are not appropriate This is not an acute coronary

syndrome and should not be treated as such. Further, if there is a pericardial effusion, heparin can place the patient at an increased risk for tamponade from hem- orrhage. Note that troponin levels are often elevated in renal insufficiency.

Indomethacin (choice E) is appropriate for many caus- es of pericarditis but not for uremic pericarditis. Dialysis is the definitive treatment. Further, whatever residual renal function this patient has can be destroyed by NSAIDs, which reduce the glomerular filtration rate by inhibiting afferent arteriole dilatation, a prostaglandin-mediated event.

22. The correct answer is B. This patient’s pain seems to be

esophageal in origin. GERD and esophageal spasm are common causes of noncardiac chest pain and often have atypical presentations that mimic coronary chest pain closely. Esophageal spasm often responds to nitro- glycerin, which can relax the esophageal smooth mus- cle. Intermittent dysphagia associated with chest pain and a history of GERD strongly suggests esophageal dysfunction. In this setting, a pH probe and outpatient manometry is an appropriate next diagnostic step. Cardiac catheterization and angiography (choice A) are not appropriate. This patient’s only cardiac risk factor is hypertension. Given her young age and completely nor- mal cardiac evaluation, cardiac catheterization is unlikely to be a high yield study and is also highly inva- sive. Similarly, given the normal thallium perfusion scan, further imaging of the heart with a transthoracic echocardiogram (choice C) is unnecessary.

If this patient were not on GERD therapy, an 8-week trial of a proton pump inhibitor (PPI) would be an appropriate first step in the management of suspected esophageal chest pain. Given that this patient is already on a PPI, the addition of an H₂ blocker (choice D) is unlikely to be beneficial.

Were the dysphagia symptoms constant, endoscopy

(choice E) would be an appropriate first step. Routine

endoscopy in the evaluation of suspected esophageal chest pain, however, is not recommended. Only 10% of patients have esophagitis, and conditions such as GERD or spasm are better evaluated with other modalities.

23. The correct answer is B. Desmopressin is an antidi-

uretic hormone (ADH) analogue that can be used to treat central diabetes insipidus (DI), the cause of this

patient’s hypernatremia. Hypernatremia in the setting of neurosurgical procedures affecting the pituitary or hypothalamic tract warrants an evaluation for DI. Mild cases of DI often resolve spontaneously, as the hypotha- lamic-pituitary access regains function. Severe damage to the pituitary, however, may result in a triphasic response. Initially the patient may have abrupt onset of DI, which then seems to resolve slowly. This is caused by an initial inhibition of ADH release, followed by inappropriate ADH response from a degenerating pos- terior pituitary. Finally, as stores of ADH are depleted, the patient once again presents with a picture of DI. As such, DI needs to be followed closely with serial sodium levels. If one is suspicious of the diagnosis, it can be confirmed with a water restriction test. Water restric- tion in a patient with normal homeostatic mechanisms should result in an increase in urine osmolality as the body attempts to retain free water. If the increase is inappropriately minimal and then improves with vaso- pressin (ADH), the diagnosis of central DI is highly likely.

Demeclocycline (choice A) is a tetracycline-type antibi- otic that blocks ADH, and is used, understandably, for treating the syndrome of inappropriate antidiuretic hormone (SIADH) release. It would likely worsen this patient’s condition.

Furosemide (choice C) is a loop diuretic. Patients tend to lose more water than salt. Indeed, the combination of salt tablets and loop diuretics can be used to treat hyponatremia caused by SIADH. As such, it should not be used to treat hypernatremia. Thiazides, which lose relatively more salt than water, are used occasionally to treat SIADH and can be quite effective.

Free water can be given to attempt to dilute the hyper- natremia. Unfortunately most is wasted by the kidneys because of the lack of ADH in the distal tubules. The administration of salt, present in hypertonic (choice D) and normal saline (choice E), should be avoided, as this can worsen the hypernatremia.

24. The correct answer is B. This patient has severe aplas-

tic anemia. This may be from a transient infection, or the antibiotic she was given may have caused it. Chloramphenicol is very common in third world nations. Although it is an extremely effective antibiotic (and is used often for nasty gastrointestinal infections like typhus), it has a high incidence of aplastic anemia. A bone marrow biopsy, which can help determine the cause of the aplastic anemia, is the next diagnostic step in this patient’s workup. In the meantime, she needs a transfusion.

Blood and stool cultures (choice A) are not necessary. This patient does not seem to be infected at this time. She has no fever, localizing signs, or evidence in her his- tory that the illness persisted after treatment. For simi- lar reasons, a CT scan of the abdomen (choice C) is not necessary at this time. If there is an infection in the marrow itself, it will be seen on bone marrow biopsy. An echocardiogram (choice D) is not necessary. This patient’s murmur, consistent with a high velocity flow murmur, will probably resolve with transfusion. An erythropoietin level (choice E) can provide indirect evidence of bone marrow function. Cytologic exami- nation (and culture), however, is necessary to deter- mine if this patient has lymphoproliferative disorder, drug-induced toxicity, viral suppression, or marrow replacement.

