Case 20 – A 1-month-old girl with failure to thrive

A 1-month-old white girl is sent to the emergency room by her pediatrician for failure to thrive. She was born at full term, weighing 2.72 kg (6 lb), via spontaneous vaginal delivery with no complications. She was discharged to home with her mother and has been feeding well; she takes 3-4 ounces of formula every 2-3 hours. Her parents deny any emesis, fevers, or diarrhea, although her mother notes frequent foul-smelling loose stools. Family history is unremarkable. She lives with her parents and four siblings. She is afebrile with normal vital signs. Her weight is 3.3 kg (7.3 lb) (<5th percentile), length is 50 cm (19.7 in) (<5th percentile), and head circumference is 37 cm (14.6 in) (at 10th percentile). She is cachetic but interactive. The remainder of her examination is unremarkable.

What is the definition of failure to thrive (FTT)?

The term FTT may be attributed to a child who meets any of the following criteria:

1. Has weight <5th percentile for age and sex
2. Has depressed weight for height
3. Has a rate of weight gain that causes a decrease across two or more major percentile lines over time
4. Has a rate of daily weight gain less than expected for age

What are the two types of FTT?

Organic causes of FTT include:

1. Abnormal loss of calories
2. An abnormal need for calories
3. Failure to ingest an appropriate number of calories
4. Failure to metabolize

Most cases of FTT are due to nonorganic causes, typically psychosocial factors.

What organic causes of FTT should be considered in patients <6 months old?

1. Cystic fibrosis
2. Gastroesophageal reflux
3. HIV infection
4. Inborn errors of metabolism
5. Milk-protein intolerance
6. Perinatal or postnatal infections
7. Renal tubular acidosis

While in the hospital the patient feeds well, but despite adequate caloric intake, she fails to gain weight. What tests should be included in the initial work-up of this patient’s cause of FTT?

Malabsorption must be considered when a patient fails to gain weight despite feeding well. Initial screening studies for malabsorption include:

1. Serum electrolytes, albumin, and total protein
2. Stool exam for Clostridium difficile, ova, and parasites and stool cultures for bacterial pathogens
3. Stool exam for occult blood, leukocytes, reducing substances, and pH
4. Urinalysis and culture

What is the most likely diagnosis in this patient, and how should it be confirmed?

Since this patient is a white person with a history of FTT, malabsorption, and foul-smelling stools, cystic fibrosis must be considered. The next step in the work-up of this patient should be a sweat chloride test, which is the gold standard for the diagnosis of cystic fibrosis.

How should this patient’s malabsorption be treated?

The mainstay of treatment for pancreatic insufficiency in cystic fibrosis is pancreatic enzyme replacement. In addition, patients should receive supplementation of fat-soluble vitamins (vitamins A, D, E, and K).

By Jessica Kagen Hart, Resident, Department of General Pediatrics, Children’s Hospital of Philadelphia; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 19 – A 27-year-old woman with fever and cough

A 27-year-old woman presents to her physician because of 5 days of fever and cough. She has no significant past medical history but has been “fighting colds” for the past 3 months, which she attributed to the winter season. She began having low-grade fevers as well as a dry cough 5 days ago. She has also become increasingly short of breath over the past 2 days. Her temperature is 38.7°C (102°F), heart rate is 110/min, respiratory rate is 24/min, blood pressure is 110/70 mm Hg, and oxygen saturation is 90% on room air. Physical examination reveals pallor and oral thrush. Lung auscultation is significant for bilateral crackles and rhonchi throughout. The remainder of her examination is unremarkable. She lives with her husband, who is HIV-positive but is currently asymptomatic. She has no pets and no recent travel history. X-ray of the chest reveals diffuse bilateral interstitial infiltrates.

What is the most likely diagnosis?

The patient’s respiratory symptoms, oral thrush, and radiographic findings are most concerning for Pneumocystis carinii pneumonia (PCP) (now called Pneumocystis jiroveci). PCP is an important cause of pneumonia in immunocompromised hosts and is a leading cause of opportunistic infection, morbidity, and mortality in patients with HIV. The fact that this patient’s husband is HIV positive makes her chance of also being HIV positive very likely.

What is the next step in diagnosis?

Specific diagnosis of PCP requires documentation of the organism in respiratory specimens. Conventional stains such as toluidine blue O, methenamine silver, or Giemsa can be used to identify the organism. Immunofluorescent staining is the most common technique currently in use.

