Respiratory variation in carotid peak systolic velocity predicts volume responsiveness in mechanically ventilated patients with septic shock: a prospective cohort study

Accuracy of Respiratory Variation in Inferior Vena Cava Diameter to Predict Fluid Responsiveness in Children Under Mechanical Ventilation

Proper assessment of fluid responsiveness using accurate predictors is crucial to guide fluid therapy and avoid the serious adverse effects of fluid overload. The main objective of this study was to investigate the accuracy of respiratory variations in inferior vena cava diameter (∆IVC) to predict fluid responsiveness in mechanically ventilated children. This prospective single-center study included 32 children (median age and weight of 17 months and 10 kg, respectively) who received a fluid infusion of 10 ml kg-1 of crystalloid solutions over 10 min. ∆IVC and respiratory variation in aortic blood flow peak velocity (∆Vpeak) were determined over one controlled respiratory cycle before and after fluid loading. Thirteen (41%) participants were fluid-responders. ∆IVC, ∆Vpeak, stroke volume index, and cardiac index were found to be predictors of fluid responsiveness. However, the area under the ROC curve of ∆IVC was smaller when compared to ∆Vpeak (0.709 vs. 0.935, p < 0.012). The best cut-off values were 7.7% for ∆IVC (sensitivity, 69.2%; specificity 78.9%, positive predictive value, 69.2%; and negative predictive value, 78.9%) and 18.2% for ∆Vpeak (sensitivity, 84.6%; specificity, 89.5%; positive predictive value, 84.6%; negative predictive value, 89.5%). Changes in stroke volume were positively correlated with ∆IVC (ρ = 0.566, p < 0.001) and ∆Vpeak (ρ = 0.603, p < 0.001). A significant correlation was also found between changes in MAP and ∆Vpeak (ρ = 0.382; p = 0.031), but the same was not observed with ∆IVC (ρ = 0.011; p = 0.951). In conclusion, ∆IVC was found to have a moderate accuracy in predicting fluid responsiveness in mechanically ventilated children and is an inferior predictor when compared to ∆Vpeak.

Predicting Fluid Responsiveness Using Carotid Ultrasound in Mechanically Ventilated Patients: A Systematic Review and Meta-Analysis of Diagnostic Test Accuracy Studies

BACKGROUND

A noninvasive and accurate method of determining fluid responsiveness in ventilated patients would help to mitigate unnecessary fluid administration. Although carotid ultrasound has been previously studied for this purpose, several studies have recently been published. We performed an updated systematic review and meta-analysis to evaluate the accuracy of carotid ultrasound as a tool to predict fluid responsiveness in ventilated patients.

METHODS

Studies eligible for review investigated the accuracy of carotid ultrasound parameters in predicting fluid responsiveness in ventilated patients, using sensitivity and specificity as markers of diagnostic accuracy (International Prospective Register of Systematic Reviews [PROSPERO] CRD42022380284). All included studies had to use an independent method of determining cardiac output and exclude spontaneously ventilated patients. Six bibliographic databases and 2 trial registries were searched. Medline, Embase, Emcare, APA PsycInfo, CINAHL, and the Cochrane Library were searched on November 4, 2022. Clinicaltrials.gov and Australian New Zealand Clinical Trials Registry were searched on February 24, 2023. Results were pooled, meta-analysis was conducted where possible, and hierarchical summary receiver operating characteristic models were used to compare carotid ultrasound parameters. Bias and evidence quality were assessed using the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) tool and the Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) guidelines.

RESULTS

Thirteen prospective clinical studies were included (n = 648 patients), representing 677 deliveries of volume expansion, with 378 episodes of fluid responsiveness (58.3%). A meta-analysis of change in carotid Doppler peak velocity (∆CDPV) yielded a sensitivity of 0.79 (95% confidence interval [CI], 0.74-0.84) and a specificity of 0.85 (95% CI, 0.76-0.90). Risk of bias relating to recruitment methodology, the independence of index testing to reference standards and exclusionary clinical criteria were evaluated. Overall quality of evidence was low. Study design heterogeneity, including a lack of clear parameter cutoffs, limited the generalizability of our results.

