DHA Medical Knowledge 2 — Questions and Answers
Question 1: A 45-year-old male presents with crushing chest pain radiating to the left arm, diaphoresis, and nausea lasting 30 minutes. His ECG shows ST-elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?
- Left anterior descending artery
- Right coronary artery (Correct answer)
- Left circumflex artery
- Left main coronary artery
Correct answer: Right coronary artery
ST-elevation in leads II, III, and aVF indicates an inferior myocardial infarction. The right coronary artery (RCA) supplies the inferior wall of the left ventricle in approximately 85% of individuals (right-dominant circulation). The LAD supplies the anterior wall, and the circumflex supplies the lateral wall.
Question 2: A 6-year-old child presents with a barking cough, inspiratory stridor, and low-grade fever. Neck X-ray shows a 'steeple sign.' What is the most appropriate initial management?
- Immediate intubation
- Nebulized epinephrine only
- Dexamethasone with or without nebulized epinephrine (Correct answer)
- Intravenous antibiotics
Correct answer: Dexamethasone with or without nebulized epinephrine
The clinical picture describes croup (laryngotracheobronchitis), most commonly caused by parainfluenza virus. The steeple sign on X-ray confirms subglottic narrowing. Corticosteroids (dexamethasone) are the mainstay of treatment; nebulized epinephrine is added for moderate-to-severe cases. Antibiotics are not indicated for viral croup.
Question 3: Which of the following best describes the mechanism of action of metformin in type 2 diabetes mellitus?
- Stimulates pancreatic beta cells to secrete more insulin
- Inhibits hepatic glucose production via activation of AMPK (Correct answer)
- Blocks intestinal absorption of glucose
- Increases renal glucose excretion by inhibiting SGLT-2
Correct answer: Inhibits hepatic glucose production via activation of AMPK
Metformin primarily works by activating AMP-activated protein kinase (AMPK) in the liver, which suppresses hepatic gluconeogenesis and glycogenolysis, reducing fasting blood glucose. It also improves peripheral insulin sensitivity. It does not stimulate insulin secretion and does not cause hypoglycemia as monotherapy.
Question 4: A 28-year-old woman at 36 weeks gestation presents with sudden-onset severe headache, visual disturbances, and a blood pressure of 165/110 mmHg. Urinalysis shows 3+ proteinuria. What is the definitive treatment for this condition?
- Oral labetalol for blood pressure control
- IV magnesium sulfate and delivery of the fetus (Correct answer)
- Bed rest and close monitoring until term
- Emergency cesarean section without magnesium
Correct answer: IV magnesium sulfate and delivery of the fetus
This patient has severe preeclampsia with severe features. The definitive treatment is delivery of the fetus and placenta, as preeclampsia is a placenta-mediated condition that only resolves after delivery. IV magnesium sulfate is administered to prevent progression to eclampsia (seizures). Antihypertensives control BP but do not treat the underlying condition.
Question 5: A patient with chronic kidney disease (GFR 20 mL/min) develops hyperkalemia (K+ = 6.2 mEq/L) with peaked T-waves on ECG. What is the FIRST priority intervention?
- Sodium polystyrene sulfonate (Kayexalate) orally
- IV sodium bicarbonate
- IV calcium gluconate (Correct answer)
- Hemodialysis
Correct answer: IV calcium gluconate
When hyperkalemia causes ECG changes (peaked T-waves, widened QRS), the immediate priority is cardiac membrane stabilization with IV calcium gluconate. It does not lower potassium but antagonizes the cardiac effects of hyperkalemia within minutes. Subsequent measures (insulin/glucose, bicarbonate, kayexalate, dialysis) then address potassium redistribution and removal.
Question 6: A 55-year-old smoker presents with progressive dyspnea, chronic productive cough for over 2 years, and FEV1/FVC ratio of 0.62 on spirometry. Which pathological finding most distinguishes chronic bronchitis from emphysema?
- Destruction of alveolar walls with air trapping
- Hypertrophy and hyperplasia of mucus-secreting glands in bronchi (Correct answer)
- Loss of lung elastic recoil
- Permanent enlargement of air spaces distal to terminal bronchioles
Correct answer: Hypertrophy and hyperplasia of mucus-secreting glands in bronchi
Chronic bronchitis is defined clinically as productive cough for at least 3 months per year for 2 consecutive years, and pathologically by hypertrophy and hyperplasia of mucous glands in the bronchial wall (Reid index > 0.5). Emphysema is characterized by permanent enlargement and destruction of air spaces distal to terminal bronchioles with loss of elastic recoil — the other answer choices.
DHA Medical Knowledge 2
A 45-year-old male presents with crushing chest pain radiating to the left arm, diaphoresis, and nausea lasting 30 minutes.
His ECG shows ST-elevation in leads II, III, and aVF.
Which coronary artery is most likely occluded?