Anesthesia for Thoracic Trauma

Introduction

• Chest trauma is the second most common cause of mortality after head trauma, and accounts for about 25% of traumatic deaths in the United States.¹
• Immediate deaths are usually due to massive injury to the heart, great vessels, or lungs.
• Early deaths occurring within 30 minutes to 3 hours are secondary to airway obstruction, hypoxemia, hemorrhage, cardiac tamponade, hemopneumothorax, and aspiration.¹
• Penetrating wounds of the chest, such as gunshot and stab wounds, can directly injure all the structures in the trajectory of the missile or weapon. Gunshot and shrapnel wounds cause both direct injury to the structures encountered by the weapon and secondary injury due to the blunt trauma-like shock wave created by the missile.¹
• Blunt forces applied to the chest wall cause injury by rapid deceleration, direct impact, and compression. Suspicion for pulmonary, cardiac, and great vessel trauma should be heightened in patients who have sustained high-energy decelerating trauma.
• Less than 10% of blunt thoracic injuries and only 15-30% of penetrating thoracic injuries require an operative intervention. Most thoracic trauma patients can be treated with bedside procedures (e.g., needle decompression of the chest) within the capabilities of clinicians trained in ATLS.²

Initial Management

• The initial management of trauma patients begins with a primary survey and definitive care, followed by a secondary survey based on the mechanism of injury and clinical presentation.
• Point of care ultrasound (POCUS) is useful in diagnosis of life threatening injuries and guiding intervention.
• Thoracic trauma can be associated with a traumatized airway and carries specific considerations which is discussed in a separate summary.

Resuscitative Thoracotomy

• Resuscitative thoracotomy involves gaining rapid access to heart and major thoracic vessels through an anterolateral chest incision to control exsanguinating hemorrhage or other life-threatening chest injuries.³
• It is almost universally performed in the emergency department (ED), and hence also called emergency department thoracotomy (EDT). They enable performing several potentially lifesaving maneuvers, such as³
  • evacuation of pericardial tamponade;
  • direct control of intrathoracic hemorrhage;
  • control of massive air-embolism;
  • open cardiac massage, and
  • cross-clamping of the descending aorta.

Specific Injuries and Anesthetic Considerations

Cardiac and Vascular Injuries

• Blunt cardiac injuries commonly involve the right ventricle due to its anterior location behind the sternum.
• The spectrum of injuries ranges from minor arrhythmias to cardiac tamponade which often necessitates pericardiocentesis. Rapid deceleration can also cause disruption.
• Penetrating injuries can cause injury to cardiac chambers and major vessels resulting in cardiac tamponade, hemothorax, or exsanguination.
• Large volume blood on placing bilateral chest tubes usually indicates major vessel injury, which might necessitate a resuscitative thoracotomy.
• The definitive repair of cardiovascular injuries may necessitate surgical intervention with thoracotomy/sternotomy, with or without cardiopulmonary bypass.

Tracheobronchial Injuries

• Tracheobronchial injuries (TBI) can be lethal due to difficulties in establishing a definitive airway and ongoing problems with oxygenation and ventilation. They are usually located within 2cm of carina, on the right side due to the rapid deceleration of the mobile lungs against a fixed carina.⁴
• The clinical presentation often includes dyspnea, subcutaneous emphysema, cough, hemoptysis, stridor, pneumothorax, etc.
• TBIs might require lung isolation using double-lumen tube or bronchial blocker.
• The goal is to place the cuff of the endotracheal tube (ETT) distal to the location of the injury.

Pulmonary Contusions

• The incidence of pulmonary contusion in patients with blunt chest trauma varies between 17% and 75%.⁵
• The clinical presentation includes tachypnea, hypoxia, hypercarbia, wheezing, and hemoptysis.
• Computerized tomography (CT) and chest x-ray may not immediately show the lesions.
• Pulmonary contusions can be painful and eventually progress to intraparenchymal hemorrhage, atelectasis, and acute respiratory distress syndrome (ARDS).
• Supportive measures include optimal pain management, including regional anesthetic techniques6 and lung-protective ventilation.

Pneumothorax

• A pneumothorax can be asymptomatic or cause pleuritic chest pain and dyspnea when not under pressure.
• Tension pneumothorax manifests with tracheal deviation, jugular venous distension, unilateral breath sounds, hypotension, and cyanosis.
• A tension pneumothorax must be immediately treated with a needle thoracostomy or a thoracostomy tube.
• It is important to remember the possibility of an undiagnosed pneumothorax that may develop tension physiology soon after intubation and initiation of positive pressure ventilation.

