Internal Medicine

During bedside rounds, the medical team evaluates a patient who was admitted four days ago for lower extremity edema and exertional dyspnea. The patient has a longstanding history of severe emphysema and right ventricular failure. Over the course of the hospitalization, aggressive intravenous furosemide has been administered, resulting in a $6\text{ kg}$ weight loss and significant symptomatic improvement. Current medications include inhaled tiotropium, oral amlodipine, and intravenous furosemide. Vital signs are within normal limits.

Laboratory studies are obtained:

Arterial blood gas (room air):

Which of the following is the most accurate interpretation of this patient's current acid-base status?

A 62-year-old man is currently in the intensive care unit on day 4 of admission for severe sepsis secondary to a perforated diverticulum. He remains intubated, sedated, and requires continuous norepinephrine infusion to maintain his mean arterial pressure. According to his family, he had no chronic medical conditions prior to this admission and did not take any medications. Routine morning laboratory studies are obtained, and the intensive care team decides to send a thyroid panel due to mild bradycardia. The results are as follows:

Thyroid-stimulating hormone (TSH): $0.2 \text{ mU/L}$ (Normal: $0.4\text{--}4.0 \text{ mU/L}$)
Total thyroxine (T4): $4.1 \text{ } \mu\text{g/dL}$ (Normal: $4.5\text{--}11.2 \text{ } \mu\text{g/dL}$)
Free triiodothyronine (T3): $1.2 \text{ pg/mL}$ (Normal: $2.3\text{--}4.2 \text{ pg/mL}$)

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

Match each set of laboratory results from a water deprivation test (followed by desmopressin administration) to the most likely pathophysiologic diagnosis.

Match each laboratory profile of serum calcium, phosphorus, and intact parathyroid hormone (PTH) to the most likely underlying clinical diagnosis.

During a winter clinical visit, a physician evaluates a patient who reports progressive exhaustion and episodic darkening of her urine over the past three months. The patient also notes that her fingers turn bluish and become painful when she is exposed to chilly morning air. She has no significant past medical history and takes no daily medications. Vital signs are within normal limits. Physical examination reveals conjunctival pallor and mild cervical lymphadenopathy. Laboratory studies show the following:

Hemoglobin: 7.8 g/dL
Mean corpuscular volume: 104 fL
Reticulocyte count: 7.5%
Lactate dehydrogenase: 650 U/L
Haptoglobin: < 10 mg/dL (normal: 41-165 mg/dL)

A direct antiglobulin test is strongly positive for C3 but negative for IgG. A peripheral blood smear demonstrates red blood cell clumping that resolves upon warming the slide.

Which of the following is the most appropriate definitive pharmacologic therapy for this patient's hematologic condition?

Match each patient's clinical presentation with the most likely corresponding coagulation profile.

A 72-year-old man is evaluated in the hospital on day 3 of admission for community-acquired pneumonia. He initially presented to the emergency department with a 2-day history of fever, productive cough, and shortness of breath. His medical history is significant for hypertension and mild chronic obstructive pulmonary disease. On admission, his temperature was $38.9^\circ\text{C}$ ($102^\circ\text{F}$), blood pressure was $118/76\text{ mmHg}$, pulse was $102/\text{min}$, and respiratory rate was $22/\text{min}$. Oxygen saturation was $92\%$ on room air. Chest radiography revealed a right lower lobe consolidation. He was empirically started on intravenous ceftriaxone and intravenous azithromycin. Today, the patient is afebrile, his pulse is $82/\text{min}$, and his respiratory rate is $16/\text{min}$. He is resting comfortably and eating a regular diet. Blood cultures drawn on admission are now growing *Streptococcus pneumoniae*. Susceptibility testing shows the organism is highly susceptible to penicillin, amoxicillin, ceftriaxone, and levofloxacin, but resistant to azithromycin. Which of the following is the most appropriate next step in antibiotic management?

A 42-year-old woman is evaluated for a 6-month history of progressive weight gain, facial rounding, and worsening hypertension. She also reports easy bruising, newly developing dark hairs on her chin, and muscle weakness when climbing stairs. She takes amlodipine and lisinopril, but her blood pressure remains poorly controlled at $162/98\text{ mmHg}$. Physical examination shows central obesity, facial plethora, supraclavicular fat pads, and wide, violaceous abdominal striae.

