A 48-year-old man comes to the physician for the evaluation of dyspnea and cough. He was diagnosed with esophageal cancer 10 months ago, for which he received radiochemotherapy. He has a history of atopic dermatitis and has smoked one pack of cigarettes daily for 30 years. Auscultation of the lungs shows decreased breath sounds bilaterally. Spirometry shows an FVC of 78% and an FEV1/FVC ratio of 95%. Which of the following is the most likely underlying condition?
Q152
A 27-year-old man comes to the physician because of a 2-month history of palpitations and shortness of breath on exertion. He has no history of serious illness. He does not smoke or use illicit drugs. His pulse is 90/min, respirations are 18/min, and blood pressure is 140/40 mm Hg. Cardiac examination shows a murmur along the left sternal border. A phonocardiogram of the murmur is shown. Which of the following additional findings is most likely in this patient?
Q153
A 6-year-old boy is brought to the physician by his mother because of a 3-month history of episodic chest pain and shortness of breath on exertion. He is at the 99th percentile for height and 40th percentile for weight. Examination shows a high-arched palate, long and slender upper extremities, and elbows and knees that can be hyperextended. Cardiac examination shows a grade 2/6 late systolic, crescendo murmur with a midsystolic click. Over which of the following labeled areas is the murmur most likely to be heard best?
Q154
A 64-year-old man presents to his primary care physician for 4 weeks of recurrent fever, night sweats, malaise, and fatigue. Associated with shortness of breath and orthopnea. Family and personal history are unremarkable. Upon physical examination, he is found with a blood pressure of 100/68 mm Hg, a heart rate of 98/min, a respiratory rate of 20/min, and a body temperature of 38.5°C (101.3°F). Cardiopulmonary auscultation reveals a high-pitched holosystolic murmur over the lower end of the left sternal border and that radiates to the left axilla. Skin lesions are found on the patient’s palms seen in the picture below. Which of the following entities predisposed this patient’s condition?
Q155
A 44-year-old woman is brought to the emergency department for confusion and lethargy for the past 2 hours. Per the husband, the patient was behaving weirdly and forgot how to get to the bathroom at her house. She was also difficult to wake up from her nap. The husband denies any fever, weight loss, headaches, dizziness, chest pain, or gastrointestinal changes. He reports that she had frequent diarrhea over the past 3 days but attributed it to food poisoning. In the emergency room, the patient had a 1-minute episode of seizure activity. Following initial resuscitation and stabilization, laboratory studies were performed and the results are shown below.
Hemoglobin: 13 g/dL
Hematocrit: 38%
Leukocyte count: 7,600/mm^3 with normal differential
Platelet count: 170,000/mm^3
Serum:
Na+: 125 mEq/L
Cl-: 90 mEq/L
K+: 3.2 mEq/L
HCO3-: 20 mEq/L
BUN: 22 mg/dL
Glucose: 101 mg/dL
Creatinine: 1.0 mg/dL
Thyroid-stimulating hormone: 3.2 µU/mL
Ca2+: 9.3 mg/dL
AST: 19 U/L
ALT: 22 U/L
What is the most appropriate treatment for this patient?
Q156
A 61-year-old man with a past medical history significant for asthma and psoriasis presents to the clinic for a wellness visit. He has no specific complaints. The patient’s blood pressure is 121/73 mm Hg, the pulse is 81/min, the respiratory rate is 16/min, and the temperature is 37.2°C (99.1°F). Physical examination reveals a 3.3 cm (1.2 in) lesion overlying his left elbow with an erythematous border, covered with a silver scale. What type of lesion is on the patient’s elbow?
Q157
A 74-year-old man comes to the attention of the inpatient hospital team because he started experiencing shortness of breath and left-sided back pain 3 days after suffering a right hip fracture that was treated with hip arthroplasty. He says that the pain is sharp and occurs with deep breathing. His past medical history is significant for diabetes and hypertension for which he takes metformin and lisinopril. On physical exam, he is found to have a friction rub best heard in the left lung base. His right calf is also swollen with erythema and induration. Given this presentation, which of the following most likely describes the status of the patient's lungs?
