Principles of trauma management (Proceedings)

Abdominal trauma

The principles surrounding the initial approach to the patient with abdominal trauma are similar to those in a patient that has sustained any form of trauma. Rapid assessment of the cardiovascular and respiratory systems should be performed, and the presence of shock should be identified. If physical examination findings are supportive of shock (tachycardia, pale mucous membranes, poor pulse quality), then a large bore intravenous catheter should be placed and fluid therapy should be initiated promptly. Regardless of the nature or severity of the abdominal injury, treatment of shock should take priority in the first few minutes after arrival to the clinic.

While in some instances the presence of abdominal trauma may be easily identified with physical examination alone (when external wounds are present), attention to detail or a raised index of suspicion may be required to identify subtle clues suggestive of abdominal trauma. The presence of wounds or bruising over the abdomen should alert the clinician to the potential for internal injuries. Abdominal distension may indicate the presence of a hemo- or uro-abdomen. Abdominal pain, while a non-specific finding, may be an early indicator of abdominal trauma. Bruising or swelling in the caudal inguinal area can be associated with urinary tract rupture. A soft fluctuant swelling under the skin may be indicative of a body wall hernia. Simple tests including packed cell volume and total solids, and blood urea nitrogen can be helpful and should be performed in every patient that has sustained trauma.

Hemoabdomen

Blood loss into the abdominal cavity is a common sequel to vehicular trauma. The source of bleeding is most often secondary to liver or splenic rupture, but can be due to less common causes such as avulsed renal artery or a fractured kidney. Pale mucous membranes should alert the clinician as to the possibility of blood loss, although poor perfusion secondary to shock and volume contraction must also be considered. In general, the presence of a hemoabdomen should be suspected in any patient that presents with signs of shock but without signs of external blood loss. Physical examination finding of a distended abdomen is supportive of hemoabdomen, although a significant amount of abdominal hemorrhage is possible before signs of abdominal distension occur. The initial PCV/TS can be helpful in identifying blood loss when the initial physical examination unremarkable. Although blood loss typically causes a reduction in PCV and TS, a normal PCV in the dog with a hemoabdomen is possible due to splenic contraction. Evaluation of the TS often provides subtle clues as to the presence of blood loss. A total protein of less than 6.0g/dl should raise the index of suspicion of blood loss in the trauma patient. The astute emergency clinician is constantly re-evaluating the trauma patient, and a repeat minimum data base (PCV/TS, BG, Azo) often confirms the initial suspicion of internal blood loss (reduced PCV and reduced TS). A lack of serosal detail on abdominal radiographs may support the presence of hemoabdomen, although a significant amount of effusion must be present before this change becomes obvious. The presence of a hemoabdomen can be confirmed with abdominocentesis, with the PCV of the abdominal blood matching or exceeding the peripheral PCV.

In most cases, patients with traumatic hemoabdomen are successfully managed medically. Treatment for shock should proceed as in any trauma patient to restore perfusion. In some cases, aggressive resuscitation may increase blood pressure sufficiently to worsen intra abdominal bleeding, and highlights the need for constant re-evaluation of the patient. In many cases a full 'shock dose' of intravenous fluids may not be necessary to restore perfusion, and the fluid therapy should be tailored to the patient to avoid over-resuscitation. Abdominal counter pressure may be applied using abdominal bandages, although this is contraindicated in patients with respiratory difficulty or a diaphragmatic hernia. Surgical management of the patient with hemoabdomen is indicated when hemodynamic instability persists despite fluid resuscitation and administration of blood products.

Uroabdomen

Abdominal trauma can also lead to rupture of the urinary bladder. The owner should always be questioned as to whether the patient has urinated since the accident, and physical examination should include palpation of the urinary bladder. In general, the presence of a urinary bladder on abdominal radiographs does not rule out the possibility of urinary tract rupture, although it is less likely. Following resuscitation, the trauma patient should be closely monitored for urinations. If the patient is non-ambulatory, then an indwelling urinary catheter will allow quantification of urinary output. The lack of urine production following resuscitation and during subsequent intravenous fluid administration should alert the clinician to the possibility of urinary tract rupture.