What is the most appropriate management for this patient?

Trimethoprim-sulfamethoxazole (TMP-SMX), which acts by inhibiting folic acid synthesis, is considered the drug of choice for all forms of pneumocystosis. Therapy is continued for 14 days in non-HIV-infected patients and for 21 days in persons infected with HIV. In patients with severe PCP, corticosteroids given in conjunction with anti-Pneumocystis therapy, decreases the incidence of mortality and respiratory failure.

What findings would one expect to see on high-resolution computed tomography (HRCT)?

A patchy or nodular ground-glass appearance is the most common finding of PCP on HRCT. HRCT has a high sensitivity for PCP among HIV-positive patients.

What prophylactic therapy should this patient use for her condition?

Indications for prophylaxis of PCP in HIV-positive patients include:

1. History of PCP
2. CD4 cell count <200/mm³
3. History of oropharyngeal candidiasis

Oral trimethoprim-sulfamethoxazole (TMP-SMX) is the preferred prophylactic regimen. Other options include pentamidine, dapsone, and atovaquone. Oral TMP-SMX is also useful in preventing toxoplasmosis and bacterial infections.

By Jessica Kagen Hart, Resident, Department of General Pediatrics, Children’s Hospital of Philadelphia; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 18 – A 60-year-old man with significant bleeding

A 60-year-old man presents to the emergency department complaining of a persistent nosebleed. His nose began bleeding spontaneously about 3 hours ago, and he has not been able to get it to stop despite direct pressure and ice packs. He denies trauma, blood disorders, cancer, or a family history of hematologic or oncologic problems. He has gastroesophageal reflux disease, for which he recently increased his dose of cimetidine, and atrial fibrillation, for which he takes metoprolol and warfarin. His temperature is 37.0°C (98.6°F), blood pressure is 120/80 mm Hg, heart rate is 90/min, and respiratory rate is 10/min. Physical examination is notable for crusted blood around his left nasal ala and slowly oozing bright red blood from his left nostril. He also has small conjunctival hemorrhages and a large bruise on his knee. The remainder of his physical examination is unremarkable, including a regular heart rate and rhythm and normal chest, abdominal, and neurologic examinations. Laboratory tests show:

WBC count: 6000/mm³
Hemoglobin: 13.5 g/dL
Hematocrit: 40%
Platelet count: 350,000/mm³
International Normalized Ratio: 12.5
Prothrombin time: Normal

What conditions should be included in the differential diagnosis?

The differential diagnosis of clinically significant hemorrhage includes trauma and disorders of hemostasis, specifically problems with platelet quantity (thrombocytopenia) and quality or clotting factor deficiency. Inherited (hemophilia, von Willebrand’s disease) and acquired (hematologic malignancy, bone marrow dysfunction, liver disease, medication, autoimmune) diseases may have identical clinical presentations, albeit frequently in different patient populations.

What is the most likely diagnosis?

This patient has clinically significant, persistent bleeding (epistaxis and other hemorrhagic phenomena) in the context of an International Normalized Ratio (INR) of 12.5 while receiving warfarin therapy. Although he may have an underlying malignancy or inherited bleeding disorder, his entire clinical presentation can be explained by his medications. Cimetidine inhibits the cytochrome P450 (CYP450) system of drug metabolism (a hepatic enzymatic system that metabolizes drugs for excretion), and warfarin is metabolized by this system. Thus, a recent increase in cimetidine dosage in a patient who takes warfarin could easily lead to dangerously high warfarin levels, evidenced in this patient by severe bleeding and a high INR.

What other risk factors are associated with this condition?

Medications and other compounds that induce the CYP45 system include:

1. Alcohol
2. Barbiturates
3. Carbamazepine
4. Dexamethasone
5. Griseofulvin
6. Phenytoin
7. Quinidine
8. Rifampin

Medications and other compounds that inhibit the CYP45 system include:

1. Cimetidine
2. Clarithromycin
3. Erythromycin
4. Grapefruit juice
5. Isoniazid
6. Ketoconazole
7. Ritonavir

What is the most appropriate management for this patient?

In patients with either severe bleeding or an INR >20 (risk factor for intracranial hemorrhage), immediate cessation of warfarin and CYP450 inhibitors is crucial. This patient should also receive nasal packing, as well as admission for observation and serial neurologic exams (for intracranial hemorrhage monitoring), INR assessments, and hemoglobin levels. Finally, this patient should be counseled to use a different histamine blocker for his gastroesophageal reflux disease, such as ranitidine, to avoid this complication in the future.

