Sunday, November 22, 2009

USMLE - Some golden rules to be remembered

1. The treatment of severe sepsis syndrome should be based on efficient resuscitation, effective antimicrobial therapy, elimination of secondary infections, euglycemia, early targeted and specific drug therapy, and establishment of therapeutic goals.
2. Acute pulmonary embolism (PE) is a difficult diagnosis to establish despite newer advances in imaging; approximately 50% of cases are diagnosed post mortem.
3. In the approach to suspected PE, keep in mind the prudent use of key diagnostic tests: (1) rapid d-dimer by ELISA is an effective screening test; (2) chest CT can help detect most PEs; and (3) a negative Doppler venous ultrasound of the legs does not exclude the diagnosis of PE.
4. The most common etiologic agent implicated in acute bacterial meningitis in the U.S. is Streptococcus pneumoniae.
5. In the newly diagnosed HIV patient, in addition to routine adult immunizations, immunizations against pneumococcal pneumonia, influenza, and both hepatitis A and B are indicated.
6. Metabolic syndrome is diagnosed on the basis of abdominal obesity, hypertriglyceridemia, low HDL cholesterol levels, hypertension, and fasting hyperglyceima.
7. Pituitary tumors cause problems for patients by two main mechanisms: mass effect, which applies pressure to surronding structures, and endocrine hyperfunction, which results in excessive secretion of a particular anterior pituitary hormone.
8. A key concept in evaluating patients with hyperfunctioning endocrine tumors is that biochemical diagnosis should always precede anatomic localization.

9. The best initial screening test for evaluation of thyroid status is the TSH, since it is the most sensitive measure of thyroid function in the majority of patients. The one exception is patients with pituitary/hypothalamic dysfunction, in whom TSH cannot reliably to assess thyroid function.
10. The most common presentation of hypogonadism is erectile dysfunction and decreased libido in men and amenorrhea and infertility in women.
11. All patients with coronary artery disease (CAD), CAD-equivalent diseases, or diabetes should be treated aggressively to reach the LDL-cholesterol target of 100 mg/dL.
12. Diabetics and patients with vascular disease should be treated with a statin lipid-lowering drug to prevent heart disease and stroke, regardless of the blood low-density lipoprotein (LDL) cholesterol level, age (from 40 to 79 years), or gender.
13. The goal blood pressure is < 130/80 mmHg in hypertensive subjects with diabetes mellitus and/or chronic kidney disease.
14. The single most life-saving treatment strategy in patients with acute ST-elevation myocardial infarction is to rapidly achieve complete reperfusion of the infarct-related artery by mechanical (balloon angioplasty or stenting) or pharmacologic means (thrombolysis).
15. Angiotensin-converting enzyme inhibitors (or angiotensin receptor blockers) and beta-adrenergic blockers are effective in reducing cardiovascular complications and improving survival in patients with systolic heart failure and are recommended in all patients with no contraindications to these drugs.
16. Noninvasive stress testing has the best predictive value for detecting CAD in patients with an intermediate (30-80&percnt pretest likelihood of CAD and is of limited value in patients with very low (< 30&percnt or very high (> 80&percnt likelihood of CAD.
17. In patients with Coccidioides immitis infections, higher titers of complement-fixing antibodies suggest more extensive disease, and rising titers suggest worsening disease.
18. Patients who present with flaccid paralysis during the summer months should be evaluated for West Nile virus infection.
19. A febrile patient with rash who presents to the emergency department during May to September in the South Atlantic and West South Central states should receive empirical doxycycline therapy for suspected Rocky Mountain spotted fever.
20. Community-acquired methicillin-resistant Staphylococcus aureus that is susceptible to clindamycin but resistant to erythromycin should not be treated with clindamycin because of the possibility for induction of resistance.
21. In patients with disseminated candidiasis, IV catheters should be removed and ophthalmologic examinations performed to evaluate for the presence of retinal disease.
22. Transmission of Borrelia burgdorferi (the causative agent of Lyme disease) from an infected Ixodes tick to a susceptible human requires the tick to have fed on the human for at least 40 hours.