Hemothorax

• A hemothorax should be suspected in trauma patients in shock or with reduced or absent unilateral breath sounds.7 A clinically significant hemothorax is when the blood loss is greater than 1500 mL or greater than 200 mL/hour for 4hrs.
• A hemothorax usually results from injuries to the pulmonary parenchyma, intercostal arteries, internal thoracic arteries, great vessels or cardiac chambers.
• Hemodynamically unstable patients are typically taken to operating room for exploration while a selective few may benefit from a resuscitative thoracotomy.
• Small hemothoraces may be asymptomatic or present with pleuritic chest pain, dyspnea, dullness to percussion and may be managed with a chest tube and observation.⁷

Chest Wall Injuries

• Management of chest wall injuries includes aggressive pain control to prevent chest splinting, hypoventilation, atelectasis, pneumonia, and prolonged mechanical ventilation.⁸
• Rib fractures
  • Present in approximately 10% of all trauma patients and their occurrence is a marker for more severe injuries. Rib fractures are associated with increased morbidity and mortality, especially in the elderly population.
  • Indications for surgical rib fixation are:
    • impending or actual respiratory failure;
    • significant chest wall deformity;
    • failure to wean from mechanical ventilation (not related to pulmonary contusion);
    • significantly displaced ribs found at thoracotomy being performed for other reasons; and
    • ongoing chest wall instability/deformity or pain due to nonunion or malunion of rib fractures
• Flail chest
  • A flail chest occurs when three or more adjacent ribs are each fractured in two places, creating a floating segment and unstable chest wall.
  • The flail segment moves paradoxically with respiration.
  • It can potentially cause inefficient ventilation, hypoventilation, atelectasis, pulmonary shunt, ventilation-perfusion mismatch, and hypoxemia.
  • Noninvasive or invasive mechanical ventilation is indicated to minimize the sequalae of paradoxical movements if not indicated for other coexisting or underlying injuries.⁹
• Esophageal injuries: Can rapidly cause mediastinitis and septic shock. Therefore, esophageal injuries are a surgical emergency even in the absence of injuries to other structures.
• Diaphragmatic injuries: Often associated with injury to other intra-abdominal (liver, spleen, and bowel) and/or thoracic organs (lungs, great vessels, cardia). Anesthetic implications are not limited to addressing significant hemorrhage and airway control with possible lung isolation.

Pain Management in Thoracic Trauma

• The mainstay of rib fracture management is aggressive multimodal pain management. Regional techniques play a critical role in perioperative pain management.
• Thoracic epidural or paravertebral catheters are the mainstay for thoracic injuries.¹⁰ Other options are erector spinae plane block, intrapleural analgesia, intercostal nerve blocks, serratus anterior plane block and pectoral blocks.
• Multimodal analgesia includes scheduled acetaminophen, nonsteroidal anti-inflammatory drugs, and intravenous opioids (via patient-controlled analgesia or nurse administered) followed by a transition to oral medications as soon as possible. Adjuncts like ketamine, lidocaine, alpha agonists, etc., should be considered.

Anesthetic Considerations for Thoracic Trauma

• Once the primary and secondary surveys are completed and patient is deemed to require either damage control or definite surgical intervention, they are rapidly transported to the operating room (OR).
• Monitors: Apart from standard American Society of Anesthesiologists (ASA) monitors, invasive monitors such as an arterial line, central venous catheter, TEE, etc., are commonly used for assessing the volume status, goal-directed fluid therapy, frequent labs, infusing vasoactive medications, and as conduits for vascular access. A second arterial line in the left upper extremity might be required in cases of aortic transection. The presence of a cervical collar and the location of pulmonary and pleural injuries often dictate the side and location of central venous access. The actual timing of placement of these monitors may differ such that they might be placed in the ED, OR before, during, or after the beginning of the procedure.
• Induction: Patients who are not intubated frequently need a rapid sequence induction/intubation due to inadequate nil per os status or decreased gastric emptying time due to trauma. Stable patients can be induced with ketamine or etomidate or a reduced dose of propofol followed by a rapid-acting neuromuscular blocker. In hemodynamically unstable patients, adjuncts like opioids, lidocaine, and midazolam can be avoided. In extreme situations, an induction agent is avoided altogether.
• If a patient suffers significant hypotension or bradycardia shortly after endotracheal intubation and positive pressure ventilation, a tension pneumothorax should be suspected, and treated accordingly.
• Maintenance: is with low to normal concentrations of volatile agents supplemented with opioids, and neuromuscular blocking agents. In case of hemodynamically significant arrhythmias due to myocardial injury, transcutaneous pacing/defibrillator pads might be required, so placing them preoperatively is prudent. Inotropes and vasopressors might be required, and hypovolemia should be aggressively corrected.
• Ventilation: Lung protective ventilation strategies are employed to minimize lung injury. Airway pressures are kept to a minimum to prevent adverse effects on cardiac function and filling pressures in patients with ventricular dysfunction from injury.
• Emergence: Emergence might be immediate or delayed with postoperative mechanical ventilation in the ICU due to multiple factors.
• Postoperative disposition: Patients with thoracic trauma often require postoperative ICU stay for mechanical ventilation or 24-48hr cardiac monitoring for arrhythmias and ventricular dysfunction. Specific indications are multiple rib fractures especially in the elderly due to the high incidence of morbidity/mortality and need for monitoring while treating pain.