Questions, Board Review

Board Review Questions: June 2019

PEER (Physician’s Evaluation and Educational Review in Emergency Medicine) is ACEP’s gold standard in self-assessment and educational review. These questions are from PEER, updated continually on its digital platform. Order PEER to prepare!

1. A 54-year-old farm worker presents with low back pain of 3 weeks’ duration that radiates down his right leg. An examination reveals decreased sensation on the lateral side of the right lower leg, dorsum of the right foot, and the lateral edge of the right foot. The right patellar reflex is normal, but the right ankle reflex is absent. A motor examination is mostly normal, except that he has trouble standing on his toes. Reflexes in the left leg are normal; he denies urinary or fecal incontinence. If an MRI of the spine were obtained, what would it show?
A. Broad-based disc bulge compressing the cauda equina
B. Herniated disc between L5 and S1
C. Lytic lesion causing cord compression between L2 and L3
D. Spinal stenosis with narrowing at L3

2. A 57-year-old man presents with fever and chills. He had a left ventricular assist device implanted 5 weeks earlier as a bridge therapy for cardiac transplantation; he has a history of severe ischemic cardiomyopathy. No obvious source of infection is noted on examination. Which component of the assist device is the most likely source of the infection?
A. Cannula
B. Driveline
C. Incision site
D. Pump pocket

3. A 24-year-old woman who is 22 weeks pregnant presents with a 1-day history of shortness of breath on exertion and an occasional nonproductive cough. She also has had mild bilateral lower leg swelling for 3 weeks. She denies fever, previous illness, orthopnea, and chest pain as well as contact with sick persons, recent travel, and surgical procedures. Vital signs are BP 131/77, P 105, R 18, and T 37°C (98.6°F); SpO2 is 98% on room air. Laboratory tests reveal a slight leukocytosis and a D-dimer of 600 ng/mL; all other findings are normal. Which of the following diagnostic studies should be ordered initially?
A. Bilateral DVT ultrasound
B. CT angiogram of the chest
C. Echocardiogram
D. MRI of the chest

4. Which of the following agents has clinical manifestations of acute toxicity most similar to those of tetanus?
A. Arsenic
B. Cyanide
C. Ricin
D. Strychnine

5. A 26-year-old man presents by ambulance after being stabbed in the neck. Paramedics established large-bore intravenous access in the patient’s right upper extremity in the field, and fluids are infusing. Vital signs include BP 118/72, P 115, and R 24; SpO2 is 99% on 6 L oxygen via nasal cannula. On examination, the patient is awake and alert. The wound is on his left anterior neck between the cricoid cartilage and the angle of the mandible. There is active bleeding from the site and an underlying expanding hematoma. The patient says his throat is tight and that he cannot swallow, and his girlfriend says his voice sounds strange. In addition to applying direct pressure to the wound, what is the best next step in management?
A. Order angiography
B. Order CT of the neck with intravenous contrast
C. Perform cricothyrotomy
D. Perform endotracheal intubation

Answers: 1. B; 2. B; 3. A; 4. D; 5. D

1. The correct answer is B, Herniated disc between L5 and S1.
Why is this the correct answer?
This patient has developed a herniated lumbar disc causing radiculopathy. Based on the physical examination, the affected spinal levels must be L5 and S1, so a disc herniation in this region explains the findings. Most patients with herniated spinal discs recover with medical and physical therapy; operative repair should be avoided. Two elements of the examination contribute to pinpointing the spinal level of the pathology: deep tendon reflexes and skin dermatomes. Deep tendon reflexes correspond to certain spinal levels; the biceps reflex is mediated by C5-C6, the patella reflex by L2-L4, and the ankle jerk by L5-S1. Spinal levels can also be identified by loss of sensation along dermatomes. In the case of this patient, the L5 dermatome runs along the lateral side of the leg and wraps around to include the toes. The S1 dermatome runs mostly along the back of the leg and wraps into the plantar surface of the foot. Because spinal nerves emerge from the vertebral column and extend inferiorly, herniating spinal discs press on the spinal levels above the level of origin (for example, an L5 herniated disc presses on spinal nerves from L4). Not every patient with back pain should be subjected to imaging, but it is indicated in certain situations. Red flags from the history that indicate the need for imaging include fever, weight loss, incontinence, elderly, intravenous drug use, and a history of cancer or aneurysm. When a neurosurgical emergency is suspected (cauda equina syndrome or spinal cord compression), the MRI is the imaging modality of choice.

Why are the other choices wrong?