23. Porcelain gallbladder is an incidental finding, more common in women who have gallstones. Because up to 50% of patients develop gallbladder carcinoma, prophylactic cholecystectomy is recommended.
24. Three liters of Coca-Cola administered via nasogastric lavage over a 12-hour period can dissolve gastric bezoars. It is thought that the cola acidifies the gastric contents and liberates carbon dioxide in the stomach, resulting in the disintegration of phytobezoars.
25. Regardless of what is done, GI bleeding stops spontaneously in about 80% of patients.
26. Patients with hereditary nonpolyposis colorectal cancer syndrome have a higher-than-average risk of developing colon and gastric cancer.
27. About 90% of patients with primary sclerosing cholangitis have underlying ulcerative colitis, but less than 10% of all patients with ulcerative colitis have primary sclerosing cholangitis.
28. In patients with suspected perforation, the minimum amount of free air that can be detected on an upright chest x-ray is 12 mL.
29. The three major openings in the diaphragm through which hernias may occur are the esophageal hiatus (most common), foramen of Bochdalex (3-5%, usually left-sided), and foramen of Morgagni (rare).
30. In a patient who has a malignancy involving the right hilum, look at the hand veins. If the veins in the hands are distended and do not collapse when the arms are lifted over the head, there is a high chance of superior vena cava obstruction.
31. In high-risk patients, the chance of developing breast cancer can be reduced by about 50% with the use of tamoxifen.
32. If a patient with lung cancer presents with hoarseness, look for vocal cord paralysis, a sign of mediastinal involvement (recurrent laryngeal nerve) that renders the patient inoperable.
33. Patients with head and neck cancer have a 30% chance of developing another cancer somewhere in the aerodigestive tract (head and neck, lung, or esophagus), especially if they continue to smoke and drink.
34. If a patient presents with hypercalcemia, look for a squamous cell cancer (lung, esophagus, head and neck, cervix, anus).

35. Up to 15% of breast cancers may not be detectable by mammogram. If the patient has a clinically suspicious lump, perform a biopsy.
36. The presence of bilateral small kidneys in a patient with azotemia confirms chronic renal failure.
37. In a diabetic patient with proteinuria, the presence of concomitant retinal disease suggests strongly (90% correlation) that the renal manifestations are due to diabetes.
38. Treatment of anemia of chronic renal failure by recombinant human erythropoietin is highly effective, but correction of iron deficiency and iron supplementation by oral or intravenous route is simpler, cheaper, and often by itself effective therapy.
39. In resistant hypertension, especially in younger (< 20 yr) or older (> 70 yr) patients, consider and rule out renovascular hypertension.
40. New onset of nephrotic proteinuria in an elderly patient warrants exclusion of an underlying malignancy.
41. The principal mechanism of bicarbonate reabsorption in the proximal tubule is through Na+-H+ exchanger (NHE3) activity.
42. D-lactic acidosis is characterized by increased serum anion gap, metabolic acidosis, and episodic encephalopathy in patients with short bowel syndrome.
43. Ethylne glycol (antifreeze) toxicity is characterized by high anion gap metabolic acidosis, neurotoxicity in the form of ataxia, seizures, and calcium oxalate crystals in the urine.
44. Bartter's syndrome is a disorder associated with normotensive hyperaldosteronism, secondary to juxtaglomerular hyperplasia, hypokalemic metabolic alkalosis, and severe renal potassium wasting.
45. Hyperkalemia is an important side effect of both ACE inhibitors and ARBs, but the problem is less frequent and smaller in magnitute with ARBs because of their less pronounced effects on aldosterone levels.
46. Hypochromic microcytic anemias are the most frequently encountered anemias in hospitalized and ambulatory patients.
47. Both iron-deficiency anemia and anemia of chronic disease have a low transferrin saturation. In iron-deficiency anemia, the TIBC is often increased, whereas anemia of chronic disease is marked by an unusually low TIBC.
48. The main clinical manifestations of sickle hemoglobinopathies are hemolytic anemia, chronic end-organ damage, periodic vaso-occlusive disease ("crises"), and hyposplenism.
