This prospective, multicenter, single-arm interventional pilot study aims to evaluate the short-term physiological effects of intravenous esmolol on sublingual microcirculation and vascular-waterfall parameters in adult patients with septic shock. Eligible patients will have septic shock according to Sepsis-3 criteria, persistent tachycardia after initial hemodynamic optimization, ongoing norepinephrine support, adequate volume status or absence of significant fluid responsiveness, and preserved or hyperdynamic cardiac function. Approximately 20 patients will be enrolled from participating intensive care units. After baseline assessment, participants will receive continuous intravenous esmolol infusion according to the study protocol and clinical safety criteria. 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 and at 3, and 6 hours after esmolol initiation. Additional systemic hemodynamic, perfusion, vasopressor, and safety variables will also be collected. The primary objective is to characterize immediate changes in sublingual microcirculation and vascular-waterfall physiology after esmolol administration and to provide preliminary data for the design of future controlled studies.
Septic shock is characterized by profound circulatory dysfunction involving both systemic hemodynamics and the microcirculation. Persistent tachycardia is common in septic shock and may reflect sympathetic overactivation, high catecholamine exposure, fever, pain, hypovolemia, or ongoing circulatory stress. After adequate fluid resuscitation, vasopressor support, analgesia and sedation, and correction of reversible causes, persistent tachycardia may contribute to increased myocardial oxygen consumption, impaired diastolic filling, reduced ventriculo-arterial coupling, and altered tissue perfusion. Esmolol is an ultra-short-acting β1-selective adrenergic blocker that can be titrated rapidly and discontinued promptly if adverse hemodynamic effects occur. Previous studies suggest that heart rate control with esmolol in selected patients with septic shock may reduce catecholamine requirements and improve cardiovascular efficiency. However, its immediate effects on sublingual microcirculation and vascular-waterfall physiology remain insufficiently characterized. The vascular-waterfall phenomenon refers to the concept that tissue perfusion may depend not only on arterial and venous pressures but also on the relationship between upstream pressure, critical closing pressure, and mean systemic filling pressure. In septic shock, changes in vascular tone, vasopressor exposure, and microvascular regulation may alter critical closing pressure and the effective pressure gradient for tissue perfusion. Evaluating these parameters together with direct sublingual microcirculatory imaging may provide mechanistic insight into the physiological effects of esmolol beyond conventional macrocirculatory variables. This is a prospective, multicenter, single-arm interventional pilot study conducted in adult intensive care unit patients with septic shock. Patients will be screened after initial hemodynamic optimization. Eligible patients must have septic shock according to Sepsis-3 criteria, persistent tachycardia, ongoing norepinephrine support, adequate volume status or no significant fluid responsiveness, and preserved or hyperdynamic cardiac function before esmolol initiation. Patients with shock predominantly due to non-septic causes, severe cardiac dysfunction, contraindications to β-blockade, or inability to obtain acceptable sublingual microcirculatory images will be excluded. After informed consent is obtained, baseline measurements will be performed immediately before esmolol initiation. Participants will then receive continuous intravenous esmolol infusion. The infusion may be started at a low dose and titrated according to heart rate, mean arterial pressure, cardiac output or cardiac index, vasopressor requirement, and clinical safety criteria. Temporary dose reduction, interruption, or discontinuation of esmolol will be permitted for safety reasons, including clinically significant hypotension, bradycardia, reduced cardiac output, worsening shock, new or worsening arrhythmia, or other adverse events judged by the treating physician or investigator. Study assessments will be performed at baseline and at 3, and 6 hours after initiation of esmolol. Sublingual microcirculatory imaging will be used to assess microvascular flow index, perfused vessel density, proportion of perfused vessels, and microcirculatory heterogeneity index. Vascular-waterfall related variables will include estimated critical closing pressure, estimated mean systemic filling pressure, and the Pcc-Pmsf gradient. Systemic hemodynamic and perfusion variables, including heart rate, mean arterial pressure, cardiac index, norepinephrine dose, arterial lactate, urine output, and predefined adverse events, will also be recorded. Approximately 20 patients will be enrolled to assess feasibility and generate preliminary estimates of physiological changes after esmolol administration. The main analyses will describe changes from baseline in sublingual microcirculatory and vascular-waterfall parameters over the 6-hour observation period. Safety events and exploratory clinical outcomes may be summarized descriptively to inform the design of subsequent controlled trials.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
20
Esmolol will be administered as a continuous intravenous infusion after initial hemodynamic optimization. The suggested initial infusion rate is 25-50 μg/kg/min and may be titrated according to heart rate, blood pressure, cardiac output, and clinical judgment. The target heart rate is generally 80-94 beats/min, unless individualized by the treating physician. Dose adjustment, temporary interruption, or discontinuation is permitted for safety reasons, including hypotension, bradycardia, reduced cardiac output, or other clinically significant adverse events. The actual dose and reasons for dose changes will be recorded at each study time point.
The First Affiliated Hospital of Wannan Medical College (Yijishan Hospital of Wannan Medical College)
Wuhu, Anhui, China
The First Affiliated Hospital of Bengbu Medical University
Bengbu, Anhu, China
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 each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
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 each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
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 each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
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 each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
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 each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
Change From Baseline in Estimated Critical Closing Pressure
Estimated critical closing pressure will be calculated using predefined hemodynamic methods. The outcome is the change in Pcc from baseline to each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
Change From Baseline in Estimated Mean Systemic Filling Pressure
Estimated mean systemic filling pressure will be calculated using predefined hemodynamic methods. The outcome is the change in Pmsf from baseline to each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
Change From Baseline in Heart Rate
Heart rate will be recorded at each study time point. The outcome is the change in heart rate from baseline to each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
Change From Baseline in Mean Arterial Pressure
Mean arterial pressure will be recorded from invasive arterial monitoring at each study time point. The outcome is the change in MAP from baseline to each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
Change From Baseline in Cardiac Index
Cardiac index will be measured using echocardiography, pulse contour analysis, transpulmonary thermodilution, or other clinically available hemodynamic monitoring methods. The outcome is the change in cardiac index from baseline to each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol
Change From Baseline in Norepinephrine Dose
Norepinephrine dose will be recorded in μg/kg/min at each study time point. The outcome is the change in norepinephrine dose from baseline to each post-esmolol time point.
Time frame: Baseline, 3 hours, and 6 hours after initiation of esmolol.
Change From Baseline in Arterial Lactate
Arterial lactate concentration will be measured according to routine clinical practice. The outcome is the change in lactate from baseline to 6 hours after initiation of esmolol.
Time frame: Baseline and 6 hours after initiation of esmolol.
ICU Length of Stay
Number of days from ICU admission to ICU discharge.
Time frame: From ICU admission to ICU discharge, assessed up to 28 days after enrollment
Ventilator-Free Days at Day 28
Number of days alive and free from invasive mechanical ventilation within 28 days after enrollment.
Time frame: 28 days after enrollment.
28-Day Mortality
All-cause mortality within 28 days after enrollment.
Time frame: 28 days after enrollment.
Incidence of Prespecified Adverse Events
Prespecified adverse events include clinically significant hypotension, bradycardia, new-onset or worsening arrhythmia, reduction in cardiac index requiring treatment modification, escalation of vasopressor or inotropic support, interruption or discontinuation of esmolol for safety reasons, cardiac arrest, or other clinically significant events during the observation period.
Time frame: From initiation of esmolol to 6 hours after initiation
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