The development of azotemia and hyperkalemia in the trauma patient should alert the clinician to the possibility of a bladder rupture. Abdominal distension with a fluid wave may be present, and abdominocentesis should be performed to differentiate uro- from hemoabdomen. Comparison of the creatinine in the abdominal fluid to that of peripheral blood is used to confirm the presence of uroabdomen, with a creatinine higher than that of peripheral blood indicating that the abdominal fluid is urine. The diagnosis of uroabdomen warrants surgical exploration with repair of defects in the urinary bladder. A positive contrast cystourethrogram is often performed prior to surgery to better locate the defect and to rule out urethral compromise. Finally, it is important to remember that abdominal trauma can lead to kidney or ureter damage and subsequent fluid accumulation in the retroperitoneal space. Retroperitoneal fluid accumulation may consist of urine if a ureter has been damaged, or blood in the case of a fractured kidney. Contrast studies should be performed prior to surgery to confirm the area of damage as well as kidney function.

Bite wounds

Injuries associated with bite wounds generally involve puncture wounds that may or may not penetrate the abdomen. Physical examination findings often include bruising as well as multiple puncture wounds. Since small animals are often shaken from side to side by larger ones, the degree of tissue damage visible on physical examination is often not reflective of the extent of damage to underlying tissues. Once treatment for shock has been initiated, then a thorough physical examination can be performed. It is often necessary to shave the hair over any areas that have sustained bruising to identify small puncture wounds. Sterile Q-tips can be used to explore puncture wounds and lacerations to identify those that penetrate the abdomen. All bite wounds that do not penetrate the abdominal cavity should be thoroughly flushed and closed over a drain. Once a wound is identified that penetrates the abdomen, then an exploratory laparotomy should be performed to rule out injuries to internal organs. The potential for internal injuries resulting from bite wounds should not be underestimated, and include punctured bowel, avulsed renal vessels and urinary tract rupture. Antibiotic therapy is indicated in all dogs that have sustained bite wounds.

Other external wounds

External wounds that occur as a result of vehicular trauma are very common. In general the principles of wound management are similar to those of bite wounds. However wounds sustained from vehicular trauma are often extensive and extend into the inguinal region. Once cardiovascular stability has been achieved, the patient is generally anesthetized (a short acting or reversible anesthetic is optimal) and maintained on inhalant anesthesia while the wounds are clipped, cleaned, draped and explored. If a wound is found to penetrate into the abdominal cavity then an exploratory laparotomy is indicated. Wounds that do not extend into the abdominal cavity can be closed over a drain, or in the case of extensive or de-gloving wounds, managed with wet to dry bandages until primary closure is possible.

Body wall hernia

Both blunt abdominal trauma and bite wounds may lead to protrusion of abdominal contents through a tear in the body wall. Traumatic body wall hernias most commonly involve the abdominal cavity, and organs commonly contained within these hernias include omentum, small intestine, and bladder. Traumatic body wall hernias may be identified as a result of physical examination or abdominal radiographs. Surgical correction is required due to the concern over strangulation of hernia contents.

Diaphragmatic hernia

Damage to the diaphragm leading to herniation of abdominal organs into the thoracic cavity is a common sequel to abdominal trauma. The possibility of a diaphragmatic hernia warrants thoracic radiographs in every patient that has sustained trauma. Physical examination findings vary depending on the organs that have been pushed into the thoracic cavity. While the palpation of a 'relatively empty' abdomen may suggest the presence of a diaphragmatic hernia, physical examination findings may be subtle (i.e. failure to palpate caudal borders of the liver or the spleen). Emergency surgery is indicated when the stomach is located in the thoracic cavity due to the possibility of gastric dilatation, when hemodynamic stability cannot be achieved, and when the respiratory system is severely compromised. An abdominal approach is typically performed, allowing retraction of abdominal organs from the chest and repair of the diaphragm.

Biliary tract rupture

While many injuries secondary to abdominal trauma are identified within 24 hours of the traumatic event, other injuries may be manifested several days to weeks later. Biliary tract rupture is an uncommon sequel to abdominal trauma. Clinical signs are non-specific and often include lethargy, inappetance, vomiting, or abdominal distension. The presence of bile in the abdominal cavity causes an inflammatory reaction leading to peritonitis, which may or may not be septic. Abdominocentesis should be performed, and cytological evaluation of the fluid typically reveals an inflammatory effusion with scattered bile pigment. Surgical management is warranted in the patient with bile peritonitis.