  • A large broad-based disc or mass pressing on the terminal fibers of the spinal cord (the cauda equina) causes cauda equina syndrome: a loss of sensation in sacral dermatomes between the legs and in the perineum (saddle anesthesia) and a loss of bowel or bladder continence. This patient has localized, distal neurologic abnormalities and no bowel or bladder symptoms.
  • A lytic lesion, suggesting a neoplasm, is a possible cause of this patient’s back pain, but a lesion compressing the L2 nerve root would lead to a decreased patella reflex and anesthesia along the thigh into the medial leg. This patient’s examination points to a lesion at the L5-S1 level.
  • A lesion compressing the L2 nerve root would lead to a decreased patellar reflex and anesthesia along the thigh into the medial leg. This patient’s examination points to a lesion at the L5-S1 level.

REFERENCES
Adams JG, Barton ED, Collings JL, et al, eds. Emergency Medicine: Clinical Essentials. 2nd ed. Philadelphia, PA: Elsevier; 2013:645-660.e1.

Marx JA, Hockberger RS, Walls RM, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 8th ed. St. Louis, MO: Elsevier; 2014:278-284.e1.

2. The correct answer is B, Driveline.
Why is this the correct answer?
Infection is a common adverse event following placement of a left ventricular assist device (LVAD), occurring in approximately 40% of patients. Infection most often occurs between 2 weeks and 2 months after implantation. The various sites of LVAD-related infection include the incision site, pump pocket, driveline, and the various cannulas. The driveline is the most common site of infection. This line exits the chest wall protected by a skin seal and is thus most susceptible to infection. Empiric antibiotic therapy should cover both staphylococcal species as well as various gram-negative organisms, including Pseudomonas.

Why are the other choices wrong?

  • The various cannulas of the LVAD circuit can be involved in the infectious process, but they are not the most common site of infection.
  • The site of the incision is also susceptible to infection, but it is not the most common site of infection following LVAD placement.
  • The pump pocket is the second most common area of infection. The driveline goes into the pump, which is contained within a pocket in the chest wall.

REFERENCES
Birks EJ, Tansley PD, Hardy J, et al. Left ventricular assist device and drug therapy for the reversal of heart failure. N Engl J Med. 2006;355(18):1873-1884.

Kovala CE, Rakitab R; AST Infectious Diseases Community of Practice. Ventricular assist device related infections and solid organ transplantation. Am J Transplant. 2013;13 Suppl 4:348-354.

Rose EA, Gelijns AC, Moskowitz AJ, et al. Long-term use of a left ventricular assist device for end-stage heart failure. N Engl J Med. 2001;345(20):1435-1443.

3. The correct answer is A, Bilateral DVT ultrasound.
Why is this the correct answer?
The differential diagnosis for shortness of breath in a pregnant patient is wide, but in this case, PE is the most likely underlying disorder. Compressive ultrasonography has been found to have a sensitivity of 97% and a specificity of 94% for the diagnosis of symptomatic proximal DVT in the general population. The test has no radiation exposure and no known risks to the mother or fetus. It is reasonable to start with a bilateral lower-extremity ultrasound examination and, if this test is positive, to treat for venous thromboembolism. If the ultrasound is negative, however, further testing is warranted for the evaluation of a suspected PE. Negative DVT ultrasonography with a positive D-dimer warrants a follow-up ultrasound examination and D-dimer in the following week if the primary concern is for DVT, but further testing for PE is warranted with a negative ultrasound examination and a high suspicion for PE. Chest xrays are often normal in PE, but unilateral basilar atelectasis, pleural-based wedge-shaped area of infiltrate (Hampton hump), or unilateral oligemia (Westermark sign) is suggestive. Chest xray often shows an alternative diagnosis.

Why are the other choices wrong?

  • Using CT pulmonary angiography exposes patients to the maximum amount of radiation, and in the case of a pregnant woman, this is not the right choice. It confers an increase in breast cancer risk over 1% and causes exposure to the fetus with amounts that increase with gestational age. If the DVT ultrasound is negative and there is still concern for PE, CT pulmonary angiography can be used, but V/Q scanning is also appropriate.
  • Point-of-care ultrasonography is indicated to evaluate cardiac functioning, and it can reveal elevated right heart pressures. Formal imaging using echocardiography, however, is best to assess for the right heart strain of a large PE. In the majority of cases, including this case, with no signs of obstructive shock or heart strain, there are no significant findings, and thus the study is unwarranted.
  • Magnetic resonance imaging is both sensitive and specific for many patients and is safer for pregnant patients. However, results are inconclusive in 30% of patients, so it has not become an accepted study in the assessment of PE.

REFERENCES
Marx JA, Hockberger RS, Walls RM, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 8th ed. St. Louis, MO: Elsevier; 2014:1157-1169.

