UWorld 4/14 pt 2

Gingival hyperplasia, like that shown in the photo above, is a common side effect of phenytoin. It occurs in 50% of patients who have had 3-4 months of phenytoin therapy. The mechanism of this side effect is associated with increased expression of_____. When gingival macrophages are exposed to increased amounts of _____, they stimulate proliferation of gingival cells and alveolar bone. Gingival hyperplasia may regress after discontinuation of phenytoin.

platelet-derived growth factor (PDGF)

RMP (resting membrane potential) for calcium

+125

Several acute physiological changes occur in response to the resulting hypobaric hypoxia:

Increased firing of peripheral chemoreceptors causes hyperventilation, which directly reduces hypoxemia and improves tissue oxygenation Increased 2,3-bisphosphoglycerate (2,3-BPG) synthesis by erythrocytes, which shifts the O2-hemoglobin dissociation curve to the right, decreasing the affinity of hemoglobin for oxygen and facilitating the offloading of oxygen in peripheral tissues

Adrenal medulla cells (parachromaffin cells) are most likely to be activated by

acetylcholine

Parasagittal lesions compressing the _____ portion of the primary somatosensory cortex in the parietal lobe can result in contralateral lower limb sensory loss along with contralateral hemineglect if there is also damage to the parietal association cortex (nondominant hemisphere)

medial

RMP (resting membrane potential) for sodium

+60

RMP (resting membrane potential) for chloride

-75

RMP (resting membrane potential) for potassium

-90

3 Standard deviations encompasses

99.7% of the data

A 63-year-old woman with a history of metastatic breast cancer comes to the office due to depressed mood. Over the past month, the patient has become increasingly sad and frequently cries when thinking about her poor prognosis and dying. She has lost 4.5 kg (10 lb) over the past month. Her energy level is low, and she has difficulty falling asleep and frequent nighttime awakenings. The patient has become very withdrawn, doesn't answer the phone, and no longer looks forward to family visits. She feels bad about not wanting to be around her grandchildren. On mental status examination, the patient is alert and oriented with depressed mood and affect. She has no suicidal ideation. Which of the following symptoms is most indicative of major depressive disorder in this patient? A. Loss of interest in family (%) B. Low energy (%) C. Sleep disturbance (%) D. Thoughts of dying (%) E. Weight loss (%)

A. Loss of interest in family (%) Somatic symptoms of depression (weight loss, low energy, sleep disturbance) are less reliable indicators of major depressive disorder in patients with advanced medical illness. Focusing on nonsomatic symptoms, such as loss of interest, anhedonia, worthlessness, excessive guilt, and suicidality, can assist in diagnosing comorbid depression in these patients

The patient is tachypneic and unable to speak in full sentences. Examination reveals prolonged expiration and prominent bilateral wheezing. Heart sounds are normal. Chest imaging shows a normal-sized heart and hyperinflated lungs with a flattened diaphragm. Bedside echocardiogram reveals no intrapericardial fluid accumulation or pericardial thickening. Which of the following physiologic changes is most likely to provide immediate relief in this patient? A. cAMP accumulation in smooth muscle cells (%) B. Cell membrane stabilization of mast cells (%) C. Inhibition of eosinophil degranulation (%) D. Interrupted histamine receptor firing in epithelial cells (%) E. Opening of calcium channels in smooth muscle cells (%)

A. cAMP accumulation in smooth muscle cells (%)

A 25-year-old woman comes to the office due to excessive facial hair growth that has worsened over the past several years. The patient is very concerned and says it makes her feel self-conscious in public. She has tried several cosmetic measures, including laser removal and waxing, but the results have been unsatisfactory. Her past medical history is insignificant, and she takes no medications. The patient's last menstrual period was 6 weeks ago, but she regularly has long cycles and otherwise feels well. She is sexually active with her boyfriend and uses condoms for contraception. Examination shows moderate obesity with mild hirsutism on the face and chest. The patient is initiated on a combination oral contraceptive. Which of the following describes the primary mechanism by which this agent reduces hirsutism? A. Blockade of ornithine decarboxylase (%) B. Decreased androgen production (%) C. Increased insulin sensitivity (%) D. Inhibition of 5-α-reductase (%) E. Inhibition of androgen receptors (%)

