Tập Đoàn Y Khoa Hoàn Mỹ - Đáp án chương trình CME

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Đáp án chương trình CME - USMLE ngày 26/11/2009

27/11/2009

1. A 57-year-old man is on maintenance hemodialysis for chronic renal failure. Which of

the following metabolic derangements can be anticipated?

(A) hypercalcemia

(B) hypophosphatemia

(D) vitamin D excess

(E) hypoparathyroidism

(C) Chronic renal failure treated with hemodialysis results in predictable metabolic abnormalities. The kidneys fail to excrete phosphate, leading to hyperphosphatemia, and fail to synthesize 1,25(OH)2D3. Vitamin D deficiency causes impaired intestinal calcium absorption. Phosphate retention, defective intestinal absorption, and skeletal resistance to parathyroid hormone (PTH) all result in hypocalcemia. Hypocalcemia causes secondary hyperparathyroidism, and the excess PTH production worsens the hyperphosphatemia by increasing phosphorus release from bone. These derangements impair collagen synthesis and maturation, resulting in skeletal abnormalities collectively referred to as renal osteodystrophy. Osteomalacia, osteosclerosis, and osteitis fibrosa cystica may all be seen. (Kasper et al., 2005, pp. 1656–1657)

Questions 2 & 3

A 54-year-old man presents to the emergency department complaining of epigastric discomfort, which began while he was walking his dog after dinner about one-half hour earlier. He has not received medical care for several years. On examination, he is moderately obese and in obvious discomfort and seems restless. His BP is 160/98 mmHg, and his examination is otherwise unremarkable. His ECG is seen in Figure 1-7.

2. Which of the following is the most likely diagnosis?

(A) gastroesophageal reflux

(B) costochondritis

(D) inferior wall myocardial infarction

(E) anterolateral myocardial infarction

3. Which of the following is the most appropriate next step in management?

(A) trial of antacid immediately

(B) reassurance and arrange outpatient follow-up

(D) begin thrombolytic therapy in the emergency department ( or PCI)

(E) arrange for urgent echocardiogram

2. (D)

3. (D)

Explanations 2&3

This ECG reveals ST-segment elevation in II, III, and AVF, indicating acute injury of the inferior wall of the myocardium. Inferior wall ischemia can be perceived as pain in the epigastric area. Anterolateral myocardial infarction would show loss of R-wave progression in V4 through V6. Pericarditis would show diffuse ST segment elevation in limb and precordial leads. Although his symptoms could suggest gastroesophageal reflux, this ECG shows this a cardiac event. Costochondritis is not present by examination. When ST segment elevation is present, a patient should be considered a candidate for reperfusion therapy or primary percutaneous intervention (PCI) such as angioplasty and stenting. If no contraindications are present and PCI is unavaliable, thrombolytic therapy should ideally be initiated within 30 minutes, right in the emergency department. The goal of both thrombolysis and PCI is prompt restoration of coronary arterial patency. Thrombolytic therapy can reduce the risk of in-hospital death by up to 50% when administered within the first hour of symptoms, so time is of the essence. Arranging for a bed may waste time for limiting

infarct size. The ECG would obviously preclude the other two options: immediate trial of antacid or

reassurance and arranging outpatient follow-up. (Kasper et al., 2005, pp. 1316–1318, 1444–1449)

Questions 4 and 5

A 42-year-old man admitted with a high fever and leukocytosis is transferred to the intensive care unit in shock.

4. Which of the following is a common finding in the early stages of septic shock?

(A) reduced cardiac output

(B) bradycardia

(D) hypertension

(E) metabolic alkalosis

5. Which of the following is an appropriate initial therapy for both septic shock and cardiogenic

shock?

(A) prophylactic antibiotics

(B) beta blockers

(D) mechanical ventilation

(E) diuretics

4. (C)

5. (C)

Explanations 4 and 5

The usual early hemodynamic response to sepsis is a hyperdynamic circulation. This includes tachycardia, elevated cardiac output, and decreased systemic resistance. Septic shock may then progress with intractable hypotension, metabolic acidosis, reduced cardiac output, oliguria, and death. The initial resuscitation of patients with all forms of shock requires rapid expansion of circulating blood volume to help maintain BP and tissue perfusion. This is usually achieved with the infusion of crystalloid fluids. When septic shock is suspected, cultures of blood, urine, and other sources along with antibiotic therapy targeted toward the most likely source is critical. Mechanical ventilation may be required when altered mental status, acidosis, and hypoxia are present. Beta-blockers and diuretics may have specific indications that cardiac ischemia and pulmonary edema are

present. (Kasper et al., 2005, pp. 1600–1606)

6. A 55-year-old man complains of severe headaches over the past few weeks. Similar episodes have occurred in past years. Which of the following supports the diagnosis of cluster headaches?

(A) Pain-free intervals can last for days and then recur.

(B) Attacks of daily pain last for 4–8 weeks.

(D) Women are affected twice as commonly as men.

(E) Caffeine is the most effective treatment for an acute attack.