By Brian Ash, MD, Resident in Anesthesia and Perioperative Care, University of California, San Francisco Medical Center; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 17 – A 29-year-old woman with substance dependence

A 26-year-old G7P3 woman at 34 weeks’ gestation presents to the emergency department because she feels she is beginning to experience contractions and does not have an obstetrician to consult. On examination her pupils are dilated and she appears agitated and nervous. She then changes her mind and says she does not want further evaluation because it has been too long since her last “smoke.” She is adamant about needing to leave right away. Upon further questioning, she states that if she does not get to smoke soon, she will become very sleepy and depressed, and will have intense food cravings. She has been in inpatient drug rehabilitation twice but always relapses back to her drug of choice. She is currently living at a halfway house, is on welfare, and does not have custody of any of her 3 children. “They will probably take this one away from me, too,” she adds as she begins to cry. She says she used to be able to get high for $10 per day, but now it costs up to $100 per day. She affords her habit by trading drugs and money for sex; she has not been tested for HIV or other sexually transmitted diseases in recent memory.

What is the most likely diagnosis?

Cocaine dependence. This patient exhibits the classic signs of addiction: she has tolerance for the drug (requires more to achieve the same effect), and experiences withdrawal symptoms without it. She has continued to use cocaine despite the negative consequences it brings, and she has been unable to bring herself to stop using despite many attempts. Smoking cocaine results in feelings of euphoria and heightened energy, while depression, hunger, and sleepiness are symptoms of withdrawal. The criteria for substance dependence can be remembered using the mnemonic WITHDrawIT:

1. Withdrawal
2. Interest or important activities given up or reduced
3. Tolerance
4. Harm (physical and psychosocial) with continued use
5. Desire to cut down or control use
6. Intended time/amount of use exceeded
7. Time spent obtaining/using the substance is increased

What behavioral changes are associated with cocaine use?

Behavioral changes may include:

1. Blunting of feelings
2. Decreased appetite
3. Euphoria and increased energy
4. Heightened anxiety, irritability, or anger
5. Hypervigilance and heightened alertness
6. Impaired judgment
7. Increase in sexual excitement and spontaneous ejaculation
8. Increased risk for psychosis
9. Increased self-confidence
10. Interpersonal sensitivity

What physical changes are associated with cocaine use?

Physical changes may include:

1. Chest pain and/or arrhythmias due to vasospasm in coronary arteries
2. Confusion, seizures, stupor, or coma
3. Diaphoresis or chills
4. Dilated pupils
5. Increased pulse and blood pressure due to vasoconstriction
6. Muscle weakness, dystonia, or dyskinesia
7. Nausea or vomiting
8. Psychomotor slowing or agitation
9. Respiratory depression
10. Weight loss

What are the risks of cocaine use to the patient’s unborn child?

Since cocaine readily crosses the placenta and is metabolized slowly in fetuses, they can be exposed to significant levels of cocaine for long periods. Because of its vasoconstrictive properties, cocaine use increases the risk of fetal hypoxia and abruptio placentae.
In humans the most common consequences of cocaine abuse during pregnancy include premature birth, lower birth weight, respiratory distress, bowel infarctions, cerebral infarctions, reduced head circumference, and increased risk of seizures. Behaviorally, these newborns show an increased degree of tremulousness, crying, and irritability, and are overreactive to environmental stimuli. Within a month of birth these behaviors recover dramatically, but never to normal levels. It is important to remember that cocaine can be found in breast milk up to 60 hours after the last use.

By Kristen Vierregger, University of Pennsylvania School of Medicine, Class of 2008; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 16 – A 19-year-old man with substance abuse

A 19-year-old student is being evaluated at his student health center. The physician notes the young man is tachycardic at 101/min with a blood pressure of 145/93 mm Hg. His pupils are constricted and there is a fine tremor in his hands. The patient appears agitated and is sweating. The student says he is just anxious about upcoming final examinations, but when questioned further he becomes angry and belligerent. He finally admits that for the past 2 weeks he has been taking pills his roommate gave him in order to help him stay awake. He says they improve his concentration and allow him to get by on only a few hours of sleep. He has not been eating as much and says his clothes are fitting more loosely on him. He does not see a problem with this, saying many people in the dormitory do the same thing, and that he will stop taking the pills after his examinations are done. The rest of the physical examination is unremarkable. On mental status examination he is alert and oriented to person, place, and time. He is mildly uncooperative, and his speech is rapid. He describes his mood as “terrific,” but his affect is angry. He denies suicidal or homicidal ideation, perceptual disturbances, or delusions. He does not have a prior history of mental illness.

