Traumatic Lung Injuries

Hi Everyone,

We treated a traumatic arrest last week caused by a penetrating right lung injury. I wanted to review treatment of penetrating lung injuries.

Background:

Thoracic injuries account for a significant portion of trauma deaths, about 25% of initial deaths. Most mortality occurs in the field due to catastrophic injuries to the great vessels or tracheobronchial tree. Only 15% of survivors only require surgery.

Workup:

In hemodyanmically stable patients, the workup is first a careful physical exam followed by an upright AP chest x-ray. Occasionally to delineate specific lung pathology, such as determining hemothorax vs lung consolidation, we will get a chest CT. For unstable patients, the basics of the primary survey and quick intervention apply to lung injuries just like any unstable trauma patient.

Specific Lung Injuries & Treatment:

Pneumothorax is the most common manifestation of penetrating lung injury followed by hemothorax or hemopneumothorax. Pneumothorax is caused by damage (direct puncture, crush, increased airway pressure, etc) to the peripheral lung parenchyma resulting is self-limiting air leak. A simple tube thoracostomy (i.e. chest tube) allowing for air evacuation and re-approximation of visceral and parietal pleura is standard treatment. It is our protocol is leave chest tube to suction (-20 cm H2O) for at least 24 hours before placing to water seal. If there is no airleak, no pneumothorax on water seal, and outputs for 24 hours are less than 100ml than the chest tube can be removed.

Tension pneumothorax develops when air continually leaks into the pleural and becomes trapped. Intrathoracic pressure increases until it exceeds the central venous and right atrial pressure leading to decreased pre-load and cardiovascular collapse. Initial treatment is needle thoracostomy with 16 or 14 gauge angiocath at the mid-clavicular line and second intercostal space followed immediately by tube thoracostomy.

Massive air leak results from major airway dysruption (trachea, large bronchi). Initial treatment is chest tube placement. Often a second chest tube is required to control the leak. Chest tubes should not be placed on suction as this can worsen the airleak. Massive air leaks are an indication for operative intervention particularly if the patient is unstable.

Hemothorax is bleeding into the pleural space. It can come from intrathoracic or intraabdominal sources (diaphragm injury). Most survivors of lung parenchymal bleeding have injury to minor vessels (lung laceration) that is self-limiting and treated with large bore (36-40 F) tube thoracostomy. Thoracentesis is not appropriate in this setting. It is important to drain as much retained blood from pleural space as possible to minimize complications such as fibrothorax.

Massive hemothorax refers to initial chest tube output of more than 1500ml or on-going output of more than 250ml / hour. This bleeding can come from lung parenchyma but also mediastinal vessels or intercostal arteries. Massive hemothorax is an indication for immediate operative intervention. If the patient is in cardiac arrest, it is an indication for bedside thoracotomy.

Air embolism in the traumatic setting is due to disruption of neighboring pulmonary veins and bronchi allowing air to escape into the venous system when the patient is under positive pressure ventilation. When discovered, this is usually a life threatening situation. Treatment is prompt control of the embolism which often entails an emergent thoracotomy and hilar cross clamping along to evacuation of the blood from the pulmonary system.

Pulmonary contusion is seen mainly with blunt thoracic trauma although it is also a component of penetrating thoracic trauma. A direct blow to the lung parenchyma causes an area of hemorrhage surrounded by a zone of edema leading to poor oxygenation and a V/Q mismatch in the damaged area of lung. It's appearance on imaging can be difficult to distinguish from aspiration pneumonia, fluid overload, ARDS, or intrapulmonary hemorrhage. We have a low threshold for non-contrast chest CTs to help clarify lung pathology. Pulmonary contusion can also present a problem because the peak dysfunction from injury may not be seen until 24-48 hours as the pulmonary contusion “blossoms” (i.e. the zone of edema develops) also radiographic evidence usually lags farther behind. Treatment is supportive with judicious use of fluids and, if vented, using maneuvers to keep plateau pressures less than 30. There is no role for steroids or empiric antibiotics.

Specific Operative Interventions:

Hilar Control. Getting control of the pulmonary hilum is key in obtain proximal control of bleeding vessels or the massively disrupted airway. All techniques require division of the inferior pulmonary ligament to allow complete encircling of the hilum. The most basic technique is manual compression. Vascular clamps can also be placed across the hilum. A simple maneuver for control, especially in patients in extremis, is the pulmonary twist. After dividing the inferior pulmonary ligament, the lung apex is rotated anterior until the lung is 180 degrees from its original orientation. This causes compression of soft vessels against the stiffer bronchi. None of these techniques are meant for long term control of bleeding or airleak but only as a means of damage control.

Pulmonary Tractotomy. This is a method of exposing underlying damaged tissue. A stapler is placed between the missile tract and the peripheral lung. This opens the lung tissue over the tract allowing for exposure and repair of bleeding vessels or ruptured bronchi.

Pneumonectomy. If repair of the lung is not possible, whether from severe damage or instability of the patient, then pneumonectomy is the definitive operation. Only 3% of patients requiring a thoracotomy for penetrating lung injury need a pneumonectomy. The procedure in the emergent setting has a high morbidity and mortality even in young, otherwise healthy patients. Complications include pulmonary edema, pulmonary hypertension, right heart failure, and stump dishiscence.

References:

Mastery of Surgery. Thoracic Trauma. Fischer et al.

Trauma. Injury to the Lung and Pleura. Richardson & Miller.

Thanks to Dr. Mike Dingeldein for this post