(B) Men are affected by cluster headaches seven to eight times more often than women. Attacks

are typically periorbital and may involve the temporal area. Cluster headaches typically occur daily over a 4- to 8-week period followed by pain-free intervals averaging 1 year. The periodicity of the attacks is often striking, with daily recurrences of pain often at the same hour. Pathogenesis is thought to be due to abnormal serotonergic neurotransmission. One hundred percent oxygen inhalation is most effective acutely. Drugs used to prevent cluster attacks include lithium, ergotamine, sodium valproate, and prednisone. (Kasper et al., 2005, pp. 85–94)

7. A 42-year-old woman is noted to have a multinodular goiter on examination. She has no symptoms and is clinically euthyroid. Which of the following statements about Hashimoto’s thyroiditis is true?

(A) The condition is associated with prior radioactive exposure.

(B) Patients diagnosed with this disorder have an increased incidence of thyroid cancer.

(D) Antinuclear antibodies are pathognomonic for this disease.

(E) Hashimoto’s thyroiditis is an autoimmune disease.

(E) Hashimoto’s thyroiditis, an autoimmune condition, is the leading cause of multinodular goiter in the United States. Although not unique to this condition, antimicrosomal antibodies are found in 70–95% of patients. Antinuclear antibodies are associated with SLE. Although an autoimmune process, steroids are of no benefit in this condition. One-third of patients experience progressive loss of glandular function, and eventually become hypothyroid, but there is no increased incidence of thyroid cancer. (Kasper et al., 2005, pp. 2109–2113)

8. A60-year-old previously healthy man presents with massive rectal bleeding. Which of the following is the most likely diagnosis?

(A) diverticulosis of the colon

(B) ulcerative colitis

(D) ischemic colitis

(E) carcinoma of the colon

(A) The causes of lower gastrointestinal (GI) bleeding include hemorrhoids and anal fissure

diverticulosis, carcinoma, vascular ectasia, colitis, and polyps. Carcinoma of the colon usually

causes chronic GI bleeding, resulting in anemia. Diverticulosis and vascular ectasia are common

causes of massive GI bleeding in the elderly patient. Inflammatory bowel disease can also

cause massive GI bleeding but is more frequent in younger age group patients. Most patients

with ischemic colitis will be quite sick and will have had symptoms before the onset of bleeding.

(Kasper et al., 2005, pp. 235–238)

9. A 35-year-old man presents with acute low back pain after lifting a couch in his home. Pain is in the lumbosacral area and increases with walking and bending. Examination reveals paraspinal muscle spasm and tenderness and negative straight leg raise bilaterally. Lower extremity strength is intact. Which of the following is the best next step in managing this patient?

(A) bed rest for 1 week

(B) referral to an orthopedic specialist

(D) treatment with anti-inflammatory medication and gradual return to normal activity

(E) referral to a pain clinic

9. (D) In younger patients, low back pain tends to be mild and self-limited, typically resolving in

4–6 weeks. Patients should be encouraged to remain active and symptom control can be achieved with pain medications. Low back pain is the leading cause of work-related disability in the United States. The absence of alarm symptoms such as unilateral or bilateral leg weakness and bladder, bowel or sexual dysfunction makes a cauda equine syndrome or other spinal cord injury unlikely. Age >50, constant pain at night, history of cancer, unexplained weight loss, and lack of response to conservative therapy make further investigation including radiologic evaluation appropriate.

(Kasper et al., 2005, pp. 94–104)

10. On the second day after an appendectomy, a 33-year-old man complains of chest pain. Vital

signs are: temperature 102°F (38°8), BP 130/70 mmHg, pulse rate 100/min, and respiration rate 22/min. Room air ABG reveals a pH of 7.50, PCO2 of 29, and PO2 of 49. His WBC count is elevated and CXR shows a right lower lobe infiltrate. Which of the following is the most likely diagnosis?

(A) pulmonary embolism

(B) myocardial infarction

(D) asthma

(E) congestive heart failure

10. (C) Asthma is characterized by bronchospasm and typically causes a prolonged expiratory

phase and retention of carbon dioxide. This degree of hypoxia (PO2 of 49) generally would not be seen with asthma. Pulmonary embolism, congestive heart failure, myocardial infarction, or pneumonia all could lead to this degree of hypoxia. The constellation of fever, elevated white count, and localized infiltrate on CXR is most characteristic of pneumonia. The most likely etiology is perioperative aspiration related to general anesthesia. (Kasper et al., 2005,

pp. 209–210, 1535–1538)

11. A hepatitis panel is ordered for a 27-year-old woman as part of a routine work-up for abdominal pain. Results of serologic testing are negative for HBeAg and HBsAg, but positive for HBsAb and IgG HBcAb. Which of the following is the appropriate conclusion?

