Thoracic Trauma

Introduction

Traumatic thoracic injury currently accounts for approximately 6-10% of all injuries seen in trauma but carries a mortality of up to 80%. This is the case for both penetrating and blunt injury which, unlike the extremities, are not amenable to the rapid, life-saving intervention of tourniquet placement.

In the modern era of trauma, high velocity projectiles, body armor and explosive blasts result in more significant injury with larger areas of tissue damage. Blast injuries are particularly devastating due to the multiplicity of concurrent mechanisms (blunt, penetrating, and thermal injuries) within a single event.^[1,2]  The advancement and use of protective body armor and armored vehicles decreases the incidence of sudden death, thereby increasing the frequency of profound multi-trauma victims in need of life saving interventions.

Initial evaluation of the thorax begins with the standard primary survey focusing on airway, breathing and circulation as traumatic injury to the thorax can dramatically impact any or all of these. For stable patients the secondary survey can rapidly identify and define injury with standard chest x ray and ultrasound.

CT scan evaluation with arterial contrast is appropriate for patients with known thoracic trauma who present as hemodynamically stable or after stabilizing emergent procedures and can be very helpful in guiding treatment. Chest tube placement is often the first step to stabilize patients with thoracic injury and can also be diagnostic. The following will review appropriate definitive treatment for trauma related injuries to the lungs, rib cage, airway, and diaphragm.  Cardiac trauma is discussed elsewhere.

Lungs

Not every patient enduring thoracic injury will require surgical intervention. Maintaining and utilizing critical care principles is crucial to the survival of patients enduring thoracic trauma.

Respiratory failure may be the most lethal result of trauma sustained by the chest and can be from a variety of causes to include pulmonary contusion from high impact injury, inhalation of chemical/biological substances such as phosgene or chlorine, as well as secondary effects of systemic inflammation from high injury severity.

Victims subjected to blast injury in an enclosed space are at significant risk for blast lung injury which can rapidly devolve into a clinical situation akin to Acute Respiratory Distress Syndrome (ARDS). ^[3,4] High clinical suspicion should be maintained in these patients as even those appearing hemodynamically normal may experience sudden and complete respiratory collapse.  Rapid intubation and supportive care are the mainstay of therapy followed by the same adjuncts of using low tidal volume ventilation, minimizing secondary trauma, use of paralytics and prone positioning. For patients who do not respond to these adjuncts, extracorporeal membrane circulation (ECMO) can be lifesaving if available.

Among patients requiring surgical intervention for thoracic trauma, one third will have a significant injury to lung parenchyma. Location and the extent of the injury largely determine the approach and specific intervention. While a thoracoscopic approach can be appropriate in circumstances of a stable patient, a standard posterolateral thoracotomy through the 5^th or 6^th interspace is more common.  A sternotomy or clamshell incision may be required for central or bilateral injuries.  

Through and through lung injuries seen with low velocity penetrating injuries can be managed with parenchyma sparing operations such as a stapled or sutured tractotomy.^[5,6] Many combat related injuries are from high velocity or blast type injuries. These mechanisms often result in large areas of tissue disruption requiring more extensive operations.

Most small lacerations or peripheral parenchymal damage account for many of these injuries and can be managed conservatively with a chest tube. Persistent or large air leaks (>2 chamber continuous on chest atrium) from these types of injuries can be managed by surgical reapproximating of the visceral pleura and underlying parenchyma with primary suture closure or stapled wedge resection of the damage area.

Larger and more central injuries of the lobe will require surgical attention with larger wedge resection, segmentectomy or formal lobectomy.^[7,8] An intimate knowledge of the pulmonary arterial and venous anatomy is required for formal anatomic resections and these are rarely indicated in the setting of trauma. Larger wedge resections and/or stapling through contused parenchyma require thick tissue cartridges.  

More central injuries will often be associated with an unstable physiology requiring emergent intervention.^[7,8] Temporizing maneuvers such as direct pressure will often provide time for stabilization and surgical planning. Packing the chest tightly with laparotomy pads and inflating the lung can be effective in some circumstances.  Proximal and distal vascular control of the hilum can be obtained with tourniquet placement around the main pulmonary artery posterior to the superior vena cava on the right and inferior to the aortic arch on the left followed by exclusion of the inferior and superior pulmonary veins.

Traumatic injury to the hilum not only subjects the victim to massive blood loss but also carries a significant risk of air embolism which can be particularly devastating when air embolizes to the left heart via the pulmonary veins.  Direct pressure or hilar clamping may be needed to stabilize these patients. This can be accomplished with blunt division of the inferior pulmonary ligament and a large curved vascular clamp. The maneuver of a ‘hilar twist’ is often discussed for rapid control of the hilum however this is often impractical and technically difficult when the inferior pulmonary ligament isn’t taken down and can result in additional vascular injury if done incorrectly.

Total pneumonectomy should be considered when patients are too unstable—and resources/expertise too thin — for extensive reconstruction. Pneumonectomy is generally better tolerated on the left side in younger patients with robust cardiovascular reserve. A test clamp of the pulmonary artery can help predict the patient’s ability to mitigate the dramatic changes to cardiac and respiratory physiology which will occur within the first 24–72 h after pneumonectomy. ^[9]

Chest Wall

Single or even multiple rib fractures seen from blunt are blast trauma can be managed with pain control and a focus on the preservation of deep breathing and cough to prevent the development of pneumonia. This will be all that is needed in the vast majority of patients with chest wall trauma. If there is hemodynamic instability in the setting of suspected rib fracture, a chest tube should be inserted to treat presumed tension pneumothorax or hemorrhage. 

