An 18-year-old man is brought to the trauma center by ambulance after he sustained a gunshot wound to the chest. Physical examination shows narrow pulse pressure, jugular venous distention, muffled heart sounds, and pulsus paradoxus. Which of the following is the most likely diagnosis? 

A 22-year-old man is brought to the emergency department after he sustained a gunshot wound to the left thigh. Pulse rate is 122/min, respirations are 18/min, and blood pressure is 128/88 mmHg. Oxygen saturation is 96% on room air. Physical examination shows a bleeding wound in the left upper thigh, just below the inguinal ligament. The left foot is pale, cool, and hyperesthetic, but peripheral pulses are absent. Surgical exploration of the wound shows destruction of a 5.5-cm portion of the superficial femoral artery. The most appropriate management is debridement of the wound and which of the following? 

A 66-year-old man is recovering in the hospital five hours after undergoing three-vessel coronary artery bypass grafting. Initial output from the mediastinal chest tube was 300 mL of bloody drainage per hour. One hour ago, no further evidence of bleeding from the tube was noted. Despite repeated intravenous bolus administration of fluid, mean arterial pressure has decreased from 80 to 40 mmHg. Central venous pressure is increased at 20 mmHg (N=2-6 mmHg), and administration of dopamine has been required for maintenance of blood pressure. Which of the following is the most appropriate next step in management of this patient's condition?

A 40-year-old man is brought to the emergency department by his wife one hour after he had sudden onset of shortness of breath. Medical history includes chronic obstructive pulmonary disease and prior spontaneous right pneumothorax. The patient has an 80–pack-year history of cigarette smoking. Temperature is 37.1°C (98.7°F), pulse rate is 95/min, respirations are 28/min, and blood pressure is 140/100 mmHg. Oxygen saturation is 87% on 2 L of oxygen via nasal cannula. On physical examination, breath sounds are distant bilaterally. Chest x-ray study shows a large right pneumothorax. After placement of an appropriately sized chest tube, which of the following is the most definitive management? 

A 58-year-old man is undergoing three-vessel coronary artery bypass grafting with replacement of the aortic valve. Multiple attempts to separate the patient from the heart-lung machine are unsuccessful. The surgeon decides that insertion of an intra-aortic balloon pump is indicated. In this patient, the primary goal of this procedure is increase in which of the following?