Answers

1. c—The only accurate value is that of oxygen consumption, which is quite high. The characteristic values in septic shock for the other parameters are cardiac index, 3.0—5.6 L/min/m² (elevated); systemic vascular resistance index, 675—1110 dynes cm-5 sec/m² (markedly vasodilated); oxygen delivery, 340—575 mL/min/m²; and pulmonary capillary wedge pressure, 8—20 mm Hg. The routinely reduced systemic vascular resistance and wedge pressure, as well as the elevated cardiac index, are due to uncontrolled vasodilation induced by sepsis.
    
2. b—Lower respiratory infections are the most common causes of nosocomial infectious deaths. Prophylactic antibiotics have not been shown to prevent them. Lower respiratory infections are difficult to document, particularly in postoperative patients. The most reliable diagnostic technique is bronchoalveolar lavage. Both urinary tract and superficial skin infections are more common than lower respiratory infections in postoperative patients. These infections are generally caused by gram-positive organisms.
    
3. d—The major advantage of laparoscopic hernia repair is the associated lower rate of wound and mesh infections. Laparoscopic hernia repairs are more expensive, have identical recurrence rates, and take longer to perform. Since open herniorrhaphies are routinely done in the outpatient setting, it is not possible to achieve shorter hospital times.
    
4. e—Afferent loop syndrome is a mechanical complication caused by obstruction of the afferent loop. Using a long loop and antecolic anastomosis increases the frequency of this complication by increasing the likelihood of kinking. Characteristically, patients vomit bile but no food. By the time the obstruction empties retrograde (by vomiting), the food is well beyond the efferent loop, so only bile is vomited. The only treatment for persistent and severe afferent loop syndrome is operative revision, and identifying and eliminating the site of obstruction.
    
5. b—Following alkali burns, the resultant extraction of water from cells causes cellular damage. Alkali burns usually occur in infants and children who accidentally spill strong bases. When they occur in adults, they are usually due to prolonged contact with cement, calcium oxide. The alkaline solutions bind to skin proteins, and the alkaline proteinates penetrate deeply into tissue, making them difficult to wash off. The heat from neutralization reactions increases tissue damage, so the addition of weak acid is detrimental. Debridement should be delayed, at least until the tissue pH is <8.
    
6. a—Bilateral disease mandates the identification of nodal disease in both axillae. The remaining distracters are contraindications, because they will not change the treatment plan. Prior axillary procedures distort the anatomy, making identification of the sentinel node difficult.
    
7. c—Although 20% of patients complain of dysphagia, only 5% have symptoms severe or persistent enough to warrant endoscopic dilation. Dysphagia is due to postmanipulation edema or hematoma and occurs despite routine use of a large bougie. Finally, delayed gastric emptying, which occurs commonly in patients with reflux disease, causes nausea, vomiting, and early satiety, but not dysphagia.
    
8. c—Even though GISTs are intramural lesions, they ulcerate the overlying mucosa and present with bleeding. These tumors generally arise in the jejunum and ileum. Since GISTs do not metastasize to lymph nodes (they usually spread to the liver, lungs, and bones), lymph node dissections are not effective. GISTs are radioresistant, and radiation therapy plays little role in their treatment. The prognosis is determined by tumor size and the number of mitoses.
    
9. e—While antacids are effective in healing ulcers, the ulcers recur rapidly after cessation of therapy, and patients have to take a large number of pills (low-dose therapy is ineffective). Antacids have to be taken on a full stomach; on an empty stomach, the medication is evacuated very rapidly, before it can be effective. All antacids have side effects, which vary among preparations. Magnesium preparations, the most effective, cause diarrhea and are not well tolerated. Antacids stimulate acid secretion by a feedback mechanism stimulated by increased gastric pH.
    
10. d—Immunocytochemistry is used to identify the cell type of mediastinal malignancies. Malignancies constitute 25% of all mediastinal neoplasms. These lesions occur mainly in patients 25 to 40 years of age, corresponding to the most common age of occurrence of lymphomas. The tumors are generally lymphomas and malignant thymomas.
     
11. c—The brachial artery is the vessel most commonly injured by penetrating trauma, followed by the femoral artery. The vessel is approached by separating the biceps and triceps muscles, and the vessel is exposed at the lateral border of the teres major muscle. The median nerve is just superficial to the brachial artery, so it is in maximal jeopardy, and not the ulnar artery, which is much better protected. Ligation results in ischemia, because there is relatively little collateralization in the upper arm.
     
12. d—Eighty percent of small (<4 cm) traumatic pseudocysts resolve spontaneously within 6 to 8 weeks. There is an excellent chance these lesions will resolve without operative or interventional therapy, so observation is indicted with subsequent repeat CT scans. The other procedures are too aggressive at this post-injury stage. Stenting of the pancreatic duct is rarely effective in this scenario, even if the cyst communicates with the pancreatic duct.