Answer: (B) Pericardial tamponade

In pericardial tamponade, the pericardium fills with fluid, often blood. Once the pericardium is maximally stretched, the building pressure compresses the heart itself, decreasing diastolic compliance and thus compromising venous return. This results in hypotension and also distention of neck veins from the elevated central venous pressure.

In penetrating trauma, cardiac injury should be suspected when any penetrating injury occurs in “the box,” a rectangle bordered superiorly by the clavicles, inferiorly by the costal margins, and laterally by the midclavicular line. However, while cardiac injury must be suspected, patients who are hypotensive and short of breath with penetrating thoracic trauma can also have other injuries. In this case, while the dyspnea is consistent with pneumothorax and pulmonary contusion, the bulging neck veins are not associated with either entity. Moreover, patients with a tension pneumothorax are likely to have tracheal deviation, and pulmonary contusions are more commonly associated with blunt trauma. While both tracheobronchial injury and esophageal injury are possible, they are less likely, given the clinical presentation.

Answer: (E) Synchronized cardioversion

New onset atrial fibrillation is a common complication after surgery, particularly following cardiothoracic surgery. After abdominal surgery, atrial fibrillation generally occurs on postoperative days 2 to 5 when the patient is no longer requiring fluid resuscitation and is beginning to mobilize extravascular fluid. This fluid mobilization results in atrial distention, which can result in atrial fibrillation.

Atrial fibrillation classically results in an irregularly irregular rhythm. Hemodynamic stability is dependent on the ventricular response. Patients with rapid ventricular response can achieve elevated heart rates resulting in hemodynamic instability.

In patients with new onset atrial fibrillation who are hemodynamically unstable and manifesting signs of organ hypoperfusion, as in this vignette, urgent synchronized cardioversion is indicated. While there are many antiarrhythmic drugs than can cause chemical cardioversion, electrical cardioversion is most prudent in hemodynamically unstable patients.

In hemodynamically stable patients, initial treatment with antiarrhythmics is indicated. In the acute setting, simply rate control will lead to conversion to sinus rhythm in close to 50% of cases. However, rate control without conversion to sinus rhythm may require long-term anticoagulation in selected patients. Therefore, in patients with new onset atrial fibrillation, early elective cardioversion to obviate the need for any anticoagulation is reasonable. If the duration of atrial fibrillation exceeds 48 hours (or is unknown), an atrial thrombus needs to be ruled out with echocardiography before cardioversion to minimize the risk of embolization.

Amiodarone is a newer and effective drug for chemical cardioversion. Metoprolol does not facilitate cardioversion but can be effective for rate control. However, it is also likely to lower blood pressure. Atropine will increase the heart rate and is inappropriate. A fluid bolus may temporarily help with
blood pressure, but fluid overload is also a likely cause of this patient’s atrial fibrillation. After cardioversion and stabilization, diuresis is likely indicated.

Answer: (A) Epidural anesthesia

Rib fractures are common following blunt traumatic injury to the chest. The severity of injury is proportional to the number of ribs fractured. The presence of three or more fractured ribs is associated with a higher incidence of underlying solid organ injuries and should prompt referral to a dedicated trauma center for evaluation and management. The finding of rib fractures should alert the clinician to the possibility of pneumothorax, hemothorax, and pulmonary contusion, and consideration must be given to admission of these patients for observation, pain control, and aggressive pulmonary toilet.

Even in the absence of underlying injuries, patients with rib fractures are at increased risk for development of atelectasis, pneumonia, and even respiratory failure due to splinting from pain and poor respiratory effort. Avoidance of the development of respiratory failure and intubation decreases the risk of pneumonia in these patients. The use of binders or taping of the chest for comfort interferes with proper pulmonary toilet by limiting chest excursion during inspiration and should be avoided.

Inadequate analgesia among patients with rib fractures is associated with hypoventilation, atelectasis, decreased clearance of secretions, and respiratory failure. Methods for pain management include oral and intravenous opioids, nonsteroidal anti-inflammatory agents, local therapy (intercostal nerve blockade, pleural blockade), and epidural-based therapies. The specific regimen is determined by the clinical scenario and patient response to a trial of pain management therapy.

The only method that has been demonstrated to have an impact on clinical outcomes following rib fractures is epidural anesthesia, typically delivered as a synergistic combination of opioids and local anesthetics. This method of pain relief is associated with improved pulmonary mechanics (increased
vital capacity and negative inspiratory force), increased oxygenation as measured by partial pressure of oxygen (PaO₂), and improved ventilation as measured by decreased partial pressure of carbon dioxide (PaCO₂). In addition, epidural use leads to decreased ventilator dependence and decreased rates of nosocomial pneumonia.

Answer: (A) Aortic valve replacement (AVR)

The timing of aortic valve intervention is largely determined by two factors: The severity of the stenosis and the presence or absence of symptoms. Aortic stenosis is graded as follows.

Patients with severe aortic stenosis and symptoms (classically angina, syncope, or dyspnea) should undergo AVR. Asymptomatic patients with severe aortic stenosis can be followed closely unless they develop symptoms during exercise testing, have an ejection fraction <50%, have severe valvular calcification, have rapid progression of their stenosis, or are undergoing another cardiac operation.

There is no indication for medical management alone in patients with severe aortic stenosis who are healthy enough to undergo surgery. Percutaneous balloon valvotomy might be reasonable as a bridge to AVR in a hemodynamically unstable patient or in a patient with severe comorbidities and prohibitively high surgical risk. Neither is the case in this vignette, however. Transcatheter AVR is currently indicated in the United States only for clinical trials in patients at very high surgical risk. Traditional open AVR remains the standard of care. There is no indication for orthotopic heart transplantation in this patient.