CONCLUSIONS

In this meta-analysis, we found that existing literature supports the ability of carotid ultrasound to predict fluid responsiveness in mechanically ventilated adults. ∆CDPV may be an accurate carotid parameter in certain contexts. Further high-quality studies with more homogenous designs are needed to further validate this technology.

Fluid Responsiveness in Critically Ill Patients Using Carotid Peak Systolic Velocity Variability: A New Frontier

Background and objectives A fluid responder is a patient who can increase his stroke volume/ cardiac output by more than 10%-15% after a fluid bolus. Left ventricular outflow tract (LVOT) velocity time integral (VTI) variability is widely used as an adynamic parameter of fluid responsiveness, but a transthoracic echo view of LVOT VTI is often time-consuming and, at times, difficult to achieve. So, in the quest for another parameter that might equally be a good surrogate marker of stroke volume variation, carotid peak systolic velocity (CPSV) variation has been studied. The objective was to assess CPSV variation in patients who are already fluid responders. Methods The sample size was calculated considering a minimum correlation coefficient of 0.5. Adult patients in whom the physician wanted to give a fluid bolus and whose average LVOT VTI was more than 15% over 3 respiratory cycles were included in the study. Demographic variables, along with hemodynamic parameters such as heart rate, blood pressure, the need for vasopressors, mode of breathing (spontaneous or mechanical ventilation), and CPSV variation,were noted and averaged over three respiratory cycles. Fluid bolus (Plasmalyte) 6 ml/kg bolus over 10-15 minutes. Post-fluid hemodynamic variables, along with averaged LVOT VTI over three respiratory cycles and averaged CPSV variation over three respiratory cycles, are noted. Results Thirty adult patients were evaluated in the study. In spontaneously breathing patients (n=12), the average CPSV variation expressed as mean + standard deviation before and after fluid administration of 6ml/kg of ideal body weight was 14.1 ± 3.4 and 5.4 ± 2.6, respectively (p < 0.05). In mechanically ventilated patients (n=18), the average CPSV variation expressed as mean + standard deviation before and after fluid administration of 6ml/kg of ideal body weight fluid was 15 ± 5.3 and 6.5 ± 3.1, respectively (p <0.005). Overall, there was a statistically significant positive correlation between LVOT VTI variation and CPSV variation before fluid therapy (correlation coefficient 0.56 and p-value 0.001) and a statistically significant moderate positive correlation post-fluid therapy (correlation coefficient 0.37 and p-value 0.043). Conclusion We found a significant decrease in CPSV variation post-fluid administration in patients who are fluid responders, which mimics a decrease in stroke volume variation after fluid administration in patients who are fluid responsive.

Can carotid artery Doppler variations induced by the end-expiratory occlusion maneuver predict fluid responsiveness in septic shock patients?

BACKGROUND

An increase in cardiac index (CI) during an end-expiratory occlusion test (EEOt) predicts fluid responsiveness in ventilated patients. However, if CI monitoring is unavailable or the echocardiographic window is difficult, using the carotid Doppler (CD) could be a feasible alternative to track CI changes. This study investigates whether changes in CD peak velocity (CDPV) and corrected flow time (cFT) during an EEOt were correlated with CI changes and if CDPV and cFT changes predicted fluid responsiveness in patients with septic shock.

METHODS

Prospective, single-center study in adults with hemodynamic instability. The CDPV and cFT on carotid artery Doppler and hemodynamic variables from the pulse contour analysis EV1000™ were recorded at baseline, during a 20-s EEOt, and after fluid challenge (500 mL). We defined responders as those who increased CI ≥ 15% after a fluid challenge.

