Echocardiographic Assessment of Cardiac Function After Fluid Resuscitation and Norepinephrine Therapy in a Porcine Model of Septic Shock

Background: Septic shock induces systemic vasodilation, endothelial dysfunction, and impaired cardiac filling, necessitating interventions that restore tissue perfusion. Aims: This study aimed to evaluate the effects of crystalloid fluid resuscitation and norepinephrine on echocardiographic indices of cardiac function in a porcine model of septic shock. Methods: A controlled experimental design was conducted using nine male pigs (40 – 60 kg) aged 12 -16 weeks divided into three groups: control (G0), fluid resuscitation (G1; Ringer-lactate 30 mL/kg with protocolized repeats), and norepinephrine titration (G2; starting at 0,05 μg/kg, adjusted to Mean Arterial Pressure ≥ 65 mmHg). M-mode echocardiography was used to measure systolic and diastolic structural measures (interventricular septum in systole and diastole, left ventricular internal dimension in systole and diastole, left ventricular posterior wall in systole and diastole), volumes (End Diastolic Volume, End Systolic Volume, Stroke Volume, Cardiac Output) and cardiac function (Ejection Fraction, Fractional Shortening, Heart Rate). Data were analyzed using two-way ANOVA (α = 0.05). Results: Septic shock over time resulted in decreased in ventricular dimensions (LVIDd), EDV, SV and CO during shock, with partial recovery after therapy. Interventricular septal thickness in systole (IVSs) increased significantly over time (p = 0.01), while treatment effects and treatment-time interactions were not statistically significant for most parameters. Post-therapy, norepinephrine significantly improved ejection fraction and fractional shortening, whereas fluid resuscitation primarily restored end-diastolic volume and stroke volume. Conclusion: Fluid resuscitation and norepinephrine administration have different physiological effects on cardiac function in septic shock. Fluid resuscitation primarily increases preload and intravascular volume, while norepinephrine predominantly improves systolic function through inotropic and vasoconstrictor mechanisms.