USMLE STEP 2 TEST QUESTIONS Session 1 Supplemental Q and A with Annotations

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USMLE STEP 2 TEST QUESTIONS Session 1 Supplemental Q and A with Annotations

  1. 1. USMLE Steps 1 and 2 Integration Individualized Tutorial Demonstration Sept. 09, 2012 Session 1 Supplemental Q&ATutor: Marc Imhotep Cray, M.DWebsite:http://www.imhotepvirtualmedsch.com/E-Mail:drcray@imhotepvirtualmedsch.comPh.: 770-322-1050Resources Used:First Aid USMLE Step 1/ 2012First Aid Q & A for the USMLE Step 1USMLE Step 2 Secrets - Brochert, et.al.First Aid Q & A for USMLE Step 2 CK
  2. 2. USMLE STEP 2 TEST QUESTIONS Session 1 Supplemental Q&A with Annotations Acid-Base and Electrolytes Reading: First Aid for the USMLE Step 2 CK Pgs. 447-455 With focus on translation and interpret of graphic and tabular data from MCQs Access primary tutorial 2
  3. 3. First Aid Q & A for the USMLE Step 1 Pg. 3047. A 2.5-month-old boy is brought to the emergency department for evaluation offever. Two days prior to admission the patient developed a fever to 39.1°C (102.3°F)and became irritable with nasal and decreased oral intake. His birth history isunremarkable. He lives at home with his mother and 6-year-old brother, who attendselementary school where several kids have been absent recently for illness. His heartrate is 137/ min, blood pressure is 72/48 mm Hg, respiratory rate is 35/min, andrectal temperature is 39.3°C (102.7°F). Neurologic examination is remarkable for alethargic- appearing child who is responsive to stimulation. His anterior fontanel isopen and bulging. The resident caring for the patient is certain that he has acutebacterial meningitis and orders a lumbar puncture. Which of the cerebrospinal fluidresults from the lumbar puncture in the table below would be most consistent withacute bacterial meningitis?(A) A(B) B(C) C(D) D(E) E 3
  4. 4. First Aid Q & A for the USMLE Step 1 Pg. 304(2)Also see: First Aid for the USMLE Step 2 CKTABL E 2 . 8 - 4 . CSF Profiles ,Pg 231 4
  5. 5. First Aid Q & A for the USMLE Step 1 Pg. 304 (3)7. The correct answer is B. Acute bacterial meningitis in an infant often manifestswith signs and symptoms similar to the vignette (i.e., fever, increased irritability orlethargy, decreased oral intake, papilledema, and a bulging fontanel). Laboratoryevaluation of cerebrospinal fluid (CSF) will demonstrate an elevated openingpressure (usually 100–300 mm H2O) with 100–10,000 WBCs/mm3, most of whichwill be polymorphonuclear leukocytes. Protein levels are elevated (100–500mg/dL), and glucose is decreased to <50% of serum glucose levels. Acute bacterialmeningitis is a life-threatening condition that must be rapidly diagnosed andtreated in affected patients to reduce morbidity and mortality. 5
  6. 6. First Aid Q & A for the USMLE Step 1 Pg. 304 (4)Answer A is incorrect. This is typical of CSF findings in a normal individual. Normal openingpressure is 50–80 mm H2O, and generally <5 WBCs/mm3 are present with 75% or morelymphocytes. Normal protein levels are 20–45 mg/dL and normal glucose levels are >50 mg/dL, or approximately 75% serum glucose.Answer C is incorrect. These CSF findings are typical of viral meningitis. In such patients,pressure is normal or slightly elevated (80–150 mm H2O), and there are rarely >1000 WBCs/present. Polymorphonuclear leukocytes predominate early in the course of the illness, andmononuclear cells predominate throughout the illness. Protein is often elevated to 50– 200mg/dL and glucose levels are often normal but may be decreased, depending on the viralpathogen.Answer D is incorrect. This is representative of fungal meningitis. Pressure is often elevated,and 5–500 WBCs/mm3 are