Quantitative analysis of tissue oxygenation trajectories in DIEP flaps using near infrared spectroscopy: A
Martin Kauke-Navarro1, Jake R Moscarelli1, Victoria Kong1
1Department of Surgery, Division of Plastic Surgery, Yale School of Medicine, New Haven, CT, USA.
Background:
Near-infrared spectroscopy (NIRS) is an adjunct for monitoring breast free flaps. However, there is a paucity of studies using large NIRS datasets to characterize how patient-, flap-, and operative-level factors and systemic hemodynamics influence postoperative tissue oxygen saturation (StO2).
Methods:
In this retrospective study, we analyzed early postoperative NIRS data from DIEP-based breast reconstructions, comprising >676,000 continuous StO₂ measurements from an exteriorized skin paddle (ViOptix). Trajectories were analyzed using linear mixed-effects models with nonlinear time effects and fixed effects for patient-, flap-, and operative-level variables. Trajectory metrics (desaturation burden, variability, and overall slope) were calculated. A separate model examined the associations with matched vital signs.
Results:
Overall, 107 flaps in 65 patients (676,308 measurements) were analyzed. StO₂ followed a non-linear postoperative course, and most variance was between the patients (67.1%) rather than within flaps. Large skin paddles were the dominant flap-level predictor, with significantly higher mean StO₂ (adjusted +9.7% points, 95% CI 3.5-16.0; p=0.003, robust across estimators), whereas coupler diameter, arterial and venous anastomosis counts, and flap weight showed no association. Among the systemic factors, higher mean arterial pressure and peripheral oxygen saturation were robustly associated with higher StO₂, whereas temperature and heart rate did not survive autocorrelation correction. Bilaterally monitored flaps diverged among the patients (median 4.9 points). Trajectory metrics separated the two venous-failure flaps from normal variation, though negative slope alone was non-specific.
Conclusions:
Postoperative DIEP flap StO₂ reflects flap characteristics and systemic physiology; small skin paddles may mimic venous compromise. Combining trajectory features with physiologic data may improve discrimination of true vascular compromise.