B. Decreased androgen production (%)

A 50-year-old man with a long history of alcohol use disorder is admitted to the hospital with difficulty breathing. Blood pressure is 90/40 mm Hg, pulse is 114/min, respirations are 22/min, and pulse oximetry is 92% on room air. Physical examination shows bilateral basal crackles, increased jugular venous pressure, hepatomegaly, ascites, and peripheral pitting edema. Chest x-ray demonstrates cardiomegaly. Scattered ecchymoses are present across each extremity. Laboratory results are as follows: Platelets 120,000/mm3 Prothrombin time 26 sec Activated partial thromboplastin time 38 sec The patient is given intramuscular vitamin K. Two days later, his laboratory results are unchanged. Which of the following is the most likely cause of this patient's laboratory abnormality? A. Dietary vitamin K deficiency (%) B. Factor VII deficiency (%) C. Factor VIII deficiency (%) D. Intrinsic platelet dysfunction (%) E. Von Willebrand factor deficiency (%)

B. Factor VII deficiency (%) This patient has liver dysfunction due to alcohol use disorder. The liver synthesizes many proteins, including clotting factors. Chronic alcohol use leads to progressive hepatic fibrosis/cirrhosis, resulting in acquired coagulopathy. Clotting factors II, VII, IX, and X are produced initially by the liver in an inactive form and then activated by vitamin K-dependent carboxylation. Factor VII, part of the extrinsic pathway, has the shortest half-life of all coagulation factors. Prothrombin time (PT) assesses the extrinsic and common pathways of coagulation and is the first to become abnormal in liver disease. This patient's PT prolongation is likely due to factor VII deficiency in the setting of cirrhosis. Because clotting factor synthesis is impaired, PT may not improve with vitamin K supplementation as there are insufficient quantities of clotting factors to undergo vitamin K-dependent carboxylation/activation. The liver also synthesizes albumin, and hypoalbuminemia results in ascites and peripheral edema. In addition, severe cirrhosis causes high-output heart failure due to chronic splanchnic vasodilation and development of mesenteric and intrahepatic arteriovenous shunts

A 55-year-old man with poorly controlled hypertension and type 2 diabetes mellitus comes to the emergency department due to difficulty seeing. He has had blurry vision for the last 2 weeks, and 1 day ago he suddenly noticed a shadow develop across the visual field of his left eye. The patient has no recent headache, double vision, vertigo, light sensitivity, or nausea. On examination, pupils are equal and reactive to light. There is an area of reduced vision in the left eye. Funduscopic examination reveals a flame-shaped hemorrhage in the left temporal hemiretina. The transmission of visual information through which of the following neural structures will be disrupted? A. Left inferior colliculus (%) B. Left lateral geniculate body (%) C. Left medial geniculate body (%) D. Medial optic chiasm (%) E. Right inferior colliculus (%) F. Right lateral geniculate body (%) G. Right medial geniculate body (%)

B. Left lateral geniculate body (%) This patient has a hypertensive hemorrhage in the left temporal hemiretina. The left temporal hemiretina receives visual information from the nasal visual field of the left eye. This visual signal is transmitted via the left optic nerve to the lateral aspect of the optic chiasm. It then joins the visual signal from the right nasal hemiretina (receives visual information from the temporal visual field of the right eye) and travels via the left optic tract to the left lateral geniculate body in the thalamus. After this homonymous visual signal leaves the left lateral geniculate body, it travels via the ipsilateral optic radiations to the ipsilateral primary visual cortex for visual processing

