Internal Medicine

A 22-year-old woman is brought to the emergency department by her roommate due to agitation, nausea, and ringing in her ears. The roommate reports finding several empty over-the-counter medication bottles in their bathroom. On physical examination, the patient appears distressed and is breathing rapidly.

Temperature is $38.1^\circ$ C ($100.6^\circ$ F), blood pressure is 112/68 mm Hg, pulse is 118/min, and respiratory rate is 26/min. Laboratory studies show:

Arterial blood gas on room air:

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

A 68-year-old man presents to the clinic with a 2-year history of progressive right knee pain. The pain typically worsens at the end of the day or after prolonged walking, and it improves with rest. He reports about 10 to 15 minutes of joint stiffness in the morning. His medical history is significant for hypertension. Physical examination reveals bony enlargement, decreased range of motion, and crepitus of the right knee without significant effusion, erythema, or warmth. Radiographs show medial joint space narrowing, subchondral sclerosis, and osteophyte formation. Arrange the following interventions in the generally recommended, step-wise sequence for the management of this patient's condition, assuming an inadequate response to each preceding step.

A 38-year-old man presents to the clinic complaining of progressive fatigue, generalized weakness, and cold intolerance over the past 8 months. He also reports a significantly decreased libido. Two years ago, he was involved in a severe motor vehicle collision that resulted in a basilar skull fracture and a prolonged intensive care unit stay. He takes no daily medications. His temperature is $36.4^\circ\text{C}$ ($97.5^\circ\text{F}$), pulse is 55/min, and blood pressure is 102/64 mmHg. Physical examination demonstrates pale, dry skin and a delayed relaxation phase of the ankle reflexes. Visual field testing is normal.

Laboratory results are as follows:

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

Emergency medical services arrive with a 74-year-old woman who became acutely lethargic at her assisted living facility. According to the staff, she had been complaining of severe, diffuse abdominal pain that was out of proportion to her physical exam findings earlier in the morning. Her medical history includes atrial fibrillation, type 2 diabetes mellitus, and severe peripheral vascular disease.

On evaluation, her blood pressure is 78/46 mm Hg, pulse is 132/min and irregularly irregular, and respirations are deep and rapid at 28/min. Physical examination reveals mottled, cool extremities and a rigid, diffusely tender abdomen.

Point-of-care laboratory testing reveals:
Serum $Na^+$: 141 mEq/L
Serum $K^+$: 4.9 mEq/L
Serum $Cl^-$: 105 mEq/L
Serum $HCO_3^-$: 14 mEq/L
Blood urea nitrogen: 32 mg/dL
Creatinine: 1.6 mg/dL
Lactate: 9.4 mmol/L (normal: 0.5-1.0 mmol/L)

Arterial blood gas on room air:
pH: 7.23
$PaO_2$: 88 mm Hg

What is the expected arterial partial pressure of carbon dioxide ($PaCO_2$) in mm Hg that indicates appropriate and isolated respiratory compensation for her primary acid-base disturbance?

Match each patient's clinical presentation and laboratory profile with the most characteristic finding expected on their microscopic urinalysis or urine sediment examination.

A 29-year-old man is evaluated in the outpatient office due to a one-year history of worsening sluggishness, weight gain, and diminished libido. He reports feeling constantly cold even when others are comfortable. His medical history is notable for a severe closed head injury sustained in a motorcycle collision three years ago, which required a two-week stay in the intensive care unit. He currently takes no medications. Vital signs show a temperature of $36.1^\circ\text{C}$ ($97.0^\circ\text{F}$), blood pressure of $105/65 \text{ mm Hg}$, and heart rate of $56/\text{min}$. Physical examination reveals dry skin and a delayed relaxation phase of the deep tendon reflexes. Testes are soft and measure $12 \text{ mL}$ bilaterally (normal $15-25 \text{ mL}$). Laboratory studies show:

Thyroid-stimulating hormone (TSH): $1.1 \text{ mU/L}$ (Reference: $0.5-5.0 \text{ mU/L}$)
Free thyroxine (T4): $0.5 \text{ ng/dL}$ (Reference: $0.9-2.4 \text{ ng/dL}$)
Total testosterone: $160 \text{ ng/dL}$ (Reference: $300-1000 \text{ ng/dL}$)

Which of the following is the most likely diagnosis?

A 42-year-old man is brought to the emergency department by his husband due to a 2-day history of progressive confusion, fatigue, and fever. The patient had a mild upper respiratory tract infection one week ago but otherwise has no significant past medical history. He takes no medications.

Vital signs are:
Temperature: 38.6°C (101.5°F)
Blood pressure: 142/88 mm Hg
Heart rate: 110/min
Respiratory rate: 18/min
Oxygen saturation: 98% on room air

Physical examination reveals a lethargic man who is oriented to person only. Scleral icterus is present. The skin examination shows widespread pinpoint, non-blanching red macules over the lower extremities and abdomen. There is no nuchal rigidity, and the remainder of the neurologic examination is nonfocal.

