Association between computed tomographic thoracic injury scores and blood gas and acid-base balance in dogs with blunt thoracic trauma.

Objective: To determine the association between thoracic injuries evaluated by computed tomography (CT) and arterial blood gas and acid-base status in dogs with blunt thoracic trauma caused by motor vehicle accidents.

Design: Prospective observational clinical study.

Setting: University teaching hospital.

Animals: Thirty-one client owned traumatized dogs and 15 healthy dogs.

Procedures: All trauma group dogs underwent a CT scan and simultaneous arterial blood gas analysis within 24 hours, but not before 4 hours, after the traumatic incident within a 45-month enrollment period.

Measurements and main results: Thorax injuries were classified as pulmonary, pleural space, or rib cage and each of these components was scored for severity using a CT composite pulmonary, pleural, and rib score. The trauma group arterial blood gas and acid-base status were evaluated for statistical difference from the control group. The pulmonary-arterial oxygen pressure was significantly lower in the trauma group compared to the control group that was supported by significant differences in the calculated variables of arterial blood oxygenation as well. There was also a significant correlation between the composite lung score and pleural score and the variables of arterial oxygen status. The pulmonary-arterial carbon dioxide pressure was not significantly different to any of the thoracic injury variables indicating normal alveolar ventilation. Acid-base imbalances were generally mild, insignificant, and variable.

Conclusions and clinical relevance: Blunt thoracic trauma causes significant pulmonary and pleural injury and the blood oxygen economy is significantly affected by this. The functional measures of arterial blood oxygenation were well correlated with thoracic CT pathology. Alveolar ventilation was mostly spared but a clinically significant ventilation perfusion mismatch was present.