A 27-year-old man is brought to the emergency department by his roommate, who found the patient barricading himself in a closet at home and saying, "They're coming to get me. No one can be trusted." The patient was laid off from his job and broke up with his girlfriend last month. He has heard voices threatening to kill him a few times daily for the past 2 weeks. He has no medical or psychiatric history and does not use alcohol or illicit drugs. Physical examination and laboratory results are unremarkable. On mental status examination, the patient is fearful and tense. He describes being followed by men in black cars who are spying on him. Which of the following is the most likely diagnosis in this patient? A. Acute stress disorder (%) B. Bipolar disorder with psychotic features (%) C. Brief psychotic disorder (%) D. Delusional disorder (%) E. Paranoid personality disorder (%) F. Schizophrenia (%) G. Schizophreniform disorder (%) H. Schizotypal personality disorder (%)

C. Brief psychotic disorder (%)

A 23-year-old woman is evaluated due to 10 days of nonproductive cough, low-grade fever, headache, and malaise. The patient has no other medical problems and takes no medications. Lung examination reveals scattered rales. Chest x-ray reveals bilateral patchy areas of consolidation. She has mild anemia and an elevated serum lactate dehydrogenase level. The patient is treated for presumed Mycoplasma pneumonia with azithromycin. Two months later, her symptoms and the anemia have resolved. Which of the following best explains the resolution of this patient's anemia? A. Elimination of bacterial cell wall antigens (%) B. Elimination of intraerythrocytic microorganisms (%) C. Fading of immune response against the bacteria (%) D. Replenishment of body iron stores (%) E. Replenishment of intracellular enzyme stores (%)

C. Fading of immune response against the bacteria (%) Mycoplasma pneumoniae is a common cause of tracheobronchitis and walking pneumonia. It attacks the respiratory epithelium by binding to an oligosaccharide (I-antigen) that is also present on the surface of erythrocytes. This leads to the formation of cross-reacting IgM antibodies that attach to red blood cells, activate the complement system, and cause erythrocyte lysis. The cross-reacting antibodies are called cold agglutinins because they bind to erythrocytes in areas where the blood temperature is below core body temperature (eg, distal extremities, nose). Most patients with cold agglutinins are asymptomatic, but some develop manifestations of intravascular hemolytic anemia such as elevated reticulocyte count and lactate dehydrogenase level. IgM titers usually begin to fall approximately 4 weeks after initial infection leading to a resolution of the hemolytic anemia (within 8 weeks). Other extrapulmonary manifestations of M pneumoniae include Stevens-Johnson syndrome, joint pain, encephalitis, cardiac rhythm disturbances, and bullous myringitis.

A 4-month-old girl is brought to the office due to a rash on her cheeks for the past 2 weeks. The rash has not spread, and the patient is often seen scratching her face. There have been no changes in bath soaps and detergents; no animals or plants are in the house. Vaccinations are up to date. The patient is exclusively breastfed, with height and weight tracking along the 50th percentiles. Vital signs are normal. Skin examination is shown in the exhibit. The remainder of the examination is unremarkable. Which of the following conditions is this patient at increased risk for developing? A. Coronary artery aneurysm (%) B. Disabling arthritis (%) C. Food allergy (%) D. Proximal muscle weakness (%) E. Transient anemia (%)

C. Food allergy (%) This infant with erythematous and pruritic patches on her cheeks has atopic dermatitis (eczema), a common childhood condition that typically begins in infancy or early childhood. The pathogenesis of atopic dermatitis is multifactorial and includes genetically mediated skin barrier dysfunction (eg, filaggrin mutation) resulting in loss of epidermal water content, increased permeability to environmental allergens/irritants, and skin inflammation. In addition, immune dysfunction, characterized by an underlying Th2 skewed response, promotes IL-4 and IL-13 release, which stimulates IgE production by plasma cells. Patients with atopic dermatitis and elevated IgE levels are at increased risk for other atopic diseases, such as allergic rhinitis, asthma, and food allergies. A compromised skin barrier facilitates allergen penetration (eg, from food) and subsequent sensitization, facilitating the development of food-induced urticaria and anaphylaxis. An earlier onset of atopic dermatitis (eg, infancy) is associated with a higher risk for developing these associated conditions