Answer: (E) Increases by 30% to 50%

During pregnancy, women experience an expansion of plasma volume and a concomitant but less substantial increase in red cell volume resulting in a modest hematocrit reduction. Total plasma volume increases by 1.1 to 1.6 L resulting in a total plasma volume of 4.7 to 5.2 L by 34 weeks of gestation. Concomitantly, red blood cell mass increases by 15% to 30%. The resulting physiologic anemia results in decreased blood viscosity, which aids in placental perfusion and lower cardiac work. The increased plasma volume also provides some reserve against peripartum blood loss and increases cardiac output to aid in placental perfusion.

Answer: (A) Alveolar hypoventilation results in an increase in the partial pressure of carbon dioxide and hypercapnia

Alveolar ventilation is defined as the gas exchange between the external environment and the alveoli and is a process which allows oxygen in the air to be delivered to the lungs during inspiration and carbon dioxide from the systemic circulation to be eliminated during expiration. There is no method for direct measurement of alveolar ventilation; rather it must be determined by measuring the tidal volume, respiratory rate, and the anatomic dead space.

There is a direct relationship between the partial pressure of oxygen and alveolar ventilation such that increases in alveolar ventilation will cause an increase in the partial pressure of oxygen, but this will eventually reach a plateau as the oxygen-carrying capacity of the blood is maximized. There is an inverse relationship between alveolar ventilation and the partial pressure of carbon dioxide in the blood. As ventilation increases, the partial pressure of carbon dioxide will decrease.

Alveolar hypoventilation exists when there is inadequate ventilation for the normal removal of carbon dioxide from the systemic circulation, leading to an increase in the partial pressure of carbon dioxide and hypercapnia. Eventually, this hypoventilation can also lead to a decreased partial pressure of oxygen and hypoxemia.

Alveolar hypoventilation can be acute or chronic and congenital or acquired. Congenital causes include congenital
central hypoventilation syndrome (CCHS) or Ondine’s curse. Acquired causes include obesity hypoventilation syndrome (OHS), chronic obstructive pulmonary disease (COPD), neuromuscular disorders (myasthenia gravis, amyotrophic lateral sclerosis, muscular dystrophy, and Guillain-Barré syndrome), or chest wall deformities (kyphoscoliosis). Often these patients can compensate for their alveolar hypoventilation by increasing their respiratory rate, effectively lowering the partial pressure of carbon dioxide in the blood and correcting their hypercapnia and hypoxia. These compensatory mechanisms can cause fatigue, however, and eventual respiratory failure may ensue.

Answer: (A) Coronary artery bypass grafting

Asymptomatic patients and patients with stable angina have similar criteria for coronary artery bypass grafting. Indications include: (1) Left main coronary artery disease (≥50% stenosis of the left coronary artery); (2) left main coronary equivalent disease (≥70% stenosis of the proximal left anterior descending artery and the circumflex artery); (3) triple vessel disease (≥70% occlusion of the left anterior descending artery, the circumflex artery, and the right coronary artery); (4) proximal left anterior descending artery stenosis with single or double vessel disease with a left ventricular ejection fraction <50%; or (5) single or double vessel disease without proximal left anterior descending artery stenosis but with large areas of viable at-risk myocardium.

In patients who meet these criteria, coronary artery bypass grafting is thought to be superior to medical management and stenting. In patients with stable angina who do not meet these criteria, bypass grafting is indicated only if the patient has severely disabling angina despite maximal medical therapy. Transmyocardial laser revascularization is experimental at present.

Answer: (D) Duplex ultrasonography

The patient is suffering from subclavian steal syndrome, which occurs when stenosis of the subclavian artery proximal to the origin of the vertebral artery results in retrograde blood flow in the ipsilateral vertebral artery. Blood flow is shunted preferentially away from the posterior circulation to the subclavian artery. Most stenoses are the result of atherosclerotic lesions. Patients are dependent on collateral blood flow through the circle of Willis, and any concomitant compromise of flow through the circle of Willis, the carotid arteries, or the contralateral vertebral artery will lead to symptoms.

Symptoms can include transient ischemic attacks, dizziness, vertigo, syncope, drop attacks, vision loss, ataxia, arm claudication, diminished or absent radial pulse, and a reduced blood pressure in the affected arm, and often occur after exercising the affected limb. The initial diagnostic test of choice is duplex ultrasonography as it has the benefit of being a noninvasive, relatively inexpensive, ionizing radiation-free imaging modality.

Answer: (B) Current cigarette smoking

In a large, population-based study in Norway, Singh et al. determined that advanced age, a history of previous or current antihypertensive medication use, and a family history of aneurysmal disease are all significant risk factors for the development of an AAA. Male gender is also associated with a four-fold increase in risk. However, the strongest risk factor for AAA was cigarette smoking, particularly current smoking (OR 7.37 [3.70-14.69] p < 0.001 for men; OR 5.82 [2.92-11.58] p < 0.001 for women). A Canadian case-control study confirmed those results and found a dose-response effect between pack-years of cigarettes smoked and the risk of AAA, underscoring the importance of smoking cessation. Diabetes mellitus is not a risk factor for the development of AAA.

Answer: (A) Endovascular aneurysm repair (EVAR), then left hemicolectomy at a later date