The following cases and commentary, which address pulmonary medicine, are excerpted from ACP's Medical Knowledge Self-Assessment Program (MKSAP 15).
Case 1: Idiopathic pulmonary fibrosis
A 73-year-old woman is evaluated in the emergency department for a 2-week history of worsening dyspnea and a dry cough. She has not had fever or any recent travel.
Idiopathic pulmonary fibrosis was diagnosed 2 years ago by open lung biopsy. She also has a history of hypertension and gastroesophageal reflux disease. Her medications are prednisone, diltiazem, hydrochlorothiazide, and omeprazole.
On physical examination, she is afebrile; the blood pressure is 142/86 mm Hg, the pulse rate is 97/min, the respiration rate is 28/min, and the BMI is 27. Oxygen saturation with the patient breathing oxygen, 10 L/min by face mask, is 90%. There are dry crackles at the lung bases extending half way up the chest bilaterally. Cardiac and abdominal examinations are normal. Gram stain of sputum is negative; culture is pending. CT scan of the chest is negative for pulmonary embolism but shows new areas of alveolar infiltrates and consolidation superimposed on previous basilar, reticular, and honeycomb changes.
Which of the following is the most appropriate next test in the evaluation of this patient?
A. Bronchoscopy with bronchoalveolar lavage
B. Fungal serologies
C. Right-heart catheterization
D. Swallowing evaluation
Case 2: Ventilator weaning
A 30-year-old man is evaluated for difficulty weaning from the ventilator. The patient was intubated 7 days ago for a severe exacerbation of asthma. Despite receiving a high-dose inhaled β-agonist; methylprednisolone, 60 mg/d; and aggressive sedation, he had persistent severe auto-positive end-expiratory pressure with elevated ventilator pressures. Therefore, a continuous infusion of vecuronium, a paralytic agent, was started and continued for 24 hours until his respiratory mechanics improved. Today, he underwent a ventilator weaning trial but became tachycardic and diaphoretic with a rapid shallow breathing index of 120.
On physical examination, the patient is alert and responsive; vital signs are normal. There is minimal expiratory wheezing and otherwise normal vesicular breath sounds. He has flaccid weakness involving all extremities, including decreased bilateral hand grip strength. There is no rash. Routine laboratory studies reveal normal liver enzyme tests and renal function.
Which of the following is the most likely cause for the patient's difficulty weaning from the ventilator?
A. Acute inflammatory demyelinating polyneuropathy (Guillain- Barré syndrome)
B. Churg-Strauss syndrome
C. Intensive care unit–acquired weakness
D. Prolonged neuromuscular blockade
Case 3: Chest pain with recent surgery
A 54-year-old man is evaluated in the emergency department for a 1-hour history of chest pain with mild dyspnea. The patient had been hospitalized 1 week ago for a colectomy for colon cancer. His medical history also includes hypertension and nephrotic syndrome secondary to membranous glomerulonephritis, and his medications are furosemide, ramipril and pravastatin.
On physical examination the temperature is 37.5°C (100°F), the pulse rate is 120/min, the respiration rate is 24/min, the blood pressure is 110/60 mm Hg, and the BMI is 30. Oxygen saturation is 89% with the patient breathing ambient air and 97% on oxygen, 4 L/min. Cardiac examination shows tachycardia and an S4. Breath sounds are normal. Chest radiograph is negative for infiltrates, widened mediastinum, and pneumothorax. Serum creatinine concentration is 2.1 mg/dL (185.6 µmol/L). Empiric unfractionated heparin therapy is begun.
Which of the following is the best test to confirm the diagnosis in this patient?
A. Assay for plasma D-dimer
B. CT angiography
C. Lower extremity ultrasonography
D. Measurement of antithrombin III
E. Ventilation/perfusion scan
Case 4: Asthma exacerbation
A 28-year-old man is evaluated in the emergency department for a 2-day history of worsening dyspnea and wheezing in conjunction with an upper respiratory tract infection. The patient has a history of asthma, and his medications are inhaled mometasone and albuterol. In the emergency department, the patient is anxious and is using accessory muscles to breathe; he cannot speak in full sentences. The oxygen saturation is 90% while he is breathing ambient air. Breath sounds are reduced bilaterally, with faint diffuse expiratory wheezes. He is given albuterol by nebulizer, and use of accessory muscles is reduced. Bedside spirometry shows an FEV1 of 35% of predicted; he is given two more treatments of nebulized albuterol.