A 32-year-old woman complains of weakness in her hands and "heaviness" in her eyelids at the end of each day. Chest imaging shows an anterior mediastinal mass. The organ from which this mass most likely originated shares its embryologic origin with: A. Thyroid gland (%) B. Superior parathyroid glands (%) C. Inferior parathyroid glands (%) D. Larynx (%) E. Palatine tonsils (%)

C. Inferior parathyroid glands (%) Myasthenia gravis causes muscle weakness, with the extraocular muscles most commonly affected. Patients often experience ptosis and diplopia. The muscle weakness worsens with activity, and patients often note that their symptoms are worse at the end of the day. The majority of patients with myasthenia gravis are found to have a thymoma or thymic hyperplasia. The thymus is derived from the third pharyngeal pouch, as are the inferior parathyroid glands. The table below lists the derivatives of the pharyngeal pouches, grooves and membranes:

A 56-year-old woman is brought to the emergency department after a generalized tonic-clonic seizure witnessed by her husband. The patient has no history of seizures or other medical conditions but has been having recurrent headaches for the past several months. Physical examination shows mild weakness with increased deep tendon reflexes in the left upper extremity. MR imaging of the brain reveals a large mass in the right frontal lobe. Stereotactic biopsy of the mass yields hypercellular white matter with extensive astrocytic aberration, microvascular proliferation, and areas of necrosis lined by tumor cells. Molecular studies of the abnormal cells are most likely to demonstrate which of the following findings? A. Abnormal tuberin and hamartin proteins (%) B. Constitutively active RET protein (%) C. Lack of merlin tumor suppressor protein (%) D. Overexpression of epidermal growth factor receptor (%) E. Presence of Epstein-Barr virus genome (%)

D. Overexpression of epidermal growth factor receptor (%) This patient's seizure, headache, motor weakness, and brain mass composed of abnormal astrocytes with necrosis and microvascular proliferation raises strong suspicion for glioblastoma (GBM), a highly aggressive tumor that stems from glial or pluripotent neural stem cells. A number of characteristic oncogenic mutations are usually present in GBM, but >95% of cases are associated with the overexpression of epidermal growth factor receptor (EGFR) on the surface of neoplastic cells. EGFR is a tyrosine-kinase signal transduction system that conducts external growth signals into the nucleus, thereby promoting cellular survival and proliferation. Mutations that enhance this pathway (eg, overexpression of EGFR or EGFR-ligand) are associated with uncontrolled cellular proliferation and are seen in GBM and other cancer types (eg, non-small cell lung cancer, breast cancer, prostate cancer). Therefore, drugs that inhibit the EGFR/EGFR-ligand interaction (eg, erlotinib) are often used as part of treatment.

A 67-year-old man comes to the emergency department due to progressive shortness of breath and chest tightness. He has had no lightheadedness or syncope. The patient takes lisinopril for hypertension and metformin for type 2 diabetes mellitus. He has smoked a pack of cigarettes daily for the last 40 years. The blood pressure cuff is inflated to 140 mm Hg and the pressure is released very slowly. At 120 mm Hg, intermittent Korotkoff sounds are heard only during expiration. At 100 mm Hg, Korotkoff sounds are heard throughout the respiratory cycle. Item 1 of 2 This physical examination finding can be seen in which of the following conditions? A. Aortic valve disease (%) B. Mitral valve disease (%) C. Myocardial ischemia (%) D. Pericardial disease (%) E. Peripheral vascular disease (%)

D. Pericardial disease (%) Systemic arterial pressure normally falls by <10 mm Hg during normal inspiration. Pulsus paradoxus refers to an exaggerated drop (>10 mm Hg) in systolic blood pressure during inspiration. It is detected by inflating a blood pressure cuff above systolic pressure and gradually deflating it. The difference between the systolic pressure at which Korotkoff sounds first become audible during expiration and the pressure at which they are heard throughout all phases of respiration quantifies pulsus paradoxus (20 mm Hg in this patient). Inspiration causes an increase in systemic venous return, resulting in increased right heart volumes. Under normal conditions, this results in expansion of the right ventricle into the pericardial space with little impact on the left side of the heart. However, in conditions that impair expansion into the pericardial space (eg, acute cardiac tamponade), the increased right ventricular volume occurring with inspiration leads to bowing of the interventricular septum toward the left ventricle. This leads to a decrease in left ventricular (LV) end-diastolic volume and stroke volume, with a resultant decrease in systolic pressure during inspiration