Q158
A 35-year-old woman comes to the clinic with complaints of joint pain and stiffness for the past few months. Her hands, lower back, and left knee are involved and associated with morning stiffness that improves throughout the day with activities. She also complains that her fingers change color upon exposure to cold. She has also noticed a tightening of the skin on her face and thinning of her lips. She feels tired throughout the day and has taken over-the-counter multivitamins that do not seem to help her much. The patient does not smoke cigarettes and drinks alcohol socially. She was diagnosed with hypertension 1 year ago and has been taking hydralazine for the past year. She lost her parents in a road traffic accident 3 years ago. Temperature is 36.7°C (98°F), blood pressure is 140/85 mm Hg, pulse is 72/min, respirations are 12/min, and BMI is 25 kg/m2. Her skin appears shiny and slightly thickened, especially her face and hands.
Laboratory investigation:
Complete blood count
Hemoglobin 9.5 g/dl
Leucocytes 5,500/mm3
Platelets 150,000/mm3
ANA positive
Anti-centromere Antibody negative
Anti Scl-70 positive
Anti Jo-1 negative
Anti-histone negative
Anti DsDNA negative
What is the most likely diagnosis in this patient?
Q159
A 73-year-old female is hospitalized following a pelvic fracture. She undergoes surgical repair without complication. Four days into her hospital stay, she develops acute dyspnea and chest pain accompanied by oxyhemoglobin desaturation. Which of the following arterial blood gas values is the patient most likely to have? (normal values: pH 7.35 - 7.45, PaO2 80 - 100 mm Hg, PaCO2 35-45 mm Hg, HCO3 22-26)
Q160
A 39-year-old female with a long history of major depressive disorder presents to the emergency room with altered mental status. Her husband found her on the floor unconscious and rushed her to the emergency room. He reports that she has been in a severe depressive episode over the past several weeks. Vital signs are temperature 38.1 degrees Celsius, heart rate 105 beats per minute, blood pressure 110/70, respiratory rate 28, and oxygen saturation 99% on room air. Serum sodium is 139, chloride is 100, and bicarbonate is 13. Arterial blood gas reveals a pH of 7.44 with a pO2 of 100 mmHg and a pCO2 of 23 mmHg. Which of the following correctly identifies the acid base disorder in this patient?
Cardiology US Medical PG Practice Questions and MCQs
Question 151: A 48-year-old man comes to the physician for the evaluation of dyspnea and cough. He was diagnosed with esophageal cancer 10 months ago, for which he received radiochemotherapy. He has a history of atopic dermatitis and has smoked one pack of cigarettes daily for 30 years. Auscultation of the lungs shows decreased breath sounds bilaterally. Spirometry shows an FVC of 78% and an FEV1/FVC ratio of 95%. Which of the following is the most likely underlying condition?
A. Pulmonary embolism
B. Chronic bronchitis
C. Pulmonary emphysema
D. Pulmonary fibrosis (Correct Answer)
E. Allergic asthma
Explanation: ***Pulmonary fibrosis***
- A history of **radiochemotherapy for esophageal cancer** significantly increases the risk of **radiation-induced pulmonary fibrosis**, which can manifest as dyspnea and cough.
- The **Spirometry results of FVC 78% and FEV1/FVC ratio of 95%** indicate a **restrictive lung disease pattern**, consistent with pulmonary fibrosis, as the FEV1/FVC ratio is preserved or even elevated.
*Pulmonary embolism*
- While pulmonary embolism can cause dyspnea, it typically presents with **acute onset** symptoms and can have risk factors such as **malignancy** or immobility.
- However, spirometry would likely show normal or mildly restrictive patterns, but not typically a preserved FEV1/FVC ratio in the setting of chronic symptoms.
*Chronic bronchitis*
- Characterized by a **chronic cough with sputum production** for at least three months in two consecutive years, often due to **smoking**.
