Blunt Thoracic Trauma

Blunt Thoracic Injuries

• Blunt trauma to the chest is the third leading cause of traumatic injury.
• Lung injury is the most common problem resulting from thoracic trauma.
• Pneumothorax occurs in up to 40% of all blunt thoracic injuries.
• Beck triad is associated with cardiac tamponade and includes:
  • Jugular venous distention
  • Muffled heart sounds
  • Hypotension

Pathophysiology of Blunt Thoracic Trauma

• Blunt trauma to the chest is the third leading cause of traumatic injury, following traumatic brain injury and extremity trauma.
• In developed nations, thoracic trauma is most often associated with motor vehicle collisions.
• Blunt thoracic trauma patients often have severe injuries and multisystem involvement.
• Blunt injuries account for 25% to 50% of all traumatic deaths.

Pulmonary Injuries

• Pulmonary contusion, pneumothorax, and hemothorax are the most common thoracic injuries associated with high-velocity trauma and abrupt deceleration.
• Pulmonary contusion is the most common lung injury, occurring in up to 70% of patients with blunt thoracic trauma, and develops over 24 hours.
• Pulmonary contusion results in the disruption of the alveolar-capillary membrane, allowing protein-rich fluid to exit the pulmonary capillaries and collect within the alveolar-capillary interstitium and alveoli.
• The degree of hypoxia and hypercarbia induced by pulmonary contusion may or may not be clinically relevant.
• Pneumothoraces occur in up to 40% of all blunt thoracic injuries, and may not be initially detected by radiographic analysis.
• Hemothorax may be acute or chronic, and requires early detection and management via tube thoracoscopy.

Chest Wall Injuries

• The exact incidence of blunt chest injuries (BCIs) following a traumatic event is unknown.
• Rib fractures are the most common chest wall injury, and may be associated with underlying pulmonary injuries.
• Fractures of three or more ribs are reflective of high-energy trauma and may be associated with brachial plexus and subclavian vascular injuries.
• A flail chest is defined as a series of three or more contiguous ribs that are fractured at two or more places, and typically occurs on the anterior or anterior lateral surface of the chest.
• Flail chest produces paradoxical chest wall movement during spontaneous breathing and is indicative of significant thoracic injury.

Cardiac Injuries

• The incidence of blunt cardiac trauma is between 5% and 50%, depending on the definition and clinical criteria used.
• Blunt cardiac trauma results from occult injury to the thorax, deceleration injuries, and compression of the heart against bony structures such as the sternum.
• Low-energy cardiac injuries are typically a result of a sudden strike to the precordium, and may cause ventricular fibrillation or cardiac arrest.
• High-energy cardiac injuries are a result of tremendous force that is transferred to the cardiac tissue, resulting in significant injury, including lethal arrhythmias, myocardial septal rupture, and massive hemorrhage.
• Perioperative management of cardiac injuries is variable and depends on the extent of the injury.

Thoracic Vascular Injuries

• Injuries sustained to the thoracic aorta are caused by rapid deceleration, resulting in intimal tears of the thoracic aorta, often near the left subclavian artery.
• If untreated, thoracic aortic injuries can result in vascular rupture and death.
• Surgical management of thoracic aortic injuries has evolved from open vascular repair to endovascular stent grafting (EVSG), which has demonstrated a significant reduction in morbidity and mortality.
• Initial management of thoracic aortic injuries should focus on deliberate blood pressure control and blood replacement.

Airway Injuries

• Airway injuries represent a potentially lethal consequence associated with blunt thoracic trauma.
• Recognition of airway injuries is often challenging, and may only be possible during direct visual inspection by bronchoscopy or CT examination.
• Management of airway injuries involves airway management and ETT intubation if hypoxia, acidosis, and respiratory distress are evident.

Airway Management in Blunt Thoracic Injuries

• In patients with high-energy blunt thoracic injuries from MVA, airway assessment is the first priority after ATLS protocol, as acute respiratory distress or impending respiratory failure require immediate airway intervention.
• Delay in airway management can lead to severe hypoxemia and acidosis, resulting in cardiopulmonary decompensation.
• Pulmonary injury is a high probability, and the anesthetist must be prepared to manage potential complications, including rapid desaturation upon induction.

Anticipating Respiratory Complications

• Reductions in functional residual capacity (FRC) from injury or pneumothorax can exacerbate arterial hypoxemia.
• Simple techniques like prolonged and thorough preoxygenation are beneficial.
• During cricoid pressure, bag-valve-mask ventilation using minimal peak pressures can help maintain oxygenation and avoid desaturation.

Recognition and Management of Pneumothorax

• The risk of gastric aspiration exists, but severe hypoxemia can negatively impact postoperative neurological condition.
• Patients should be closely monitored for signs of unrecognized pneumothorax and/or tension pneumothorax after ETT placement.
• Absence of pneumothorax on radiograph does not guarantee lung injury, and tension pneumothorax is a clinical diagnosis based on cardiovascular collapse after positive pressure ventilation.
• Needle decompression or chest tube thoracoscopy should be performed immediately if decompensation occurs.

Acute Respiratory Distress Syndrome (ARDS)

• ARDS occurs acutely within 24-48 hours after traumatic injury, resulting from direct pulmonary injury (aspiration, blunt thoracic trauma) or extrapulmonary injury (sepsis, multiple organ dysfunction syndrome).
• Diagnosis is based on factors including a PaO/FiOz ratio of < 300 mmHg, bilateral infiltrates on chest radiograph, and absence of cardiogenic pulmonary edema.

Blunt Thoracic Injuries

• Signs of cardiac tamponade include:
• Tachycardia
• Hypoxemia
• Hypercarbia
• Myocardial ischemia
• Dysrhythmias
• Pulsus paradoxus
• Widened mediastinum
• Decreased cardiac output
• Equivalent left- and right-sided heart pressures
• Beck triad

Perioperative Strategies for ARDS Management

• Key strategies for managing ARDS patients perioperatively:
• Maintain tidal volume at 6-8 mL/kg
• Minimize peak inspiratory pressure