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Initial Trauma Assessment - The Anaesthetist's
Role Ian Zunder MD FRCPC, Department of
Anaesthesia Objectives
Introduction
Trauma is the leading cause of death in the first four decades of life within modern industrialized countries. Death from trauma has a trimodal distribution:
Trauma cuts across the entire field of medicine, requiring the physician to have a broad knowledge base of treatment principles and an appreciation for multiple varieties of injury. An organized consistent approach to the trauma patient affords an optimal outcome. The Advanced Trauma Life Support (ATLS) Course was developed in Nebraska and soon adopted by the American College of Surgeons in 1979. The primary focus of ATLS is on the first hour of trauma management, when rapid assessment and resuscitation can be carried out to reduce deaths within the Golden Hour. Today, this course is taught throughout the world. Involvement of anaesthesia personnel in trauma resuscitation is commonplace whether it be in the small country hospital or the big city Trauma Center. Anaesthetists now take an active part in the teaching of ATLS skills, especially with regards to airway management. Course content and recommendations have changed over the years to reflect the insight of the anesthesia providers. This lecture will focus on our role as anaesthetists in the "primary survey" as defined by the ATLS. During the primary survey, life threatening conditions are identified and management is begun simultaneously.
As an anaesthesia provider, our skills with the Airway, Breathing and ventilation are often called upon. It is important to remember that it is impossible to completely isolate each component and that in reality, these management goals are inter-related. Airway / Breathing As well, immobilization of the cervical spine is the accepted standard of care to prevent secondary neurologic injury. The most effective device for this purpose is the halo vest although it tends to be inappropriate in the emergency setting. The most practical apparatus is a combination of a hard collar and sandbags on opposite sides of the head. Tape is then extended from one side of the spine board over the forehead of the patient to the opposite side of the board. This provides near complete cessation of movement.(1) On its own, a hard collar provides only moderate protection and a soft collar offers minimal benefit. Begin the assessment by establishing verbal contact with the patient. Clear phonation by the patient establishes that the airway is patent.
Further intervention will depend on:
ASSESS: Neurological
Stability
A depressed level of consciousness is considered to be intracranial pathology until proven otherwise, although altered mentation is often due to drugs, alcohol or medical causes. A brief neuro exam can be done during the primary survey:
One can also determine
the Glasgow Coma Scale (GCS). It is generally accepted that a
GCS < 8 requires definite airway intervention to prevent aspiration
pneumonitis, to insure adequate oxygen delivery and to avoid hypercarbia.
If a patient is responding only to painful stimuli or is unresponsive/unconscious,
the GCS is or has a high likelihood of being less than 8.
ASSESS: Adequacy of Gas Exchange
- Physical Examination Airway patency does not insure adequate ventilation. Look What is the nature of the injury? Maxillofacial trauma/airway burns have the potential for airway compromise. Is there obvious airway or chest trauma (sucking chest wounds, flail segments) or cyanosis? Is there tachypnea, use of accessory muscles of respiration or evidence of tracheal shift? Listen Stridor indicates upper airway compromise. Hyperresonance to percussion/lack of air entry suggests pneumothorax while dullness to percussion/lack of air entry suggests hemothorax. (Note that this is often difficult to determine in the setting of a noisy resuscitation room) Bowel sounds in the chest may be indicative of a ruptured diaphragm. Feel Place a hand over the mouth and feel for air exchange. If necessary, insert a finger and sweep to clear the mouth of any foreign bodies (especially dislodged teeth) and to evaluate for evidence of maxillofacial trauma. ASSESS: Adequacy of Gas Exchange
- Monitoring/Laboratory Pulse oximetry gives immediate feedback although it is necessary to be aware of its pitfalls (motion, peripheral vasoconstriction, carboxy/methaemoglobinemia). The only parameter measured by oximetry is haemoglobin saturation. Arterial blood gases provide a more complete picture of the patient although there is a defined waiting period (institution dependent). Results provide feedback on oxygenation, ventilation and tissue perfusion. Intervention Securing the Airway 1) How quickly must the airway be secured? Airway intervention can be classified as being immediate, emergent or urgent.