Influence of vagal injury on acute traumatic reaction after blast injury

A prospectively randomised, controlled animal study was conducted to analyse the influence of vagal injury on acute cardio-respiratory responses to blast injury.

We used a previously described model of blast-fragment combined injuries to divide dogs randomly into three groups: normal control, blast injury with fragment shot at the masseter and blast injury with fragment shot at the neck. The vagal histomorphologic changes were investigated by haematoxylin-eosin staining and immunocytochemical analysis of neuron-specific enolase and glial fibrillary acidic protein. The indices of respiration, heart rate, blood pressure and body temperature were recorded continuously before and after blast exposure.

The vagal injury was more severe in the neck-injured than in the face-injured group. However, bradycardia, hypotension and absence of compensatory peripheral vasoconstriction, which are typically seen in animals subjected to blast injury without vagal nerve injuries, were partly inhibited when the vagal nerve was injured.

A vagally mediated reflex, such as a cardio-respiratory system defensive reflex that caused shock, was observed immediately after blast pressure wave injury. These observations may have important implications for the emergency management of blast injury cases.