What is the most likely diagnosis?

Amphetamine intoxication. He admits to recent use of pills acquired from his roommate to help him study. Although it is not known exactly what kind of pills he has been taking, the illicit use of dextroamphetamines is a significant problem on college campuses. He exhibits many of the diagnostic criteria found in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) for amphetamine intoxication: he has not been sleeping or eating regularly and there is evidence of recent weight loss; his pulse and blood pressure are elevated, his pupils are dilated, and a tremor is present. He also exhibits behavioral and psychological changes of euphoria, anxiety, tension, and anger. Abuse of stimulants may also result in symptoms of psychosis such as paranoid delusions.

What are the DSM-IV-TR criteria for substance abuse?

The criteria for substance abuse can be remembered using the mnemonic HARP:

1. Hazardous use (eg, driving while intoxicated)
2. Arrests (legal problems)
3. Role failure (repeated work absences due to substance use)
4. Persistent use despite consequences

Only one of these four criteria need be met during a 12-month period. Still, this patient does not meet the criteria for substance dependency. The criteria for substance dependence can be remembered using the mnemonic WITHDrawIT:

1. Withdrawal
2. Interest or important activities given up or reduced
3. Tolerance
4. Harm (physical and psychosocial) with continued use
5. Desire to cut down or control use
6. Intended time/amount of use exceeded
7. Time spent obtaining/using the substance is increased

Three of these seven criteria must be met within a 12-month period to diagnose substance dependency.

What would happen if the patient suddenly stopped taking the pills?

Amphetamine withdrawal is characterized by fatigue, depression, nightmares, headache, profuse sweating, muscle cramps, and hunger. Withdrawal symptoms such as intense dysphoria usually peak in 2-4 days and resolve within 1 week.

Is treatment necessary for patients in amphetamine withdrawal?

Since amphetamine intoxication and withdrawal are generally self-limiting, no specific treatment is necessary. Benzodiazepines (eg, diazepam, lorazepam) can be used to treat agitation or anxiety, but have their own abuse potential. Therapeutic drugs to treat the withdrawal are not routinely used in clinical practice.

By Kristen Vierregger, University of Pennsylvania School of Medicine, Class of 2008; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 15 – A 25-year-old man after a motor vehicle accident

A 25-year-old man is brought to the emergency department by ambulance after a motor vehicle accident. The paramedics report that his vehicle, which was not equipped with airbags, hit a telephone pole at a speed of approximately 35 mph. His temperature is 37.0°C (98.6°F), heart rate is 91/min, respiratory rate is 13/min, and blood pressure is 116/78 mm Hg. He is alert and oriented to person and place, but does not recall the date or any of the events leading up to the accident. He also reports that he feels very dizzy whenever he looks up at the ceiling. Examination of the head and neck reveals slight enophthalmos of the left orbit with infraorbital and upper lip anesthesia.

What is the most likely diagnosis?

Orbital fracture. Blowout fractures are the result of blunt trauma to the globe with rapid expansion of the orbital contents and rupture through the bony floor. A blowout fracture can also be the result of a direct blow to the orbital rim.

What is the etiology of this condition?

Facial fractures secondary to motor vehicle and recreational accidents are more common in rural areas, whereas penetrating trauma and assault-related injuries are more common in urban populations. Domestic violence and abuse should always be considered as a possible cause of the injury.

What other symptoms are common in patients with this condition?

Diplopia on upward gaze suggests inferior rectus muscle entrapment, but the etiology may be multifactorial. Infraorbital anesthesia is the result of a contused infraorbital nerve and anesthesia of the maxillary teeth and upper lip is common. Rarely, patients demonstrate enophthalmos, or sunken globe, when a large section of the globe has ruptured. Occasionally, a step-off deformity can be palpated over the intraorbital rim, or subcutaneous emphysema results from fracture into a sinus or nasal antrum.

What tests and/or imaging tools could be used to confirm the diagnosis?