present, with polymorphonuclear leukocytes predominating earlyin the course, and mononuclear cells predominate throughout the majority of the illness.Protein levels are often 25–500 mg/dL and glucose levels are generally <50 mg/dL.Answer E is incorrect. Acute syphilis and leptospirosis will provide CSF fi ndings consistentwith those seen in this option. Pressure is elevated at 50–500 mm H2O and WBCs arepredominantly present, 50–200 mg/dL of protein is found, and glucose levels are usuallynormal.Reading , USMLE Step 2 Secrets – Brochert, Pg 287, Queries 42 to 46 6
  7. 7. First Aid Q & A for the USMLE Step 1 Pg. 366 (1)29. A 65-year-old patient with a history of bipolar disorder, well-controlled with lithium, is beingevaluated for hypernatremia. Her only complaint is 4 months of polyuria and thirst. Herblood pressure is 106/68 mm Hg and pulse is 102/min. Physical examination reveals her mucousmembranes are dry, and skin turgor is normal. The remainder of the physical examination isunremarkable. Laboratory tests show:Na+: 147 mEq/LK+: 4.7 mEq/LCl−: 110 mEq/LHCO3−: 24 mEq/LBUN: 12 mg/dLCreatinine: 1.1 mg/dLPlasma osmolality: 305 mOsm/kgUrine osmolality: 200 mOsm/kgWhich of the following is most likely to resolvethis patient’s electrolyte imbalance?(A) Exogenous ADH(B) Fluid restriction(C) Intravenous fluids(D) Potassium restriction(E) Thiazide diuretic 7
  8. 8. First Aid Q & A for the USMLE Step 1 Pg. 366 (2)29. The correct answer is E. This patient is suffering from lithium-induced nephrogenicdiabetes insipidus (DI) and demonstrates typical elevations in plasma osmolality withoutcompensatoryelevations in urine osmolality. Indeed, normal renal function would yield aurine osmolality closer to 700 mOsm/kg or higher in this situation. In the setting of prolongedlithium exposure, there is a 20% risk of permanent insensitivity to ADH. In most cases,however, normal renal function returns with cessation of lithium therapy. Appropriatetreatment of lithium- induced DI includes the administration of a thiazide diuretic, whichdecreases the delivery of filtrate to the distal tubule and limits urine volume. Othertherapeutic options include nonsteroidal anti-inflammatory drugs (to decrease filtration atthe glomerulus), amiloride (to prevent accumulation of lithium in the collecting duct cells),and, in cases of known partial DI, DDAVP (synthetic ADH). 8
  9. 9. First Aid Q & A for the USMLE Step 1 Pg. 366 (3)Answer A is incorrect. ADH is effective for the diagnosis and treatment of central DI. However,this patient has nephrogenic resistance to ADH, and thus is unlikely to respond to exogenousADH administration.Answer B is incorrect. Temporary fluid restriction is a useful tool in the evaluation of polyuriaand hyponatremia. In the setting of elevated plasma sodium levels and likely volumedepletion, however, fluid restriction is inappropriate and may worsen the hypernatremia.Answer C is incorrect. Intravenous fluids are a necessary step in the resuscitation phase for themanagement of acute dehydration. This patient is likely to be dehydrated, but simplyadministering fluids will have little overall effect on her condition.Answer D is incorrect. The use of diuretics actually reduces serum potassium levels.Therefore, potassium restriction in not recommended when using diuretics. In fact, apotassium-rich diet or a second diuretic such as spironolactone or amiloride is often usedin these patients to maintain serum potassium levels.Reading , USMLE Step 2 Secrets – Brochert, Pg 136, Queries 37 to 43 9