After treatment, the patient is alert with slight use of accessory muscles; he can speak in short full sentences. Vital signs are stable; oxygen saturation is 98% with the patient receiving oxygen, 2 L/min. Breath sounds are louder than on initial examination, and wheezing is more intense. Spirometry shows an FEV1 of 50% of predicted.
Which of the following is the most appropriate next step in the management of this patient?
A. Admit the patient to a regular medicine ward
B. Discharge the patient on his baseline asthma treatment regimen
C. Intubate and admit the patient to the intensive care unit
D. Monitor the patient in the intensive care unit
Case 5: Post-partum complications
A 35-year-old woman is evaluated in the hospital for chest pain and dyspnea 1 day after vaginal delivery of her second child. She had an uncomplicated pregnancy but a prolonged labor.
On physical examination, the temperature is 37.0°C (98.6°F), the blood pressure is 100/60 mm Hg, the pulse rate is 115/min, and the respiration rate is 22/min. The lungs are clear, heart sounds are normal, and there is no evidence of bleeding on pelvic examination. Complete blood count on admission revealed a hematocrit of 34% and a platelet count of 150,000/µL (150 × 109/L). Chest radiograph is normal. Ventilation/perfusion scan shows mismatched perfusion defects in 20% of her lung volume.
Which of the following would be an acceptable therapy for this patient?
A. Inferior vena cava filter
B. Intravenous argatroban
C. Intravenous low-molecular-weight heparin
D. Subcutaneous unfractionated heparin
Case 6: Dyspnea after femur fracture
A 42-year-old man is evaluated in the hospital for dyspnea and pleuritic chest pain. The patient had a fracture of the right femur 3 weeks ago. He has hypertension, and his only medication is hydrochlorothiazide.
On physical examination, the temperature is 38.1°C (100.6°F), the pulse rate is 110/min, the respiration rate is 22/min, the blood pressure is 130/78 mm Hg, and the BMI is 24. Routine laboratory studies are normal; serum troponins are undetectable. Electrocardiography shows increased height of R waves in leads V4-V6; the QRS complex has a leftward axis. Contrast-enhanced CT scan shows pulmonary emboli in the arteries perfusing the lingula and the posterior basal segment of the left lower lobe.
Which of the following is the most appropriate treatment for this patient?
A. Inferior vena cava filter
B. Intravenous unfractionated heparin
C. Intravenous tissue plasminogen activator
D. Mechanical clot dissolution
E. Surgical embolectomy
Answers and commentary
Correct answer: A. Bronchoscopy with bronchoalveolar lavage.
The two immediate diagnostic considerations in this patient are respiratory infection and an acute exacerbation of pulmonary fibrosis. Both diagnostic possibilities may be evaluated by bronchoalveolar lavage with studies to detect bacterial organisms, opportunistic pathogens (for example, Pneumocystis jirovecii), and viral pathogens.
Routine sputum evaluation for Gram stain and culture is not sensitive enough to detect opportunistic infectious organisms. Diagnostic criteria for an acute exacerbation of pulmonary fibrosis include exclusion of opportunistic respiratory infections via endotracheal aspiration or bronchoalveolar lavage as well as exclusion of pulmonary embolism, left ventricular failure, and other causes of acute lung injury. The incidence of an acute exacerbation of idiopathic pulmonary fibrosis is not certain but likely ranges between 5% and 40%. In patients with pulmonary fibrosis admitted to the intensive care unit for respiratory failure, the incidence may be as high as 60% with a reported mortality rate between 80% and 100%. No therapy has been shown to be beneficial.
Fungal serologies may be helpful to diagnose opportunistic infection in this patient. However, bronchoalveolar lavage is more sensitive, and results more readily available for detecting other opportunistic pathogens that need to be excluded in this immunosuppressed patient. Right-heart catheterization is not part of the initial evaluation of patients with a suspected acute exacerbation of idiopathic pulmonary fibrosis. Aspiration may cause acute lung injury and may trigger an acute exacerbation of idiopathic pulmonary fibrosis, but swallowing evaluation is unlikely to be diagnostic in this patient with no history of aspiration.