25. The correct answer is C. This patient has paroxysmal

nocturnal hemoglobinuria (PNH), a cause of hyperco- agulability and hemolytic anemia that is intermittent and difficult to diagnosis. A defect in the hemopoietic cells renders them vulnerable to complement-mediated lysis, which is precipitated by even a mild acidosis, such as the mild respiratory acidosis that may occur during sleep. The increased activation of complement also is accompanied by platelet aggregation, enhanced expres- sion of tissue factor, and impaired fibrinolysis, all of which place these patients at risk for recurrent clots, particularly in the hepatic and intra-abdominal organs. The presence of PNH should be suspected in any patient with unexplained or intermittent hemolytic anemia, particularly if accompanied by recurrent venous thrombosis and pancytopenia. An appropriate diagnostic test is a Ham’s acidification test. The red blood cells are exposed to an acidic solution that acti- vates complement. Abnormal cells lyse, whereas normal ones do not.

Although the anemia and leukopenia seen in these patients are complement mediated, complement levels are not a useful test. Unless there is significant, ongoing hemolysis, they will not be markedly abnormal. Further, the measurement of complement levels

(choice A) is a nonspecific test, unlike a Ham test.

Gel electrophoresis (choice B) can be used to look for abnormal cell membrane proteins and sometimes is used to confirm conditions such as hereditary spherocytosis. This technique is not used commonly to diagnosis PNH. A lactate dehydrogenase level (choice D) can provide further evidence of hemolysis if elevated but does not assist in the diagnosis of this patient’s condition.

An osmotic fragility test (choice E) is used to test for hereditary spherocytosis. The abnormal morphology is seen easily on a peripheral smear, not seen in this case. The abnormal cells, which have a reduced surface area relative to volume, lyse when placed in a hypotonic fluid.

26. The correct answer is D. This patient has hereditary

spherocytosis, the most common hemolytic anemia caused by a red blood cell membrane defect. An elevat- ed MCHC and RDW combined with the finding of spherocytes are almost pathognomonic for the condi- tion. A positive osmotic fragility test further solidifies the diagnosis. In this test, the spherocytes, with an already reduced surface area to volume ratio, lyse when placed in a hypotonic solution. Patients often present in childhood, but mild or intermittent cases may be picked up in young adults. The definitive treatment is splenectomy.

Hereditary spherocytosis is caused by a genetic defect resulting in abnormal cell membranes that the spleen then destroys. It is not a classic autoimmune disease, and thus should not be treated with corticosteroids

(choice A).

These patients have an appropriate reticulocytosis and are unlikely to benefit from additional exogenous ery- thropoietin (choice B). Further, the definitive treatment is to stop the hemolysis, not replace the lost cells. As such, splenectomy is the most definitive treatment. If this patient has a mild case or does not want surgery, then no additional treatment (choice C) is necessary. These patients should take supplemental vitamins, par- ticularly folate, to help with the hemolytic anemia, and may need transfusions if the anemia becomes symp- tomatic.

Stem cell transplant (choice E) is a dramatic intervention that this condition does not warrant. Although in theory it can treat hereditary spherocytosis, patients respond well to a safer and more cost-efficient splenectomy.

27. The correct answer is A. This patient has a classic pre-

sentation of atrioventricular nodal reentrant tachycar- dia (AVNRT). Regardless of whether you recognize the classic EKG findings (initiation by an atrial premature beat; pseudo-R waves representing a buried, late P-wave), you should recognize the treatment for a sta- ble, supraventricular tachycardia. The first intervention should be a vagal maneuver, such as direct pressure on the eyes, carotid massage, a Valsalva maneuver, or sud- den immersion in cold water (to name a few). If these interventions fail, as they often do, a small bolus of adenosine, which can be doubled and repeated, is the next appropriate intervention. Adenosine will block the

AV node temporarily. If the rhythm is supraventricular, the atrial rhythm will be easier to see. If the rhythm is nodal in origin, it can be suppressed, allowing for the native rhythm to take over.

Amiodarone (choice B) does have nodal blocking prop- erties but is usually not necessary for AVNRT, which can be chronically suppressed with selective nodal blocking agents that have a safer side-effect profile. Amlodipine (choice C) is a calcium channel blocker that acts mainly on the peripheral vasculature. If adenosine fails, a nondihydropyridine calcium channel blocker such as diltiazem or verapamil can be used. DC cardioversion (choice D) is appropriate if the patient is unstable. This patient, although uncomfort- able, is maintaining an adequate blood pressure. Digoxin (choice E) can block the atrioventricular node, mainly through increased vagal activity. Adenosine, with much easier dosing and a much shorter half-life, is a much more appropriate acute therapy. Digoxin is reserved as an option for chronic treatment of AVNRT, and SVT in general.

28. The correct answer is A. This patient has new-onset

congestive heart failure. Her history is very clear for the telltale signs of increasing left heart filling pressures: paroxysmal nocturnal dyspnea, orthopnea, decreased exercise tolerance, and pulmonary congestion. Given her age and track record of never having been hospital- ized, the correct course of action is to obtain an echocardiogram as an inpatient and then begin a med- ication regimen while in the hospital.

Limiting her activity (choice B) and salt intake (choice