After this course, the participant should be able to:
Patients presenting with major and multiple injuries requiring emergency surgery are a great challenge to the anaesthetist. The causes of perioperative morbidity and mortality in patients with blunt thoracic trauma are; airway obstruction, respiratory failure and haemorrhage. The anaesthetist is ideally suited and trained to deal with these problems.
Trauma is a disease of the young and is the leading cause of death in the first three decades of life. Injury accounts for more than 50% of deaths in children and is the third leading cause of death after cancer and atherosclerosis in all age groups. It has been estimated in the United States that thoracic trauma accounts for one quarter of all trauma deaths (1). In a 5 year Canadian study of patients admitted to an urban trauma unit, 96.3% had sustained blunt trauma while the remaining 3.7% were injured with a penetrating mechanism. The causes of blunt injuries were attributed to motor vehicle accidents (70%), suicides (10%), falls (8%), homicides (7%) and others (5%). The incidence of thoracic trauma was 46%. Patients with thoracic injuries had a mortality rate of 15.7% while those without thoracic injuries had a mortality of 12.8% (2). When patients present to the operating room within 24 hours of admission, the incidence of blunt thoracic trauma has been reported as high as 62.5% (3).
The most common blunt thoracic injury in both adult and pediatric age groups is rib fractures (4,5). The incidence of fractured ribs in patients presenting to the operating room for emergency surgery is 67.3% (3). Rib fractures are frequently associated with other injuries such as flail chest, pulmonary contusion and pneumothorax. Pain may result in splinting which may lead to atelectasis and secretion retention. Pain management becomes an important postoperative issue (6). In conscious patients fractured ribs can be easily detected with physical examination. Chest radiography should be obtained preoperatively not only to detect rib fractures but to look for associated injuries such as pneumothorax, haemothorax or pulmonary contusion as these may need to be managed before taking the patient to the operating room. The only intraoperative concern regarding rib fractures is that a fractured rib edge may cause a pneumothorax when the patient is placed on positive pressure ventilation after the induction of anaesthesia. We have advocated the placement of a prophylactic chest tube in patients with fractured ribs undergoing anaesthesia with positive pressure ventilation.
A flail chest occurs when there are enough rib fractures to result in a free or floating segment of chest wall. As a result, during spontaneous ventilation the floating segment moves in the opposite direction or paradoxically to the rest of the chest wall. Flail chest, therefore, is a purely clinical diagnosis that can only be made during spontaneous ventilation. The incidence of flail chest in patients with blunt thoracic trauma presenting to the operating room is 23.1% (3). Because of the pliant nature of a child's ribs, flail chest is rarely seen in the pediatric population (5). Flail chest is almost always associated with an underlying pulmonary contusion. Splinting of respiration from pain and intrusion of the flail segment on the underlying pulmonary contusion leads to increased work of breathing and intrapulmonary shunting with hypoxia. Management is directed towards pain control and intermittent positive pressure ventilation where indicated (Table I) (7).
Indications for Tracheal Intubation and Mechanical Ventilation (7)
| Criteria | Indication |
|---|---|
| PaO2 | <70 mmHg with rebreathing mask |
| PaCO2 | >50 mmHg |
| Respiratory Rate | >35/min |
| Vital Capacity | <15 ml/kg |
| Negative Inspiratory Force | <20 cm H2O |
The incidence of pulmonary contusion in adult patients presenting to the operating room for emergency surgery is 65% (3). Pulmonary contusion is a concussive loss of vessel integrity resulting in intraparenchymal and alveolar haemorrhage, decreased pulmonary compliance and increased shunt fraction (8). There are few clinical signs, consequently the diagnosis is made radiographically. Pulmonary contusion presents as a diffuse non-segmental airspace consolidation on the antero-posterior chest radiograph. Haemorrhage into the tracheobronchial tree occurs in approximately 10% of patients with pulmonary contusion. The main method of management of haemorrhage into the tracheobronchial tree is frequent tracheal tube aspiration. Lung isolation procedures may be required in 33% of patients with airway bleeding (3). Other treatment modalities for pulmonary contusion such as fluid restriction, diuretics and corticosteroids have not shown any benefit (9). Positive end expiratory pressure will improve hypoxaemia but does not change the underlying contusion (8).
