Answers and Discussion
Case #4-- Flail Chest Following a Dog Fight
Answers and Discussions to the Questions:
The traditional concepts of flail chest injury emphasized the pathophysiological parodoxical chest wall motion. In instances of severe flail chest injury, inspired gases were thought to flow from the lung lobes affected by the flail into the normal hemithorax and back into the flail lungs during the paradoxical exhalation. This pendulum-like gas flow (originally described as pendulufft), from one side to the other was believed to increase dead space ventilation, thereby decreasing effective alveolar ventilation.
Based upon these pathophysiological concepts, therapeutic goals focused upon stabilization of the thoracic wall to prevent the paradoxical motion. Later, intubation with mechanical ventilation provided the concept of "internal pressure splints" for chest wall stabilization. Unfortunately, aggressive measures to stabilize the thoracic injuries did not improve mortality in blunt injuries. In fact, human patients managed with prolonged mechanical ventilation developed nosocomial pneumonia, which further complicated their course.
Normal acidbase: pH = normal, PCO2 = slightly decreased, HCO3 = normal, ABE = normal, O2 Sat = slightly decreased..
Ventilation: Slight hyperventilation (slight decrease in PCO2).
Oxygenation: Calculate the alveolar-arterial (A-a) oxygen gradient.
A = (642 - 47).21 - 29.2/0.8 = 88.45
a = PO2 = 54.8
A - a = 88.45 - 54.8 = 33.6
Interpretation: Acute respiratory distress syndrome
Numerous fractured ribs, fractured sternabrae, pulmonary contusions, pneumothorax, and thoracic drain in the cranial-dorsal thorax.
Click here to review the ventrodorsal radiograph Click here to review the lateral radiograph
The emergency treatment of a flail thoracic injury depends upon how the patient is tolerating the injury. Spontaneously breathing animals who do not demonstrate respiratory compromise (decreased oxygenation and/or ventilation) can be carefully observed. Intercostal nerve blocks are useful for analgesia.
The decision to provide a tracheostomy and mechanically ventilate is determined by the presence of respiratory failure with impaired gas exchange. Mechanical ventilation is directed at improving gas exchange rather than primarily stabilizing the unstable chest wall. The ideal mode of mechanical ventilation has not been determined. Recommendations for humans have emphasized the importance of intermittent manitory ventilation (IMV) with positive end-expiratory pressure (PEEP).
Follow-Up: The thoracic bite wounds were debrided, Prince was housed in an oxygen cage at 40% oxygen concentration, and analgesia provided with intercostal nerve blocks, a constant rate infusion of fentanyl, and a fentanyl patch. Prince made slow but progressive improvement.
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