A 34-year-old woman arrives at the emergency department complaining of severe nausea, vomiting, and diarrhea that began approximately four hours ago. She describes eating several dishes at a family potluck earlier in the day, including potato salad, deviled eggs, and cream-filled pastries. The patient notes that the food was left out for several hours in warm weather before it was served. Her symptoms started abruptly after she returned home, with significant nausea and repeated episodes of vomiting, followed by watery diarrhea. She denies any blood in her stool or fever but reports mild abdominal cramping. The patient has no significant medical history and does not take any regular medications. She denies recent travel, antibiotic use, or contact with anyone experiencing similar symptoms. She lives with her husband and two children, who have not yet shown any signs of illness. She does not smoke or drink alcohol and works as an administrative assistant. On examination, the patient appears mildly dehydrated but is alert and oriented. Her vital signs are stable, with a temperature of 98.8°F (37.1°C), heart rate of 90 beats per minute, blood pressure of 115/70 mm Hg, and respiratory rate of 16 breaths per minute. Abdominal examination reveals mild diffuse tenderness without rebound or guarding, and bowel sounds are hyperactive. There are no signs of peritonitis or other abnormalities on physical examination. Given the rapid onset of symptoms following the ingestion of improperly stored food and the absence of systemic signs such as fever, a clinical diagnosis of Staphylococcus aureus gastroenteritis is made.  Which of the following best describes the mechanism of illness in this patient?

An 18-year-old male comes to your primary care clinic complaining of pain near the breastbone for the last three days. It is a sharp pain that gets worse when he presses on the bone, moves sideways, and when he takes a deep breath, coughs, or sneezes. He can’t even laugh comfortably. The pain has no relationship with meals. His grandmother gave him a nitroglycerin tablet, but it did not relieve the pain. He also took some over-the-counter antacids without any relief. On further questioning, he reveals that he has been doing lots of exercises as part of his athletic training, including lifting heavy weights in the gym to develop a “six-pack” physique. Vital signs: Temperature: 98.8 °F Heart rate: 67 beats/min Blood pressure: 110/78 mm Hg Respirations: 15 breaths/min Oxygen saturation: 98% on room air Physical examination: Significant for tenderness over the sternum and right-sided ribs. ECG: Normal. Laboratory tests: Normal troponin levels. What is the most likely diagnosis in this patient?

A 43-year-old woman presents to the clinic with a 6-month history of progressive shortness of breath, especially with exertion. She also reports occasional fatigue and lightheadedness during physical activity but denies chest pain or syncope. Physical examination reveals mild jugular venous distention, a loud pulmonary component of the second heart sound (P2), and peripheral edema. She is being evaluated for possible pulmonary hypertension. Of the following, which is the most common symptom of pulmonary hypertension?

A 38-year-old woman presents to the primary care clinic with progressive shortness of breath on exertion over the past several weeks. She reports episodes of chest pain, nonproductive cough, fatigue, and lightheadedness. She works as a teacher in a middle school. Physical examination reveals: Oxygen saturation: 92% on room air Loud P2 and right ventricular heave Jugular venous distention and lower extremity edema An ECG shows: Right axis deviation Tall R waves in the right precordial leads R-to-S wave ratio >1 in lead V1 Atrial fibrillation Right heart catheterization demonstrates a pulmonary artery pressure of 32 mm Hg. Which of the following is the most likely cause of this patient’s symptoms?

A 34-year-old man is brought to the emergency room with altered mental status after taking an unknown dose of a beta blocker to manage anxiety before a public lecture. His vital signs are as follows: temperature 99°F, heart rate 59 beats per minute, respiratory rate 14 breaths per minute, and blood pressure 80/55 mm Hg. On examination, he is disoriented but recognizes his wife, with cold extremities, bradycardia, and decreased breath sounds. ECG shows bradycardia with PR prolongation and first-degree heart block. Which of the following beta blockers is the most toxic in overdose?

A 52-year-old man presents to the emergency room with nausea, vomiting, muscle cramps, and weakness that began three days ago. He recently started Penicillin G for pharyngitis and is also taking lisinopril, atorvastatin, and spironolactone. On examination, he appears anxious, has difficulty walking, and exhibits decreased sensations and reflexes. Laboratory studies reveal a potassium level of 6.8 mmol/L, and his ECG shows changes consistent with hyperkalemia. Which of the following is the antidote of choice for life-threatening arrhythmias caused by hyperkalemia?