Blunt Trauma

BLUNT TRAUMA

Although blunt chest trauma is more common, it is often diffi-cult to identify the extent of the damage because the symptoms may be generalized and vague. In addition, patients may not seek immediate medical attention, which may complicate the problem.

Pathophysiology

Injuries to the chest are often life-threatening and result in one or more of the following pathologic mechanisms:

·         Hypoxemia from disruption of the airway; injury to the lung parenchyma, rib cage, and respiratory musculature; massive hemorrhage; collapsed lung; and pneumothorax

·        Hypovolemia from massive fluid loss from the great vessels, cardiac rupture, or hemothorax

·        Cardiac failure from cardiac tamponade, cardiac contusion, or increased intrathoracic pressure

These mechanisms frequently result in impaired ventilation and perfusion leading to ARF, hypovolemic shock, and death.

Assessment and Diagnostic Findings

Time is critical in treating chest trauma. Therefore, it is essential to assess the patient immediately to determine the following:

·        When the injury occurred

·         Mechanism of injury

·         Level of responsiveness

·         Specific injuries

·         Estimated blood loss

·         Recent drug or alcohol use

·         Prehospital treatment

The initial assessment of thoracic injuries includes assessment of the patient for airway obstruction, tension pneumothorax, open pneumothorax, massive hemothorax, flail chest, and cardiac tamponade. These injuries are life-threatening and need imme-diate treatment. Secondary assessment would include simple pneumothorax, hemothorax, pulmonary contusion, traumatic aortic rupture, tracheobronchial disruption, esophageal perfora-tion, traumatic diaphragmatic injury, and penetrating wounds to the mediastinum (Owens, Chaudry, Eggerstedt & Smith, 2000). Although listed as secondary, these injuries may be life-threatening as well depending upon the circumstances.

The physical examination includes inspection of the airway, thorax, neck veins, and breathing difficulty. Specifics include as-sessing the rate and depth of breathing for abnormalities, such as stridor, cyanosis, nasal flaring, use of accessory muscles, drooling, and overt trauma to the face, mouth, or neck. The chest should be assessed for symmetric movement, symmetry of breath sounds, open chest wounds, entrance or exit wounds, impaled objects, tracheal shift, distended neck veins, subcutaneous emphysema, and paradoxical chest wall motion. In addition, the chest wall should be assessed for bruising, petechiae, lacerations, and burns. The vital signs and skin color are assessed for signs of shock. The thorax is palpated for tenderness and crepitus; the position of the trachea is also assessed.

The initial diagnostic workup includes a chest x-ray, CT scan, complete blood count, clotting studies, type and cross-match, electrolytes, oxygen saturation, arterial blood gas analysis, and ECG. The patient is completely undressed to avoid missing ad-ditional injuries that can complicate care. Many patients with in-juries involving the chest have associated head and abdominal injuries that require attention. Ongoing assessment is essential to monitor the patient’s response to treatment and to detect early signs of clinical deterioration.

Medical Management

The goals of treatment are to evaluate the patient’s condition and to initiate aggressive resuscitation. An airway is immediately es-tablished with oxygen support and, in some cases, intubation and ventilatory support. Re-establishing fluid volume and negative in-trapleural pressure and draining intrapleural fluid and blood are essential.

The potential for massive blood loss and exsanguination with blunt or penetrating chest injuries is high because of injury to the great blood vessels. Many patients die at the scene or are in shock by the time help arrives. Agitation and irrational and combative behavior are signs of decreased oxygen delivery to the cerebral cortex. Strategies to restore and maintain cardiopulmonary func-tion include ensuring an adequate airway and ventilation, stabi-lizing and re-establishing chest wall integrity, occluding any opening into the chest (open pneumothorax), and draining or re-moving any air or fluid from the thorax to relieve pneumothorax, hemothorax, or cardiac tamponade. Hypovolemia and low car-diac output must be corrected. Many of these treatment efforts, along with the control of hemorrhage, are usually carried out si-multaneously at the scene of the injury or in the emergency de-partment. Depending on the success of efforts to control the hemorrhage in the emergency department, the patient may be taken immediately to the operating room. Principles of manage-ment are essentially those pertaining to care of the postoperative thoracic patient.

Sternal and Rib Fractures

Sternal fractures are most common in motor vehicle crashes with a direct blow to the sternum via the steering wheel and are most common in women, patients over age 50, and those using shoul-der restraints (Owens, Chaudry, Eggerstedt & Smith, 2000).