- Spirometry in chronic bronchitis typically shows an **obstructive pattern**, with a **reduced FEV1/FVC ratio**, which is not present here.
*Pulmonary emphysema*
- Also strongly associated with **smoking**, emphysema primarily causes **airflow obstruction** due to destruction of alveolar walls.
- Spirometry would reveal an **obstructive pattern** with a **decreased FEV1/FVC ratio**, which contradicts the patient's spirometry findings.
*Allergic asthma*
- Allergic asthma is characterized by **reversible airway obstruction** and hyperresponsiveness, often triggered by allergens.
- Spirometry would show an **obstructive pattern**, typically with a **reduced FEV1/FVC ratio** that improves with bronchodilators, which is inconsistent with the given data.
Question 152: A 27-year-old man comes to the physician because of a 2-month history of palpitations and shortness of breath on exertion. He has no history of serious illness. He does not smoke or use illicit drugs. His pulse is 90/min, respirations are 18/min, and blood pressure is 140/40 mm Hg. Cardiac examination shows a murmur along the left sternal border. A phonocardiogram of the murmur is shown. Which of the following additional findings is most likely in this patient?
A. Decreased left ventricular wall stress
B. Decreased left ventricular wall compliance
C. Increased right ventricular oxygen saturation
D. Decreased pulmonary capillary wedge pressure
E. Increased left ventricular end-diastolic volume (Correct Answer)
Explanation: ***Increased left ventricular end-diastolic volume***
- The patient's symptoms (palpitations, shortness of breath), physical findings (wide pulse pressure 140/40), and the description of a murmur along the left sternal border are highly suggestive of **aortic regurgitation**.
- In aortic regurgitation, blood regurgitates from the aorta into the left ventricle during diastole, leading to an **increased volume load** on the left ventricle and consequently an increased **left ventricular end-diastolic volume**.
*Decreased left ventricular wall stress*
- **Left ventricular wall stress** is actually **increased** in aortic regurgitation due to the increased volume load and subsequent left ventricular dilation.
- This increased stress is a key factor in the compensatory **left ventricular hypertrophy** that often develops.
*Decreased left ventricular wall compliance*
- Initially, the left ventricle may maintain compliance, but with chronic volume overload and subsequent hypertrophy and dilation, the **left ventricular wall compliance** may ultimately **decrease** in advanced stages due to fibrosis and remodeling.
- However, the most direct and immediate consequence of the regurgitant volume is an increased end-diastolic volume.
*Increased right ventricular oxygen saturation*
- An increase in right ventricular oxygen saturation would suggest a **left-to-right shunt**, such as a ventricular septal defect, which is not indicated by the patient's presentation or the phonocardiogram.
- Aortic regurgitation primarily affects the left heart chambers.
*Decreased pulmonary capillary wedge pressure*
- The **pulmonary capillary wedge pressure (PCWP)** reflects left atrial and left ventricular end-diastolic pressure.
- In aortic regurgitation, especially with symptoms of shortness of breath, there is often **increased left ventricular end-diastolic pressure** and consequently **increased PCWP** due to volume overload and potential heart failure.
Question 153: A 6-year-old boy is brought to the physician by his mother because of a 3-month history of episodic chest pain and shortness of breath on exertion. He is at the 99th percentile for height and 40th percentile for weight. Examination shows a high-arched palate, long and slender upper extremities, and elbows and knees that can be hyperextended. Cardiac examination shows a grade 2/6 late systolic, crescendo murmur with a midsystolic click. Over which of the following labeled areas is the murmur most likely to be heard best?
A. Area F (Correct Answer)
B. Area E
C. Area A
D. Area G
E. Area C
Explanation: ***Area F***
- The patient's presentation with **tall stature**, **long slender limbs**, **high-arched palate**, and **joint hyperextensibility** is highly suggestive of **Marfan syndrome**.
- Marfan syndrome is frequently associated with **mitral valve prolapse (MVP)**, which produces a **late systolic crescendo murmur** with a **midsystolic click**, best heard at the **apex** (Area F).