Plain films are useful in the diagnosis of blowout fractures. The “hanging teardrop” sign suggests orbital fat herniating into the maxillary sinus. Once a blowout fracture is suspected, a CT scan of the face with coronal sections can be used to determine the surface area of the broken orbital floor.

What is the most appropriate management for this patient?

All orbital fractures may have repair delayed for 1-2 weeks; however, opinions regarding surgical repair vary among providers. Antibiotics against sinus pathogens are recommended for patients with subcutaneous emphysema.

By Julie Katz, MD, Resident in Anatomic and Clinical Pathology, The Johns Hopkins Hospital; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 14 – A 68-year-old man with lower abdominal pain

A 68-year-old man presents to the emergency department with severe lower abdominal pain. He has a constant desire to urinate but can only produce a small amount of urine. His past medical history is unremarkable, but he says he has experienced hesitancy before the onset of urination and decreased strength of his urinary stream for several months. Physical examination is significant for trace pedal edema, and his blood pressure is 140/86 mm Hg, with no orthostatic changes. He has marked tenderness in the suprapubic region and dullness to percussion to the level of the umbilicus. Rectal examination reveals a large, smooth, firm, midline mass located anteriorly. Laboratory tests show:

Sodium: 142 mEq/L
Potassium: 6.0 mEq/L
Chloride: 113 mEq/L
Bicarbonate: 17 mmol/L
Blood urea nitrogen: 110 mg/dL
Creatinine: 7 mg/dL
Hemoglobin: 15 g/dL
Hematocrit: 45%

What is the most likely cause of this patient’s lower abdominal pain?

This is an example of post-renal (obstructive) acute renal failure. The patient’s early symptoms are suggestive of a partial bladder outlet obstruction. His current symptoms suggest that the obstruction is essentially complete. The suprapubic tenderness and dullness to percussion are due to a distended bladder. These signs and symptoms in elderly men are most commonly caused by benign prostatic hyperplasia, but prostate cancer must also be considered.

How do the laboratory findings help to confirm the diagnosis?

The elevations in blood urea nitrogen (BUN) and creatinine levels indicate a significant reduction in glomerular filtration rate (GFR). This is due to the increased tubular hydrostatic pressure from the obstruction, which offsets glomerular capillary hydrostatic pressure. The BUN:creatinine ratio is increased because of decreased flow through the collecting duct, which causes enhanced urea reabsorption. The normal hemoglobin and hematocrit levels indicate that this is acute and not chronic renal failure, which almost always causes a hypoproliferative anemia.

How could this diagnosis be confirmed?

A catheter bypassing the obstruction may be placed in the bladder. This is sometimes difficult to do when the prostate is very enlarged. An ultrasound of the kidneys would show dilated renal collecting ducts and bilateral ureteral dilatation. A bladder scan would show a markedly enlarged bladder.

What is the most appropriate management for this patient?

Temporary relief may be achieved with a transurethral catheter, if possible. A suprapubic catheter should be considered if the prostate is too large to pass a catheter by. A transurethral prostatectomy is the definitive procedure. In addition, a work-up to distinguish benign from malignant prostatic disease should be conducted.

What are potential consequences of the treatment?

A postobstructive diuresis is typical after the relief of prolonged urinary tract obstruction. The magnitude of the diuresis can reach several liters per day. One mechanism for this is due to the elimination of sodium and water retained during the period of obstruction. Once the obstruction is removed, GFR increases and the excess sodium and water can be eliminated, which is a self-limiting process. Another mechanism is osmotic diuresis from retained urea, which is eliminated as GFR recovers.

By Kristen Vierregger, University of Pennsylvania School of Medicine, Class of 2008; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 13 – A 70-year-old man with narcotic overdose

A 70-year-old man with a history of chronic obstructive pulmonary disease (COPD), congestive heart failure (CHF), myasthenia gravis, and chronic back pain is recovering after a motor vehicle accident. The patient fractured both tibiae and multiple ribs, but remains without serious internal organ injury. His problem during this hospitalization has been pain control. He has recently been transitioned to oral oxycodone, but morphine injections are still being used for breakthrough pain. At the 4 a.m. vital sign check, the night nurse notes the patient is unarousable. He has a respiratory rate of 5/min and an oxygen saturation of 80% by pulse oximetry. His heart rate is 80/min and blood pressure is 130/80 mm Hg. He has pinpoint pupils, a normal cardiac examination, and clear lung fields. Arterial blood gas analysis shows a pH of 7.02, partial pressure of carbon dioxide of 90 mm Hg, partial pressure of oxygen of 45 mm Hg, and bicarbonate of 15 mEq/L. Administration of 100% oxygen via a non-rebreather mask raises the oxygen saturation to 95%. Review of the medication logs shows that the patient accidentally got two morphine boluses in addition to his maximum oxycodone dosage.

