ECFMG Medical Knowledge & Clinical Science 4 — Questions and Answers
Question 1: A 68-year-old man with COPD has PaO2 55 mmHg and PaCO2 58 mmHg on ABG. What is the primary acid-base disorder?
- Metabolic acidosis
- Respiratory alkalosis
- Respiratory acidosis with metabolic compensation (Correct answer)
- Mixed respiratory and metabolic acidosis
Correct answer: Respiratory acidosis with metabolic compensation
Chronic CO2 retention (respiratory acidosis) in COPD is accompanied by renal bicarbonate retention (metabolic compensation), reflected by an elevated serum HCO3.
Question 2: A 30-year-old woman is found unconscious. ABG: pH 7.24, PaCO2 20 mmHg, HCO3 8 mEq/L. Serum glucose is 540 mg/dL with ketonuria. What drives the respiratory response?
- Central chemoreceptor response to hypoxia
- Peripheral chemoreceptor response to hypercapnia
- Kussmaul breathing as compensation for metabolic acidosis (Correct answer)
- Increased work of breathing from pulmonary edema
Correct answer: Kussmaul breathing as compensation for metabolic acidosis
Kussmaul breathing (deep, rapid respirations) is the compensatory hyperventilation that reduces PaCO2 in response to severe metabolic acidosis in DKA.
Question 3: A 55-year-old woman presents with a palpable thyroid nodule. Fine needle aspiration shows follicular neoplasm. What is the NEXT best step?
- Repeat ultrasound in 6 months
- Thyroid scan with radioiodine
- Thyroidectomy or hemithyroidectomy (Correct answer)
- TSH suppression with levothyroxine
Correct answer: Thyroidectomy or hemithyroidectomy
Follicular neoplasm on FNA cannot distinguish adenoma from carcinoma cytologically; surgical excision is required for definitive diagnosis.
Question 4: A 4-year-old boy presents with periorbital edema, proteinuria of 4 g/day, hypoalbuminemia, and hyperlipidemia. Kidney biopsy shows effacement of foot processes on electron microscopy. What is the treatment of choice?
- Cyclophosphamide
- Mycophenolate mofetil
- Prednisone (Correct answer)
- Rituximab
Correct answer: Prednisone
Minimal change disease (nephrotic syndrome in children with foot process effacement) responds to corticosteroids as first-line therapy in over 90% of cases.
Question 5: A 45-year-old woman develops proximal muscle weakness, heliotrope rash around the eyes, and Gottron's papules over the knuckles. Which malignancy is MOST commonly associated with this condition in adults?
- Breast cancer
- Ovarian cancer (Correct answer)
- Colorectal cancer
- Lymphoma
Correct answer: Ovarian cancer
Dermatomyositis in adult women is most commonly associated with ovarian cancer, making gynecologic malignancy screening essential.
Question 6: A patient takes warfarin and is started on fluconazole. His INR rises to 6.5 without bleeding. What is the mechanism of this drug interaction?
- Increased warfarin absorption
- CYP2C9 inhibition reducing warfarin metabolism (Correct answer)
- Displacement of warfarin from albumin
- Decreased vitamin K absorption
Correct answer: CYP2C9 inhibition reducing warfarin metabolism
Fluconazole inhibits CYP2C9, the primary enzyme metabolizing the more potent S-warfarin enantiomer, leading to elevated warfarin levels and INR.
Question 7: A 72-year-old man with a history of atrial fibrillation on warfarin suddenly develops left hemiplegia and right gaze deviation. CT head is negative. What is the NEXT most appropriate step?
- Administer IV alteplase immediately
- Check INR before deciding on thrombolysis (Correct answer)
- Begin heparin infusion
- Perform CT angiography and consider mechanical thrombectomy
Correct answer: Check INR before deciding on thrombolysis
In patients on warfarin, INR must be checked before thrombolytics because an INR >1.7 is a contraindication to IV tPA.
ECFMG Medical Knowledge & Clinical Science 4
A 68-year-old man with COPD has PaO2 55 mmHg and PaCO2 58 mmHg on ABG.
What is the primary acid-base disorder?