Dynamics of ventriculo-arterial coupling and peripheral tissue perfusion during early resuscitation of septic shock.

Background: Left ventriculo-arterial coupling (LVAC), the ratio of arterial elastance to left ventricular end-systolic elastance, is a dimensionless index that depicts the interaction between arterial load and cardiac contractility, reflecting energy transmission from the heart to the proximal arterial tree. Nevertheless, how dynamic variations of LVAC may impact tissue perfusion remains unclear. We evaluated the dynamic relationship between LVAC and capillary refill time (CRT), a peripheral perfusion surrogate, during early resuscitation of septic shock. Methods: Adult patients were prospectively included within 4-h of meeting Sepsis-3.0 septic shock criteria. LVAC was estimated at inclusion and 6-hours later by combining transthoracic echocardiography with arterial pressure monitoring, while CRT was simultaneously assessed. Patients were classified as uncoupled when LVAC > 1.36. Variations in CRT between baseline and 6-h were compared across four groups defined by LVAC evolution: (1) coupled-to-coupled; (2) coupled-to-uncoupled; (3) uncoupled-to-coupled; (4) uncoupled-to-uncoupled. Additionally, paired measurements before/after fluid loading and/or dobutamine initiation were analyzed. CRT differences among groups were compared using Kruskal-Wallis testing, followed by Dunn's post-hoc test for pairwise comparisons. Paired-Wilcoxon tests assessed CRT variations before/after interventions according to pre-intervention LVAC status. Results: Eighty-four patients were included. CRT variation between baseline and 6-h differed significantly among groups (Kruskal-Wallis, p = 0.013), with CRT improvement in uncoupled-to-coupled (-33.8 [-53.1 to -1.2]%, p = 0.013) and worsening in coupled-to-uncoupled patients (17.5 [7.1-31.3]%, p = 0.013). Persistently coupled and uncoupled groups exhibited heterogeneous CRT responses at 6-h. Thirty-one fluid loads and thirty-two inotrope interventions were also analyzed. CRT decreased after dobutamine in initially uncoupled patients (-26.2%, p = 0.007) but not after fluid loading (-9.5%, p = 0.656) despite both interventions significantly increasing stroke volume in uncoupled LVAC condition (+14.0%, p = 0.021 and +14.2%, p < 0.001, for fluids and dobutamine, respectively). CRT did not change after either intervention in patients already coupled. Conclusion: Although LVAC improvement was associated with recovery of peripheral perfusion in some patients, and its deterioration with CRT prolongation in others, this relationship proved to be weak. Indeed, inconsistent CRT behavior among persistently coupled or uncoupled patients, and the heterogeneous response to resuscitative interventions suggest peripheral perfusion often evolves independently of energy transmitted from the heart to proximal arterial tree.