(2) Immediate If apnea is evident on the primary survey, immediate endotracheal intubation is warranted. However, simple mechanical means of opening the airway and providing ventilation should not be overlooked in the rush to intubate. As previously noted, inspect the mouth for foreign bodies. Blood and secretions should be suctioned. Breathing should be assisted with bag- mask ventilation as preparations are made to intubate. Consideration of possible spinal cord injuries or direct traumatic tracheal injuries should not prevent attempts at lifesaving translaryngeal intubation. Emergent Patients who are hypoventilating, have significant head injury, or are cyanotic require emergency intervention to establish a patent airway and effective ventilation. Occasionally, opening the airway and providing bag-valve-mask ventilation sufficiently improves oxygen- ation to allow use of a more elective method of tracheal intubation. Otherwise, these patients should be treated as above. N.B. In both immediate and emergent intubations, do not hesitate to proceed to a surgical airway if initial attempts are unsuccessful. Urgent Patients with burns, maxillofacial injury and cervical hematomas will likely require a secure airway to prevent upper airway obstruction. Patients with chest wall and pulmonary injuries are usually initially well compensated but may eventually require mechanical ventilation. With these patients, there is often time for a history, appropriate physical exam and cervical radiographs such that a planned approach to the airway may be undertaken. 2) Which route of intubation is to be employed? (oral vs. nasal) Prior to the most recent revision of the ATLS course, a very simplistic approach to the airway was taken (see fig. 1). Blind nasotracheal intubation was heavily relied upon although most anaesthetists are more comfortable with direct orotracheal intubation. Blind nasotracheal intubation requires a spontaneously breathing unconscious or cooperative conscious patient. There is an unacceptable failure rate (35%) and it requires 3.7 vs. 1.3 oral attempts. Nasal intubations are contraindicated in the patient with basal skull or mid-face fracture. The procedure can precipitate epistaxis which may interfere with subsequent alternative attempts at intubation if unsuccessful. There is a high incidence of sinusitis if a tube is left in place greater than 72 hours. Current teaching recognizes the integral role of the anaesthesia provider. The most important determinant of whether to proceed with orotracheal or nasotracheal intubation is the experience of the physician. Both techniques are safe and effective if performed properly.(3) 3) What is the status of the cervical spine? N.B. Assume the cervical spine to be unstable until proven otherwise. Up to 50% of patients sustaining cervical spine trauma develop neurologic abnormalities ranging from nerve root compression and weakness to quadri- plegia, and in many instances, death. As many as 10% of patient with cervical spinal cord injury are initially neurologically intact, but develop deficits during the course of emergency care.(4)
The radiographic dictum "one view is no view" is nowhere more apt than in the roentgenographic evaluation of acute spinal injury. (i.e. a single cross table lateral is not enough). In the lateral view, one must be able to demonstrate all 7 cervical vertebrae and preferably including T1 as approximately 30% of injuries occur at the C7-T1 level. The AP view is assessed for vertical alignment of the spinous and articular process and abnormalities in joint and disc spaces. The open mouth view is used to assess the integrity of the atlanto-occipital and atlanto-axial joints as well as the odontoid process. Oblique views may be used to detail more clearly the intervertebral foramen and the vertebral arches. Most authors feel that a technically adequate, normal three view series can be used to clear the C-spine when there is appropriate correlation with the clinical picture. Pleuridirectional and CT scanning are used to rule out injury when the plain radiographs are suspicious or equivocal or when there is clinical evidence of a cord injury despite negative radiographs. The lateral cervical spine has a sensitivity of about 85%. This increases to 92% in a three view series and up to 100% when selective CT scanning is employed.(5) Radiographic Analysis Anaesthetists should be skilled at basic interpretation of the C-spine films. Secondary spinal injury is often a result of misinterpretation of films. When reading a C-spine film, concentrate on:
1) Abnormal soft tissue can provide significant information with regards to the localization of C-spine trauma. A prevertebral hematoma is usually associated with a fracture and should draw attention to a hyperextension injury. Normally, the distance between the posterior pharyngeal air column and the anterior inferior aspect of C2 is less than 7 mm. and the distance from C6 should be 22 mm. in adults (not valid when Nasogastric/Orotracheal tubes are in place). 2) Normally, the cervical spine has a lordotic curve. Some contend that the loss of lordosis is suggestive of muscle spasm and C-spine injury although this is not totally reliable. Spinal muscles do not play a significant role in neck stability. Instead, it is mainly dependent on the ligamentous and bony complex. Four lines can be drawn to assess alignment:
Disruption of any one of these smooth lines are suggestive of injury. Biomechanical studies by White and coworkers6 have shown that instability of the cervical spine exists if 1) all the anterior or posterior elements are destroyed, 2) there is greater than 3 1/2 mm horizontal displacement of one vertebral body onto another, or 3) there is greater than 11 degrees of kyphotic hyperangulation. Additional helpful findings include widening of the intervertebral disk space, prevertebral hematoma and displacement of the apophyseal joints. 4) How do airway management techniques affect C spine movement? Basic Airway Maneuvers
In a study where all ligaments in a cadaveric model were transected between C5-6 leaving only the muscles intact, various airway management techniques were applied with and without collars used to splint the unstable spine. A chin lift / jaw thrust produced significant (>5mm.) increase in disc space despite the presence of either a hard / soft collar. Likewise, oral endotracheal intubation (curved or straight blade) produced a 3-4 mm increase in disc space. In contrast, oral / nasal airway insertion was responsible for 2 mm posterior subluxation (i.e minimal change).(7) Advanced Airway Maneuvers In another study, a group of healthy, anaesthetized and paralyzed volunteers scheduled for elective surgery were investigated for cervical spine movement during intubation. Significant movement was noted during routine intubation regardless of blade choice (Macintosh vs. Miller). The presence of a Philadelphia collar was inconsequential. However, there was a significant decrease in cervical spine movement (not complete elimination) during orotracheal intubation when the patient was placed on a short spine board and an assistant applied "in line immobilization".(8) Cricoid Pressure Cricoid pressure is considered the standard of care in the trauma patient. Sellick's maneuver increases the convexity of the cervical spine, stretches the esophagus taut, and thus improves its fixation by the posterior aspect of the cricoid cartilage. A potential concern exists regarding the application of cricoid pressure against a potentially unstable C-spine, especially at the C5-7 level. Some authors state that instability at this level is a contraindication to cricoid pressure. However, this appears to be more of a theoretical than practical concern. In many situations, the status of the C-spine is not clearly defined when airway management is initiated. As well, information from large volume trauma centers where cricoid pressure is routinely applied does not reveal an increased incidence of secondary neurologic injury. Contraindications to the application of cricoid pressure are:
5) If the spine is unstable, should the airway be secured with the patient awake or asleep? The optimal mode of intubation is controversial. As part of the early efforts aimed at reducing secondary neurologic injury, a hypothesis was generated that the airway of patients with unstable cervical spines could not be safely managed by oral intubation. Although never proven, it was assumed that movement associated with oral intubation and "in line immobilization" would lead to secondary neurologic injury.(9) Suderman et al(10) showed no difference in new neurologic deficits in a study comparing awake vs. anaesthetized oral/nasal intubations in a ten year review of 150 patients. Rosen (11) has labeled this unsubstantiated hypothesis as a "therapeutic legend of emergency medicine". There are numerous studies showing that induction of anaesthesia and oral intubation in neck-injured patients results in outcomes similar to those patients undergoing awake intubation. Optimum care does not necessarily mean the same care. Different centres may choose different approaches as long as the essential elements are preserved.(9) 6) Which drugs are most appropriate in the trauma setting? Securing the airway can be performed with or without pharmacologic assistance. Patients with maxillofacial trauma, evidence of airway obstruction / injury or other objective evidence which may suggest a difficult laryngeal visualization should have their airway secured while awake. Consider the use of local anaesthetic topicalization with / without the addition of sedative medication (e.g. fentanyl / midazolam). For the patient with anticipated normal anatomy, a rapid sequence intubation is an appropriate choice. If possible, the patient is preoxygenated for 3-5 minutes or asked to take several vital capacity breaths. Pre-curarization (when considering the use of succinylcholine) Cons
Pros
Supplemental Drugs In hemodynamically stable trauma patients, rapid sequence induction is likely to produce an exaggerated hemodynamic response that may be associated with:
The use of titrated doses of narcotics, short acting ß-blockers (e.g. esmolol) and lidocaine, whether alone or in combin- ation can be beneficial in attenuating the response to laryngoscopy/intubation. Induction Agents A large variety of intravenous induction agents are available for the rapid sequence induction of anaesthesia. With the possible exception of ketamine, these drugs are all cardiovascular depressants and should be administered in reduced (25-50% of normal) doses. In severely hemodynamically compromised patients, these agents should be omitted entirely. The most common drug given at trauma centres throughout the world for the purpose of intubation is sodium thiopental. Although not available in Canada, etomidate has gained popularity because of its supposed hemodynamic stability in euvolemic patients at usual induction doses. Muscle Relaxants It is the opinion of this author that succinylcholine is still the drug of choice for intubation of the trauma patient. At the time of writing, none of the non- depolarizers can match succinylcholine in either its speed of onset or offset. Succinylcholine:
Contraindications to succinylcholine include:
Nondepolarizing Muscle Relaxants: The use of these drugs avoids the potential complications from succinylcholine. However, large doses of these agents are required to produce an acceptable onset time. This greatly increases the duration of action of the drug. The drug of choice at the present time is vecuronium which is given in a dose of 0.15-.0.25 mg/kg. It has no cardiovascular effects. Although mivacurium has a short duration of action, it has a long onset time. Increasing the induction dose would speed onset at the expense of unacceptable histamine release and hypotension. Rocuronium will probably become the NDMR of choice once available in Canada as it has an even shorter onset time than vecuronium. What do you do when the airway cannot be secured with traditional techniques? The following is a list of alternative techniques to secure the airway: Gum Rubber Bougie When this device is placed in the trachea, one can sense the "bumps" of the tracheal rings in contrast to the smooth sensation of the esophagus. The endotracheal tube is then fed over the bougie. Lighted Stylet A good technique for the patient with potential C-spine injury as the neck is maintained in the neutral position. However, most of the commercially available stylets require low light levels and concomitant resuscitation may be slowed. Newer models claim superior brightness such that dimming the room lights may no longer be required. Fiberoptic Bronchoscope This technique requires considerable expertise as well as a cooperative patient. It is best to use the largest scope possible as airway bleeding and/or secretions may limit success. Tip: attach oxygen source to suction port so as to both oxygenate the patient and clear secretions. Retrograde or Translaryngeal Route This is probably the route of choice in the setting of maxillofacial trauma. Various techniques have been described.(13,14) The common denominator is the passage of a needle / wire system through the cricothyroid membrane up into the oropharynx with subsequent antegrade threading of an endotracheal tube over the wire into the trachea. Cricothyroid Puncture All anaesthesia providers should be familiar with this skill. Equipment to perform this procedure should be immediately available. Personnel should be readily available to proceed to a formal cricothyroidotomy or tracheostomy. Laryngeal Mask The laryngeal mask is used for the "cannot intubate, cannot ventilate" scenario. It is relatively easy to insert although a learning curve does exist. It can be placed blindly or with the aid of a laryngoscope. Remem- ber that the airway is not secure with a laryngeal mask. It is a stop-gap measure only. Combitube The Combitube is a field airway device which is inserted blindly into the esophagus and allows for indirect ventilation via a double lumen design. It is the opinion of the author that this is the tube of choice for the "cannot intubate, cannot ventilate" scenario. No learning curve exists and it is superior to the laryngeal mask for airway protection.
References 1. Podolsky S. Efficacy of Cervical Spine Immobilization Methods. J. Trauma; 23:6 461-64 2. Grande C. Textbook of Trauma Anesthesia and Critical Care. Mosby Year Book 1993 3. Advanced Trauma Life Support Course for Physicians. The American College of Surgeons; 1993 4. Rogers WA. Fractures and dislocations of the cervical spine: An end result study. J. Bone Surg 1957;39-A:341-76 5. Ross S.E. et al. Clearing the Cervical Spine: Initial Radiologic Evaluation. J.Trauma 27:9 1055-1060 6. White AA. et al. Biomechanical analysis of clinical stability in the cervical spine. Clin Orthop 1975;109:85-96 7. Aprahamian C. et al. Experimental Cervical Spine Injury Model: Evaluation of Airway Management and Splinting Techniques. Ann Emerg Med 13:8 584-87 8. Majernick TG et al. Cervical Spine Movement During Orotracheal Intubation. Ann Emerg Med 15:4 417-20 9. Crosby ET. Tracheal intubation in the cervical spine-injured patient-Editorial. Can J Anaesth 1992; 39:2 105-9 10. Suderman V, Crosby ET, Lui A. Elective oral tracheal intubation in cervical spine-injured adults. Can J Anaesth 1991; 38:6 785-9 11. Rosen P, Wolfe RE. Therapeutic legends of emergency medicine. J Emerg Med 1989;7: 387-9 12. Kovarik WD, et al; Succinylcholine Does Not Change Intracranial Pressure, Cerebral Blood Flow Velocity, or The Electroencephalogram in Patients with Neurologic Injury. Anesth Analg 1994;78:469-73 13. Barriot P, Riou B. Retrograde technique for tracheal intubation in trauma patients. Crit Care Med; 16:7 712-14 14. King HK. et al. Tranlaryngeal guided intubation for difficult intubation. Crit Care Med; 15-9 869-71. |