- Bronchoalveolar lavage is the diagnostic procedure to exclude opportunistic infection in an apparent acute exacerbation of idiopathic pulmonary fibrosis.
Correct answer: C. Intensive care unit-acquired weakness.
Patients with intensive care unit (ICU)-acquired weakness have diffuse weakness and decreased muscle tone. The disorder may be first recognized in patients with unexplained difficulty weaning from the ventilator. ICU-acquired weakness is a term used to encompass critical-illness poly-neuropathy and critical-illness myopathy. Treatment with paralytic agents and systemic corticosteroids, as well as sepsis and immobilization, increase the risk of developing ICU-acquired weakness. Treatment is supportive, including discontinuation or reduction of corticosteroids, aggressive management of existing disorders, and physical rehabilitation.
Acute inflammatory demyelinating polyneuropathy (Guillain-Barré syndrome) can also cause diffuse weakness, but in contrast to this patient, weakness is the presenting symptom. Furthermore, weakness associated with acute inflammatory demyelinating polyneuropathy typically develops gradually over a longer time course (1 to 2 weeks) and typically is preceded by an infection.
Prolonged neuromuscular blockade is a condition in which the effect of paralytic agents, such as vecuronium, can persist for days after discontinuing the medication. However, this is rarely encountered and is caused by altered drug metabolism due to liver and/or renal dysfunction, neither of which this patient has.
Churg-Strauss syndrome is associated with asthma and, in the vasculitic stage, can cause weakness. However, the syndrome most often manifests as mononeuritis multiplex rather than generalized weakness. Furthermore, this patient does not have other manifestations of vasculitis such as rash or renal dysfunction.
- Patients with intensive care unit a>acquired weakness have diffuse, flaccid weakness and often present with difficulty with ventilator weaning.
Correct answer: E. Ventilation/perfusion scan.
This patient is at high risk for pulmonary embolism because of his recent hospitalization, cancer, and nephrotic syndrome. A positive ventilation/perfusion scan would confirm the diagnosis of pulmonary embolism in this patient with a high pretest probability for the condition, especially in the absence of parenchymal lung defects on chest radiograph.
The probability of pulmonary embolism was very high based on this presentation that included chest pain, dyspnea, recent hospitalization and surgery, active cancer, and a protein-losing nephropathy. A negative D-dimer test would not be sufficient evidence to rule out a pulmonary embolism under these circumstances, and a high D-dimer level would add little to the diagnostic work-up. Decreased antithrombin III levels may result from nephrotic syndrome, and levels are lowered during acute thrombosis, especially during treatment with heparin. Therefore, measuring antithrombin III would add little to the accuracy of the diagnosis of pulmonary embolism or have any implication for immediate management decisions. Lower extremity ultrasonography can disclose asymptomatic deep venous thrombosis in a small percentage of patients presenting with symptoms of pulmonary embolism. However, the yield is relatively low and ventilation/perfusion scanning would have a much higher degree of accuracy. CT angiography is an acceptable modality to diagnose acute pulmonary embolism but requires a significant amount of contrast infusion (as much as a pulmonary angiogram) which would be contraindicated in a patient with an elevated serum creatinine level.
- Either ventilation/perfusion scanning or contrast-enhanced CT scanning (if not contraindicated) performed with a specific protocol to detect pulmonary embolism is an appropriate noninvasive test to diagnose acute pulmonary embolism.
Correct answer: A. Admit the patient to a regular medicine ward.
This patient presented with signs of a severe asthma exacerbation. Decreased breath sounds, accessory muscle use, sternocleidomastoid or suprasternal retractions, inability to speak in full sentences, and paradoxical pulse greater than 15 mm Hg are associated with severe airflow obstruction, although the absence of these findings does not necessarily exclude the presence of a high-risk exacerbation. However, the initial physical examination and findings are less predictive of the clinical course in a patient with asthma than the response to bronchodilators. This patient has responded well to bronchodilators, with improved ability to speak and reduced accessory muscle use.