*Area E*
- Area E corresponds to the **tricuspid area**, where murmurs associated with the **tricuspid valve** (e.g., tricuspid regurgitation, tricuspid stenosis) would be best auscultated.
- The described murmur is characteristic of mitral valve pathology, not tricuspid.
*Area A*
- Area A is the **aortic area**, where murmurs from the **aortic valve** (e.g., aortic stenosis, aortic regurgitation) are heard.
- An aortic stenosis murmur is typically a **systolic ejection murmur**, but the late systolic crescendo with a click is more specific for MVP.
*Area G*
- Area G is a general area over the **left sternal border** but does not specifically pinpoint a valve. Murmurs in this area might be associated with conditions like **ventricular septal defects** or **hypertrophic cardiomyopathy**.
- The specific characteristics of the murmur and the patient's Marfanoid habitus point away from these conditions.
*Area C*
- Area C corresponds to the **pulmonic area**, where murmurs related to the **pulmonary valve** (e.g., pulmonic stenosis, pulmonic regurgitation) would be best auscultated.
- The murmur described is not typical for pulmonic valve disease.
Question 154: A 64-year-old man presents to his primary care physician for 4 weeks of recurrent fever, night sweats, malaise, and fatigue. Associated with shortness of breath and orthopnea. Family and personal history are unremarkable. Upon physical examination, he is found with a blood pressure of 100/68 mm Hg, a heart rate of 98/min, a respiratory rate of 20/min, and a body temperature of 38.5°C (101.3°F). Cardiopulmonary auscultation reveals a high-pitched holosystolic murmur over the lower end of the left sternal border and that radiates to the left axilla. Skin lesions are found on the patient’s palms seen in the picture below. Which of the following entities predisposed this patient’s condition?
A. Bicuspid aortic valve
B. Pulmonary stenosis
C. Systemic lupus erythematosus
D. Mitral valve prolapse (Correct Answer)
E. Rheumatic heart disease
Explanation: ***Mitral valve prolapse***
- The clinical presentation with **fever, night sweats, malaise, fatigue, and new murmur, along with Janeway lesions (on palms)**, is highly suggestive of **infective endocarditis**.
- The **holosystolic murmur at the lower left sternal border radiating to the left axilla** is characteristic of **mitral regurgitation**.
- **Mitral valve prolapse (MVP)** is one of the most common predisposing cardiac conditions for infective endocarditis in developed countries, particularly when associated with **mitral regurgitation**.
- MVP causes **myxomatous degeneration** of valve leaflets, creating turbulent flow and endothelial damage that increases susceptibility to bacterial colonization.
*Bicuspid aortic valve*
- While **bicuspid aortic valve** is an important predisposing factor for infective endocarditis, it typically presents with:
- **Aortic stenosis**: crescendo-decrescendo systolic murmur at right upper sternal border radiating to carotids
- **Aortic regurgitation**: early diastolic murmur at left sternal border
- The **holosystolic murmur radiating to the axilla** described in this case is not consistent with bicuspid aortic valve pathology.
*Rheumatic heart disease*
- **Rheumatic heart disease** can affect the mitral valve and predispose to endocarditis.
- However, the patient has an **unremarkable personal history**, making childhood rheumatic fever (required for rheumatic heart disease) unlikely.
- In developed countries, rheumatic heart disease prevalence has significantly decreased, making MVP a more likely predisposing factor in this demographic.
*Pulmonary stenosis*
- **Pulmonary stenosis** affects the right-sided circulation (right ventricle to pulmonary artery).
- It rarely predisposes to **left-sided endocarditis**, which is indicated by the murmur pattern consistent with mitral or aortic involvement.
- Right-sided endocarditis is more commonly associated with **IV drug use** and typically involves the tricuspid valve.
*Systemic lupus erythematosus*
- **Systemic lupus erythematosus (SLE)** can cause **Libman-Sacks endocarditis**, which consists of **sterile vegetations**.
- These do not cause the **systemic signs of bacterial infection** (fever, night sweats, positive blood cultures) characteristic of **infective endocarditis**.