49. The triad of thrombocytopenia, fragmentation hemolysis, and fluctuating neurologic signs suggests thrombotic thrombocytopenic purpura (TTP), perhaps the most spectacular of the fragmentation syndromes.
50. The cytogenetic marker of chronic myelogenous leukemia is the 9:22 translocation, in which portions of the long arms of chromosomes 9 and 22 are exchanged, resulting in a shortened 22 or Philadelphia chromosome (Ph1). Some patients with acute lymphoblastic leukemia (ALL) also have 9:22 translocations - a poor prognostic marker in ALL.
51. The classic cell seen in the lymph nodes of patients with Hodgkin's disease is the Reed-Sternberg (RS) cell, a large cell with two nuclei, each possessing a distinct nucleolus.
52. Secondary monoclonal gammopathy must be distinguished from the monoclonal gammopathy associated with multiple myeloma, benign monoclonal gammopathy of uncertain significance, solitary plasmacytoma, amyloidosis, lymphoma, and Waldenström's macroglobulinemia.
53. Deep venous thrombosis in a young person, a family history of thrombosis, thrombosis at unusual sites (such as the mesenteric vein), or recurrent thrombosis without precipitating factors suggests a hypercoagulable state.
54. Any condition that leads to V/Q mismatching can cause hypoxemia. Most pulmonary disorders are associated with some degree of V/Q mismatching. This is the most common cause of hypoxemia and is responsive to oxygen therapy.
55. Assuming that you are at sea level and breathing room air, an easy way to calculate the A-a difference is as follows: (150-40/0.Cool - PaO2 measured by ABG.
56. Although the anterior segment of the upper lobes may be affected by TB, a lesion found only in the anterior segment suggests a diagnosis other than TB (e.g., malignancy).
57. Incidence of lung cancer now exceeds breast cancer in women. Women develop lung cancer at an earlier age and after fewer years of smoking.
58. Pleural fluid glucose < 30 mg/dL and pH < 7.30 suggest rheumatoid effusion, TB, lupus, or malignancy.
59. Mesothelioma, a pleural malignancy associated with asbestosis exposure, is not associated with tobacco use.
60. Early, aggressive intervention with disease-modifying antirheumatic drugs reduces the morbidity (deformity leading to reduced functionality and disability) and mortality associated with rheumatoid arthritis. 61. Antinuclear antibody (ANA) titers are not associated with activity of disease.
62. COX2 NSAIDs are no more efficacious than older standard NSAIDs but are significantly less toxic.
63. A patient with low positive rheumatoid factor (RF) and arthralgia should be checked for hepatitis C, which can produce a low-grade synovitis and cryoglobulins (which in turn can produce a falsely positive RF).
64. Always check for Sjögren's antibodies (SSA/SSB) and phospholipid antibodies in a young woman with lupus before conception. Sjögren's antibodies increase the risk of neonatal lupus (rash, thrombocytopenia, heart block), and phospholipid antibodies can significantly increase the risk for miscarriage, premature labor, or intrauterine growth delay.
65. Packed red cells in freshly acquired blood may include lymphocytes that can mount a graft-versus-host reaction if the patient's own immune system is unable to rapidly kill and inactivate these transfused allogeneic leukocytes.
66. Intranasal steroids are the single most effective drug for treatment of allergic rhinitis. Decongestion with topical adrenergic agents may be needed initially to allow corticosteroids access to the deeper nasal mucosa.
67. The clinical manifestations of anaphylaxis include flushing, sense of foreboding, urticaria or angioedema, pruritus, hoarseness, stridor, bronchospasm, hypotension, tachycardia, nausea, vomiting, abdominal pain, diarrhea, headache, and syncope.
68. ACE inhibitors are often-forgotten causes of angioedema and chronic cough.
69. Chronic urticaria may require treatment with a combination of both H1 and H2 antihistamines, reflecting the distribution of these receptors in the skin. Work-up for an allergic etiology is rarely informative. 70. Beta blockers should be avoided whenever possible in patients with asthma because they may accentuate the severity of anaphylaxis, prolong its cardiovascular and pulmonary manifestations, and greatly decrease the effectiveness of epinephrine and albuterol in reversing the life-threatening manifestations of anaphylaxis.