What is the most likely diagnosis?

Acute hypercarbic respiratory failure secondary to narcotic overdose. Opiates depress the central drive to breathe, first causing hypercarbia and then hypoxia. Some of the other causes suggested by the patient’s history include COPD or asthma exacerbation, flash pulmonary edema secondary to CHF, or respiratory muscle weakness due to myasthenia gravis. However, the clinical picture of decreased mental status, depressed respiratory rate, and overmedication suggest narcotic overdose.

How is the diagnosis approached?

The first step should be an arterial blood gas analysis. This will differentiate between hypercarbic or hypoxemic respiratory failure. Pure inhaled oxygen should also be administered. If this improves oxygenation, the pathology is due to ventilation/perfusion (V/Q) mismatch. If oxygenation does not improve, a shunt physiology is suggested.

How is the A-a gradient calculated and what is its significance?

The A-a gradient is the difference between alveolar and arterial oxygenation. It is calculated as:

[(PATM ? 47) × FIO2] ? [(PAO2 ? PACO2 / 0.8)]

A normal A-a gradient is 5-10 mm Hg. An increased gradient indicates a problem getting alveolar oxygen into the bloodstream. Hypoventilation alone results in hypoxemia with a normal A-a gradient.

What other conditions should be included in the differential diagnosis?

The differential list for acute respiratory failure is very broad and can be divided into two categories: hypercarbic and hypoxemic. Hypercarbia is caused by decreased ventilation, due to loss of central drive (secondary to toxins or brain stem injury) or respiratory muscle failure (due to myasthenia gravis, Guillain-Barré syndrome, or botulism). Hypoxemia that corrects with oxygen therapy can be due to V/Q mismatch, often due to intrinsic lung disease such as COPD, asthma, interstitial lung disease, or a pulmonary embolus. Hypoxemia due to shunt physiology can be the result of a true vascular or intracardiac shunt; severe alveolar filling as seen in pneumonia, pulmonary edema, or hemothorax; or alveolar collapse as seen in COPD or asthma.

What is the most appropriate management for this patient?

The underlying disease process must be addressed; in this case, naloxone should be given to reverse the effects of the narcotics. Oxygenation can be improved by increasing FIO2 and adding positive end-expiratory pressure in a mechanically ventilated patient. Hypercarbia is controlled by changing minute ventilation (increasing respiratory rate and/or tidal volume).

By Melissa Rosenstein, MD, Resident in Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco Medical Center; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 12 – A 35-year-old man with opioid withdrawal

A 35-year-old homeless man is admitted to the medical ward for treatment of an acute asthma exacerbation. He has a medical history significant for chronic severe asthma with multiple hospital admissions as well as tobacco use, heroin abuse, hypertension, and chronic, untreated tinea corporis infection. He is on his third day of supportive treatment with nebulized albuterol, metered-dose inhaled fluticasone, and an oral prednisone taper when he develops nausea, vomiting, and non-bloody diarrhea. He denies chest pain, palpitations, shortness of breath, dizziness, abdominal pain, fevers, or chills. His vital signs are within normal limits, and he has teary eyes with dilated pupils; he is yawning and sneezing intermittently.

What is the most likely diagnosis?

This constellation of signs and symptoms most likely represents opioid withdrawal. Pupillary dilation, lacrimation, rhinorrhea, yawning, piloerection, sneezing, nausea, vomiting, and diarrhea are the most common signs and symptoms of acute opioid withdrawal. Given his history of heroin use, it is likely that the patient was actively using heroin immediately prior to his hospitalization.

What is the epidemiology of this condition?

Approximately 2.4 million people have used heroin in the U.S., as reported in the 1998 National Household Survey on Drug Abuse. Heroin-related emergency department visits more than doubled between 1990 and 1996 to approximately 70,000, according to the U.S. Department of Health and Human Services.

What factors determine the severity and duration of this condition?