(A) The patient has been exposed to hepatitis B and has completely recovered

(B) The patient has been exposed to hepatitis B and is in the acute disease phase

(D) The patient has been exposed to hepatitis B and is now chronically infected

(E) The patient has been exposed to hepatitis B but was never infected

11.The correct answer is A. This patient has been exposed to hepatitis B and has completely recovered, as is demonstrated by her serologic markers. She does not carry the hepatitis B surface antigen (HBsAg), which is found on the surface of the hepatitis B virus and indicates a carrier state. She does carry the surface antibody, which indicates that she was exposed to hepatitis B and made antibodies to convey immunity. The fact that she also has IgG antibody to the core antibody (HBcAb) shows that she has recovered. HBcAb is also positive in the chronic state, but in that case she would not also have HBsAb. To have both HBcAb and HBsAb without HBsAg is an indication of complete recovery.

12. A 28-year-old man comes to the physician because of worsening muscle weakness that began in his legs and feet 3 days ago, and has now spread to his arms and hands. Other than having a fl u-like illness 2 weeks ago, the patient has been in good health. Cerebrospinal fluid analysis shows an increased protein concentration, a normal cell count, and a normal glucose level. An infection with which of the following organisms is the most likely cause of the nervous system syndrome described in this patient?

(A) Candida albicans

(B) Legionella pneumophila

(D) Pseudomonas aeruginosa

(E) Streptococcus pneumoniae

12. The correct answer is C. The syndrome described is Guillain-Barré syndrome, a common cause of acute peripheral neuropathy that results in progressive weakness over a period of days. Although one-third of patients report no history of an antecedent infection, the other two-thirds have recently experienced an acute gastrointestinal or infl uenza-like illness prior to developing the neuropathy. The most common epidemiologic associations involve infections with Campylobacter jejuni, Hae mophilus infl uenzae, CMV, EBV, Mycoplasma pneumoniae, and VZV. Laboratory abnormalities associated with Guillain-Barré syndrome include elevated gamma-globulin, decreased nerve conduction velocity indicative of demyelination, and albuminocytologic dissociation (CSF shows increased protein concentration with normal cell count in the setting of normal glucose). Although the organisms listed frequently precede the syndrome, there has never been any consistent demonstration of any single infectious agent in the peripheral nerves of these patients, and the cause of the disease is thought to be

mediated by hypersensitive T lymphocytes.

13.You are following a 56-year-old Caucasian patient who has been diagnosed with hypertension and diabetes for 4 years. He does fairly well with diet and exercise, and has remained compliant with his medications. Laboratory evaluation demonstrates a normal serum creatinine, no microalbuminuria, but a GFR of 70 mL/min. According to the National Kidney Foundation staging guidelines, what stage of renal failure does this represent?

A. Stage 0 renal failure

B. Stage 1 renal failure

C. Stage 2 renal failure

D. Stage 3 renal failure

E. Stage 4 renal failure

13. C

EXPLANATION: The National Kidney Foundation staging system is useful to clinicians as it helps guide appropriate testing and referral for patients with kidney failure. Stage 0 represents people at risk for renal failure, but with a GFR greater than 90 mL/min. In these people, control of blood pressure and diabetes may forestall the progression to kidney failure. Stage 1 renal failure represents evidence of renal damage (either microalbuminuria or proteinuria), but with a GFR greater than 90 mL/min. Stage 2 renal failure represents mildly reduced GFR (values between 60-90 mL/min). In stage 3, the GFR is between 30 to 59 mL/min. Stage 4 represents moderate to severe renal failure with GFR levels from 15 to 29 mL/min,

and stage 5 represents severe renal failure with GFR less than 15 mL/min.

14. A 56-year-old woman arrives in the emergency department complaining of dizziness and headache. Her blood pressure is 210/140 mm Hg. She is currently not taking any medications and has not seen a doctor for several years. The physician decides to address her hypertension urgently. Which of the following drugs is contraindicated in this patient?

(A) Intravenous diltiazem

(B) Intravenous labetalol

(D) Oral captopril

(E) Sublingual nifedipine

14.The correct answer is E. Nifedipine is a dihydropyridine class calcium channel blocker that

could be used in the long-term control of hypertension. However, in the case of a hypertensive

emergency, nifedipine used sublingually can cause dangerous fluctuations in blood pressure that are difficult to control and can lead to more harm than good.

15. A 58-year-old woman presented to her physician after discovering a lump in her left breast. The physician examines the lump and finds it to be hard, nontender, and moveable. Which of the following increases this woman’s risk of breast cancer?

(A) Drinking 4 cups of coffee every day

(B) Having a history of a cyst that drained straw-colored fluid

(D) Having gone through menopause 2 years ago

(E) Taking St. John’s wort every day

15.The correct answer is D. Late menopause (>50 years old) is associated with an increased risk of breast cancer. Other risk factors include being female, older age, early first menarche (<12 years old), delayed fi rst pregnancy (>30 years old), and family history of a first-degree

relative with breast cancer at a young age.

Answer A is incorrect. Breast cancer risk is not increased by caffeine intake.

Answer B is incorrect. Breast cancer risk is not increased by nonhyperplastic cysts. Had the

cyst drained bloody fl uid, it would have been more worrisome for a malignant process.

Answer C is incorrect. Breast cancer risk is not increased by fi broadenoma.

Answer E is incorrect. Breast cancer risk is not increased by use of St. John’s wort (thảo dược Hypericum perforatum để trị trầm cảm)

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