An air medical team is called to the scene of a rollover motor vehicle crash along a rural highway 32 nautical miles away. Ground personnel on scene report that the patient is an unrestrained passenger who was ejected from the vehicle. He is awake, complaining of chest and abdominal pain, and experiencing moderate dyspnea. The driver of the vehicle was pronounced dead at the scene.
Ten minutes in to the flight, EMS on scene request that the aircraft divert to a local community hospital six minutes from the scene for an intercept. Due to the deterioration of the patient’s clinical condition, county medical control directs the ground unit to transport the patient to the local emergency room for stabilization while awaiting the incoming aircraft. Estimated time of arrival for the new destination is approximately 14 minutes.
Upon arrival of the medical crew to the trauma room, the patient is intubated and is ventilated manually by the respiratory therapist. There is visible emesis on the patient’s face. He is grimacing and restless as the emergency physician is suturing in the chest tube that has been placed on the right side following bilateral needle thoracostomy. A bed sheet is wrapped and tied in place around the patient’s pelvis secondary to an unstable pelvis per clinical exam. Two large bore intravenous catheters are in place and the second and third liters of normal saline are infusing.
Initial plain films are positive for bilateral pulmonary contusions and an “open-book” pelvic fracture. Current vital signs include a heart rate of 128 beats/minute, a respiratory rate of approximately 20 to 30 breaths /minute by manual ventilation, a blood pressure of 88/42 (MAP of 57 mmHg), and an arterial oxygen saturation of 85 percent.
The Clinical Challenge
The multiple trauma patient poses an incredible challenge to prehospital and emergency department staff alike. While the “cure” more often than not is the operating room, the challenge becomes proper stabilization of the patient, long enough to get them to surgery. In the above scenario, the ability to maintain adequate perfusion and oxygenation tested this air medical crew’s skills. The two obvious major injuries creating these challenges were the unstable pelvic fracture and blunt chest trauma.
A Brief Review
Unstable Pelvic Fractures
The pelvic ring is made up from right and left innominate bones (ilium, ischium and pubis, which form together at the acetabulum), the sacrum, and the coccyx. This ring provides protection, serves as attachment points for muscles, and transmits weight from the trunk to the lower limbs. Strong posterior ligaments provide support, and their disruption due to injury causes significant instability1. Of greater concern with respect to disruption of the pelvic ring is the vast supply of blood vessels, including the left and right internal iliac arteries, and posterior pelvic venous complex. An extensive network of collateral circulation exists for both the arterial and venous circulation within the pelvic girdle. Hemorrhage from pelvic fractures results from lacerations of this rich vascular network and collects in the retroperitoneal space. Considerable bleeding can also occur from marrow at the fracture sites1.
Clinically, pelvic stability can be assessed by visualizing leg-length discrepancy or abnormal rotation. Manual manipulation, while an important indicator of pelvic ring stability, should only be performed once, as repeated manipulation may dislodge clots that could reduce bleeding in the interim2. Coagulopathy is a cause of persistent bleeding and should be considered when the patient does not respond to fluid and blood resuscitation1.
Management priorities include optimizing oxygenation and tissue perfusion, as well as splinting the pelvic ring. A number of commercially prepared pelvic binders are available. The use of a bed sheet wrapped around the pelvis and securely fastened in place is just as effective. The use of the pneumatic anti-shock garment (PASG) is also a very acceptable alternative, keeping in mind contraindications (e.g., penetrating chest trauma and late-term pregnancy).
Pulmonary Contusion
Per definition, a pulmonary contusion is parenchymal damage to the lung with edema and hemorrhage, without actual pulmonary laceration3. It results from significant blunt chest trauma. The pathophysiology of this injury process has three basic components4:
- “Spalling” refers to how the gas /liquid interface of the lung parenchyma shears against the chest wall due to the application of an external force.
- “Inertia” is secondary to the force of acceleration on alveolar tissue. Due to the difference in rates of acceleration, the terminal lung units are stripped from the hilum.
- “Implosion” comes as a result of rebounding and overexpansion of gas bubbles from the shock wave produced.
Clinical manifestations include: decreased lung compliance with increased work of breathing, hypoxemia, hypercarbia, and possibly respiratory failure. Radiographic findings may look consistent with those found in pneumonia (UTD 1). Patients are at increased risk of a systemic inflammatory response and ARDS.
Management of patients with pulmonary contusions is generally supportive. Supplemental oxygen is important, as it is for any trauma patient. Watch the patient’s ventilatory status carefully. Adequate pain control is paramount for the patient who is awake.
Maintain adequate intravascular volume. However, carefully manage this, as excessive volume resuscitation has the potential for further lung damage. Current recommendations surround maintenance of adequate end-organ perfusion4.
While the degree of respiratory failure may occur over time rather than immediately post-injury, patients with significant hypoxia (PaO2 of 65 mmHg or less and / or SaO2 less than or equal to 90 percent), require immediate intervention with aggressive airway management and mechanical ventilation2. Pulse oximetry and blood gas values typically guide therapy.
Management Considerations
Several questions in this scenario come to mind. How do we maintain oxygenation? How do we maintain perfusion? How do we know that resuscitation is effective?
In the above scenario, oxygenation — as evidenced by decreasing saturations — is obviously impaired. The patient is already receiving high-flow oxygen. The next step to improve the diffusion of oxygen across the alveolar-capillary membrane is to increase Mean Airway Pressure (mPaw). This can be accomplished by increasing the level of PEEP (Positive End Expiratory Pressure) and/or lengthening the ventilator inspiratory time (Ti), thus changing the inspiratory-to-expiratory ratio (I:E).
While in the acute phase of trauma management, aggressively maintaining oxygenation may be required. The clinician should bear in mind that excessive airway pressures in the injured lung increases the risk of barotrauma and the development of Ventilator Associated Lung Injury (VALI). Also, higher airway pressures can increase intrathoracic pressures, reduce venous return to the heart, and may contribute to hypotension5.
While this information may seem contradictory, it is at times a balancing act among maintaining adequate Mean Arterial Pressure (MAP), adequate oxygenation and avoiding further lung injury. In this scenario, MAP should be maintained with volume resuscitation, splinting of the pelvic ring, treating coagulapathies with blood products, and avoiding hypothermia. It seems reasonable to assume that an adequate MAP will allow more aggressive ventilatory strategies by alleviating the reduced venous return imposed by higher intrathoracic pressures.
Ultimately, effectiveness of resuscitation is determined by endpoint values, such as base deficit and serum lactate levels. While this is practical at the bedside, it becomes difficult at the roadside. In the prehospital environment, the clinical examination is our most important tool for evaluating resuscitation. This should include evaluating mental status, pulse strength and quality, skin color and temperature, and an acceptable MAP.
References
- 1. Marx JA, Hockenberger RS and Walls RM (Eds). Rosen’s Emergency Medicine: Concepts and Clinical Practice. Mosby Elsevier (6th Edition) 2006. pp 717-718.
- 2. ACS Committee on Trauma. Advanced Trauma Life Support Manual (7th Ed.). 2004. Pg. 110, 140-141.
- 3. Caviness AC. Pulmonary Contusion in Children. Up to Date Online. http://www.uptodate.com. Version 16.1. Accessed July 7, 2008.
- 4. George RP, Light RW, Matthay MA and Matthay RA. Chest Medicine: Essentials of Pulmonary and Critical Care Medicine (4th Ed). Lippincott, Williams and Wilkins (2000). pp. 607-609.
- 5. Hou P. Mechanical Ventilation in the Emergency Department. Up to Date Online. http://www.uptodate.com. Version 16.1. Accessed July 9, 2008.
