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.

 **Please note the date change from the 19th to the 20th**

Dr. Tao Le (series editor for the First Aid for the USMLE Step 1) invites you to a free Webinar this Thursday (Dec 20th) from 9-10pm EDT!

This high-yield talk will cover the basics of the USMLE Step 1 including an overview of the boards, goal setting, high-yield topics in each subject area, study strategies, review resources, and study schedules. There will be an opportunity for a live Q & A session at the end of the talk.

The way it works:

1. Register to hold your place now (space is limited).
2. Make sure that your computer meets the system requirements for the visual portion of the online conference (details below).
3. Be able to call the conference phone number to listen to Tao’s presentation. This can be done with a home phone, cell phone, or internet phone.
4. Mark your calendar for December 20th at 9:00pm EDT and come with questions!

---

Title: First Aid for the USMLE Step 1 by Dr. Tao LeDate: Thursday, December 20th, 2007
Time: 9:00 PM - 10:00 PM EDTSystem Requirements
Required: Windows® 2000, XP Home, XP Pro, 2003 Server, Vista OR
Required: Mac OS® X 10.3.9 (Panther®) or newerReserve your Webinar seat now at:
https://www.gotomeeting.comhttps://www1.gotomeeting.com/register/748595351

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.