Hyperspectral Imaging Reveals Superior Preservation of Renal Microcirculatory Oxygenation with Crystalloid-Based Resuscitation During Hemorrhagic Shock—An Experimental Study

Background/Objectives: Hemorrhagic shock leads to critical malperfusion of organs including the kidneys. Current hemodynamic approaches focus on macrocirculatory targets such as mean arterial pressure (MAP), which may not reliably reflect organ-level perfusion. Hyperspectral imaging (HSI) offers quantitative real-time assessment of tissue oxygenation, enabling the assessment of renal microcirculation. This study investigates the effects of crystalloid and norepinephrine therapy on renal microcirculatory oxygenation during hemorrhagic shock in a porcine model and contextualizes the hemorrhage state compared to renal arterial ischemia and venous congestion using HSI. Methods: Renal states of physiological perfusion, arterial ischemia, and venous congestion were induced in 72 pigs as a reference dataset. Thirty-two pigs were induced with hemorrhagic shock and received (I) permissive hypotension, (II) norepinephrine, (III) crystalloid volume, and combined crystalloid–norepinephrine therapy (IV) (8 per group). Renal oxygenation assessed with the TIVITA® oxygenation index (StO2) was quantified at baseline (T1), post-hemorrhage (T2), and 60 and 120 min (T3/4) after intervention. Results: The renal hemorrhage state was spectrally distinct from other malperfusion states, but most similar to arterial ischemia. Hemorrhage induced a reduction in renal oxygenation from 73% StO2 at the baseline (T1) to 59% after shock (T2). At 120 min (T4), crystalloid therapy continued to achieve the most effective recovery (68%), followed by combined therapy (56%). Only crystalloid-based resuscitation reduced lactate and restored microvascular oxygenation. Conclusions and Clinical Implications: Crystalloid resuscitation, alone or with moderate catecholamine support, achieves superior renal microcirculatory oxygenation compared to exclusively vasopressor-driven or hypotensive strategies in this experimental setting, but clinical translation is not self-evident. The findings reveal a dissociation between systemic pressure restoration and tissue-level reperfusion, highlighting volume-guided, microcirculation-oriented resuscitation.