Decreased fluorescence latency and plateau intensity ratio as predictive markers of intraoperative hypoperfusion: quantitative indocyanine green perfusion analysis in colorectal cancer surgery

Purpose: Intraoperative hypoperfusion is a major risk factor for postoperative anastomotic complications in colorectal surgery. Although most perfusion assessments emphasize arterial inflow, the roles of latency, sustained fluorescence, and venous outflow remain underexplored. This study aimed to identify quantitative indocyanine green (ICG) fluorescence parameters predictive of intraoperative hypoperfusion. Methods: Eighty patients who underwent colorectal cancer resection between 2018 and 2022 were analyzed. Intraoperative perfusion was evaluated qualitatively using near-infrared ICG angiography and quantitatively through post hoc analysis of fluorescence time-intensity curves. Associations with hypoperfusion were assessed using group comparisons and receiver operating characteristic (ROC) analysis. Results: Qualitative evaluation indicated hypoperfusion requiring intraoperative relocation of the anastomotic site in 12 patients (15%), with postoperative leakage in 1 patient (1.2%) despite revision of the anastomosis. Quantitative analysis showed that latency was significantly shorter in hypoperfused cases (5.5 seconds [interquartile range (IQR), 1.0-13.0 seconds] vs. 20.0 seconds [IQR, 6.8-27.0 seconds]; P = 0.003), and the plateau intensity ratio (PIR; Fplateau/Fmax) was markedly decreased (0.6 [IQR, 0.6-0.7] vs. 0.8 [IQR, 0.6-0.9]; P = 0.045). The ROC analysis demonstrated good diagnostic performance for latency (area under the curve [AUC], 0.76; sensitivity, 33.3% [95% confidence interval (CI), 13.8-60.9]; specificity, 92.8% [95% CI, 84.1-96.9]; positive likelihood ratio, 4.6) and moderate accuracy for PIR (AUC, 0.68; sensitivity, 66.7% [95% CI, 39.1-86.2]; specificity, 68.1% [95% CI, 56.4-77.9]; positive likelihood ratio, 2.1). Conclusion: Quantitative fluorescence analysis identified latency and PIR as complementary markers of perfusion dynamics. Whereas latency reflects early arterial inflow kinetics, PIR captures outflow characteristics related to microvascular and venous integrity. Combining these metrics may improve intraoperative detection of hypoperfusion and support data-driven decisions regarding anastomotic site selection.