Laboratory studies reveal:
Hemoglobin: 7.6 g/dL
Mean corpuscular volume (MCV): 88 fL
Platelets: 18,000/mm³
Leukocytes: 9,200/mm³
Blood urea nitrogen (BUN): 42 mg/dL
Creatinine: 2.3 mg/dL
Total bilirubin: 4.8 mg/dL
Indirect bilirubin: 3.9 mg/dL
Lactate dehydrogenase (LDH): 1,450 U/L
Haptoglobin: 8 mg/dL (Normal: 50–200 mg/dL)
Prothrombin time (PT): 12 seconds
Activated partial thromboplastin time (aPTT): 28 seconds
Direct antiglobulin (Coombs) test: Negative

Peripheral blood smear reveals numerous fragmented red blood cells.

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

A 38-year-old woman is admitted to the medical ward due to a sudden onset of severe headache, palpitations, and profuse diaphoresis. Her blood pressure is 185/115 mm Hg, and her heart rate is 118/min. She reports experiencing three similar episodes over the past month. The clinical presentation is highly suspicious for a catecholamine-secreting neuroendocrine tumor. Arrange the following steps in the most appropriate chronological sequence for the comprehensive diagnostic evaluation and perioperative management of this patient's suspected condition. Assume each step yields confirmatory findings that warrant progression to the subsequent step.

A 45-year-old male is evaluated in the emergency department for altered mental status. His spouse found him acting confused and stumbling in their basement next to several open containers of antifreeze. Vital signs are temperature $36.7^\circ C$ ($98.1^\circ F$), blood pressure $115/78$ mm Hg, pulse $95$/min, and respirations $26$/min. He appears intoxicated but has no scent of alcohol on his breath. Laboratory results are as follows:

Based on these findings, what is the patient's serum osmolar gap?

A male college student, aged $19$, is brought to the emergency department after his roommate found him confused and vomiting. He has been complaining of abdominal pain for the past day. On physical examination, he appears lethargic and has dry mucous membranes. Vital signs demonstrate a heart rate of $120$ beats per minute and a blood pressure of $90/60$ mmHg. Point-of-care capillary glucose testing shows a level of $480$ mg/dL. An arterial blood gas analysis reveals a pH of $7.12$. A dipstick urinalysis is strongly positive for ketones. The patient is diagnosed with diabetic ketoacidosis. Arrange the following interventions in the most appropriate chronological order for his initial management.

While rounding in the surgical intensive care unit, a physician is urgently called to the bedside of a 68-year-old male patient who abruptly developed respiratory distress. The patient underwent a right hemicolectomy for stage III colon cancer two days ago. Two hours prior to the acute event, his hemoglobin level was noted to be $6.8$ g/dL, prompting the initiation of a cross-matched packed red blood cell transfusion. Approximately $30$ minutes after the transfusion began, the patient reported the sudden onset of shaking chills and severe pain in his right flank.

Vital signs reveal a temperature of $39.2^\circ\text{C}$ ($102.6^\circ\text{F}$), heart rate of $122/\text{min}$, blood pressure of $85/50$ mm Hg, and respiratory rate of $24/\text{min}$. Pulse oximetry shows an oxygen saturation of $94\%$ on room air.

Physical examination shows profound diaphoresis and anxiety. Jugular venous pulsations are not elevated. Auscultation of the chest reveals clear breath sounds in all lung fields. The surgical incision is intact without erythema or purulent drainage. Inspection of the Foley catheter drainage system reveals that the previously clear, yellow urine has acutely transitioned to a dark, reddish-brown color.

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

A 35-year-old man with untreated HIV infection is brought to the emergency department by his partner due to a 2-week history of progressively worsening headache, fever, and confusion. His temperature is 38.6°C (101.5°F), blood pressure is 120/78 mmHg, and heart rate is 102/min. Physical examination reveals nuchal rigidity and bilateral sixth cranial nerve palsies. Laboratory studies show a CD4 cell count of 28/mm³. A lumbar puncture is performed, and cerebrospinal fluid (CSF) analysis reveals a leukocyte count of 350/mm³ (85% lymphocytes), glucose of 30 mg/dL, and protein of 150 mg/dL. CSF acid-fast bacilli smear is positive. The patient is admitted to the intensive care unit and started on isoniazid, rifampin, pyrazinamide, ethambutol, and intravenous dexamethasone. Which of the following is the most appropriate timing for initiating antiretroviral therapy in this patient?

A 24-year-old man with a history of type 1 diabetes mellitus is brought to the emergency department with altered mental status, vomiting, and diffuse abdominal pain. His blood pressure is 90/60 mmHg, heart rate is 125/min, and respiratory rate is 28/min with deep, rapid breaths. Laboratory studies reveal a blood glucose of 650 mg/dL, arterial pH of 7.12, serum bicarbonate of 10 mEq/L, and a high anion gap. Urinalysis is strongly positive for ketones. Arrange the following steps in the management of this patient's condition in the most appropriate chronological order.

