Pulmonary contusion (PC) is a common consequence of blunt trauma to the chest. PC occurs in 30-75% of cases of chest trauma, and in many cases this is further complicated by severe bone injuries of the chest wall. Despite much research into the subject, mortality and morbidity has not significantly improved in the past three decades. Advances in imaging have similarly failed to have any impact on outcomes.
The consequences of PC are manifold and include both local and systemic effects. Some of the local effects are: laceration of lung tissue, hemorrhage-filled alveoli, reduced compliance, increase in shunt fraction leading to a decrease in PO2, increased pulmonary resistance, and decreased pulmonary blood flow. Furthermore, both the ipsi- and contra-lateral lungs may undergo pathological changes such as: thickened septa leading to diffusion defects, a decrease in alveolar diameter, vacuolation of the tissues, delayed capillary leak with increased BAL protein, and the recruitment of neutrophils in the lung parenchyma. Systemic effects of PC are: Increased terminal complement component, a decrease in complement, increased inflammatory cytokines, decreases in macrophages and splenocytes, and ultimately increased mortality.
Management of PC is complicated and multi-modal. Patients with chest trauma should not be placed on excessive fluid restriction; indeed, isotonic crystalloid or colloid infusions should be given so as to maintain adequate perfusion of the tissues. However, once resuscitated, excessive administration of fluids must be carefully avoided. Following this, a pulmonary artery catheter might prove useful to prevent fluid overload. Mechanical ventilation should also be avoided unless there is respiratory failure. The ventilator should be removed as soon as practicable and either positive end-expiratory pressure or continuous positive airway pressure should also be included in treatment protocols. Steroids must be avoided, whereas analgesia and aggressive physiotherapy should be used to minimize the risk of respiratory failure.
Early intervention with intubation and PEEP has been shown to decrease the size of the pulmonary contusion. In the 1970s the standards demanded that all patients receive mechanical ventilation, however, there was no data that showed that this approach increased survivability. In a study performed by Trinkle et al, in 1973, intubation was avoided in about 80% of PC patients with no negative sequelae. PEEP has been shown to improve the oxygenation of patients. Compared to mechanical ventilation, CPAP has been shown to have reduced levels of pulmonary complications such as atelectasis, or pneumonia. Other methods of ventilation include independent lung ventilation, which has been used on patients with unilateral chest trauma. This method has been shown to significantly improve PaO2 and shunt fraction.
Another important factor in therapy is pain control. Local anesthetic patches are applied to the skin that contains 5% lidocaine. This is an off-label use of the drug, and the efficacy is not conclusive. Indeed, one study showed that there was no difference in narcotic utilization between a group receiving placebo and a group put on the lidocaine patch. Vasopressin has also been assessed for its use in pulmonary contusion and in pigs it was shown to improve mortality.
In sum, treatment and management of PC is dependent on clinician preference. The basics involve analgesia, respiratory management, and observation. PC is a common injury, however, it rarely leads to death. On the other hand, it contributes significantly to long-term disability and ultimate choice of management by the physician. No modalities have been definitively proven better than another, and thus physician choice and experience should guide treatment choices.
References:
Bruce S, Ebert J, Bokhari F, et al. Management of pulmonary contusion and flail chest: An Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012; 73(5): s351-s361