- No other clinical features of SLE are mentioned in this case.
Question 155: A 44-year-old woman is brought to the emergency department for confusion and lethargy for the past 2 hours. Per the husband, the patient was behaving weirdly and forgot how to get to the bathroom at her house. She was also difficult to wake up from her nap. The husband denies any fever, weight loss, headaches, dizziness, chest pain, or gastrointestinal changes. He reports that she had frequent diarrhea over the past 3 days but attributed it to food poisoning. In the emergency room, the patient had a 1-minute episode of seizure activity. Following initial resuscitation and stabilization, laboratory studies were performed and the results are shown below.
Hemoglobin: 13 g/dL
Hematocrit: 38%
Leukocyte count: 7,600/mm^3 with normal differential
Platelet count: 170,000/mm^3
Serum:
Na+: 125 mEq/L
Cl-: 90 mEq/L
K+: 3.2 mEq/L
HCO3-: 20 mEq/L
BUN: 22 mg/dL
Glucose: 101 mg/dL
Creatinine: 1.0 mg/dL
Thyroid-stimulating hormone: 3.2 µU/mL
Ca2+: 9.3 mg/dL
AST: 19 U/L
ALT: 22 U/L
What is the most appropriate treatment for this patient?
A. Restrict fluids
B. Start patient on maintenance anti-epileptic medications
C. Increase the serum sodium slowly with hypertonic saline solution (Correct Answer)
D. Increase the serum sodium slowly with normal saline solution
E. Increase the serum potassium with potassium solution
Explanation: ***Increase the serum sodium slowly with hypertonic saline solution***
- The patient presents with **severe symptomatic hyponatremia** (Na+ 125 mEq/L) evidenced by confusion, lethargy, and a new-onset seizure. This warrants intervention with **hypertonic saline** to raise serum sodium levels.
- Due to the chronicity and symptoms, the sodium should be raised cautiously (e.g., 4-6 mEq/L in the first few hours) to avoid **osmotic demyelination syndrome**.
*Restrict fluids*
- Fluid restriction is appropriate for **asymptomatic mild to moderate hyponatremia**, often in the context of SIADH or dilutional hyponatremia, but not for severe symptomatic cases.
- Given the patient's neurological symptoms and seizure, fluid restriction alone would be insufficient and potentially dangerous as it would not rapidly correct the sodium deficit.
*Start patient on maintenance anti-epileptic medications*
- The seizure is likely a direct consequence of **severe hyponatremia**, which lowers the seizure threshold.
- Addressing the underlying electrolyte imbalance is the primary treatment; anti-epileptic medications are generally not needed for seizures caused solely by reversible metabolic derangements once the cause is corrected.
*Increase the serum sodium slowly with normal saline solution*
- **Normal saline (0.9% NaCl)** contains 154 mEq/L of sodium, which is only slightly higher than the patient's current serum sodium of 125 mEq/L.
- This would not effectively or rapidly increase serum sodium in a patient with severe symptomatic hyponatremia, and it could even worsen hyponatremia if her effective circulating volume is not depleted.
*Increase the serum potassium with potassium solution*
- The patient's **potassium level (3.2 mEq/L)** is slightly low but not critically so, and it is not the primary cause of her severe neurological symptoms.
- Addressing hyponatremia is the priority; while potassium replacement might be considered later, it does not address the acute, life-threatening issue.
Question 156: A 61-year-old man with a past medical history significant for asthma and psoriasis presents to the clinic for a wellness visit. He has no specific complaints. The patient’s blood pressure is 121/73 mm Hg, the pulse is 81/min, the respiratory rate is 16/min, and the temperature is 37.2°C (99.1°F). Physical examination reveals a 3.3 cm (1.2 in) lesion overlying his left elbow with an erythematous border, covered with a silver scale. What type of lesion is on the patient’s elbow?
A. Patch
B. Lichenification
C. Papule
D. Plaque (Correct Answer)
E. Excoriation
Explanation: ***Plaque***
- A **plaque** is a **solid, elevated lesion** greater than 1 cm in diameter, often formed by the coalescence of papules.