The time of onset, severity of symptoms, and duration of symptoms are directly related to the pharmacokinetics of the particular opioid involved. Of the most commonly abused opioids, heroin has an earlier, higher peak of severity (approximately 3 days of abstinence) compared with buprenorphine (4 days) and methadone (7-8 days), as well as a shorter overall duration of withdrawal symptoms.

What is the most appropriate management for this patient?

Methadone is the most widely accepted first-line treatment for opioid withdrawal, although the FDA restricts its use to the management of opioid addiction. A point scoring system of clinical signs can be used, in which a score of zero is given if a sign is absent, a score of one if it is present, and a score of two if it is severe. The signs to be scored include dilated pupils, runny nose, watery eyes, “goose” flesh, nausea or vomiting, diarrhea, yawning, cramps, restlessness, voiced complaints, and increased vital signs. The point total is equated with a total dosage of methadone to be given, in milligrams. The patient should be re-scored and re-dosed at 6-hour intervals. A 24-hour total should be calculated, and then after the patient has been stabilized, should be reduced by 10% per day. After the acute withdrawal period has ended, the patient should be referred to an outpatient opioid maintenance program (ie, a methadone clinic) or an abstinence-based program (eg, Narcotics Anonymous) to prevent further drug abuse and related physical, social, and legal morbidity.

By Brian Ash, MD, Resident in Anesthesia and Perioperative Care, University of California, San Francisco Medical Center; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.

Case 11 – A 45-year-old woman with disseminated disease

A 45-year-old woman from Cincinnati presents to her physician complaining of cough, dyspnea, fevers, and weight loss. She has been HIV positive for 20 years and has been using highly active antiretroviral therapy for the past decade. Although she continues to take her medications, this past year she lost her health insurance and has been unable to see her regular physician. Her temperature is 39°C (102.2°F), heart rate is 90/min, and respiratory rate is 20/min. Chest examination is notable for diffuse rales, while other physical examination findings include hepatosplenomegaly and lymphadenopathy. X-ray of the chest reveals reticulonodular infiltrates with a few calcified granulomas. Laboratory studies show:

CD4 count: 100/mm³
Hemoglobin: 10.0 g/dL
WBC count: 4000/mm³
Platelet count: 50,000/mm³

What is the most likely diagnosis?

Disseminated endemic fungal infection, likely histoplasmosis. The endemic fungi are soil-based fungi seen in particular geographic areas and include histoplasmosis and blastomycosis (Ohio and Mississippi River valleys), coccidioidomycosis (southwestern United States), and paracoccidioidomycosis (Latin America). In endemic areas, these fungi commonly cause asymptomatic infection in healthy patients. In patients with a large inoculum, an acute pulmonary infection is seen. Patients with underlying lung disease can develop chronic cavitary disease, which resembles tuberculosis. In immunocompromised patients, especially those with AIDS, disseminated disease can be life-threatening.

What is the differential diagnosis of this condition?

The differential diagnosis of a febrile wasting disease with lymphadenopathy in a patient with AIDS includes the Mycobacterium avium complex, lymphoma, or miliary tuberculosis. In acute pulmonary cases in patients without AIDS, the differential list also includes sarcoidosis, which can have a very similar clinical presentation.

What is the pathogenesis of this condition?

The endemic mycoses are dimorphic fungi that live in the soil. When the spores are aerosolized and inhaled, they revert to fungal forms and incite a T-cell response that usually clears the infection within 2 weeks. Immunocompromised patients can either develop disseminated disease immediately or as a reactivation of latent infection. Disseminated disease can demonstrate gastrointestinal involvement with ulcerations and polyp development, skin lesions, adrenal involvement, and central nervous system disease.

How is the diagnosis made?

Rapid antigen detection tests can identify the Histoplasma polysaccharide antigen in urine, blood, or bronchoalveolar lavage fluid. Direct visualization and culture of the fungus can be done with blood or tissue samples, although culture may take weeks.

What is the most appropriate management for this patient?

The current recommendation for disseminated histoplasmosis in patients with AIDS is liposomal amphotericin B, followed by itraconazole suppressive therapy for life. The majority of acute pulmonary histoplasmosis infections in immunocompetent patients do not require treatment.

By Melissa Rosenstein, MD, Resident in Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco Medical Center; in association with Le TT, Schabelman E, Shivaram A, and Klein J, eds: First Aid Cases for the USMLE Step 2 CK. New York: McGraw-Hill, 2007.