  10. 10. Calculated osmolarity (CO)Calculated osmolarity (CO)In medical lab reports, this quantity often appears as "Osmo, Calc" or "Osmo (Calc)."According to the international SI unit use the following equation :Calculated osmolarity = 2 Na + Glucose + Urea ( all in mmol/L).orCalculated osmolarity = 2 Na + 2 K + Glucose + Urea ( all in mmol/L).To calculate plasma osmolarity use the following equation (typical in the US):= 2[Na+] + [Glucose]/18 + [ BUN ]/2.8 where [Glucose] and [BUN] are measured in mg/dL.Simplifications are sometimes used:= 2[Na+] + [Glucose]/20 + BUN/3 – 2http://labtestsonline.org/understanding/analytes/osmolality/tab/glance 10
  11. 11. First Aid Q & A for the USMLE Step 1 Pg. 625 (1)3. A 62-year-old woman presents to the emergency department after a sudden syncopalepisode. She has no chronic medical conditions and takes no medications. However, duringthe past 36 hours she has felt acutely ill, with abdominal pain and repeated episodes ofdiarrhea and vomiting. Her blood pressure is 144/85 mm Hg, pulse is 70/min, respiratory rateis 10/min, and temperature is 37.9°C (100.3°F). Laboratory studies show:Na+: 155 mEq/LK+: 2.1 mEq/LCl−: 105 mEq/LHCO3−: 36 mEq/LAn ECG demonstrates flattened T waves and prominent U waves that normalize after potassiumrepletion. Further tests reveal normal 24- hour urine-free cortisol levels and persistentlydiminished plasma renin activity. Which of the following is the most likely diagnosis?(A) 21-Hydroxylase deficiency(B) Addison’s disease(C) Conn’s syndrome(D) Cushing’s disease(E) Cushing’s syndrome 11
  12. 12. First Aid Q & A for the USMLE Step 1 Pg. 625 (2)3. The correct answer is C. Conn’s syndrome, or primary hyperaldosteronism, results from anadrenal adenoma. It is manifested by hypertension, hypokalemia, hypernatremia, low plasmarenin, and increased plasma aldosterone. In this case, an episode of viral gastroenteritis likelyresulted in gastrointestinal loss of potassium, aggravating the chronic hypokalemia seen withthis disorder. The patient’s syncopal episode could have been caused by a hypokalemia- inducedventricular arrhythmia. 12
  13. 13. First Aid Q & A for the USMLE Step 1 Pg. 625 (3)Answer A is incorrect. 21-Hydroxylase deficiency is a congenital salt-wasting syndrome.Hypertension and hypernatremia would not be seen.Answer B is incorrect. Addison’s disease is incorrect because this entails adrenal insufficiencyand thus the electrolyte disturbances (hyponatremia with hyperkalemia) would be the oppositeof those seen here. Hyperpigmentation of the skin, weight loss, weakness, and eosinophiliaare often seen in adrenal insufficiency.Answer D is incorrect. Cushing’s disease refers to those cases of Cushing’s syndrome caused bya pituitary adenoma. It would be characterized by increased cortisol.Answer E is incorrect. Twenty-four-hour urine free cortisol levels would be expected to beelevated in endogenous causes of Cushing’s syndrome, and we have no history to suggestthat this patient has taken exogenous glucocorticoids (the most common cause of Cushing’ssyndrome).Reading , USMLE Step 2 Secrets – Brochert, Pg 39, Queries 20 to 28 13
  14. 14. diagnostic algorithm for acid-base disordersFirst Aid for the USMLE Step 2 CK, Pg. 452 14
  15. 15. ACUTE RENAL FAILURE (ARF)An abrupt ↓ in renal function → the retention of creatinine and BUN.↓ urine output (i.e., oliguria, defined as < 500 cc/day) is not requiredfor ARF. ARF is categorized as follows First Aid for the USMLE Step 2 CK, Pg. 453 15
  16. 16. ACUTE RENAL FAILURE (ARF) (2) First Aid for the USMLE Step 2 CK, Pg. 454Reading , USMLE Step 2 Secrets – Brochert, Pg 299-300, Queries1 to 8 16
  17. 17. RENAL TUBULAR ACIDOSIS (RTA)A net ↓ in either tubular H+ secretion or HCO3− reabsorption that → anon–anion gap metabolic acidosis. There are three main types of RTA; type IV(distal) is the most common form 17
