease (COPD) and heart failure with preserved ejection fraction. For the past three days, he has experienced a worsening fever, productive cough, and profuse, intractable vomiting, leaving him unable to tolerate oral intake. His home medications include furosemide, lisinopril, and inhaled tiotropium.

On presentation, his temperature is 38.6°C (101.5°F), blood pressure is 82/50 mm Hg, pulse is 118/min, and respiratory rate is 26/min. Physical examination reveals lethargy, dry mucous membranes, and delayed capillary refill. Chest auscultation reveals diffuse wheezing and bilateral coarse crackles.

Laboratory studies show:

Arterial blood gas on room air:

Based on the laboratory findings, which of the following combinations best describes this patient's current acid-base disturbances?

A 42-year-old man is brought to the emergency department by his wife due to fever, severe headache, and confusion for the past 24 hours. His temperature is 39.2°C (102.6°F), blood pressure is 110/70 mm Hg, and pulse is 112/min. Physical examination reveals nuchal rigidity and lethargy. He withdraws all four extremities to pain but does not follow commands. There is no papilledema, but his altered mental status raises concern for increased intracranial pressure.

Arrange the following steps in the most appropriate sequence for the management of this patient.

A $38$-year-old woman comes to the clinic due to progressive fatigue, weight gain, and cold intolerance over the past $4$ months. She also reports that she has not had a menstrual period for the past $5$ months. She takes no medications and her past medical history is unremarkable. Her vital signs include a temperature of $36.1^\circ$ C ($97.0^\circ$ F), blood pressure of $105/65$ mmHg, and a pulse of $56$/min. Physical examination reveals dry skin, facial puffiness, and delayed relaxation of the deep tendon reflexes. A urine pregnancy test is negative.

Laboratory results show:
Thyroid-stimulating hormone (TSH): $0.6 \mu$ U/mL (Normal: $0.4-4.2 \mu$ U/mL)
Free thyroxine (T4): $0.4$ ng/dL (Normal: $0.8-2.8$ ng/dL)

Which of the following is the most likely diagnosis?

A $31$-year-old man is evaluated in the emergency department for a $1$-week history of worsening right upper quadrant abdominal pain and abdominal swelling. He also reports profound generalized fatigue and notes that his urine is dark reddish-brown in the morning, which clears as the day progresses. His temperature is $37.3^\circ\text{C}$ ($99.1^\circ\text{F}$), blood pressure is $132/84\text{ mmHg}$, and pulse is $98/\text{min}$. Physical examination reveals mild scleral icterus and a tender, distended abdomen with shifting dullness. Hepatomegaly is appreciated, but there is no guarding or rebound tenderness.

Laboratory studies show:

Doppler ultrasonography of the abdomen demonstrates ascites and an absence of blood flow in the hepatic veins.

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

A $39$-year-old man comes to the clinic reporting a $6$-month history of profound fatigue, decreased libido, and a $5\text{-kg}$ ($11\text{-lb}$) weight gain. He has no prior medical history but was involved in a severe motorcycle collision $18$ months ago, sustaining a basilar skull fracture that required a $3$-week intensive care unit stay. His blood pressure is $100/65\text{ mmHg}$ and heart rate is $56\text{/min}$. Physical examination shows pale, dry skin, loss of axillary and pubic hair, and a delayed relaxation phase of the deep tendon reflexes. Laboratory results are as follows:

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

A 58-year-old man is evaluated in the intensive care unit for ongoing antibiotic management. He was admitted 10 days ago following a severe traumatic brain injury that required mechanical ventilation. Five days ago, he developed a new fever of 38.9°C (102.0°F), increased purulent endotracheal secretions, and worsening oxygenation. A portable chest radiograph revealed a new right lower lobe infiltrate. He was empirically started on intravenous vancomycin and piperacillin-tazobactam for presumed ventilator-associated pneumonia. Today, the patient's temperature is 37.2°C (99.0°F), and his oxygen requirements have steadily decreased. A bronchoalveolar lavage culture obtained 48 hours ago has finalized, growing >$10^5$ CFU/mL of methicillin-susceptible *Staphylococcus aureus* (MSSA). Blood cultures drawn at the time of the fever remain sterile. Which of the following is the most appropriate next step in pharmacotherapy?

A 34-year-old woman comes to the outpatient clinic due to profound fatigue, weight gain, cold intolerance, and constipation that have progressively worsened over the last 6 months. She also notes that her menstrual cycles, which were previously regular, have been absent for the past 8 months. She takes no medications and has no other medical conditions. Her blood pressure is 98/60 mm Hg and pulse is 54/min. Physical examination demonstrates dry skin, brittle hair, and delayed relaxation phase of the deep tendon reflexes. Visual fields are full to confrontation.

Laboratory results are as follows:

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

A 34-year-old woman is evaluated for progressive weight gain, profound fatigue, and easy bruising over the past 8 months. Physical examination reveals facial plethora, marked central adiposity, supraclavicular fat pads, and wide violaceous abdominal striae. Her blood pressure is 158/96 mmHg. She takes no medications and has not used any exogenous glucocorticoids. Endogenous Cushing syndrome is suspected.

Arrange the following interventions in the most appropriate chronological sequence for the diagnostic workup and definitive management of this patient. Assume that the patient is ultimately proven to have Cushing disease caused by a biochemically active but radiologically equivocal (4-mm) pituitary microadenoma.

A 27-year-old woman is brought to the emergency department by her roommate due to persistent nausea, vomiting, and diffuse abdominal pain for the past 24 hours. She has a history of type 1 diabetes mellitus and reports that she ran out of her insulin prescription two days ago. On physical examination, she appears lethargic but is easily arousable. Her respiratory rate is $26/\text{min}$ and breaths are deep and rapid.

Laboratory testing reveals the following:

Which of the following most accurately describes this patient's primary acid-base disturbance?