Evaluation of factors affecting the visualization of dye after transbronchial dye injection: an animal experiment

BACKGROUND: Since peripheral lung lesions can be frequently visualized on computed tomography (CT), various methods of localization for thoracoscopic surgery have been developed. In the case of transbronchial dye injection (TDI), there can be difficulties with dye visualization through the thoracoscope depending on early disappearance of the dye due to diffusion before field exposure. Herein, we performed an animal experiment to determine the appropriate dye amount and the duration of visualization. METHODS: Twelve pigs were experimented as following four groups (n=3): group 1 received 0.6 mL of dye; group 2 as 0.8 mL; and group 3 as 1.0 mL, all followed by 2.0 mL of air injection and group 4, with 1.0 mL of dye followed no air injection to evaluate the utility of air injection. The detection, the peak time, the wash-out time were measured. RESULTS: The mean detection times, the peak time, and the mean wash-out times for 0.6, 0.8, and 1.0 mL of dye were not significantly different (P=0.195, 0.092, 0.06). However, regardless of the injected amount, it usually lasts in 2 hours. Comparing with non-air injection group, the peak time and wash-out time were statistically significantly different in injected group; P=0.07 and 0.001. CONCLUSIONS: The marking could be identified clearly at about 2 hours after TDI regardless of the amount of indigo carmine injected. However, in cases with longer duration to exposure, especially in cases with severe adhesions, it might be necessary to discover the mixture of dye which will last longer for visualization of lung nodules.