The incidence of pneumothorax in adult patients presenting to the operating room for emergency surgery is 30% (3). Possible etiologies of pneumothorax in blunt trauma include alveolar rupture with perivascular spread of gas to the hilum and connection of a distal airway to the pleural space (10). A simple pneumothorax can become a tension pneumothorax under anaesthesia because of the institution of positive pressure ventilation and/or the administration of nitrous oxide. A tension pneumothorax is a life-threatening condition. Elevated pressure in the pleural space results in hypoventilation and hypoxaemia. Decreased venous return due to kinking of the pulmonary veins and vena cava produces profound hypotension and if uncorrected will result in cardiac arrest. Diagnosis of pneumothorax during general anaesthesia is notoriously difficult. Controlled ventilation and the noisy environment of the operating room make auscultatory findings unreliable (10). Frequently pneumothorax is only suspected when the physical signs of tension such as hypotension, elevated airway pressure, distended neck veins and a deviated trachea are present. A high index of suspicion and willingness to perform needle or tube thoracostomy is needed to prevent a fatal outcome from this injury.
The incidence of haemothorax in adult patients presenting to the operating room for emergency surgery is 26% (3). Bleeding may be minimal or massive as one hemithorax can accommodate 30 to 40% of a blood volume. Such a massive haemorrhage usually indicates injury to the heart or great vessels. A massive haemothorax is defined as more than 1500 ml of blood in the pleural space and will cause hypovolaemic shock. Mediastinal shift can occur and will cause further cardiovascular embarrassment and ultimately cardiovascular collapse. Physical examination is difficult in the operating room but findings such as decreased breath sounds and tracheal deviation from the affected hemithorax should be elicited. The diagnosis is confirmed with radiography. A supine film will demonstrate an increased density over the affected hemithorax. Tube thoracostomy is the treatment of choice (1). Insertion of a chest tube results in evacuation of the haemothorax improving ventilation and allows for monitoring of any ongoing thoracic blood loss.
The incidence of diaphragmatic rupture in patients with blunt thoracic trauma presenting to the operating room is 9.1% (3). Diaphragmatic rupture likely occurs as result of a sudden and massive increase in intra-abdominal pressure. If the diaphragmatic tear is large enough, the relatively negative pleural pressure during spontaneous ventilation encourages herniation of abdominal organs into the chest compressing the adjacent lung leading to respiratory embarrassment. Diaphragmatic injuries are more frequent on the left side as the liver affords some protection to the right hemidiaphragm. Physical examination is not very helpful in making the diagnosis of diaphragmatic injury in the patient with multiple injuries. Chest radiography demonstrating elevation of the left hemidiaphragm with an arch-like shadow suggesting an abnormally high diaphragm, bowel gas patterns in the left hemithorax and shift of the heart and mediastinal structures to the opposite side of the defect suggest a diaphragmatic injury. Diagnosis can be confirmed by passing a nasogastric tube as the tip of the tube may be seen in an intra-thoracic stomach (11). Aspiration is a risk in the presence of intra-thoracic herniation of abdominal contents. Tracheal intubation and positive pressure ventilation will alleviate respiratory distress and protect the airway.
Blunt injury of the heart can take many forms ranging from subtle alterations in electrical conduction and cardiac function to myocardial rupture and death. True structural injury to the heart is rare. One ventricular laceration was reported in 201 patients with blunt thoracic trauma presenting to the operating room in a 2 year Canadian series (12). The frequency of myocardial contusion in patients with blunt thoracic trauma when based on radionuclide angiographic or autopsy diagnosis is 2.6% (13). The incidence of this entity in patients with blunt thoracic trauma presenting to the operating room for emergency surgery using similar diagnostic criteria was 5.7%. While the intraoperative and overall mortality rates were higher in patients with myocardial contusion, these patients were more severely injured. The incidence of hypotension or dysrhythmias was similar whether or not a myocardial contusion was present. The leading cause of intraoperative deaths in adult patients with myocardial contusion was hypovolaemia rather than the cardiac injury (12). Children with radionuclide proven myocardial contusion seem to tolerate emergency surgery without incident (14).
The incidence of traumatic rupture of the aorta in patients with blunt thoracic trauma presenting to the operating room is 4.8% (3). The natural history of traumatic aortic rupture is controversial. Up to 90% of patients with aortic rupture exsanguinate at the accident scene or arrive in the emergency department with absent vital signs. The remaining 10% survive to reach hospital because the aortic rupture is contained by an intact adventia (15). Rupture of the aorta may not be imminent in patients with aortic injury surviving long enough to reach hospital. Diagnosis requires a high index of suspicion as patients who may have this injury present urgently to the operating room for surgical management of other life threatening injuries before appropriate investigations can be completed. The injury is frequently first suspected on the plain chest radiograph. Radiographic findings suggestive of thoracic aortic injury include; widening of the superior mediastinum, loss of the aortic knob, deviation of the nasogastric tube to the right and left apical cap. Early repair of the aortic injury may exacerbate coexisting injuries such as pulmonary or myocardial contusions or significant head injuries. Delaying surgery for associated life or limb threatening injuries in patients with traumatic disruption of the thoracic aorta will lead to significant morbidity and mortality from the associated injuries. Definitive diagnosis, aortography, frequently must wait until life and limb threatening injuries have been dealt with. Once the patient has achieved haemodynamic and respiratory stability, investigation and management of the aortic injury can take place. If aortic injury is suspected or present during an urgent surgical procedure the blood pressure should be continuously monitored. Hypertensive episodes should be avoided and mean arterial pressure should be maintained between 70 and 80 mmHg with the use of beta blockers and vasodilators (15).