- The description of a 3.3 cm lesion with an erythematous border and silver scale, in a patient with **psoriasis**, is classic for a psoriatic plaque.
*Patch*
- A **patch** is a large, **flat discoloration** (>1 cm) of the skin that is not elevated or depressed.
- The described lesion is elevated and palpable, which distinguishes it from a patch.
*Lichenification*
- **Lichenification** refers to a **thickening of the skin** with exaggerated normal skin lines, usually due to chronic scratching or rubbing.
- While associated with chronic skin conditions, the described lesion's size and scaly appearance do not fit the definition of lichenification.
*Papule*
- A **papule** is a **solid, elevated lesion** that is less than 1 cm in diameter.
- The lesion described is 3.3 cm, making it too large to be classified as a papule.
*Excoriation*
- An **excoriation** is a **linear break in the skin** surface, often caused by scratching.
- The described lesion is a raised, scaly patch, not a break in the skin from scratching.
Question 157: A 74-year-old man comes to the attention of the inpatient hospital team because he started experiencing shortness of breath and left-sided back pain 3 days after suffering a right hip fracture that was treated with hip arthroplasty. He says that the pain is sharp and occurs with deep breathing. His past medical history is significant for diabetes and hypertension for which he takes metformin and lisinopril. On physical exam, he is found to have a friction rub best heard in the left lung base. His right calf is also swollen with erythema and induration. Given this presentation, which of the following most likely describes the status of the patient's lungs?
A. Hypoventilation
B. Creation of a shunt
C. Obstructive lung disease
D. Restrictive lung disease
E. Increased dead space (Correct Answer)
Explanation: ***Increased dead space***
- The patient's symptoms (shortness of breath, left-sided back pain, friction rub, swollen leg) 3 days after hip surgery are highly suggestive of a **pulmonary embolism (PE)**.
- A PE causes **increased dead space** by obstructing blood flow to a portion of the lung, where ventilation continues but gas exchange cannot occur due to lack of perfusion.
*Hypoventilation*
- Hypoventilation refers to reduced ventilation, typically leading to increased PCO2 and decreased PO2.
- While patients with PE may appear tachypneic due to dyspnea, their underlying lung issue is a **perfusion defect**, not primarily a problem with moving air in and out of the lungs.
*Creation of a shunt*
- A shunt occurs when there is perfusion without adequate ventilation (e.g., in pneumonia or atelectasis), leading to deoxygenated blood bypassing gas exchange.
- In PE, the primary problem is the opposite: **ventilation without perfusion**, which leads to increased dead space rather than shunting.
*Obstructive lung disease*
- Obstructive lung diseases (e.g., asthma, COPD) are characterized by **airflow limitation**, making it difficult to exhale air.
- The patient's symptoms and risk factors point to an acute vascular event, not a chronic airway obstruction.
*Restrictive lung disease*
- Restrictive lung diseases (e.g., pulmonary fibrosis) involve reduced lung volumes and compliance, making it difficult to inhale air.
- There is nothing in the patient's presentation that suggests a chronic restrictive lung pathology; his symptoms are acute and related to surgery.
Question 158: A 35-year-old woman comes to the clinic with complaints of joint pain and stiffness for the past few months. Her hands, lower back, and left knee are involved and associated with morning stiffness that improves throughout the day with activities. She also complains that her fingers change color upon exposure to cold. She has also noticed a tightening of the skin on her face and thinning of her lips. She feels tired throughout the day and has taken over-the-counter multivitamins that do not seem to help her much. The patient does not smoke cigarettes and drinks alcohol socially. She was diagnosed with hypertension 1 year ago and has been taking hydralazine for the past year. She lost her parents in a road traffic accident 3 years ago. Temperature is 36.7°C (98°F), blood pressure is 140/85 mm Hg, pulse is 72/min, respirations are 12/min, and BMI is 25 kg/m2. Her skin appears shiny and slightly thickened, especially her face and hands.
