Shock and Hypoxia in Blunt Chest Trauma
A 26-year old male is involved in a high-speed, single vehicle MVC. He required extrication by paramedics who reported significant damage to the vehicle. Initial vitals on scene were T 37.0, HR 130 bpm, BP 90/40, RR 38, O2 Sat 78%, up to 88% with a non-rebreather. GCS is 12. A bolus of crystalloid is started and the patient is brought into your emergency department. You work in a regional centre with general and thoracic surgery. But you are not a trauma center, nearest trauma center is 50 mins by flight.
Primary survey reveals a patent airway without stridor or signs of blunt or penetrating injury. Patient is in a C-collar. There is vomitus on the patient’s face and chest. There is significant ecchymosis of the chest bilaterally and subcutaneous emphysema on the left. Abdomen is soft without ecchymosis.
You perform 2 finger thoracostomies in the 4th intercostal space. A gush of air is returned. You insert a 32 F chest tube. Chest X-Ray confirms chest tube placement – 2 on the left in good position; chest tube on the right position not ideal but is acceptable. You call your regional trauma team for transfer, but it is determined that the patient is “too sick” for transport at this time.
The patient then returns to DI to complete the pan-scan. Shortly after returning from the scanner, the radiologist calls you. CT shows no intra-abdominal or intracranial injury. There are multiple rib fractures with extensive pulmonary contusions bilaterally, more so on the left, with bilateral hemopneumothoraces. The radiologist tells you there’s still deviation of the mediastinum to the right. Looking back at the Chest X-Ray obtained post second chest tube insertion, you realize this also showed over-inflation of the left lung with shift of the mediastinum.
Repeat vitals: HR 110, systolic BP 80-90, Oxygen Sat 85%. You note that there is still continuous bubbling at the water seal, which again stops with clamping of the chest tube at the patient.
You call your thoracic surgeon on call who happens to be in hospital. He recommends a third chest tube on the left side as a temporizing measure as this patient will likely require an emergency thoracotomy to repair the fistula if his hemodynamics do not improve. He also suggests this patient may need ECMO. In the meantime, you place a third chest tube on the left side in the 5th intercostal space. You call the transport team and tertiary center, but there is ongoing concern about the patient’s stability for transport. You call your anesthesiologist to help with managing the patient on the ventilator and in case the patient might need to go to the OR for a thoracotomy.
Positive pressure ventilation of patients with bronchopleural fistula poses significant challenges, as ventilations delivered to the lung pass directly to the pleural space causing loss of tidal volumes and atelectasis.
The goal of mechanical ventilation is to minimize flow across the fistula by keeping airway pressure below the critical opening pressure of the fistula.
- Minimize PEEP
- Short inspiratory time
- Low tidal volumes
- Ideally spontaneous breathing (likely not feasible in this case)
- Permissive hypercapnia
Peak airway pressures over 30 cm H20 are associated with increased air leaks. Also, negative suction on chest tubes can perpetuate flow through the fistula and should be avoided.
Are there any other temporizing measures that can improve the patient’s ventilation to stabilize the patient enough for transport?
The patient requires significant ventilatory support of severe bilateral pulmonary contusions, but the large bronchopleural fistula requires lower airway pressures. When the ventilatory needs of the two lungs differ, treating them as single unit is detrimental. Differential lung ventilation is used to manage respiratory failure when there is marked difference in the pulmonary mechanics of the right and left lung due to a unilateral lung pathology, such as in severe pneumonia, massive pulmonary hemorrhage, and as in this case, a bronchopleural fistula