Complex damage to the chest wall such as open chest wounds, flail chest, tension pneumothorax and even traumatic rib cage hernias can occur in patients who have been subjected to high velocity or blast trauma.^[10] Primary focus should be on reinstating appropriate chest wall mechanics and controlling life-threatening hemorrhage with definitive reconstruction reserved for stable patients. Initially defects should be debrided of devitalized tissue including bone fragments and foreign materials. ^[11]

Open or ‘sucking’ chest wounds (defects larger than the patient’s trachea) have the potential to rapidly create tension physiology. This can be temporized, and tension pneumothorax avoided by simply placing a partially occluding 3- sided dressing in addition to placement of a chest tube. ^[8,11]

Significant hemorrhage from chest wall trauma may need to be addressed with early chest tube drainage and intercostal artery ligation by placing suture around the rib proximal (toward the spine) to the fracture encompassing the neurovascular bundle.^[11]  A flail segment is identified by paradoxical motion of the chest wall due to 3 or more ribs being displaced in 2 areas along the contour of the chest.

Treatment with early rib plating for these patients may result in avoidance of respiratory demise.  Importantly, it should be remembered that practically all flail chest victims suffer from some degree of pulmonary contusion. Conservative management with minimization of fluids, early rib plating, and aggressive pulmonary hygiene are key to the prevention of ARDS in this population. One should keep a low threshold for intubation with lung protective ventilation.

Large chest wall defects secondary to trauma may result in traumatic rib cage hernias with protrusion of lung or intraabdominal organs through the defect. Initial management should address the herniated organ to prevent tissue loss. Anterior and lateral defects will require reconstruction. Thick (2mm) Goretex mesh, pulled taught over the defect in an underlay fashion is a simple and effective repair technique.

If early repair is needed in a grossly contaminated wound, then biologic or Vicryl mesh can be used with the understanding that delayed definitive repair may be needed.^[10] Surgeons should have a high degree of suspicion for diaphragm disruption in high velocity or penetrating injury to the lower chest and/or upper abdomen.  This is often under-recognized and can present in a delayed fashion with intrathoracic herniation of abdominal viscera (see below). 

Airway

Disruption of the tracheobronchial tree is relatively rare and is either the result of penetrating trauma or high impact acceleration-deceleration injury. These patients will often present with dramatic subcutaneous emphysema, large or even tension pneumothorax, with profound respiratory distress.  Chest tube drainage may not provide resolution of the pneumothorax and has the potential to potentiate respiratory distress when the chest tube is placed to suction. Bronchoscopy is typically diagnostic and should guide the securing of a definitive airway as blind passage of an endotracheal tube can enlarge the defect. ^[12]

Intubation beyond the defect in the trachea or intentional mainsteming of the endotracheal tube opposite of the defect are acceptable temporizing measures when patient instability and/or surgical expertise limits definitive repair. Following stabilization, a more durable approach can be determined. Proximal tracheal injuries can typically be repaired from the neck and repaired primarily.  While concurrent vascular injury to carotid artery and jugular often results in sudden death, esophageal injury can be occult and needs to be evaluated, ideally with an endoscopy.  In addition, one needs to consider cervical spine injury depending upon the mechanism.

Tracheal defects in the distal 1/3 (approximately 3-4 cm from the carina) can be accessed via a right thoracotomy.  Pedicled intercostal muscle should be harvested during thoracotomy to buttress the repair. Primary repair is often possible.  Bronchoplasty (wedge resection with reapproximation) or sleeve resection (intersegment excision with end-to-end anastomosis) should be considered for injuries with tissue loss >30-50% though this requires considerable expertise.

Muscle or thymic flaps should be placed between all repair and vascular structures to prevent fatal broncho-vascular fistula. ^[13] Pulmonary resection should be reserved as a salvage maneuver for non-repairable airway injuries.

Diaphragm

Injuries localized anywhere from the level of the nipple to the crest of the iliac spine have the potential to cause an injury to the diaphragm. Traditionally the left side has been taught as the more frequently injured side as it is not protected by the liver. Imaging often fails to identify injury and laparoscopic or thoracoscopic exploration is often the best way to identify a defect. One should maintain a low threshold for exploration as missed diaphragmatic injury will result in bowel or lung hernia in 90% of people by 3 years. ^[14]

The diaphragm is forgiving, and most defects can be repaired primarily using pledgeted nonabsorbable interrupted or mattressed sutures. Reattachment to the chest wall can be accomplished by anchoring stitches around the inferior ribs.  Major tissue loss may require the use of Gortex mesh.^[15]

Biologic and vicryl mesh can be used when there is concern for gross contamination. The pleural space should be effectively drained after any diaphragm repair. When mesh is utilized, suction drainage should be maintained until output is low to aide in visceral pleural apposition, preventing persistent pleural effusion.

Conclusion

Thoracic injury related to trauma can be devastating. Recognizing injury patterns and understanding the crucial role of surgical intervention can have lifesaving effects. Temporization with a chest tube with a triaged approach to all injuries sustained is often effective.

Preservation of lung parenchymal is preferred but is a secondary concern when managing life threatening bleeding from the hilum. Thoracic injuries can be among the most daunting for a general or trauma surgeon. Intimate knowledge and virtual practice can make these injuries manageable and interventions successful.

References

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