A 10-year-old boy is brought to the emergency department after being involved in a motor vehicle collision. Trauma workup is negative for major injuries but significant for bruising and severe pain over the right chest. Chest x-ray is normal. Over the next 6 hours of observation, the patient develops progressive tachycardia and tachypnea with need for supplemental oxygen. Temperature is 36.7 C (98 F), blood pressure is 110/66 mm Hg, pulse is 110/min, and respirations are 24/min. Breath sounds are decreased on the right side. Arterial blood gas results on 6 L of oxygen are as follows: Repeat chest x-ray reveals patchy, irregular alveolar infiltrates of the peripheral right middle and lower lobes. Which of the following is the most likely diagnosis?

Question

A 10-year-old boy is brought to the emergency department after being involved in a motor vehicle collision.  Trauma workup is negative for major injuries but significant for bruising and severe pain over the right chest.  Chest x-ray is normal.  Over the next 6 hours of observation, the patient develops progressive tachycardia and tachypnea with need for supplemental oxygen.  Temperature is 36.7 C (98 F), blood pressure is 110/66 mm Hg, pulse is 110/min, and respirations are 24/min.  Breath sounds are decreased on the right side.  Arterial blood gas results on 6 L of oxygen are as follows:  Repeat chest x-ray reveals patchy, irregular alveolar infiltrates of the peripheral right middle and lower lobes.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec25c8_d1ff_5036_bc81_9f6b3ec1a2b6_MD0003_00 This patient with blunt thoracic trauma (eg, right chest wall bruising) has progressively worsening tachypnea, hypoxemia, and ipsilateral irregular infiltrates on chest x-ray, concerning for pulmonary contusion. Pulmonary contusion represents lung parenchymal bruising (due to transmitted kinetic energy) with resulting alveolar hemorrhage and edema. It is frequently associated with rib fractures but may occur in their absence, especially in children (whose more elastic chest walls can transmit more kinetic energy without fracturing). Manifestations of pulmonary contusion include tachypnea, hypoxemia, and (often) decreased breath sounds (due to alveolar infiltrates). Because clinically significant alveolar edema may take hours to accumulate, the initial chest x-ray is often negative. CT scan (more sensitive) or repeat chest x-ray (as in this patient) may be necessary to reveal the patchy, irregular alveolar infiltrates characteristic of pulmonary contusion. Because these infiltrates reflect alveolar damage in the lung tissue adjacent to the injury site (eg, right peripheral lung in this patient), they are typically nonlobular (not restricted by anatomic landmarks). Management is supportive and involves pain control, pulmonary hygiene, and respiratory support. (Choice A) Acute respiratory distress syndrome can cause increasing dyspnea, hypoxemia, and alveolar infiltrates following trauma; however, the alveolar infiltrates are typically bilateral and do not manifest until 24-48 hours following the traumatic event. (Choice B) Aspiration pneumonia can cause tachypnea and hypoxemia but typically has accompanying fever, cough, and purulent sputum. (Choice C) Chest wall pain following trauma can lead to shallow breathing and atelectasis (lung tissue collapse), with resulting tachypnea and hypoxemia. However, atelectasis typically manifests on x-ray with bilateral, linear densities in the dependent, collapsed portions of the lungs. (Choice D) Fat embolism can cause hypoxemia but typically occurs after long bone or pelvic fracture and is accompanied by petechial rash and neurologic changes. (Choices E and F) Both hemothorax (eg, bleeding from injured lung parenchyma) and pneumothorax can cause tachypnea and hypoxemia. However, hemothorax would cause an effusion with partial opacification of the hemithorax or blunting of the costophrenic angle on upright chest x-ray. Pneumothorax would cause an area without lung markings, bordered by a visceral pleural line. Pneumothorax (Choice H) Trauma causes an inflammatory state that increases the risk of pulmonary embolism. However, chest x-ray is usually normal, and pulmonary embolism does not explain this patient's unilaterally decreased breath sounds with irregular alveolar infiltrates. Educational objective: Even without chest wall fracture, blunt thoracic trauma can cause pulmonary contusion. Tachypnea and hypoxemia are classic symptoms, and imaging often demonstrates patchy, irregular alveolar infiltrates. References: Lung contusion: a clinico-pathological entity with unpredictable clinical course. (http://www.ncbi.nlm.nih.gov/pubmed/27162815) Pulmonary contusion. (http://www.ncbi.nlm.nih.gov/pubmed/30906578)

A 10-Year-Old Boy Is Brought to the Emergency Department After