Revel MP, Sanchez O, Couchon S, et al. Diagnostic accuracy of magnetic resonance imaging for an acute pulmonary embolism: results of the ‘IRM-EP’ study. J Thromb Haemost. 2012;10(5):743-750.

Tintinalli JE, Stapczynski JS, Ma OJ, et al, eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 8th ed. New York, NY: McGraw-Hill; 2012:1496-1500.

4. The correct answer is D, Strychnine.
Why is this the correct answer?
The clinical manifestations of poisoning with strychnine are very similar to those seen with tetanus. Strychnine antagonizes glycine receptors, one of the major inhibitory neurotransmitters in the spinal cord; tetanus toxin (tetanospasmin) prevents the release of presynaptic glycine. In both situations, because the transmission of glycine is disrupted, recurrent, episodic involuntary muscular contractions occur, often in response to minimal stimuli. Strength differences in regional muscle groups account for why classic findings of opisthotonos (spine and extremities bent forward, body resting on head and heels) and risus sardonicus (sustained facial muscle spasm that appears to produce grinning) can occur. The development of respiratory compromise can be life-threatening, as can hyperthermia, rhabdomyolysis, and severe acidemia that result from excessive muscular contractions. Although the muscular contractions can appear to be convulsions, in strychnine poisoning the sensorium is unaffected. Strychnine poisoning typically has a more rapid onset and shorter duration than tetanus. Supportive care, including benzodiazepines and/or barbiturates to raise the stimulus threshold to initiate muscular contractions, airway control, cooling, and hydration are the mainstays of treatment.

Why are the other choices wrong?

  • Recurrent, episodic involuntary muscular contractions, often in response to minimal stimuli as seen in strychnine poisoning and tetanus, are not a feature of arsenic poisoning. Acute ingestions of arsenic cause profound vomiting and diarrhea. Hypotension can result from large fluid losses, and cardiac dysfunction can occur from direct toxicity.
  • Recurrent, episodic involuntary muscular contractions also are not a feature of cyanide poisoning. By inhibition of oxidative phosphorylation in cyanide poisoning, cells are unable to use oxygen. Acute cyanide poisoning is characterized by the rapid onset of coma, apnea, metabolic acidosis, and often hypotension.
  • Ricin is a toxin derived from the castor bean that disrupts protein synthesis. Ricin poisoning is characterized by initial GI symptoms of vomiting and diarrhea that can be followed by multisystem organ failure, not by recurrent, episodic involuntary muscular contractions.

REFERENCES
Hoffman RS, Howland MA, Lewin NA, et al, eds. Goldfrank’s Toxicologic Emergencies. 10th ed. New York, NY: McGraw-Hill; 2015:1456-1457, 1528. 

Wolfson AB, Hendey GW, Ling LJ, et al, eds. Harwood-Nuss’ Clinical Practice of Emergency Medicine. 6th ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2014:320e-321e.

5. The correct answer is D, Perform endotracheal intubation.
Why is this the correct answer?
This patient has sustained a Zone II neck injury. He is demonstrating signs of impending airway obstruction with an expanding anterior neck hematoma, dysphagia, and dysphonia. The primary focus in the care of this patient and any other patient presenting following a traumatic injury should be the ABCs. This particular patient should be intubated right away: He is at risk for rapid deterioration and respiratory failure. Indications for establishing a definitive airway in the setting of penetrating neck trauma include respiratory distress, altered mental status, bloody secretions in the oropharynx, subcutaneous emphysema, expanding hematoma, and tracheal shift. Other signs of potential airway compromise include dysphagia and dysphonia. Orotracheal intubation is preferred in a penetrating neck injury, but backup airway techniques should be available. If quickly available, awake fiberoptic intubation may be considered.

Why are the other choices wrong?

  • The patient’s presentation is critical. As soon as the airway is established, he should be transported immediately to the OR. Performing angiography would inappropriately delay management. All symptomatic patients with penetrating injuries to Zone II require surgical exploration.
  • Again, sending the patient for a CT scan would delay appropriate management. Additionally, CT is more appropriate in the evaluation of blunt trauma.
  • Cricothyrotomy should be avoided when an anterior neck hematoma is present. If the patient were more stable on arrival, intubation could be delayed until the patient reached the OR.

REFERENCES
Tintinalli JE, Stapczynski JS, Ma OJ, et al, eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide. 8th ed. New York, NY: McGraw-Hill; 2012:1733-1740.

Wolfson AB, Hendey GW, Ling LJ, et al, eds. Harwood-Nuss’ Clinical Practice of Emergency Medicine. 6th ed. Philadelphia, PA: Lippincott, Williams & Wilkins; 2014:183-188.

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