  18. 18. First Aid Q & A for the USMLE Step 1 Pg. 659 (1)3. A 65-year-old man with type 2 diabetes mellitus and eczema presents to his physician for aroutine office visit. He is currently taking metformin and atorvastatin. His blood pressure is140/86 mm Hg, heart rate is 75/min, and respiratory rate is 26/min. An ECG shows normalsinus rhythm with peaked T waves. Urinalysis shows a urine pH of 5.0; it is negative for ketones,WBC esterase, and nitrite, but is positive for protein. Arterial blood gas analysis and laboratorytests show:pH: 7.3Partial pressure of carbon dioxide: 32 mm HgPartial pressure of oxygen: 98 mm HgOxygen saturation: 99% on room airNa+: 140 mEq/LK+: 6.0 mEq/LCl−: 120 mEq/LHCO3−: 14 mEq/LBlood urea nitrogen: 16 mg/LCreatinine: 1.1 mg/LWhich of the following is the most likely diagnosis?(A) Hyperkalemia(B) Hyperventilation(C) Ketoacidosis(D) Lactic acidosis(E) Renal tubular acidosis 18
  19. 19. First Aid Q & A for the USMLE Step 1 Pg. 659 (2)3. The correct answer is E. The clinical scenario represents type IV renal tubular acidosis (RTA),the most common type of RTA. The disturbance can be thought of as relative aldosteronedeficiency or resistance, which is most commonly found in diabetic nephropathy. Ahypoaldosterone state leads to hyperkalemia, resulting in decreased ammonium productionand urine acidification. The patient’s arterial blood gas shows a process consistent with ametabolic acidosis with respiratory compensation, while his electrolyte panel shows that theacidosis is hyperchloremic in nature. The ECG findings reflect the changes found inhyperkalemia. Type IV RTA can also be seen with tubulointerstitial renal diseases, hypertensivenephrosclerosis, and HIV nephropathy. Drugs such as angiotensin-converting enzymeinhibitors, nonsteroidal anti-inflammatory drugs, and trimethoprim can all cause hyperkalemialeading to type IV RTA. Treatment is furosemide and potassium binding agents suchas sodium polystyrene sulfonate. 19
  20. 20. First Aid Q & A for the USMLE Step 1 Pg. 659 (3)Answer A is incorrect. The hyperkalemia that is present is secondary to relative aldosteronedeficiency. Hyperkalemia is not the precipitating event.Answer B is incorrect. Hyperventilation may cause a primary respiratory alkalosis. This patienthas a primary metabolic acidosis with respiratory compensation.Answer C is incorrect. Ketoacidosis occurs almost exclusively in type 1 diabetes mellitus.Furthermore, the urinalysis was negative for ketones, and there is not an anion gap, makingovert ketoacidosis unlikely.Answer D is incorrect. Metformin can cause lactic acidosis, which should cause an aniongap metabolic acidosis. Based on the laboratory values, the anion gap is normal with a value of 6. 20
  21. 21. MOA and Side Effects of Diuretics 21
  22. 22. End of SessionServices provided by Imhotep Virtual Medical SchoolIndividualized Webcam facilitated USMLE Step 1 Tutorials with Dr. Cray Starting at $50.00/hr., depending onpre-assessment. 1 BMS Unit is 4 hr. General Principles and some Organ System require multiple units tocomplete in preparation for the USMLE Step 1A HIGH YIELD FOCUS in Biochemistry / Cell Biology, Microbiology / Immunology, the 4 P’s-Physiology, Pathophys., Path and Pharm and Intro to Clinical MedicineWebcam Facilitated USMLE Step 2 Clinical Knowledge and Clinical Skills didactic tutorials starting at $75.00per hour /1 Unit is 4 hours, individualized one-on-one and group sessions, Including Introduction to ClinicalMedicine and all Internal Medicine sub-specialities at the clerkship level. For questions or more information..drcray@imhotepvirtualmedsch.comALL e-books and learning tools provided 22

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