Skin Microcirculatory Parameters as Diagnostic Markers of Central and Cerebral Circulatory Disorders in Hemorrhagic Shock

The aim of the study was to evaluate the relationship between skin microcirculatory parameters and central and cerebral hemodynamic parameters during progressive blood loss. Materials and Methods. A randomized, prospective, controlled in vivo experimental study was performed using male Wistar rats (250–350 g, N =23) divided into two groups: «hemorrhagic shock» (HS, N =13), with blood loss of 15% and subsequently 35% of estimated circulating blood volume (CBV), and «sham-operated» controls (SO, N =10). After combined anesthesia, femoral artery catheterization, and craniotomy, the following were measured at baseline (stage 1): mean arterial pressure (MAP), cortical cerebral perfusion (LSCI brain ), and skin perfusion in the hindlimb (LSCI skin ) using laser speckle contrast imaging (LSCI). These measurements were repeated after 15% CBV loss (stage 2) and 35% CBV loss (stage 3). Cerebral (CVC brain =LSCI brain /MAP) and cutaneous (CVC skin =LSCI skin /MAP) vascular conductance indices were calculated. At stage 3, parameters of post-occlusive reactive hyperemia (PORH) in hindlimb skin were additionally assessed. Statistical analysis was performed using STATISTICA 13.0 with non-parametric methods. Spearman's correlation coefficient ( R ) was used to assess associations between circulatory parameters. Results. A 15% CBV loss led to a 26% reduction in LSCI skin ( P =0.003 vs SO), with no significant change in LSCI brain . With further blood loss and a 43% reduction in LSCI skin (P<0.001 vs SO), LSCIbrain decreased by 14% ( P 0.001 vs SO). These changes were accompanied by a sustained increase in CVC brain ( P 0.001 vs SO at stage 3), while CVC skin remained unchanged throughout the experiment. In the HS group, blood loss led to a significant decrease in PORH amplitude ( P =0.003 vs SO), while microvascular flow reserve increased ( P =0.036 vs SO). Before blood loss, moderate positive correlations were found between LSCI skin , CVC skin , and CVC brain . In HS, LSCI brain correlated with the degree of LSCI skin reduction ( R =0.57, P =0.041), and skin microvascular flow reserve showed a strong positive correlation with arterial blood pH and base excess (BE) ( R =0.84, P =0.001). The correlation between LSCI skin and MAP shifted from a moderate negative correlation at stage 1 to a strong positive correlation at stage 3. Conclusion. Skin microcirculation parameters (LSCI skin , CVC skin , and PORH), as assessed by laser speckle contrast imaging, are promising diagnostic markers of central and cerebral hemodynamic impairment during progressive blood loss and warrant further validation.