Hyperspectral imaging for objective microcirculatory assessment in trauma patients

Hyperspectral imaging (HSI) is a non-invasive technology capable of assessing microcirculatory impairment. This study evaluated whether HSI can detect early microcirculatory alterations in trauma patients and differentiate between those with hemodynamic instability or stability during initial trauma resuscitation. In this prospective single-center observational study at a German level I trauma center (01/2023-10/2024), patients underwent HSI (TIVITA^® 2.0) at three time points: during the primary survey, after resuscitation room care, and 24 h after admission. HSI approximates four microcirculatory parameters: tissue oxygenation saturation (StO₂), tissue water index (TWI), tissue hemoglobin index (THI), and near-infrared perfusion index (NIR). Hemodynamic instability was defined as systolic blood pressure < 90 mmHg for > 10 min, catecholamine use > 10 min, or pronounced clinical signs of hypoperfusion. The primary outcome was the difference in StO₂ between patients with and without hemodynamic instability at the initial HSI measurement. Secondary outcomes included comparison of all HSI parameters between groups, correlations with Injury Severity Score (ISS), biomarkers (lactate, bicarbonate, base excess), and mortality. Statistical analyses comprised t-tests, receiver operator curve (ROC) analyses, diagnostic accuracy, and DeLong's test. A total of 163 patients were analyzed (18 hemodynamic instability, 145 hemodynamic stability). No significant difference in initial StO₂ was observed between groups (hemodynamic instability: 56.50 (SD 17.08) vs. hemodynamic stability: 59.48 (SD 10.92); p = 0.311). Likewise, TWI, THI, and NIR showed no significant differences. Initial elevated lactate levels (≥ 2 mmol/L) were associated with significantly lower StO₂ levels (p = 0.002). ROC analysis of StO₂ for predicting in-hospital mortality showed an area under the curve of 0.677 (95% CI 0.529-0.825). The optimal mortality cut-off (StO₂ ≤ 54%) demonstrated a sensitivity of 0.70, specificity of 0.66, positive predictive value of 0.22, and negative predictive value (NPV) of 0.94. AUCs of StO₂, lactate, bicarbonate, and base excess overlapped, with no significant pairwise differences. HSI did not discriminate between hemodynamically unstable and stable patients at initial trauma assessment but correlated well with high lactate levels. However, its high NPV for mortality suggests potential value as an objective, non-invasive tool for early trauma team downgrading.Trial registration: German Clinical Trials Register (DRKS ID DRKS00030986) on 27th December 2022.