Wheezing may become more prominent in the early stages of recovery owing to improved airflow through narrowed airways. According to the newest National Asthma Education and Prevention Program's guidelines, admission to the intensive care unit is recommended for symptomatic patients with even mild carbon dioxide retention (PCO2 greater than 42 mm Hg) or severely decreased lung function despite aggressive bronchodilator treatment (persistent FEV1 or peak expiratory flow less than 40% of predicted). This patient does not meet the criteria for admission to the intensive care unit or intubation and mechanical ventilation at this time. The best disposition for this patient would be admission to the hospital ward; his FEV1 has not improved enough to warrant discharge.
- The response to inhaled bronchodilators is more predictive of the clinical course in a patient with asthma than initial physical examination and findings.
Correct answer: D. Subcutaneous unfractionated heparin.
This patient has had an acute pulmonary embolism one day post partum. The patient has no evidence of active bleeding, and there is no increased risk for bleeding from anticoagulation. Subcutaneous administration of unfractionated heparin, low-molecular-weight heparins, and fondaparinux are all safe and effective for the treatment of acute pulmonary embolism. A recent clinical trial showed that high-dose subcutaneous unfractionated heparin, administered without dose adjustment guided by the activated partial thromboplastin time, was as safe and effective as low-molecular-weight heparin administered in the same fashion.
Intravenous argatroban, a direct thrombin inhibitor, might be useful in the setting of heparin-induced thrombocytopenia. However, the patient's platelet count is normal. Monitoring of the platelet count would be appropriate after initiating either unfractionated or low-molecular-weight heparin, but the patient's current platelet count is not a contraindication for either drug; therefore, there is no indication to begin treatment with argatroban. Neither low-molecular-weight heparins nor fondaparinux has been evaluated in large clinical trials for intravenous use. Therefore, although it may be theoretically possible to use these agents intravenously, appropriate dosing and monitoring guidelines have not been validated. There are four generally accepted indications for placement of an inferior vena cava filter: (1) absolute contraindication to anticoagulation (for example, active bleeding); (2) recurrent pulmonary embolism despite adequate anticoagulation therapy; (3) bleeding complication of anticoagulation therapy; and (4) hemodynamic or respiratory compromise severe enough that a subsequent pulmonary embolism might be lethal. This patient has no indication for an inferior vena cava filter.
- Acute pulmonary embolism can be treated initially with subcutaneous unfractionated heparin, low-molecular-weight heparins, or fondaparinux without the need for dosage adjustment.
Correct answer: B. Intravenous unfractionated heparin.
The patient has an acute pulmonary embolism. In the absence of contraindications, the patient should be treated initially with intravenous or subcutaneous unfractionated heparin, low-molecular-weight heparin, or fondaparinux. Electrocardiographic abnormalities are present in 70% of patients with pulmonary embolism. Most common abnormalities are ST segment and T wave changes (49%). Cor pulmonale, right axis deviation, right bundle branch block, and right ventricular hypertrophy occur less frequently. T wave inversions in precordial leads may indicate more severe right ventricular dysfunction. This patient's electrocardiographic findings support the diagnosis of left ventricular hypertrophy/strain, most likely because of his essential hypertension.
Patients with hemodynamically unstable pulmonary embolism have a high mortality rate. The role of thrombolytic agents in pulmonary embolism is unclear. There are no clinical trials comparing thrombolytic agents with other forms of therapy for massive pulmonary embolism, and management decisions must therefore be made by inference from studies in stable patients. The Urokinase in Pulmonary Embolism Trial reported a short-term improvement in cardiac output and pulmonary pressure with thrombolytic therapy but no improvement in morbidity or mortality and increased bleeding.
Acute pulmonary embolectomy is rarely warranted because medical therapy is successful, patient selection difficult, and the results of acute embolectomy unimpressive. However, if experienced surgical intervention is possible, embolectomy may be considered for a confirmed, massive embolism that fails to respond promptly to medical therapy. Mechanical clot dissolution has been performed in a small number of patients in cardiogenic shock secondary to massive pulmonary embolism. The mortality rate is high, and this intervention is not readily available in most institutions.
Placement of an inferior vena cava filter might be considered in a patient with a contraindication to anticoagulation, the onset of clinically important bleeding during anticoagulation, recurrent pulmonary embolism despite adequate anticoagulation, or in hemodynamically unstable patients.
- Unfractionated heparin, low-molecular-weight heparin, or fondaparinux is generally sufficient initial therapy for acute pulmonary embolism.