Figure 24-1. Rib fractures on CXR.
There are two randomized clinical studies comparing surgical repair of ribs (open reduction and internal fixation) versus mechanical ventilation alone.10,11 Both studies suggest a benefit in surgical repair in terms of days on the ventilator, pneumonia, and function at 6 and 12 months. Therefore, it is recommended for those with large flail chest (five or more ribs) on mechanical ventilation without a reason for prolonged intubation, that is, severe traumatic brain injury, to undergo rib fixation. This conclusion has also been supported by other nonrandomized trials.12,13 There are multiple types of rib fixators available (Fig. 24-3) and no repair has proven superior. The majority of ribs repaired are number 4 to 9, approached via a thoracotomy incision (Fig. 24-4).
Figure 24-2. Pathophysiology of flail chest. A: Inspiratory phase: chest wall collapses inward, causing air to move out of the bronchus of the involved lung into the trachea and bronchus of the uninvolved lung, causing a shift of mediastinum to the uninvolved side. B: Expiratory phase: chest wall balloons outward so that air is expelled from the lung on the uninvolved side and enters the lung on the involved side with an associated shift of mediastinum to the involved side.
Figure 24-3. Rib fixation with plates.
For patients who do not have large flail chests, which is the majority, the indications for rib fixation remain elusive. In general, the author’s approach is to consider rib fixation for any patient with three or more ribs fractured with severe displacement (more than the width of a rib). The patient population that would significantly benefit from fixation is unclear and at this point the decision is made on a case-specific basis.
Pneumothoraces can be classified into three subtypes: occult, simple, and tension. The initial diagnosis can be made with physical examination by auscultation. Auscultation is the first diagnostic test performed during the “Breathing” portion of the primary survey. One should be sure to auscultate the chest in two primary positions (bilateral midaxillary lines). This provides the examiner with the greatest specificity since these positions represent the most distant portions of the hemithorax from the contralateral hemithorax. Anterior positions can often be falsely positive for breath sounds secondary to overlapping pleura or transmitted sounds from the contralateral side.
Figure 24-4. Rib Fixation with plates (photo).
The next most commonly used diagnostic test is ultrasound during the extended FAST examination looking specifically for lung sliding. Lung sliding has a high sensitivity and specificity (78.6% and 98.4%)14 for the presence or absence of a pneumothorax as described above. The standard of care in the trauma bay is upright (if spine is cleared) or supine AP X-ray if the spine is not cleared. Although radiographs are less sensitive than ultrasound for small pneumothoraces they are used to screen for other associated injuries as described above.
An occult pneumothorax is one that is seen on CT scan (which is the most sensitive test for pneumothorax) but not seen on CXR (Fig. 24-5A, B). Subcutaneous emphysema is a sign that should alert the clinician to pneumothorax (Fig. 24-6). A simple pneumothorax is one that is seen on either CT scan or CXR but is not associated with hemodynamic compromise. Those patients with a pneumothorax and hemodynamic compromise must be considered a tension pneumothorax until proven otherwise. Tension pneumothorax is not a radiologic diagnosis but rather a clinical diagnosis. A tension pneumothorax is a pneumothorax that has progressed to the point that the mediastinum is shifted compromising in-flow to the heart. Kinking of the great vessels is the pathophysiology that leads to an acute decrease in cardiac output and shock. Unless tension is released the patient will die. Signs and symptoms of a tension pneumothorax include; shortness of breath, dyspnea, tachypnea, hypotension, distended neck veins, and tracheal deviation (away from the site of injury). If any of these signs are present immediate decompression is necessary.
Treatment of Pneumothorax
If the patient is unstable and a tension pneumothorax is suspected needle decompression may be considered. A large–bore, 14- to 16-gauge angiocatheter is inserted into either the anterior second intercostal space in the midclavicular line or the fifth intercostal space in the midaxillary line. There is some cadaveric data that suggests that the fifth intercostal space in the midaxillary line has the least distance from the skin to the pleural cavity and therefore, may be superior to the anterior position.15 This converts the tension pneumothorax to a simple pneumothorax which can subsequently be drained with a proper tube.
For those patients who have a simple (or occult) pneumothorax one should be guided by progression of the pneumothorax or the development of signs/symptoms of cardiopulmonary compromise. In a series of 146 patients with pneumothoraces, 90% of pneumothoraces that were 3.5 cm in widest dimension were successfully observed. This holds true in the intubated patient on positive pressure ventilation as well.18 Therefore, as a general rule, if the patient is stable one should repeat the CXR and if the pneumothorax is significantly larger (definition of significantly larger varies) or if the patient becomes symptomatic then a tube should be placed to reexpand the lung. No longer is there a need for a mandatory chest tube for pneumothoraces, even for those on positive pressure ventilation.
