This prospective, multicenter, single-arm, open-label interventional pilot study aims to evaluate the short-term physiological effects of intravenous dexmedetomidine on sublingual microcirculation and vascular-waterfall parameters in adult patients with septic shock.
Eligible patients will have septic shock according to Sepsis-3 criteria, require norepinephrine support after adequate fluid resuscitation, receive invasive mechanical ventilation, and have PiCCO-based hemodynamic monitoring available before dexmedetomidine initiation. After baseline assessment, participants will receive intravenous dexmedetomidine according to the study protocol. Dexmedetomidine will be administered as a continuous intravenous infusion at 0.2-0.7 µg/kg/hour without a loading dose. The infusion rate may be adjusted according to the target sedation level, hemodynamic status, and adverse effects.
Sublingual microcirculatory variables, including microvascular flow index, perfused vessel density, proportion of perfused vessels, and heterogeneity index, as well as vascular-waterfall parameters, including estimated critical closing pressure, estimated mean systemic filling pressure, and the Pcc-Pmsf gradient, will be measured at baseline, 3 hours, and 6 hours after initiation of dexmedetomidine. Systemic hemodynamic, perfusion, vasopressor, PiCCO-derived, sedation-related, and safety outcomes will also be collected.
The primary objective is to characterize immediate changes in sublingual microcirculation and vascular-waterfall physiology after dexmedetomidine administration and to provide preliminary data for future controlled studies.
Age 18-85 years.
Diagnosis of septic shock according to Sepsis-3 criteria, defined as suspected or documented infection with vasopressor requirement 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 invasive mechanical ventilation.
Shock primarily caused by non-septic etiologies, including cardiogenic, hypovolemic, obstructive, hemorrhagic, or anaphylactic shock.
Expected death or withdrawal of life-sustaining treatment within 24 hours.
Known allergy or hypersensitivity to dexmedetomidine.
Severe bradycardia or clinically significant conduction abnormality before enrollment, including heart rate <50 beats/min, second-degree or third-degree atrioventricular block, sick sinus syndrome, or other conduction abnormality without a functioning pacemaker.
Single group
Dexmedetomidine Intravenous Infusion
DrugDexmedetomidine will be administered as a continuous intravenous infusion at 0.2-0.7 µg/kg/hour without a loading dose. The infusion rate may be adjusted according to the target sedation level, heart rate, mean arterial pressure, vasopressor requirement, PiCCO-derived hemodynamic variables, and adverse effects. Dose reduction, temporary interruption, or discontinuation is permitted for safety reasons, including clinically significant hypotension, bradycardia, new-onset or worsening arrhythmia, high-grade atrioventricular block, suspected myocardial ischemia, increased vasopressor requirement, or other clinically significant adverse events. The actual dose, infusion duration, and reasons for dose adjustment or discontinuation will be recorded.
Change From Baseline in Pcc-Pmsf Gradient
The vascular-waterfall pressure gradient will be calculated as the difference between estimated critical closing pressure and estimated mean systemic filling pressure. The outcome is the change in Pcc-Pmsf from baseline to 3 and 6 hours after dexmedetomidine initiation.
Change From Baseline in Sublingual Microvascular Flow Index
Microvascular flow index will be assessed using sublingual microcirculatory imaging. Three to five sublingual video fields will be recorded at each time point, and MFI will be calculated according to standard microcirculatory scoring methods. The outcome is the change in MFI from baseline to 3 and 6 hours after dexmedetomidine initiation
Change From Baseline in Perfused Vessel Density
Perfused vessel density will be measured from sublingual microcirculatory images. The outcome is the change in PVD from baseline to 3 and 6 hours after dexmedetomidine initiation
Change From Baseline in Proportion of Perfused Vessels
Proportion of perfused vessels will be measured from sublingual microcirculatory images. The outcome is the change in PPV from baseline to 3 and 6 hours after dexmedetomidine initiation
Change From Baseline in Microcirculatory Heterogeneity Index
Microcirculatory heterogeneity index will be calculated from sublingual microcirculatory measurements. The outcome is the change in HI from baseline to 3 and 6 hours after dexmedetomidine initiation.
Change From Baseline in Estimated Critical Closing Pressure
Estimated critical closing pressure will be calculated using predefined hemodynamic methods based on arterial pressure waveform-derived parameters and PiCCO-based cardiac output measurements. The outcome is the change in Pcc from baseline to 3 and 6 hours after dexmedetomidine initiation.
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