A 48-year-old man comes to the office due to right inguinal discomfort. The patient first noticed "bumps" in his groin when he was dressing in the morning. He does not know how long they have been present but thinks they are relatively new. The patient was treated for gonorrhea several years ago but has no other medical problems. He drinks alcohol occasionally but does not use tobacco or illicit drugs. His mother died of metastatic melanoma. Cardiopulmonary examination is normal. The abdomen is soft and nontender. The right inguinal lymph nodes are enlarged and tender, as are several nodes in the right popliteal area. The distribution of lymphadenopathy in this patient would most likely be seen in which of the following conditions? A. Asymmetric, hard prostate nodules (%) B. Firm, nontender right testicular mass (%) C. Large, irregular mole on the right great toe (%) D. Purulent laceration on the right lateral foot (%) E. Ulcerative lesion on the glans penis (%)

D. Purulent laceration on the right lateral foot (%) The lymphatic system of the extremities is divided into the superficial lymphatic vessels, which follow the venous system, and the deep lymphatic vessels, which follow the arterial system. The superficial vessels receive lymph from the skin and subcutaneous tissues, whereas the deep vessels drain both the deep muscles and the superficial vessels. In the lower extremities, the superficial lymphatic system is divided into medial and lateral tracks. The medial track runs along the long saphenous vein up to the superficial inguinal lymph nodes, bypassing the popliteal nodes. Consequently, lesions on the medial foot cause inguinal lymphadenopathy (Choice C). In contrast, lateral lesions, which drain via the lateral track and communicate with the popliteal and inguinal nodes, are more likely to cause lymphadenopathy in both the popliteal and inguinal areas

A 68-year-old man comes to the emergency department due to lightheadedness, generalized weakness, and palpitations. The patient has a prolonged history of hypertension and takes amlodipine. He does not use tobacco or alcohol. His blood pressure is 110/60 mm Hg and pulse is 144/min and irregular. ECG shows an irregularly irregular rhythm and absent P waves. The patient is started on beta blocker therapy for rate control, with improvement in his heart rate. Long-term anticoagulation is initiated to prevent atrial thrombus formation, and he is eventually discharged home on warfarin. Which of the following is the best test to monitor the anticoagulation effect of warfarin in this patient? A. Activated partial thromboplastin time (%) B. Bleeding time (%) C. Fibrin split products (%) D. Fibrinogen levels (%) E. Prothrombin time (%)

E. Prothrombin time (%)

A 52-year-old woman with a history of locally advanced breast cancer comes to the office for follow-up. The patient is undergoing trastuzumab-based chemotherapy but has not received radiation therapy. She has no symptoms except mild fatigue. Blood pressure is 120/72 mm Hg and pulse is 85/min and regular. The patient is afebrile. Transthoracic echocardiography reveals a left ventricular ejection fraction of 40% with no evidence of valvular disease. Cardiac assessment prior to chemotherapy initiation was normal. Which of the following pathologic findings is most likely to be present in this patient's heart? A. Abnormal protein accumulation in the extracellular space (%) B. Focal ischemic cardiomyocyte necrosis (%) C. Myocardial tumor cell infiltration (%) D. Patchy cardiomyocyte necrosis with diffuse myocardial fibrosis (%) E. Reduced cardiomyocyte contractility with no fibrosis (%)

