Evaluation of Burn Depth using Indocyanine Green: Discrepancies Between Macroscopic Visualization and the
Mary Junak1, Héctor García2, Aiping Liu1
1Department of Surgery, University of Wisconsin, Madison, WI, 53792, USA.
Background:
Burn wound management is guided by the depth of dermal tissue damage. Standard practice for this depth assessment is daily visual evaluation of the wound by an experienced burn surgeon, which is inherently subjective and at times inaccurate. Perioperative fluorescence imaging with indocyanine green (ICG) has emerged as a potential tool to objectively evaluate burn depth. The current study aims to explore the relationship between ICG angiography (ICGA), Second-window ICG (SWIG), and burn depth, with the goal of understanding how this technology could guide the prognosis and treatment of human burn wounds.
Methods:
Patients (n = 14) with indeterminate depth or deep partial thickness burns received an infusion of ICG on post-burn day 2-3 or the day before surgery. Imaging was performed immediately after injection for angiography as well as the following day for SWIG. A full-thickness tissue biopsy was obtained for histologic evaluation. In vitro primary human fibroblasts and keratinocytes were cultured, subjected to heat injury (65 deg C for 2.5 or 5 minutes), and incubated with ICG. Flow cytometry was used to classify the cells as live, apoptotic, or necrotic based and to quantify ICG uptake.
Results:
ICGA perfusion parameters are increased in burn wounds that did not require grafting and ICGA egress slope correlates to SWIG fluorescence intensity. Furthermore, SWIG microscopic fluorescence intensity correlates to histologic burn depth and colocalizes in necrotic region of burn injury, however there is high interpatient variability between SWIG fluorescence intensity and histologic burn depth, predicted healing potential, and graft status. Flow cytometric analysis of in vitro skin cells shows that preferential ICG binding to necrotic cells contributes to SWIG signal in a burn, with binding influenced by cell type and injury severity.
Conclusions:
Overall, this study suggests that fluorescence imaging has the potential to aid in the assessment of healing potential, although current challenges related to imaging variability, interpretation, and clinical integration must be addressed to optimize its utility in burn management.Clinical trials number: NCT05593523.