Laboratory findings:
- Serum potassium: $3.3\text{ mEq/L}$
- 24-hour urine free cortisol: $420\ \mu\text{g}$ (Normal: $< 45\ \mu\text{g}$)
- Overnight 1-mg dexamethasone suppression test: Serum cortisol is $15\ \mu\text{g/dL}$ (Normal: $< 1.8\ \mu\text{g/dL}$)
- Plasma ACTH: $110\text{ pg/mL}$ (Normal: $10-60\text{ pg/mL}$)

An MRI of the brain with contrast reveals a $4\text{ mm}$ focal hypointense lesion in the anterior pituitary gland.

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

A 28-year-old male with type 1 diabetes mellitus arrives at the acute care clinic complaining of severe nausea, diffuse abdominal cramping, and frequent emesis for the past 72 hours. He states he has been unable to tolerate oral intake and has missed his last four insulin doses. On physical examination, he appears lethargic with markedly dry mucous membranes and poor skin turgor. Blood pressure is $100/60 \text{ mmHg}$, heart rate is $118\text{/min}$, and respiratory rate is $24\text{/min}$.

Laboratory results:
Sodium: $142 \text{ mEq/L}$
Potassium: $3.2 \text{ mEq/L}$
Chloride: $90 \text{ mEq/L}$
Bicarbonate: $16 \text{ mEq/L}$
Blood urea nitrogen: $38 \text{ mg/dL}$
Creatinine: $1.8 \text{ mg/dL}$
Glucose: $450 \text{ mg/dL}$

Assuming a normal anion gap of $12 \text{ mEq/L}$, what is the patient's calculated corrected bicarbonate (also known as the expected starting bicarbonate or delta-delta) in mEq/L?

Match each clinical presentation of acute renal impairment to the pharmacological agent most likely responsible for its underlying pathogenesis.

A 54-year-old man presents to the clinic with a 5-day history of fever, severe fatigue, drenching sweats, and dark urine. He recently returned from a 2-week camping trip in Nantucket, Massachusetts. Two days ago, he was evaluated at an urgent care center where a 6-cm expanding erythematous plaque with central clearing was noted on his right thigh. He was prescribed oral doxycycline for presumed early localized Lyme disease. Despite compliance with the medication, his fever and fatigue have persisted and worsened. His temperature is 38.9°C (102.0°F), blood pressure is 116/74 mm Hg, and pulse is 108/min. Physical examination reveals pale conjunctivae, mild scleral icterus, and a fading erythematous patch on the right thigh. There is no respiratory distress. Laboratory studies show:

Hemoglobin: 9.2 g/dL
Platelets: 88,000/mm³
Leukocytes: 4,500/mm³
Total bilirubin: 3.4 mg/dL
Indirect bilirubin: 2.8 mg/dL
Lactate dehydrogenase: 650 U/L

A peripheral blood smear demonstrates pleomorphic intraerythrocytic ring forms and occasional tetrads. Which of the following is the most appropriate pharmacotherapy for this patient's current condition?

A 27-year-old woman is admitted to the hospital with a 4-day history of severe, frequent, watery diarrhea and diffuse abdominal pain. She has a history of ulcerative colitis and takes oral mesalamine. Her temperature is $38.8^\circ C$ ($101.8^\circ F$), blood pressure is $96/60$ mm Hg, pulse is 118/min, and respirations are 26/min. The patient appears acutely ill, diaphoretic, and in moderate distress due to abdominal cramping.

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

Match the following calcium and bone metabolism disorders with their characteristic initial laboratory findings for serum calcium, parathyroid hormone (PTH), and phosphorus.

During bedside rounds in the surgical intensive care unit, a critical care team evaluates a 68-year-old individual who underwent an emergency exploratory laparotomy 24 hours ago for acute mesenteric ischemia. The postoperative course has been complicated by massive fluid shifts and a need for continuous nasogastric tube suctioning, which is currently draining approximately 1,500 mL of bilious fluid daily. The patient is intubated and sedated. Vital signs demonstrate a blood pressure of 88/50 mm Hg and a heart rate of 122/min.