E. Reduced cardiomyocyte contractility with no fibrosis (%) Trastuzumab is a monoclonal antibody used in the treatment of breast cancer caused by tumor cells that overexpress human epidermal growth factor receptor-2 (HER2). By binding to HER2, trastuzumab blocks downstream signaling that promotes cellular proliferation and thereby encourages malignant cell apoptosis. The major adverse effect of trastuzumab is a risk of cardiotoxicity, likely because HER2 signaling plays a role in minimizing oxidative stress on cardiomyocytes and preserving cardiomyocyte function. Cardiotoxicity typically manifests as a decrease in myocardial contractility (myocardial stunning) without cardiomyocyte destruction or myocardial fibrosis. Patients usually experience an asymptomatic decline in left ventricular ejection fraction; however, overt heart failure can also occur. Unlike the cardiotoxicity that occurs with anthracyclines (eg, doxorubicin), trastuzumab-induced cardiotoxicity is not related to the cumulative chemotherapy dose and is often reversible with discontinuation of therapy.

A 45-year-old woman comes to the office due to polyuria and nocturia. She has no fever, dysuria, or abdominal pain. The patient has no significant medical problems and takes no medications. Her temperature is 36.7 C (98 F), blood pressure is 120/80 mm Hg, and pulse is 76/min. The patient's mucous membranes appear dry. The remainder of her physical examination is normal. Her urine output and osmolality remain unchanged with water deprivation for several hours, but after administration of desmopressin, urine output decreases and urine osmolality increases. Renal clearance of which of the following substances would decrease the most after this patient's injection? A. Calcium (%) B. Creatinine (%) C. Glucose (%) D. Para-amino hippuric acid (%) E. Urea (%)

E. Urea (%) polyuria that resolves with the administration of desmopressin (DDAVP, synthetic analogue of vasopressin) is likely secondary to deficient vasopressin secretion (central diabetes insipidus). Vasopressin produces a V2 receptor-mediated increase in water permeability within the cortical and medullary collecting ducts. As water leaves the tubular fluid, urea concentration greatly increases in these tubular segments. Although the cortical collecting duct is impermeable to urea, vasopressin activates urea transporters in the medullary collecting duct, increasing urea reabsorption and decreasing renal urea clearance. This passive reabsorption of urea into the medullary interstitium in the presence of ADH significantly increases the medullary osmotic gradient, allowing the production of maximally concentrated urine

A small-for-gestational-age infant is born prematurely to a 38-year-old woman who had inconsistent prenatal care. Physical examination shows a small head and eyes as well as a cleft lip and palate. There is a small, round punched-out lesion with an overlying thin membrane on the patient's scalp. A small, membranous sac with a loop of bowel protrudes from the patient's abdominal midline. The infant is transferred to the neonatal intensive care unit for further workup and management. Which of the following is most likely responsible for this patient's condition? A. Down syndrome (%) B. Edwards syndrome (%) C. Maternal nicotine use (%) D. Maternal phenytoin ingestion (%) E. Maternal rubella infection (%) F. Patau syndrome (%) G. Williams syndrome (%)

F. Patau syndrome (%) Patau syndrome, or trisomy 13, is a severe genetic disorder with phenotypic features reflecting a defect in the fusion of the prechordal mesoderm, an integral embryological structure affecting growth of the midface, eyes, and forebrain. This results in catastrophic midline defects, including holoprosencephaly, microcephaly, microphthalmia, cleft lip/palate, and omphalocele. Abnormal brain development results in intellectual disability and seizures. Additional abnormalities include polydactyly and cutis aplasia (focal skin defect of the scalp). The majority of patients with Patau syndrome die in utero; only 5% survive beyond 6 months. Cytogenetic studies usually demonstrate meiotic nondisjunction, which is the failure of chromosomal separation during meiosis, causing inheritance of a chromosome pair from 1 parent rather than a single chromatid. Maternal age >35 is an important risk factor for this abnormality of oocyte division. Nondisjunction results in a fetus with 3 complete copies of chromosome 13 (47, XX, +13). (Choice A) Patients with Down syndrome (trisomy 21) typically have a flat facial profile, upslanting palpebral fissures, low-set small ears, redundant skin at the nape of the neck, single transverse palmar crease, and hypotonia. Increased rates of duodenal atresia and Hirschsprung disease are seen in these patients. (Choice B) Clinical manifestations of Edwards syndrome (trisomy 18) include fetal growth retardation, hypertonia, micrognathia, and congenital heart defects. Additional features include clenched hands with overlapping fingers, Meckel's diverticulum, and malrotation. (Choice C) Nicotine use during pregnancy increases the risk of prematurity and low birth weight. Related pregnancy complications include placenta previa and abruption. (Choice D) Fetal exposure to maternal phenytoin has been associated with several congenital anomalies (eg, cardiac defects, cleft lip/palate, hypoplastic nails). It is not associated with cutis aplasia or omphalocele. (Choice E) Congenital rubella syndrome typically occurs after a first trimester maternal rubella infection. Abnormalities classically include hearing loss, cataracts, and cardiac defects. (Choice G) Williams syndrome is a genetic disorder classically associated with "elfin" facies, supravalvular aortic stenosis, and an extroverted personality

