The effect of one‐lung ventilation on sentinel lymph node mapping in dog lungs

OBJECTIVE: To determine the sentinel lymph node (SLN) for the caudal lung lobe using indocyanine green (ICG) and near infra-red fluorescence (NIRF) in normal dogs. The secondary objective was to determine the effect of one lung ventilation (OLV) on time to SLN detection. STUDY DESIGN: Prospective, randomized experimental study. ANIMALS: Purpose-bred Beagles (n = 21). METHODS: Dogs were randomized to undergo OLV or normal ventilation (NV) and to undergo right or left caudal lung injections with ICG through lateral intercostal thoracoscopy. The draining lymph nodes (DLNs) were visualized at 10 min intervals. RESULTS: A fluorescent lymph node (FLN) was detected in 19/21 dogs (90%) and was the right or left tracheobronchial lymph node (LN) in 79% of dogs. Six dogs had multiple FLNs detected simultaneously. In 4/19 dogs (21%) the first FLN(s) was the central tracheobronchial LN, sternal LN, cranial mediastinal LN or a combination of these LNs. The median time to fluorescence in the first FLN was 30 min (range: 10-50 min) for the OLV group and 10 min (range: 10-20 min) for the NV group (p = .0012). CONCLUSION: The SLN or DLN for the caudal lung in normal dogs was variable, but often included the tracheobronchial LN. One lung ventilation slowed the detection of ICG in the lymphatics. CLINICAL SIGNIFICANCE: Biopsy of tracheobronchial LNs for caudal lung tumors without SLN mapping may provide inaccurate staging information in some dogs. During NIRF-guided SLN mapping, delaying OLV induction may improve SLN identification.