To evaluate perioperative changes in cutaneous microcirculation and microvascular reactivity using hyperspectral imaging (HSI) with a standardized vascular occlusion test (VOT) in cardiac surgery with cardiopulmonary bypass (CPB), and to explore associations with vasoactive support, systemic markers, and outcomes.

Prospective, monocentric, hypothesis-generating observational pilot study.

Single-center university hospital.

Twenty-nine adults undergoing elective cardiac surgery with CPB, of whom 25 with complete datasets were analyzed.

Palmar HSI (TIVITA tissue) before induction (T0), after induction (T1) and after skin closure (T2), yielding tissue oxygenation (StO₂) and near-infrared perfusion index (NPI) data. A standardized VOT (5-minute arterial occlusion) at T1 and T2 assessed reactive hyperemia amplitude and time to peak (PORH_ttp).

A total of 600 HSI measurements were obtained. StO₂ and NPI values were increased after induction and decreased at T2 despite stable macrocirculation, with no correlation with macrocirculatory variables. At T2, StO₂ correlated negatively with norepinephrine equivalents (r = −0.43), lactate (r = −0.61), procalcitonin (r = −0.67) and CPB time (r = −0.65), whereas associations with interleukin-6 and syndecan-1 were weak. After CPB, the hyperemic StO₂ amplitude was preserved (Δ +30% v +31%), whereas the NPI response was markedly attenuated (Δ +12 AU v +28 AU) and PORH_ttp was prolonged (71.6 ± 36.5 s v 46.3 ± 17.6 s). Three patients requiring mechanical circulatory support showed lower HSI values and worse outcomes.

HSI-based VOT detected microcirculatory alterations after CPB—preserved superficial oxygenation amplitude with blunted deeper perfusion and delayed reactive hyperemia—that static HSI parameters alone did not capture. These hypothesis-generating findings require prospective validation before HSI can complement established hemodynamic monitoring.