A 78-year-old man comes to the office due to a one-month history of progressive dyspnea, generalized weakness, fatigue, and palpitations. He also reports tingling and numbness in both lower limbs. His daughter, who is visiting from another state, adds that since his wife's death a year ago, the patient has not been taking care of himself. Blood pressure is 105/50 mm Hg and pulse is 104/min. Cardiovascular examination shows a displaced apical impulse at the sixth intercostal space, a third heart sound, and high-volume, collapsing carotid pulses. Bilateral basal crackles, 2+ bilateral pedal edema, and mild hepatomegaly are also present. Neurologic examination shows decreased light touch and vibration sense in the feet, with decreased knee and ankle reflexes bilaterally. Laboratory evaluation shows normal blood counts. Deficiency of which of the following nutrients is most likely responsible for this patient's symptoms? A. Ascorbic acid (%) B. Cobalamin (%) C. Niacin (%) D. Pyridoxine (%) E. Retinol (%) F. Riboflavin (%) G. Thiamine (%)

G. Thiamine (%)

PPV

TP/(TP+FP)

A 60-year-old man comes to the clinic due to a 3-week history of fatigue, shortness of breath, and fever. The patient has a 35-pack-year history of cigarette smoking but has no other significant medical history. Temperature is 38.6 C (101.5 F), blood pressure is 140/92 mm Hg, pulse is 110/min, and respirations are 24/min. There is dullness to percussion at the right lung base. Chest radiograph shows a moderate-sized loculated pleural effusion on the right side. Ultrasonography reveals multiple separate fluid pockets within the pleural space. Chest tube placement produces only a small amount of thick pus. Intrapleural administration of a medication with which of the following effects would most likely improve chest tube drainage in this patient? A. Activation of fibrin-bound plasminogen (40%) B. Decreased interstitial edema formation (24%) C. Inhibition of factor Xa production (5%) D. Inhibition of platelet activity (7%) E. Irritation of the mesothelial pleural lining (22%)

This patient's several weeks of fever, shortness of breath, and fatigue with imaging showing a loculated pleural effusion with complex septations represents a classic presentation of empyema. Empyema is an advanced form of complicated parapneumonic effusion in which bacterial invasion into the pleural space is followed by progressive inflammation with pus accumulation and organized fibrosis. Treatment requires prompt drainage of the infected fluid via a chest tube, but such effusions are often difficult to drain due to numerous loculations (ie, separated fluid pockets) and high fluid viscosity. In some cases, intrapleural administration of a fibrinolytic agent (eg, tissue plasminogen activator [tPA], streptokinase) in combination with deoxyribonuclease (DNase) can improve drainage of a loculated empyema and help resolve the effusion via chest tube drainage. The tPA activates fibrin-bound plasminogen to break down organized fibrin, and the DNase enzyme may assist by cleaving nucleic acids that increase fluid viscosity after being deposited by lysed leukocytes (eg, neutrophil extracellular traps). A complicated parapneumonic effusion or empyema that cannot be successfully drained following the administration of tPA and DNase typically requires surgical drainage via video-assisted thoracoscopic surgery.