Tracheobronchial injuries are rare with a reported incidence of 0.8% in patients with blunt thoracic trauma (4). Many patients with this injury die at the accident scene. Haemoptysis and subcutaneous emphysema should alert the anaesthetist to the possibility of this injury. Radiographic findings of an intra-thoracic tracheobronchial injury are pneumothorax and mediastinal emphysema (16). A tracheobronchial injury should be seriously considered when a patient has a pneumothorax with a massive air leak that is not evacuated by insertion of a chest tube. This injury is confirmed by fibreoptic bronchoscopy. Many patients will require control of the airway with tracheal intubation because of the tracheobronchial or other associated injuries. Intubation is ideally performed with a fibreoptic bronchoscope to aid in tube placement and to properly examine and evaluate the injury (16). Some patients with injuries in the main bronchi may require lung isolation procedures because of large air leaks or haemoptysis.
Blunt laryngeal injuries are also rare (17). The incidence of laryngeal injuries in patients presenting to the operating room with blunt thoracic trauma is 0.3% (3). The classical signs of laryngeal injury include; hoarseness, subcutaneous emphysema in the neck and haemoptysis. Signs of airway compromise must be sought on initial presentation. Even in the absence of airway compromise, examination of the upper airway by endoscopy and computed tomography is necessary to determine the degree of injury and predict whether airway obstruction could occur (17). Patients arriving with laryngeal injuries and an apparently normal airway may develop upper airway obstruction within hours of admission. Early tracheal intubation may be required depending on the findings at laryngoscopy. Tracheostomy is indicated in all patients requiring an artificial airway and may be the method of choice to secure the airway when it is compromised (17).
Patients with blunt thoracic trauma frequently present to the operating room in an urgent manner. There is generally little time to fully evaluate the patient. The antecedent history is often sparse. Useful information from an anaesthetic perspective includes mechanism of injury, recent meals, alcohol or recreational drug use, current medications and any known underlying cardiovascular or pulmonary disease. Preoperative evaluation should include a brief neurological assessment (pupillary and motor responses), careful assessment of the airway and an examination of the thorax looking for evidence of injuries such as haemothorax, pneumothorax, tension pneumothorax, fractured ribs and flail chest. Preoperative preparation should include chest radiography, haemoglobin determination, arterial blood gas and electrolyte analysis (7).
Standard monitoring such as electrocardiogram, blood pressure by cuff, temperature, airway pressure, peripheral nerve stimulator, pulse oximetry and end-tidal carbon dioxide measurement is essential. Other monitors such as arterial cannulation and urinary catheterization are vital in theses critically ill patients. An indwelling arterial catheter allows for continuous blood pressure measurement, blood gas, haematological and chemistry analysis freeing the anaesthetist's hands for other aspects of the ongoing resuscitation. Other monitors such as central venous pressure or pulmonary artery catheters are less useful and should not delay resuscitation or definitive care. As pneumothoraces may develop intra-operatively, the use of prophylactic chest tubes on the side of rib fractures should be considered. Placement of prophylactic chest tubes in addition to preventing the development of an intraoperative pneumothorax allows the anaesthetist to monitor ongoing bleeding from the affected hemithorax (3).
Airway management remains controversial. Up to 30% of patients with blunt thoracic trauma undergoing emergency surgery may have an abnormal airway due to mandibular and/or maxillary fractures or cervical spine and/or cord injuries. Frequently, due to the urgency of injuries the cervical spine cannot be fully evaluated before surgery yet the incidence of cervical spine injuries in patients presenting to the operating room may be as high as 12% (3). A cervical spine injury should be suspected in all patients with blunt trauma until proven otherwise. Other concerns include the presence of an intestinal ileus, head injury and hypovolaemic shock. The techniques of airway management are beyond the scope of this presentation.
Victims of blunt trauma are invariably hypovolaemic when they arrive at the operating room. Adequate volume replacement before the induction of anaesthesia is mandatory. Drugs that exert a negative inotropic or have peripheral vasodilatory effects should be used with caution and reduced dosage or not at all. The use of specific agents for induction and maintenance of anaesthesia is less important than applying the appropriate physiological and pharmacological principles to the polytraumatized patient in shock.
