A rat model for cerebral air microembolisation

Subtle cerebral air microembolisation (CAM) is a typical complication of various medical interventions such as open heart surgery or angiography and can cause transient or permanent neurological and neuropsychological deficits. Evaluation of the underlying pathophysiology requires animal models that allow embolisation of air bubbles of defined diameter and number. Herein we present a method for the production of gas bubbles of defined diameter and their injection into the carotid artery of rats. The number of gas microemboli injected is quantified digitally using a high speed optical image capturing system and a custom-made software. In a first pilot study, 0, 50, 100, 400 and 800 gas bubbles of 160 microm in diameter were injected into the carotid artery of rats. Offline evaluation revealed a high constancy of the bubble diameters (mean 159.95+/-9.25 microm, range 144-188 microm) and the number of bubbles injected. First preliminary data indicate that with increasing number of bubbles embolised, more animals revealed neurological deficits and (particularly with higher bubble counts) brain infarctions on TTC-staining. Interestingly, also animals without overt infarcts on TTC-staining displayed neurological deficits in an apparently dose dependent fashion, indicating subtle brain damage by air embolism. In conclusion, the method presented allows injecting air bubbles of defined number and diameter into cerebral arteries of rats. This technique facilitates animal research in the field of air embolisation.