Respiratory Variability of Pulmonary Velocity-Time Integral As a New Gauge of Fluid Responsiveness For Mechanically Ventilated Patients in the ICU*:

RESPIRATORY VARIABILITY OF VALVULAR PEAK SYSTOLIC VELOCITY AS A NEW INDICATOR OF FLUID RESPONSIVENESS IN PATIENTS WITH SEPTIC SHOCK

ABSTRACT

Objective: The aim of this study was to evaluate the reliability and feasibility of pulse Doppler measurements of peak velocity respiratory variability of mitral and tricuspid valve rings during systole as new dynamic indicators of fluid responsiveness in patients with septic shock. Methods: Transthoracic echocardiography (TTE) was performed to measure the respiratory variability of aortic velocity-time integral (∆VTI), respiratory variability of tricuspid annulus systolic peak velocity (∆RVS), respiratory variability of mitral annulus systolic peak velocity (∆LVS), and other related indicators. Fluid responsiveness was defined as a 10% increase in cardiac output after fluid expansion, assessed by TTE. Results: A total of 33 patients with septic shock were enrolled in this study. First, there was no significant difference in the population characteristics between the fluid responsiveness positive group (n = 17) and the fluid responsiveness negative group (n = 16) ( P > 0.05). Second, Pearson correlation test showed that ∆RVS, ∆LVS, and TAPSE with the relative increase in cardiac output after fluid expansion ( R = 0.55, P = 0.001; R = 0.40, P = 0.02; R = 0.36, P = 0.041). Third, multiple logistic regression analysis demonstrated that ∆RVS, ∆LVS, and TAPSE were significantly correlated with fluid responsiveness in patients with septic shock. Fourth, receiver operating characteristic (ROC) curve analysis revealed that ∆VTI, ∆LVS, ∆RVS, and TAPSE had good predictive ability for fluid responsiveness in patients with septic shock. The area under the curve (AUC) of ∆VTI, ∆LVS, ∆RVS, and TAPSE for predicting fluid responsiveness was 0.952, 0.802, 0.822, and 0.713, respectively. The sensitivity (Se) values were 1.00, 0.73, 0.81, and 0.83, whereas the specificity (Sp) values were 0.84, 0.91, 0.76, and 0.67, respectively. The optimal thresholds were 0.128, 0.129, 0.130, and 13.9 mm, respectively. Conclusion: Tissue Doppler ultrasound evaluation of respiratory variability of mitral and tricuspid annular peak systolic velocity could be a feasible and reliable method for the simple assessment of fluid responsiveness in patients with septic shock.

The Accuracy of Velocity-Time Integral Variation and Peak Velocity Variation of the Left Ventricular Outflow Tract in Predicting Fluid Responsiveness in Postoperative Patients Mechanically Ventilated at Low Tidal Volumes

OBJECTIVE

To assess whether velocity-time integral (VTI) variation and peak velocity (Vpeak) variation of the left ventricular outflow tract (LVOT) accurately could predict fluid responsiveness in postoperative critically ill patients mechanically ventilated at low tidal volumes.

DESIGN

A prospective, single-center, observational study.

SETTING

A surgical intensive care unit at a tertiary hospital.

PARTICIPANTS

Sixty postoperative critically ill patients with deep sedation and mechanical ventilation (tidal volume <8 mL/kg) were included in this study.

INTERVENTIONS

Passive leg raising (PLR).

MEASUREMENT AND MAIN RESULTS

Pulse pressure variation (PPV), VTI variation, and Vpeak variation were measured at baseline and after PLR by transthoracic echocardiography. The fluid responsiveness was defined as an increase (>10%) in stroke volume after PLR. Thirty-two (53.3%) patients were fluid responders. The areas under the receiver operating characteristic (AUROC) curves for PPV were 0.797, and the gray zone was large and included 58.3% of patients. Both VTI variation and Vpeak variation predicted fluid responsiveness with the AUROC of 0.919 and 0.905; meanwhile, the best cutoff values were 12.51% (sensitivity of 71.9%; specificity of 75.0%) and 11.76% (sensitivity of 81.3%; specificity of 89.3%). The gray zones of VTI variation and Vpeak variation were from 7.41% to 11.88% (contained 23.3% patients) and from 9.96% to 13.10% (contained 28.3% patients).

CONCLUSIONS

In postoperative critically ill patients mechanically ventilated with tidal volume <8 mL/kg, the VTI variation and Vpeak variation of LVOT accurately could predict fluid responsiveness, and VTI variation showed more accuracy than Vpeak variation in predicting fluid responsiveness.