The main cause of intraoperative death in patients with blunt thoracic trauma remains exsanguination (3,12). Multiple large bore intravenous catheters should be inserted. Many of these patients require massive blood replacement. Significant transfusion problems in the intraoperative setting include coagulopathy, hypothermia and hypocalcaemia.
Coagulopathy after massive transfusion is a clinical diagnosis with lab testing playing a confirmatory role and guiding therapy. The coagulopathy is caused by dilution and increased consumption of platelets and clotting factors. Disseminated intravascular coagulation (DIC) may supervene exacerbating the coagulopathy if the haemorrhagic shock state persists. After replacement of one blood volume the platelet count may be low enough to induce a coagulopathy. After replacement of two blood volumes clotting factors have been diluted enough to result in a coagulopathy. Prolongation of the prothrombin and partial thromboplastin times in the absence of DIC is most likely caused by hypofibrinogenemia. Management of dilutional coagulopathy is accomplished with platelet and factor replacement. Management of DIC is directed toward treating the underlying cause and factor replacement if coagulopathy is the major presenting component (18).
Hypothermia is common in trauma patients because of environmental exposure at the time of injury, rapid infusion of cold fluids and blood, altered temperature homeostasis because of anaesthesia and exposure of abdominal and thoracic contents at the time of surgery. Body temperature is determined by the balance of heat loss and heat gain. Anaesthesia and surgery promote heat loss while inhibiting or abolishing all mechanisms of heat gain. There are four mechanisms of heat loss (Table II). There are only a limited number of acute responses to a cold stimulus. They include; change in behavior to conserve heat, superficial vasoconstriction, shivering and non shivering thermogenesis. Anaesthetics promote reduction in temperature by preventing vasoconstriction, abolishing shivering, depressing metabolic rate and prohibiting appropriate behavioral responses. Since radiation is the chief form of heal loss, management of the temperature of the ambient air is the most efficient way of controlling patient temperature. Humidification of airway gases will reduce heat loss by 10-15%. Warming blood and intravenous fluids is essential during large volume resuscitations. Warming blankets are the least efficient method of preventing heat loss with some studies showing no effectiveness (19).
Hypocalcaemia associated with massive transfusion is rare but may be seen with; a blood transfusion rate of greater than 1 unit every 5 minutes, persistent hypovolaemic shock with inadequate hepatic perfusion, hypothermia and clamping of the porta hepatis to control hepatic bleeding. Hypocalcaemia is detected when unexplained hypotension is present with a prolonged QT interval on the electrocardiogram (20).
| Mechanism | Definition | Heat Loss |
|---|---|---|
| Radiation | Transfer of energy via infrared electromagnetic radiation |
40-50% |
| Convection | Transfer of energy from body surface to moving air molecules |
25-35% |
| Evaporation | Heat loss required to vaporize water |
10-20% |
| Conduction | Direct contact with cold objects resulting in direct transfer |
5-15% |
Intraoperative ventilation problems present as elevated airway pressure and desaturation. Ventilation problems in patients with blunt thoracic trauma have been attributed to; bleeding into the airway, pulmonary oedema from aggressive resuscitation and intraoperative pneumothorax. Haemorrhage into the airway can result in soiling of the remaining good lung leading to profound hypoxia. Bleeding may be severe enough to require isolation of the haemorrhagic lung (3).
Anaesthetic care often continues into the intensive care unit. A large proportion of patients with blunt thoracic trauma undergoing emergency surgery will require postoperative ventilation. The most common indicators for postoperative ventilatory support appear the severity of head injuries and/or thoracic injuries. Coexisting factors such as abdominal injuries and/or surgery as well as head and spinal cord injury must be taken into account when choosing whether postoperative ventilation is necessary. Mechanical ventilation should be considered in patients with flail chest and significant head injuries and postoperatively in patients undergoing emergent thoracotomy or upper abdominal laparotomy. In a review at our institution 69% of patients with blunt thoracic trauma requiring urgent surgery within 24 hr of admission required postoperative ventilation. The requirement for postoperative ventilation was correlated directly with the intraoperative alveolar-arterial partial pressure gradient for oxygen (A-a DO2) and inversely with the preoperative Glasgow coma score (3).
Victims of blunt thoracic trauma are some of the most severely injured presenting to the operating room for emergency surgery. These individuals tax both anaesthesia and critical care skills during the intraoperative period. The major causes of intraoperative death are exsanguination and asphyxia. The anaesthetist is the best qualified individual to deal with these intraoperative problems.
a) Which of the following statements is FALSE?
b) Which of the following statements is TRUE?
c) Select the TRUE statement:
d) With respect to anaesthesia for the blunt trauma victim, which statement is FALSE:
Answers
Winterlude 95 Programme