Association between the resistance indices of the radial and splenic arteries and tissue perfusion markers in patients with septic

Background Septic shock is a distributive form of circulatory failure in which alterations in peripheral vascular tone play a key role in hemodynamic instability and are strongly associated with increased mortality. The Radial Artery Resistance Index (RARI) and Splenic Artery Resistance Index (SARI), measured by bedside Doppler ultrasonography, may offer accurate, noninvasive markers for assessing peripheral and visceral vascular tone in real time. Objective To evaluate the utility of the Radial Artery Resistance Index (RARI) and Splenic Artery Resistance Index (SARI), measured by point-of-care Doppler ultrasonography (POCUS), in predicting tissue perfusion in patients with septic shock. Methods This prospective observational study was conducted in the Intensive Care Unit of the University Hospital of Brasília from March 2022 to March 2024. A total of 143 adult patients were included: 112 with a confirmed diagnosis of septic shock and 31 hemodynamically stable postoperative patients without clinical or laboratory evidence of infection, who served as the control group. The following variables were assessed simultaneously: RARI, SARI, capillary refill time (CRT), peripheral perfusion index (PPI), central venous oxygen saturation (ScvO₂), serum lactate concentration, standard hemodynamic parameters, and the Sequential Organ Failure Assessment (SOFA) score. Results Patients with septic shock presented significantly higher serum lactate levels and SOFA scores compared to controls. RARI showed a strong positive correlation with lactate levels (r = 0.71, p < 0.0001) and CRT (r = 0.67, p < 0.0001), and a moderate negative correlation with PPI (r = − 0.46, p < 0.0001). SARI demonstrated a weak but statistically significant positive correlation with the SOFA score (r = 0.17, p = 0.0418) and a moderate negative correlation with ScvO₂ (r = − 0.57, p < 0.0001). Conclusion Resistance indices of the radial and splenic arteries were significantly associated with clinical and laboratory markers of tissue hypoperfusion in patients with septic shock. These findings support the use of bedside Doppler ultrasonography as a valuable adjunctive tool for assessing peripheral and splanchnic perfusion in critically ill patients.