Figure 24-5. A: AP CXR in trauma bay with no evidence of pneumothorax. B: Occult pneumothorax seen on CT scan C: Measurement of largest air pocket in a line drawn perpendicular to the chest wall.
Figure 24-6. Subcutaneous emphysema.
Figure 24-7. Zone of safety.
In the presence of flail chest or multiple rib fractures one may observe a significant decrease in the PaO2/FiO2 ratio. Rather than a function of the mechanics of the chest wall this is most consistently a result of underlying lung contusion. Lung contusion is the extravasation of blood into the interstitial space of the lung parenchyma. Bleeding may extend to the alveolar space as well in severe cases.
The treatment for lung contusion complicated by hypoxia is primarily supportive, with administration of positive end-expiratory pressure (PEEP). PEEP may be applied either noninvasively (face mask) or through an endotracheal tube. In a small study, it was found that 100% of patients who had five or more ribs fractures, two-thirds or more of lung affected by contusion, and a decrease in mental status (GCS ≤14) required intubation.19 Intubations did not necessarily occur on the first day but often on the second day. Therefore, it is important to identify patients at risk for intubation and place them in a higher level of care. Other key aspects of care include minimizing intravenous crystalloid fluids, early mobilization, and encouraging cough/deep breathing.
Initial imaging is the screening CXR. This x-ray is often a supine AP film that may make the diagnosis of a hemothorax challenging. In the supine film the blood layers in the posterior recess of the hemithorax and the x-ray may appear hazy when compared to the contralateral side. In the face of a large hemothorax the x-ray can appear as a white out. Ultrasonography during the extended FAST examination has a high sensitivity for detecting a hemothorax.
The causes of hemothorax are varied, the most common being rib fractures/intercostal muscle to intercostal artery laceration, pulmonary laceration, or cardiac injury with communication to the pleura via injury to the pericardium. The urgency of the treatment is dictated by the physiologic state of the patient with rapid control of hemorrhage is the first priority.
Retained hemothoraces may occur in 30% of the patients.22 A retained hemothorax is defined as hemothorax that persists despite an attempt at drainage. If the hemothorax is not adequately drained in a 24-hour period it may be necessary to differentiate the hemothorax from atelectasis. A CT scan will help the surgeon differentiate between the two and allow one to calculate the amount retained.
If the amount is moderate to large there are two options; (1) early video-assisted thoracostomy to evacuate the clot or (2) tissue plasminogen activator (TPA) with or without DNAase. The key point is that early intervention allows the clot to be evacuated and prevent a fibrothorax from forming. Ideally, surgical drainage should be performed within 7 days to optimize the ability to successfully perform thoracoscopy.
Those patients with evidence of mediastinal hematoma on CXR, as described above, or those with a high-risk mechanism, that is, same-side motor vehicle collision (t-bone collision) should have a CT scan of the chest with intravenous contrast. CT scan has become the standard of care for diagnosis and classification of aortic injuries. Aortic injuries most commonly occur at points of fixation. These locations in decreasing order of occurrence include; (1) ligamentum arteriosa (just distal to the left subclavian artery), (2) diaphragmatic hiatus, and (3) root of the aorta (these usually die at the scene). The current classification of aortic injuries divides the extent of injury into four grades; (1) small intimal tear, (2) intramural hematoma (3) pseudoaneurysm (Fig. 24-8A,B), (4) periaortic rupture. The treatment of these injuries has evolved.
Injuries may be the result of either penetrating or blunt trauma. The average size of a diaphragmatic injury for penetrating trauma is approximately 2 cm and the average size of the injury for blunt trauma is 8 cm. In a 2015 review, there were 3,873 diaphragmatic injuries among the sample size of 833,309 giving an incidence of 0.46%.24 Initial imaging begins with CXR and is often followed by CT scan. The sensitivity for diaphragmatic injuries on CT scan is approximately 70% (range is from 50% to 90%). For penetrating trauma CXR and CT scan have very poor sensitivities and one must maintain a high index of suspicion depending upon the trajectory of the knife or bullet. If there is a penetrating trauma to the thoracoabdominal region (nipple line to costal margin) particularly on the left side one should perform a diagnostic laparoscopy after a 24-hour window. This 24-hour window allows the surgeon to effectively exclude an associated hollow viscus injury since these patients would manifest as peritonitis prior to 24 hours.
Figure 24-8. A: Axial view of type III blunt aortic injury with pseudoaneurysm. B: Sagital view of type III blunt aortic injury with pseudoaneurysm.