Vascular insults

Other uncommon sequelae of abdominal trauma include infarction of renal, splenic, or other vessels, and avulsion of mesenteric vessels. Infarction of major vessels, for example the splenic vein, may lead to necrosis and septic peritonitis. Avulsion of mesenteric vessels, while not causing substantial blood loss, leads to segmental bowel necrosis 3-7 days following a traumatic event. Since these injuries are not recognized immediately, the development of lethargy, anorexia, vomiting or fever a few days or a few weeks following a traumatic event warrants re-evaluation of the patient.

Abdominal injuries secondary to traumatic events can be manifested immediately or several days following trauma. Initial efforts should be directed at identification and treatment of shock and patient stabilization. Once cardiovascular stability has been achieved and perfusion has been restored, the extent of abdominal trauma can be investigated. Hemoperitoneum can be managed medically in most instances, while other types of abdominal trauma including uroabdomen and bile peritonitis require surgical intervention.

Thoracic Trauma

Thoracic trauma is common encountered as a result of both blunt and penetrating thoracic injury. Thoracic injuries that are commonly encountered in the small animal trauma patient include pneumothorax, hemothorax, pulmonary contusion, rib fractures and thoracic wounds. As in all trauma patients, treatment for shock should be initiated as soon as it is identified. Oxygen can be administered via a mask while venous access is obtained. Physical examination findings including respiratory rate and effort as well as auscultation of the thorax can provide important clues as to the nature of the thoracic injury. Pain secondary to rib fractures may also affect chest excursions and should not be underestimated. Oxygenation and ventilation status are ideally evaluated using an arterial blood gas, and pulse oximetry can provide some information relative to oxgenation. In general oxygen supplementation is indicated when the PaO2 is less than 75-80 mmHg. It is important to relate the blood gas findings to the degree of effort and quality of the breaths being taken. For example a PaO2 of 80 mm Hg maybe considered at the lower limit of normal. However if the patient is working very hard to achieve this PaO2 then this patient is in danger of respiratory fatigue and should receive supplemental oxygen immediately. In general, intubation and administration of 100% oxygen should be performed if adequate oxygenation cannot be achieved using a mask or nasal oxygen supplementation. Mechanical ventilation is indicated with a PaO2 <50-60mmHg despite supplementation, or PaCO2 > 50 mmHg.

Pulmonary contusion

Pulmonary contusion is one of the most common complications of thoracic trauma, and can range in severity from mild to life threatening. Radiographic evidence of pulmonary contusion can range from interstitial to severe alveolar pulmonary patterns. Harsh lung sounds are often ausculted on physical examination. Treatment for pulmonary contusion varies according to severity. In mild cases of pulmonary contusion no specific treatment is required. More severely affected patients may require oxygen support and in some cases, mechanical ventilation. As in all trauma patients, treatment for shock should be initiated immediately to restore perfusion. In the presence of pulmonary contusion, however, aggressive fluid therapy may lead to worsening of the respiratory status and excessive fluid administration should be avoided. Pulmonary contusion may worsen in the first 24-48 hours following a traumatic event and resolves over 4-7 days. The presence of pulmonary contusion does not automatically warrant antibiotic therapy, and diuretics are generally not indicated.

Pneumothorax

Pneumothorax, or air leakage into the pleural space, also occurs commonly secondary to thoracic trauma. A pneumothorax can occur secondary to raised intrathoracic pressure causing alveolar rupture, or may develop due to a penetrating wound or rib fracture. The diagnosis of pneumothorax is commonly based on thoracic radiographs. Signs of pneumothorax on thoracic radiographs include a cardiac silhouette that is raised off of the sternum, collapsed lung lobes, and loss of pulmonary vascular markings near the periphery. However, physical examination can also be helpful in the diagnosis of a pneumothorax, as auscultation of the thorax typically reveals quiet lung sounds relative to the degree of respiratory effort. Treatment of pneumothorax varies according to severity. Mild cases of pneumothorax may not necessitate any treatment, while other cases may require thoracocentesis or thoracostomy tube placement. In general, a thoracostomy tube is indicated when repeated thoracocentesis are required or when an endpoint of air removed via thoracocentesis cannot be reached. A tension pneumothorax is the most severe and life threatening form of pneumothorax. This occurs when air leakage into the pleural space occurs in a fashion similar to a one-way valve. Severe increases in pleural pressure due to accumulation of air during inspiration lead to reductions in cardiac output and venous return. Physical examination findings include respiratory distress along with a barrel chested appearance and cyanosis. Emergent thoracostomy tube placement is the treatment of choice of the tension pneumothorax. Traumatic pneumothorax is typically self-limiting. However air leakage into the pleural space may continue for several days following thoracic trauma.

