Anesthetic Considerations for Penetrating Thoracic Trauma

Abstract

Summary T he thorax is the upper part of the trunk. It consists of an external musculoskeletal cage, the thoracic wall, and an internal cavity that contains the heart, lungs, esophagus, trachea, thymus, the vagus and phrenic nerves and the right and left sympathetic trunks, the thoracic duct and major systemic and pulmonary blood vessels. Inferiorly the thorax is separated from the abdominal cavity by the diaphragm, superiorly it communicates with the neck and the upper limbs (Michael, 2009). Thoracic trauma is characterized based on the mechanism of injury. Penetrating chest trauma is often related to stab and gunshot wounds. Blunt chest trauma is most commonly associated with motor vehicle collision, fall from height, crush, blast and assault. Thoracic trauma can result in respiratory distress due to pulmonary contusion, multiple rib fractures, flail chest, pneumothorax, aspiration, tracheobronchial injury or hemothorax. Thoracic trauma may also result in shock from hemorrhage, ventricular dysfunction, cardiac tamponade or tension pneumothorax (Astley and Smith, 2012). Appropriate preoperative evaluation and preparationof patients scheduled for elective thoracicsurgery can significantly reduce the rate of postoperative complications.The acute nature of injuryand the surgical procedures that are associatedwith the trauma preclude such a formalpreparation. The initial evaluation is directed atdiagnosing and treating life-threatening complicationsrelated to the airway and the cardiopulmonarysystems. A secondary survey shouldrapidly be done to search for other concealed injuriesthat may require immediate attention (Taine et al., 2002). The major goals in thoracic trauma resuscitation are repletion of intravascular volume, normalization of tissue oxygen delivery, and control of bleeding. Thoracic trauma patients often present with shock due to hemorrhage, but may also have other causes of shock such as tension pneumothorax, pericardial tamponade, and cardiac injuries (David Cherkas, 2011). While the majority of patients with thoracic trauma canbe managed conservatively or with a simple intercostal catheter (ICC), a small but significant number ofblunt (10%) and penetrating (15–30%) injuries require thoracotomy as a component of initial resuscitation.Often patients will have multiple coexisting injuries also requiring urgent surgery (Meredith and Hoth, 2007). Standard monitoring, including auscultation of breath and heart sounds, and secure venous access is the cornerstone of any anesthetic technique for patients with cardiothoracic trauma. Standard monitoring for cardiothoracic trauma includes ECG, noninvasive Blood Pressure (BP), pulse oximetry, end-tidal CO2, precordial or esophageal stethoscope, and core temperature. If a chest tube has been placed, ongoing blood loss from the affected hemithorax can be monitored (Cheryl Hilty et al., 2007). The ASA algorithm for management of difficult airways is a useful starting point for the trauma anesthesiologist, whether in the emergency department (ED) or the operating theatre. However, as the algorithm suggests, reawakening a patient after difficulty in securing the airway is usually not an option; tracheal intubation must be achieved using conventional or surgical means. A surgical airway may be the first or the best option in certain conditions(Ferson and Chi, 2005). The ‘ideal’ emergency anesthetic induction agent is one which rapidly achieves unconsciousness and yet does not itself cause hemodynamic compromise. One philosophy is to argue that in certain circumstances, any induction of anesthesia is too hazardous. The obtunded patient is assumed to be sufficiently unconscious to allow surgery to progress without the need for any anesthetic agent (with its attendant side-effects). However, in practice emergency (and cardiac) anesthesia is well documented to be associated with an increased incidence of awareness (Morris et al., 2009). Patients sustaining thoracic trauma often require postoperativesupport of the respiratory and cardiovascularsystems and optimization of oxygen delivery in an intensive care unit (ICU).Care is directed towards management of general problemssuch as fluids, pain control, nausea and vomiting, centralnervous system (CNS) depression, agitation, and complicationsof unsuspected drug abuse. Serial chest x-rays,assessmentof chest tube drainage,and monitoring for complicationsrelated to the initial injuries such as pulmonary contusion, adult respiratory distress syndrome(ARDS),retained hemothorax, empyema, pulmonary lesions, and non-cardiothoracic injuries (e.g., head,spinal cord, abdominal, retroperitoneal, orthopedic, and vascular injuries) may be necessary (Cheryl et al., 2007).