A 19-year-old man with type 1 diabetes mellitus is brought to the emergency department due to altered mental status, generalized weakness, and recurrent vomiting for the past 24 hours. He recently had a respiratory tract infection. Vital signs show a blood pressure of 90/60 mm Hg, heart rate of 124/min, and respiratory rate of 28/min with deep, sighing breaths. Laboratory results show:

Arrange the following management steps in the most appropriate chronological order from first to last.

A 71-year-old man comes to the clinic for a 4-month history of progressive lower back pain and severe fatigue. He states that the pain is a constant, deep ache that does not improve with rest or over-the-counter ibuprofen. Over the same period, he has developed increasing constipation. He has no prior medical history and takes no daily medications. Vital signs are within normal limits. Physical examination reveals generalized pallor and localized tenderness to palpation over the mid-lumbar spine. Neurologic examination is unremarkable. Laboratory studies show the following:

Which of the following is the most appropriate next step in establishing the diagnosis?

A 54-year-old woman is evaluated in the oncology ward for a new-onset fever. She is currently on day 10 of induction chemotherapy for acute myeloid leukemia. Her temperature is 38.8°C (101.8°F), blood pressure is 105/65 mmHg, and heart rate is 112/min. Laboratory analysis shows a white blood cell count of 400/mm³ with an absolute neutrophil count (ANC) of 150/mm³. She has a central venous port in her right internal jugular vein.

Arrange the following interventions in the most appropriate chronological sequence for managing this patient's condition.

A pulmonology consultation is requested for a hospitalized patient who was admitted two days ago for an acute exacerbation of chronic obstructive pulmonary disease. The patient has a history of type 2 diabetes mellitus and has developed severe nausea and intractable emesis over the last 24 hours after starting a new medication regimen. Current vital signs show a temperature of $37.8^\circ C$ ($100^\circ F$), blood pressure of $110/68$ mm Hg, pulse of $115$/min, and respirations of $28$/min. Physical examination reveals distant breath sounds with prolonged expiration and dry mucous membranes. A comprehensive metabolic panel and arterial blood gas analysis are obtained on room air.

Based on the laboratory data provided, which of the following accurately describes the primary and concurrent acid-base processes occurring in this patient?

A 65-year-old woman is evaluated in the clinic for progressive fatigue and generalized weakness over the past month. Her past medical history is significant for type 2 diabetes mellitus, essential hypertension, and heart failure with preserved ejection fraction. Two months ago, a new medication was added to her regimen to improve fluid balance and blood pressure control. Her current medications include metformin, amlodipine, empagliflozin, and the newly prescribed drug.

Her temperature is 37.0°C (98.6°F), blood pressure is 128/78 mm Hg, pulse is 72/min, and respirations are 16/min. Physical examination reveals clear lungs and no lower extremity edema.

Laboratory studies are obtained:

An arterial blood gas on room air shows:

Which of the following best explains the underlying pathophysiology of this patient's current acid-base and electrolyte abnormalities?

A $52$-year-old man presents for a routine follow-up appointment due to progressive fatigue, a $4\text{-kg}$ ($8.8\text{-lb}$) weight gain, and an inability to tolerate cold environments over the past $5$ months. Three years ago, he underwent surgical resection of a large pituitary adenoma. His temperature is $36.4^\circ\text{C}$ ($97.5^\circ\text{F}$), blood pressure is $115/75\text{ mmHg}$, and pulse is $56/\text{min}$. Physical examination reveals dry skin and delayed relaxation of the deep tendon reflexes. Laboratory testing shows:

Serum free $\text{T}_4$: $0.4\text{ ng/dL}$ (normal: $0.9-1.7\text{ ng/dL}$)
Serum $\text{TSH}$: $1.1\text{ }\mu\text{U/mL}$ (normal: $0.5-5.0\text{ }\mu\text{U/mL}$)

Which of the following is the most likely diagnosis?

A 71-year-old man presents to the emergency department with a 4-day history of productive cough, chills, and progressive dyspnea. On physical examination, he appears lethargic and is using accessory respiratory muscles. Vital signs are:

Temperature: 38.8°C (101.8°F)
Blood pressure: 92/58 mm Hg
Heart rate: 115/min
Respiratory rate: 28/min

Arterial blood gas analysis on room air reveals:
pH: 7.18
pCO2: 38 mm Hg
pO2: 54 mm Hg

Serum laboratory studies reveal:
Sodium: 139 mEq/L
Potassium: 4.6 mEq/L
Chloride: 101 mEq/L
Bicarbonate: 14 mEq/L
Blood urea nitrogen: 32 mg/dL
Creatinine: 1.6 mg/dL
Lactate: 5.4 mmol/L

Based on the patient's laboratory findings, which of the following is the most accurate description of his current acid-base status?