Papaverine and Sublingual Microcirculation in Septic Shock

Inclusion Criteria: * Age 18-85 years. * Septic shock according to Sepsis-3 criteria, defined as suspected or documented infection requiring vasopressors to maintain mean arterial pressure ≥65 mmHg and serum lactate \>2 mmol/L after adequate fluid resuscitation. * Enrollment within 24 hours after diagnosis of septic shock in the ICU. * Receiving continuous norepinephrine infusion at enrollment. * Receiving invasive mechanical ventilation at enrollment, allowing assessment of vascular waterfall-related hemodynamic variables. * PiCCO-based hemodynamic monitoring, invasive arterial pressure monitoring, and central venous access available before papaverine administration. * Ability to obtain sublingual microcirculatory images of acceptable quality at baseline. * Written informed consent obtained from the patient or legally authorized representative. Exclusion Criteria: * Shock primarily caused by non-septic etiologies, including cardiogenic, hypovolemic, obstructive, hemorrhagic, or anaphylactic shock. * Expected death or planned withdrawal of life-sustaining treatment within 24 hours. * Known allergy or hypersensitivity to papaverine. * Severe hemodynamic instability judged unsuitable for papaverine by the treating physician, including refractory hypotension or rapidly escalating vasopressor requirement. * Clinically significant arrhythmia, high-grade atrioventricular block, acute coronary syndrome, or active myocardial ischemia before enrollment. * Severe hepatic dysfunction…