Serum laboratory analysis reveals:
$Na^+$: 142 mEq/L
$K^+$: 3.2 mEq/L
$Cl^-$: 88 mEq/L
$HCO_3^-$: 16 mEq/L
BUN: 45 mg/dL
Creatinine: 2.1 mg/dL

Arterial blood gas analysis on 40% $FiO_2$ demonstrates:
pH: 7.28
$P_{CO2}$: 34 mm Hg
$P_{O2}$: 92 mm Hg

Assuming a reference normal anion gap of 12 mEq/L and a reference normal bicarbonate of 24 mEq/L, calculate the patient's corrected bicarbonate level (often used to assess for a tertiary acid-base disorder via the delta-delta gap) in mEq/L.

A 68-year-old man is admitted to the hospital due to a 3-week history of low-grade fevers, progressive fatigue, and dyspnea on exertion. He has a history of hypertension and osteoarthritis. His temperature is 38.2°C (100.8°F), blood pressure is 128/76 mm Hg, pulse is 92/min, and respirations are 16/min. Physical examination reveals a new grade 3/6 holosystolic murmur best heard at the cardiac apex and radiating to the axilla. Splinter hemorrhages are noted on the fingernails. Transesophageal echocardiography demonstrates a 1.2-cm mobile vegetation on the anterior leaflet of the mitral valve with moderate mitral regurgitation. Three sets of blood cultures are obtained, and the patient is started on empiric intravenous vancomycin and cefepime. Forty-eight hours later, all three blood cultures grow *Enterococcus faecalis*. Antimicrobial susceptibility testing results are as follows:

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

A $59$-year-old man with metastatic melanoma is brought to the emergency department by his wife due to profound fatigue, generalized weakness, and nausea that have progressively worsened over the past two weeks. He has been receiving immunotherapy with ipilimumab and nivolumab for the past four months. His temperature is $36.8^\circ\text{C}$ ($98.2^\circ\text{F}$), blood pressure is $88/56\text{ mm Hg}$, and pulse is $98/\text{min}$. When he stands, his blood pressure drops to $76/45\text{ mm Hg}$ and he feels dizzy. Physical examination shows a lethargic man. Mucous membranes are dry, and there is no abnormal skin pigmentation.

Laboratory studies show:

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

A newly admitted 19-year-old male with a history of type 1 diabetes mellitus is evaluated on the medical ward for persistent nausea, recurrent vomiting, and diffuse abdominal pain. The patient admits to missing his insulin doses over the past three days. The following initial serum chemistry panel is obtained:

* Sodium: 138 mEq/L
* Potassium: 5.1 mEq/L
* Chloride: 99 mEq/L
* Bicarbonate: 14 mEq/L
* Blood urea nitrogen: 28 mg/dL
* Creatinine: 1.2 mg/dL
* Glucose: 485 mg/dL

Calculate the patient's serum anion gap in mEq/L.

A 34-year-old woman comes to the clinic reporting progressive fatigue, weight gain, and cold intolerance over the past 4 months. She has not had a menstrual period since giving birth 6 months ago. Her pregnancy was complicated by a severe postpartum hemorrhage requiring emergency fluid resuscitation and multiple blood transfusions. She was unable to breastfeed her infant despite repeated attempts. Her pulse is 58/min, and blood pressure is 90/60 mm Hg. Physical examination shows dry skin and delayed relaxation of the deep tendon reflexes. Laboratory studies show:

* Thyroid-stimulating hormone (TSH): $1.1\text{ mU/L}$ (Reference: $0.4-4.0\text{ mU/L}$)
* Free thyroxine (T4): $0.4\text{ ng/dL}$ (Reference: $0.9-1.7\text{ ng/dL}$)

Which of the following is the most likely underlying mechanism for this patient's clinical and laboratory findings?

Match the following complex thyroid function laboratory profiles to the most accurate underlying pathophysiologic diagnosis.

Match each of the following high-risk infectious exposure scenarios with the most appropriate immediate management or post-exposure prophylaxis (PEP) step.