71. HIV infection is preventable and treatable but never curable.
72. If you are thinking of mononucleosis as a diagnosis, think about and test for HIV.
73. Adherence to anti-HIV therapy must be > 95% for a durable response. HIV treatment guidelines change frequently - always verify your information.
74. A person under care for HIV should not develop pneumocyotic carinii pneumonia (PCP). It is entirely preventable.
75. There is a critical interaction between HIV and tuberculosis. When one infection is present, you must look for the other.
76. If you have diagnosed one sexually transmitted disease (STD), you must consider others, especially HIV.
77. Most back pain is not caused by a radiculopathy. 78. The most common cause of dizziness is benign paroxysmal positional vertigo.
79. The leading causes of death after a stroke are medical complications, not the stroke itself.
80. Heparin has no value in the acute treatment of strokes.
81. The sudden onset of a severe headache may indicate an intracranial hemorrhage.
82. Coma is usually caused by medical problems, not neurologic ones.
83. Elective surgery should be postponed for further evaluation if the patient has signs or symptoms of unstable or inadequately treated chronic disease.
84. Patients who have undergone coronary revascularization within 5 years of a proposed elective surgery and have no signs or symptoms of recurrent ischemia can usually undergo surgery without further evaluation.
85. Acute dyspnea in a patient who has had major surgery should raise the suspicion of pulmonary embolism, even if the patient has received prophylaxis.
86. All patients who take oral agents for diabetes may continue them until the day of surgery unless they have chronic liver or renal disease or are on a first-generation sulfonylurea. In these cases the oral agent should be held at least several days in advance of the surgery.
87. Pacemakers and implanted cardioverters/defibrillators should be assessed both before and after surgery, radiation therapy, or lithotripsy.
88. Surgery patients on any antiplatelet agent should be told when to stop the medication before surgery and when to resume it afterward to minimize perioperative bleeding.
89. Strict bed rest is not needed for the treatment of acute lumbosacral strain.
90. Influenza virus vaccination reduces hospitalization and death from influenza and its complications in elderly and high-risk patients.
91. Always examine the feet and pedal pulses of diabetic patients regularly, looking for ulcerations, injury, or reduced blood flow.
92. Closely monitor patients with blood pressure measurements defined as "prehypertension," and encourage lifestyle changes to prevent progression to hypertension.
93. Reduce the risk of hip fracture in elderly and high-risk patients with calcium and vitamin D supplements, exercise prescription, hip pads, and medications to treat osteoporosis, when indicated.
94. Assess a woman's risk of coronary disease, stroke, thromboembolism, and breast cancer before prescribing estrogen/progesterone therapy in menopause.
95. Older adults currently constitute the fastest-growing population in the United States - a trend that is expected to continue for the foreseeable future.
96. Commonly used instruments for a comprehensive geriatric assessment include the Mini Mental State Exam, the Geriatric Depression Scale, activities of daily living, instrumental activities of daily living, and assessment of stability and mobililty (e.g., Tinnetti or "Get Up and Go" test).
97. Dementia and short-term memory loss are not caused by aging.
98. Delirium carries tremendous mortality and morbidity rates and should be identified, worked up aggressively, and treated as any medical emergency.
99. Diastolic dysfunction, as distinct from systolic dysfunction, results from impaired relaxation in heart failure with preserved ejection fraction and may account for half of all cases of heart failure in people over
80. Although the symptoms of diastolic and systolic dysfunction may be similar, the traditional therapy for systolic dysfunction can actually worsen ventricular filling and increase the risk of orthostasis and syncope in cases of diastolic dysfunction.
100. Fifteen percent of elderly patients who fall and fracture a hip report prior falls. It is essential to ask about falls, assess for fall risk, and then act accordingly, given the significant mortality and morbidity of hip fractures


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