USMLE-STEP-2 Online Practice Questions and Answers

Correct Answer: C

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

Correct Answer: B

Heparin is the drug of choice for anticoagulation in pregnancy. Little of it crosses the placenta, and it is not associated with congenital birth defects. Experience with low molecular weight heparin in pregnancy is increasing and appears to be safe for mother and fetus. In full therapeutic doses, low molecular weight heparin offers the advantage of less or no monitoring of its anticoagulant effect. Coumadin readily crosses the placenta and is associated with birth defects in 1525% of fetuses exposed throughout the first trimester. Aspirin is ineffective as an anticoagulant, although the risk of maternal or fetal bleeding (e.g., placental abruption, fetal intracranial bleeding) is increased. There is no clinical experience with TPA in pregnancy. Because pregnancy itself is a thrombogenic condition, anticoagulation throughout pregnancy is indicated. Vena caval filters offer no advantage over heparin and require an invasive procedure.

Correct Answer: C

Knowing the incubation period (average and range) of a pathogen can be important in determining the source of infection in food-borne disease. Knowing what food was eaten on the day of an attack of food poisoning may not help in establishing C. botulinum as the cause of illness, since certain strains of S. aureus cause food-borne disease by the production of enterotoxin. As no time is required after ingestion for the growth of colonies in the infected host, and the toxin affects the vagus nerve in the stomach, the incubation period is under 4 hours. C. perfringens, formerly known as Clostridium welchii, causes food-borne disease, after 824 hours when enterotoxin is released when C. perfringens passes from stomach to intestine. Meat prepared in bulk for consumption at a banquet or in an institution is a possible source. Spores that survive incomplete cooking may start reproducing during cooling and may persist if subsequent rewarming is not completed to a temperature above 60°C (140°F) required to kill the organisms. Salmonella has an incubation time of 1236 hours. It may also survive in meat and other products if cooking is inadequate and heat does not penetrate below the surface of the food. The organisms multiply in the gut of the infected host, and low infective doses may therefore have longer incubation periods

Correct Answer: F

The USPSTF strongly recommends screening for cervical cancer (Pap smear) at least every 3 years in women who have been sexually active or are 21 years old, and have a cervix. It recommends against screening after a normal hysterectomy, or after age 65, if recent Pap smears were normal and the woman is not at high risk. (Note: Although evidence is still considered insufficient, screening for human papilloma virus [HPV] infection shows promise as a part of cervical cancer prevention. Vaccination against HPV is expected to greatly decrease the incidence of cervical cancer in the future.)

Correct Answer: A

The incubation period for diphtheria is 17 days. The incubation period for chicken pox is 1021 days, average 14. Infectious mononucleosis, caused by the Epstein-Barr virus, has an estimated incubation period of 3050 days. The incubation period following infection by the mumps virus is usually 1618 days but, like chicken pox, may vary from 14 to 25 days. Pertussis has a shorter incubation period, usually 710 days, with a variation of 421 days. The usual period from contamination with tetanus spores to clinical symptoms is generally 68 days. For rubella, the incubation period is from 14 to 21 days, but usually ranges from 16 to 18 days.

Correct Answer: E

The design of a cohort study requires a follow-up of a group of subjects who are susceptible but free of the disease of interest at the beginning of the study period.

Correct Answer: C

Active surveillance is used in urgent situations, such as active and ongoing epidemics. Health agencies contact those data sources most likely to have current information regarding cases. The collection of data which has been voluntarily submitted is referred to as passive surveillance. Case-control studies are a form of investigation and represent a "next step" after surveillance. These studies seek to identify further information regarding the health problem y studying individuals with the disease. Surveillance systems on the other hand are used primarily to identify whether or not a problem exists and how it is changing through time. Monitoring disease in animal population or in other specific populations that are higher or earlier risk is referred to as sentinel data collection or surveillance. Identifying where cattle were purchased may help to identify the extent of disease spread in animals, but does not describe active surveillance of human cases.

Correct Answer: C

Valproate can be associated with thrombocytopenia and platelet dysfunction especially at high doses. Leukocytosis is a common benign effect of lithium. Clozaril can cause agranulocytosis in 12% of patients. Agranulocytosis can be an idiosyncratic adverse event with carbamazepine

Correct Answer: C

The stage of colon cancer is based on the depth of invasion, nodal involvement, and distant metastases. Stage 0 represents carcinoma in situ, stage I invasion of the submucosa or muscularis propria without node involvement, stage II invasion through the muscularis propria or directly invading other organs without nodal involvement, stage III any depth of invasion with nodal metastasis, and stage IV any depth of invasion or nodal status with distant metastases. Adjuvant therapy has been shown to be beneficial in patients with stage III disease in randomized studies. The recommended regimen is 5-fluorouracil-based chemotherapy with leucovorin, rather than 5-fluorouracil alone. Adriamycin therapy, either alone or with other agents, has not been shown to be beneficial in patients with colon cancer. No adjuvant therapy would be indicated for patients with stage 0, I, or II disease, although some patients with stage II disease manifesting poor prognostic indicators may be candidates for adjuvant therapy.

Correct Answer: D

The diagnosis of arterial embolism is suggested when the patient presents with an acute onset of severe pain, pallor, pulselessness, paresthesia, and paralysis (five P's). The presence of atrial fibrillation is strongly suggestive of a cardiac source of the emboli. The first step in management is immediate heparinization to prevent propagation of the clot and maintain patency of collaterals. The cornerstone of treatment is thromboembolectomy. Thrombolytic therapy is reserved for treatment of irretrievable clots in small vessels. Fasciotomy, alkalinization of the urine, and mannitol diuresis are adjuncts to treatment, particularly if there is a delay in operation, increasing the risk of a reperfusion injury. Anticoagulation has been shown to reduce the rate of recurrent embolism.