Laboratory investigation:
Complete blood count
Hemoglobin 9.5 g/dl
Leucocytes 5,500/mm3
Platelets 150,000/mm3
ANA positive
Anti-centromere Antibody negative
Anti Scl-70 positive
Anti Jo-1 negative
Anti-histone negative
Anti DsDNA negative
What is the most likely diagnosis in this patient?
A. Polymyositis
B. SLE
C. Limited cutaneous systemic scleroderma
D. Diffuse cutaneous systemic scleroderma (Correct Answer)
E. Drug-induced lupus
Explanation: ***Diffuse cutaneous systemic scleroderma***
- The presence of **anti-Scl-70 (anti-topoisomerase I) antibodies**, along with **widespread skin thickening** involving the hands and face, and **internal organ involvement** (hypertension, joint pain, Raynaud's phenomenon), points to diffuse cutaneous systemic scleroderma.
- This variant is associated with rapid skin thickening, significant internal organ involvement (e.g., lung fibrosis, renal crisis), and a poorer prognosis compared to the limited form.
*Polymyositis*
- Characterized primarily by **proximal muscle weakness** and elevated muscle enzymes (e.g., CK), which are not described as prominent features in this patient's presentation.
- While ANA can be positive, **anti-Jo-1 antibodies** are more specific for polymyositis/dermatomyositis, and they are negative in this case.
*SLE*
- Although the patient presents with **arthralgias**, **fatigue**, and **positive ANA**, several key features of SLE, such as malar rash, discoid rash, serositis, renal involvement (beyond hypertension, which can be seen in scleroderma), are absent.
- The prominent **skin thickening** and **positive anti-Scl-70** are not typical for SLE and make this diagnosis less likely.
*Limited cutaneous systemic scleroderma*
- This variant is characterized by **skin thickening restricted** to areas distal to the elbows and knees, with or without face/neck involvement.
- It is strongly associated with **anti-centromere antibodies**, which are negative in this patient, and typically has a slower progression and is associated with PAH.
*Drug-induced lupus*
- Although the patient is on **hydralazine**, a known cause of drug-induced lupus, the negative **anti-histone antibodies** make this diagnosis less likely.
- The extensive **skin thickening**, **Raynaud's phenomenon**, and **anti-Scl-70 antibodies** are not characteristic features of drug-induced lupus.
Question 159: A 73-year-old female is hospitalized following a pelvic fracture. She undergoes surgical repair without complication. Four days into her hospital stay, she develops acute dyspnea and chest pain accompanied by oxyhemoglobin desaturation. Which of the following arterial blood gas values is the patient most likely to have? (normal values: pH 7.35 - 7.45, PaO2 80 - 100 mm Hg, PaCO2 35-45 mm Hg, HCO3 22-26)
Explanation: ***pH 7.5, PaO2 60, PaCO2 30, HCO3 22***
- This patient's presentation with acute **dyspnea**, **chest pain**, and **desaturation** after a pelvic fracture and surgery is highly suggestive of a **pulmonary embolism (PE)**. A PE leads to **hypoxemia (PaO2 60)** and often causes **hyperventilation** due to irritation and compensatory mechanisms, leading to a **low PaCO2 (30)** and consequently **respiratory alkalosis (pH 7.5)**.
- The **bicarbonate (HCO3 22)** is within the normal range, indicating an **uncompensated respiratory alkalosis**, which is typical for an acute event like PE.
*pH 7.3, PaO2 60, PaCO2 30, HCO3 20*
- This represents a **metabolic acidosis (low pH, low HCO3)** with a compensatory **respiratory alkalosis (low PaCO2)**.
- While there is hypoxemia, the primary acid-base disturbance here is metabolic acidosis, which is not characteristic of an acute pulmonary embolism as the initial presentation.
*pH 7.4, PaO2 60, PaCO2 40, HCO3 24*
- This ABG shows **hypoxemia (PaO2 60)** but otherwise **normal pH, PaCO2, and HCO3**, suggesting an **uncompensated hypoxemia** without an acute acid-base disturbance.