Hemothorax

Blood loss into the pleural space can occur secondary to thoracic trauma. Most commonly, blood loss due to hemothorax is mild and self-limiting. Severe cases of hemothorax may warrant thoracocentesis to alleviate respiratory distress and rarely, administration of blood products.

Rib fractures

Rib fractures are common with thoracic trauma and are easily identified on chest radiographs. Rib fractures are often associated with subcutaneous emphysema, focal hemorrage, and pneumothorax. Most rib fractures are not repaired surgically. However, pain management is important as pain associated with rib fractures can discourage the patient from taking adequate deep breaths and can lead to hypoventilation. Pure opioids (Morphine, Hydromorphone, Fentanyl) are commonly chosen for pain management of the trauma patient. Local analgesia using intercostals nerve blocks can also be performed by injecting 0.25ml Bupivicaine dorsally caudal to the affected ribs.

Flail chest injury occurs when at least 2 ribs are fractured in 2 locations. This leads to a segment of thoracic wall that shows paradoxical movement relative to respiration. The flail segment collapses on inspiration while the rest of the chest wall expands, and is pushed out during expiration when the rest of the chest wall collapses. Small flail segments may not cause respiratory compromise, while large flail segments or concurrent pulmonary contusion can be associated with severe dyspnea. Treatment of flail chest injury is mostly supportive, consisting of oxygen support, treatment of shock, and pain management. Mild cases often resolve with medical management alone. However, a variety of surgical techniques have been described for stabilization of flail chest segments and surgical stabilization may be indicated in cases of severe respiratory compromise

Thoracic wounds

All wounds located over the thorax should be explored and penetration into the thorax must be ruled out. The general principles of wound management apply in the patient with wounds located over the thorax. Chest radiographs are always indicated for identification of pneumothorax, pulmonary contusion, and rib fractures. Trauma patients with wounds located over the chest should always be intubated and monitored during exploration of the wound, as manipulation of the tissues can lead to pneumothorax. A thoracotomy is indicated when penetration into the thorax has been identified, and the thoracic structures assessed for further damage. Penetrating thoracic foreign bodies should be approached with caution. For example, the dog that presents with a stick protruding from the thoracic cavity should have minimal wound exploration performed prior to a thoracotomy. In these cases, the external wound is often small, however the extent of internal damage should not be underestimated. Premature removal of the penetrating foreign body may lead to pneumothorax, hemothorax, and rapid cardiovascular decompensation.

Tracheal compromise

While severe damage to the major airway is rare, tracheal laceration occasionally occurs in animals that have sustained bite wounds to the neck. Physical examination finding of subcutaneous emphysema in the neck region is supportive of tracheal laceration. Mild cases may not be associated with respiratory compromise, while severe respiratory distress may occur with severe lacerations or tracheal avulsions. Mild tracheal lacerations resolve with time and supportive care. All trauma patients with subcutaneous emphysema should have chest radiographs performed and the thoracic trachea examined for air leakage. If bite wounds to the neck are present, the cervical trachea can be examined during exploration of the wound and a tracheal laceration can be repaired at that time. Major tracheal laceration or tracheal avulsion can lead to pneumomediastinum or less commonly, pneumothorax. Thoracocentesis or chest tube may be required if a pneumothorax is present. Long term complications of tracheal damage include tracheal necrosis and tracheal stenosis.

Thoracic trauma is common in the veterinary trauma patient. Serial assessment of oxygenation and ventilation status is imperative to successful management of these patients. Pulmonary contusion and pneumothorax secondary to thoracic trauma can often be managed medically with oxygen supplementation and placement of a thoracostomy tube. Mechanical ventilation may be required in cases of respiratory failure that is not responsive to oxygen administration. Penetrating thoracic wounds should not be removed until the animal is anesthetized and prepped for surgery due to the high likelihood of inducing pneumothorax and intrathoracic bleeding.