Rib fractures are the most common type of chest trauma, oc-curring in more than 60% of patients admitted with blunt chest injury. Most rib fractures are benign and are treated conserva-tively. Fractures of the first three ribs are rare but can result in a high mortality rate because they are associated with laceration of the subclavian artery or vein. The fifth through ninth ribs are the most common sites of fractures. Fractures of the lower ribs are as-sociated with injury to the spleen and liver, which may be lacer-ated by fragmented sections of the rib.

CLINICAL MANIFESTATIONS

The patient with sternal fractures has anterior chest pain, over-lying tenderness, ecchymosis, crepitus, swelling, and the poten-tial of a chest wall deformity. For the patient with rib fractures, clinical manifestations are similar: severe pain, point tenderness,and muscle spasm over the area of the fracture, which is aggra-vated by coughing, deep breathing, and movement. The area around the fracture may be bruised. To reduce the pain, the patient splints the chest by breathing in a shallow manner and avoids sighs, deep breaths, coughing, and movement. This reluctance to move or breathe deeply results in diminished ventilation, collapse of unaerated alveoli (atelectasis), pneumonitis, and hypoxemia. Respiratory insufficiency and failure can be the outcomes of such a cycle.

ASSESSMENT AND DIAGNOSTIC FINDINGS

The patient with a sternal fracture must be closely evaluated for underlying cardiac injuries. A crackling, grating sound in the tho-rax (subcutaneous crepitus) may be detected with auscultation. The diagnostic workup may include a chest x-ray, rib films of a specific area, ECG, continuous pulse oximetry, and arterial blood gas analysis.

MEDICAL MANAGEMENT

Medical management of the patient with a sternal fracture is di-rected toward controlling pain, avoiding excessive activity, and treating any associated injuries. Surgical fixation is rarely neces-sary unless fragments are grossly displaced and pose a potential for further injury.

The goals of treatment for rib fractures are to control pain and to detect and treat the injury. Sedation is used to relieve pain and to allow deep breathing and coughing. Care must be taken to avoid oversedation and suppression of the respiratory drive. Alter-native strategies to relieve pain include an intercostal nerve block and ice over the fracture site; a chest binder may decrease pain on movement. Usually the pain abates in 5 to 7 days, and discom-fort can be controlled with epidural analgesia, patient-controlled analgesia, or nonopioid analgesia. Most rib fractures heal in 3 to 6 weeks. The patient is monitored closely for signs and symptoms of associated injuries.

Flail Chest

Flail chest is frequently a complication of blunt chest trauma from a steering wheel injury. It usually occurs when three or more adjacent ribs (multiple contiguous ribs) are fractured at two or more sites, resulting in free-floating rib segments. It may also result as a combination fracture of ribs and costal cartilages or ster-num (Owens, Chaudry, Eggerstedt & Smith, 2000). As a result, the chest wall loses stability and there is subsequent respiratory impairment and usually severe respiratory distress.

PATHOPHYSIOLOGY

During inspiration, as the chest expands, the detached part of the rib segment (flail segment) moves in a paradoxical manner (pen-delluft movement) in that it is pulled inward during inspiration, reducing the amount of air that can be drawn into the lungs. On expiration, because the intrathoracic pressure exceeds atmospheric pressure, the flail segment bulges outward, impairing the patient’s ability to exhale. The mediastinum then shifts back to the affected side (Fig. 23-8). This paradoxical action results in increased dead space, a reduction in alveolar ventilation, and decreased compli-ance. Retained airway secretions and atelectasis frequently ac-company flail chest. The patient has hypoxemia, and if gas exchange is greatly compromised, respiratory acidosis develops as a result of CO₂ retention. Hypotension, inadequate tissue perfu-sion, and metabolic acidosis often follow as the paradoxical mo-tion of the mediastinum decreases cardiac output.

MEDICAL MANAGEMENT

As with rib fracture, treatment of flail chest is usually supportive. Management includes providing ventilatory support, clearing se-cretions from the lungs, and controlling pain. The specific man-agement depends on the degree of respiratory dysfunction. If only a small segment of the chest is involved, the objectives are to clear the airway through positioning, coughing, deep breathing, and suctioning to aid in the expansion of the lung, and to relieve pain by intercostal nerve blocks, high thoracic epidural blocks, or cau-tious use of intravenous opioids.

For mild to moderate flail chest injuries, the underlying pul-monary contusion is treated by monitoring fluid intake and ap-propriate fluid replacement, while at the same time relieving chest pain. Pulmonary physiotherapy focusing on lung volume expan-sion and secretion management techniques are performed. The patient is closely monitored for further respiratory compromise.

When a severe flail chest injury is encountered, endotracheal intubation and mechanical ventilation are required to provide in-ternal pneumatic stabilization of the flail chest and to correct ab-normalities in gas exchange. 