- An acute PE typically causes significant ventilatory changes leading to an acid-base imbalance, most commonly respiratory alkalosis, rather than a completely compensated picture.
*pH 7.5, PaO2 60, PaCO2 50, HCO3 28*
- This ABG indicates **hypoxemia (PaO2 60)** and **metabolic alkalosis (high pH, high HCO3)** with concomitant **respiratory acidosis (high PaCO2)**.
- While hypoxemia is present, this specific combination of acid-base disturbances is not typical for an acute pulmonary embolism.
*pH 7.3, PaO2 60, PaCO2 50, HCO3 24*
- This ABG demonstrates **hypoxemia (PaO2 60)** and **respiratory acidosis (low pH, high PaCO2)** with normal bicarbonate.
- This would suggest **hypoventilation**, which is contrary to the hyperventilation commonly seen in acute pulmonary embolism.
Question 160: A 39-year-old female with a long history of major depressive disorder presents to the emergency room with altered mental status. Her husband found her on the floor unconscious and rushed her to the emergency room. He reports that she has been in a severe depressive episode over the past several weeks. Vital signs are temperature 38.1 degrees Celsius, heart rate 105 beats per minute, blood pressure 110/70, respiratory rate 28, and oxygen saturation 99% on room air. Serum sodium is 139, chloride is 100, and bicarbonate is 13. Arterial blood gas reveals a pH of 7.44 with a pO2 of 100 mmHg and a pCO2 of 23 mmHg. Which of the following correctly identifies the acid base disorder in this patient?
A. Mixed respiratory alkalosis and anion gap metabolic acidosis (Correct Answer)
B. Pure non-gap metabolic acidosis
C. Mixed respiratory acidosis and metabolic alkalosis
D. Mixed respiratory alkalosis and non-gap metabolic acidosis
E. Pure respiratory alkalosis
Explanation: ***Mixed respiratory alkalosis and anion gap metabolic acidosis***
- The **pH of 7.44** indicates a mild alkalemia. The **bicarbonate of 13 mEq/L** suggests a metabolic acidosis, while the **pCO2 of 23 mmHg** indicates a respiratory alkalosis.
- Calculation of the **anion gap ([Na+] - [Cl-] - [HCO3-])** = 139 - 100 - 13 = 26 mEq/L) reveals a high anion gap, confirming an **anion gap metabolic acidosis**. Using **Winter's formula**, the expected pCO2 for metabolic acidosis compensation (1.5 × HCO3 + 8 ± 2 = 1.5 × 13 + 8 = 27.5-29.5 mmHg) is higher than the measured pCO2 of 23 mmHg, indicating an additional **respiratory alkalosis** beyond appropriate compensation. Therefore, given the significant metabolic acidosis and prominent respiratory alkalosis with an essentially normal pH, a **mixed acid-base disorder** is present.
*Pure non-gap metabolic acidosis*
- This is incorrect because the **anion gap is elevated (26 mEq/L)**, not normal.
- A pure non-gap metabolic acidosis would have a **normal anion gap (8-12 mEq/L)** and typically a lower pH than observed here, unless partially compensated.
*Mixed respiratory acidosis and metabolic alkalosis*
- This is incorrect because the **pCO2 is low (23 mmHg)**, indicating respiratory alkalosis, not acidosis.
- The **bicarbonate is low (13 mEq/L)**, suggesting metabolic acidosis, not alkalosis.
*Mixed respiratory alkalosis and non-gap metabolic acidosis*
- This is incorrect because the **anion gap is elevated (26 mEq/L)**, not normal, ruling out a non-gap metabolic acidosis.
- While respiratory alkalosis is present, the metabolic component is high anion gap.
*Pure respiratory alkalosis*
- This is incorrect because the **bicarbonate is significantly low (13 mEq/L)**, which is not consistent with a pure respiratory alkalosis where bicarbonate would be near normal or only slightly decreased as compensation.
- A pure respiratory alkalosis would have a high pH due to low pCO2, but a relatively normal bicarbonate or only a minimal compensatory decrease.
