Heterogeneous cardiovascular responses to acute mean arterial pressure augmentation in septic shock: the role of ventriculo-arterial coupling and venous return

In patients with septic shock, vasopressor-induced mean arterial pressure (MAP) augmentation is commonly used to restore tissue perfusion; however, patients may exhibit divergent cardiovascular responses despite achieving similar arterial pressure targets. We hypothesized that this heterogeneity reflects the differences in ventricular adaptation to increases in arterial load and venous return determinants. We conducted a prospective physiological observational study in mechanically ventilated adults with septic shock who underwent transient MAP augmentation from approximately 65 to 85 mmHg after the initial hemodynamic resuscitation. MAP was increased by norepinephrine dose escalation or by adding vasopressin according to clinical judgment. Comprehensive transthoracic echocardiography was performed immediately before and after MAP augmentation. Patients were classified a priori according to the relative changes in cardiac output (CO): flow recruitment (> 15% increase), stable flow (− 15% to + 15%), or flow deterioration (> 15% decrease). Changes in effective arterial elastance (Ea), end-systolic elastance (Ees), VA coupling (Ea/Ees), stroke volume, left ventricular ejection fraction (LVEF), analogue mean systemic filling pressure (Pmsa), and derived venous return variables were analyzed. Thirty-two patients were included. Despite comparable increases in MAP, the cardiovascular responses were heterogeneous: 10 patients (31%) exhibited flow recruitment, 17 (53%) maintained a stable flow, and 5 (16%) developed flow deterioration. Patients with flow deterioration showed a greater increase in Ea without a proportional increase in Ees, resulting in worsening VA coupling (ΔEa/Ees + 0.22 IQR [0.01–0.81]), whereas VA coupling remained stable or improved in patients with preserved or increased flow ( p = 0.035). Flow deterioration was also associated with reduced LVEF and changes in the derived venous return indices, which may have contributed to the observed reduction in forward flow. Changes in VA coupling correlated with changes in IVCT (ρ = 0.788, p < 0.0001), MPI (ρ = 0.599, p < 0.0003), stroke volume (ρ =−0.418, p = 0.017), and LVEF (ρ=−0.431, p = 0.0139). Acute MAP augmentation elicits heterogeneous cardiovascular responses in patients with septic shock despite similar increases in arterial pressure. Flow deterioration is characterized by worsening VA coupling, reduced stroke volume, and impaired systolic adaptation, potentially modulated by changes in the derived venous return indices.