The goal of this clinical trial is to learn whether early administration of dexmedetomidine can improve autonomic nervous system regulation and clinical outcomes in adult patients with septic shock. It will also evaluate the safety of dexmedetomidine in this population.

The main questions it aims to answer are:

Does early dexmedetomidine improve sympathetic nervous system activity, as measured by heart rate variability (HRV) and blood pressure variability (BPV)?

Does dexmedetomidine reduce endogenous catecholamine levels and vasopressor requirements?

Does early autonomic modulation improve organ function and survival outcomes in septic shock? Researchers will compare dexmedetomidine to a placebo (normal saline) to determine whether dexmedetomidine improves hemodynamic stability and prognosis in patients with septic shock.

Participants will:

Be randomly assigned to receive dexmedetomidine (0.5 μg/kg/h) or placebo by continuous intravenous infusion for 48 hours

Undergo continuous ECG and invasive blood pressure monitoring

Have blood samples collected at predefined time points to measure inflammatory markers and endogenous catecholamine levels

Be assessed for organ function, vasopressor use, and perfusion parameters during the first 48 hours

Be followed up for 28-day and 90-day survival outcomes

Inclusion Criteria:

Age ≥ 18 year Septic shock defined by Sepsis-3 criteria Enrollment within 24 hours of diagnosis APACHE II score > 10

Exclusion Criteria:

Pregnancy or lactation Second- or third-degree atrioventricular block Persistent bradycardia (HR <50 bpm) requiring intervention Hypersensitivity to dexmedetomidine Norepinephrine dose >0.5 μg/kg/min End-stage disease or life expectancy <72 hours Any condition deemed unsuitable by the investigator