This helps to treat the underlying pulmonary contusion, serves to stabilize the thoracic cage to allow the fractures to heal, and improves alveolar ventilation and in-trathoracic volume by decreasing the work of breathing. This treatment modality requires endotracheal intubation and venti-lator support. Differing modes of ventilation are used depending on the patient’s underlying disease and specific needs.

In rare circumstances, surgery may be required to more quickly stabilize the flail segment. This may be used in the patient who is difficult to ventilate or the high-risk patient with under-lying lung disease who may be difficult to wean from mechanical ventilation.

Regardless of the type of treatment, the patient is carefully monitored by serial chest x-rays, arterial blood gas analysis, pulse oximetry, and bedside pulmonary function monitoring. Pain management is key to successful treatment. Patient-controlled analgesia, intercostal nerve blocks, epidural analgesia, and intra-pleural administration of opioids may be used to control tho-racic pain.

Pulmonary Contusion

Pulmonary contusion is observed in about 20% of adult patients with multiple traumatic injuries and in a higher percentage of children due to increased compliance of the chest wall. It is de-fined as damage to the lung tissues resulting in hemorrhage and localized edema. It is associated with chest trauma when there is rapid compression and decompression to the chest wall (ie, blunt trauma). It may not be evident initially on examination but will develop in the posttraumatic period.

PATHOPHYSIOLOGY

The primary pathologic defect is an abnormal accumulation of fluid in the interstitial and intra-alveolar spaces. It is thought that injury to the lung parenchyma and its capillary network results in a leakage of serum protein and plasma. The leaking serum protein exerts an osmotic pressure that enhances loss of fluid from the cap-illaries. Blood, edema, and cellular debris (from cellular response to injury) enter the lung and accumulate in the bronchioles and alveolar surface, where they interfere with gas exchange. An in-crease in pulmonary vascular resistance and pulmonary artery pressure occurs. The patient has hypoxemia and carbon dioxide retention. Occasionally, a contused lung occurs on the other side of the point of body impact; this is called a contrecoup contusion.

CLINICAL MANIFESTATIONS

Pulmonary contusion may be mild, moderate, or severe. The clinical manifestations vary from tachypnea, tachycardia, pleu-ritic chest pain, hypoxemia, and blood-tinged secretions to more severe tachypnea, tachycardia, crackles, frank bleeding, severe hy-poxemia, and respiratory acidosis. Changes in sensorium, in-cluding increased agitation or combative irrational behavior, may be signs of hypoxemia.

In addition, the patient with moderate pulmonary contusion has a large amount of mucus, serum, and frank blood in the tra-cheobronchial tree; the patient often has a constant cough but cannot clear the secretions. A patient with severe pulmonary con-tusion has the signs and symptoms of ARDS; these may include central cyanosis, agitation, combativeness, and productive cough with frothy, bloody secretions.

ASSESSMENT AND DIAGNOSTIC FINDINGS

The efficiency of gas exchange is determined by pulse oximetry and arterial blood gas measurements. Pulse oximetry is also used to measure oxygen saturation continuously. The chest x-ray may show pulmonary infiltration. The initial chest x-ray may show no changes; in fact, changes may not appear for 1 or 2 days after the injury.

MEDICAL MANAGEMENT

Treatment priorities include maintaining the airway, providing adequate oxygenation, and controlling pain. In mild pulmonary contusion, adequate hydration via intravenous fluids and oral in-take is important to mobilize secretions. However, fluid intake must be closely monitored to avoid hypervolemia. Volume ex-pansion techniques, postural drainage, physiotherapy including coughing, and endotracheal suctioning are used to remove the se-cretions. Pain is managed by intercostal nerve blocks or by opi-oids via patient-controlled analgesia or other methods. Usually, antimicrobial therapy is administered because the damaged lung is susceptible to infection. Supplemental oxygen is usually given by mask or cannula for 24 to 36 hours.

The patient with moderate pulmonary contusion may require bronchoscopy to remove secretions; intubation and mechanical ventilation with PEEP may also be necessary to maintain the pressure and keep the lungs inflated. Diuretics may be given to reduce edema. A nasogastric tube is inserted to relieve gastro-intestinal distention.

The patient with severe contusion may develop respiratory failure and may require aggressive treatment with endotracheal intubation and ventilatory support, diuretics, and fluid restric-tion. Colloids and crystalloid solutions may be used to treat hypovolemia.

Antimicrobial medications may be prescribed for the treat-ment of pulmonary infection. This is a common complication of pulmonary contusion (especially pneumonia in the contused seg-ment), because the fluid and blood that extravasates into the alve-olar and interstitial spaces serve as an excellent culture medium.