Fluid challenge in critically ill patients receiving haemodynamic monitoring: a systematic review and comparison of two decades

Introduction

Fluid challenges are widely adopted in critically ill patients to reverse haemodynamic instability. We reviewed the literature to appraise fluid challenge characteristics in intensive care unit (ICU) patients receiving haemodynamic monitoring and considered two decades: 2000–2010 and 2011–2021.

Methods

We assessed research studies and collected data regarding study setting, patient population, fluid challenge characteristics, and monitoring. MEDLINE, Embase, and Cochrane search engines were used. A fluid challenge was defined as an infusion of a definite quantity of fluid (expressed as a volume in mL or ml/kg) in a fixed time (expressed in minutes), whose outcome was defined as a change in predefined haemodynamic variables above a predetermined threshold.

Results

We included 124 studies, 32 (25.8%) published in 2000–2010 and 92 (74.2%) in 2011–2021, overall enrolling 6,086 patients, who presented sepsis/septic shock in 50.6% of cases. The fluid challenge usually consisted of 500 mL (76.6%) of crystalloids (56.6%) infused with a rate of 25 mL/min. Fluid responsiveness was usually defined by a cardiac output/index (CO/CI) increase ≥ 15% (70.9%). The infusion time was quicker (15 min vs 30 min), and crystalloids were more frequent in the 2011–2021 compared to the 2000–2010 period.

Conclusions

In the literature, fluid challenges are usually performed by infusing 500 mL of crystalloids bolus in less than 20 min. A positive fluid challenge response, reported in 52% of ICU patients, is generally defined by a CO/CI increase ≥ 15%. Compared to the 2000–2010 decade, in 2011–2021 the infusion time of the fluid challenge was shorter, and crystalloids were more frequently used.

Platform introducing individually tailored variability in nerve stimulations and dietary regimen to prevent weight regain following weight loss in patients with obesity

Prevention of weight regain following successful weight loss is a major challenge in the treatment of obesity, irrespective of the weight reduction method used. The majority of individuals regain the lost weight over time; thus, achieving long-term sustainability in weight loss remains an unresolved issue. A compensatory adaptation to the weight loss methods occurs in several body organs and partly explains the lack of sustainable effect. Variability is inherent in many biological systems, and patterns of variability constitute a body mechanism that is active at several levels, starting from the genes and cellular pathways through to the whole-organ level. This study aimed to describe a platform that introduces individually tailored variability in vagal nerve stimulation and dietary regimen to ensure prolonged and sustainable weight loss and prevent weight regain. The platform is intended to provide a method that can overcome the body's compensatory adaptation mechanisms while ensuring a prolonged beneficial effect.

Time course of fluid responsiveness in sepsis: the fluid challenge revisiting (FCREV) study

BACKGROUND

Fluid challenge (FC) is one of the most common practices in Intensive Care Unit (ICU). The present study aimed to evaluate whether echocardiographic assessment of the response to FC at the end of the infusion or 20 min later could affect the results of the FC.

METHODS

This is a prospective, observational, multicenter study including all ICU patients in septic shock requiring a FC of 500 mL crystalloids over 10 min. Fluid responsiveness was defined as a > 15% increase in stroke volume (SV) assessed by velocity-time integral (VTI) measurements at baseline (T₀), at the end of FC (T₁₀), then 10 (T₂₀) and 20 min (T₃₀) after the end of FC.

RESULTS

From May 20, 2014, to January 7, 2016, a total of 143 patients were enrolled in 11 French ICUs (mean age 64 ± 14 years, median IGS II 53 [43-63], median SOFA score 10 [8-12]). Among the 76/143 (53%) patient responders to FC at T₁₀, 37 patients were transient responders (TR), i.e., became non-responders (NR) at T₃₀ (49%, 95%CI = [37-60]), and 39 (51%, 95%CI = [38-62]) patients were persistent responders (PR), i.e., remained responders at T₃₀. Among the 67 NR at T₁₀, 4 became responders at T30, (6%, 95%CI = [1.9-15.3]). In the subgroup analysis, no statistical difference in hemodynamic and echocardiographic parameters was found between groups.

CONCLUSIONS

This study shows that 51.3% of initial responders have a persistent response to fluid 30 min after the beginning of fluid infusion and only 41.3% have a transient response highlighting that fluid responsiveness is time dependent.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT02116413 . Registered on April 16, 2014.