RESULTS

We performed 44 measurements in 18 mechanically ventilated patients with septic shock and without arrhythmias. The fluid responsiveness rate was 43.2%. The changes in CDPV were significantly correlated with changes in CI during EEOt (r = 0.51 [0.26-0.71]). A significant, albeit lower correlation, was found for cFT (r = 0.35 [0.1-0.58]). An increase in CI ≥ 5.35% during EEOt predicted fluid responsiveness with 78.9% sensitivity and 91.7% specificity, with an area under the ROC curve (AUROC) of 0.85. An increase in CDPV ≥ 10.5% during an EEOt predicted fluid responsiveness with 96.2% specificity and 53.0% sensitivity with an AUROC of 0.74. Sixty-one percent of CDPV measurements (from - 13.5 to 9.5 cm/s) fell within the gray zone. The cFT changes during EEOt did not accurately predict fluid responsiveness.

CONCLUSIONS

In septic shock patients without arrhythmias, an increase in CDPV greater than 10.5% during a 20-s EEOt predicted fluid responsiveness with > 95% specificity. Carotid Doppler combined with EEOt may help optimize preload when invasive hemodynamic monitoring is unavailable. However, the 61% gray zone is a major limitation (retrospectively registered on Clinicaltrials.gov NCT04470856 on July 14, 2020).

Early adjunctive methylene blue in patients with septic shock: a randomized controlled trial

PURPOSE

Methylene blue (MB) has been tested as a rescue therapy for patients with refractory septic shock. However, there is a lack of evidence on MB as an adjuvant therapy, its' optimal timing, dosing and safety profile. We aimed to assess whether early adjunctive MB can reduce time to vasopressor discontinuation in patients with septic shock.

METHODS

In this single-center randomized controlled trial, we assigned patients with septic shock according to Sepsis-3 criteria to MB or placebo. Primary outcome was time to vasopressor discontinuation at 28 days. Secondary outcomes included vasopressor-free days at 28 days, days on mechanical ventilator, length of stay in ICU and hospital, and mortality at 28 days.

RESULTS

Among 91 randomized patients, forty-five were assigned to MB and 46 to placebo. The MB group had a shorter time to vasopressor discontinuation (69 h [IQR 59-83] vs 94 h [IQR 74-141]; p < 0.001), one more day of vasopressor-free days at day 28 (p = 0.008), a shorter ICU length of stay by 1.5 days (p = 0.039) and shorter hospital length of stay by 2.7 days (p = 0.027) compared to patients in the control group. Days on mechanical ventilator and mortality were similar. There were no serious adverse effects related to MB administration.

CONCLUSION

In patients with septic shock, MB initiated within 24 h reduced time to vasopressor discontinuation and increased vasopressor-free days at 28 days. It also reduced length of stay in ICU and hospital without adverse effects. Our study supports further research regarding MB in larger randomized clinical trials. Trial registration ClinicalTrials.gov registration number NCT04446871 , June 25, 2020, retrospectively registered.

Indications, Clinical Impact, and Complications of Critical Care Transesophageal Echocardiography: A Scoping Review

BACKGROUND

Critical care transesophageal echocardiography (ccTEE) is an increasingly popular tool used by intensivists to characterize and manage hemodynamics at the bedside. Its usage appears to be driven by expanded diagnostic scope as well as the limitations of transthoracic echocardiography (TTE) - lack of acoustic windows, patient positioning, and competing clinical interests (eg, the need to perform chest compressions). The objectives of this scoping review were to determine the indications, clinical impact, and complications of ccTEE.

METHODS

MEDLINE, EMBASE, Cochrane, and six major conferences were searched without a time or language restriction on March 31^st, 2021. Studies were included if they assessed TEE performed for adult critically ill patients by intensivists, emergency physicians, or anesthesiologists. Intraoperative or post-cardiac surgical TEE studies were excluded. Study demographics, indication for TEE, main results, and complications were extracted in duplicate.

RESULTS

Of the 4403 abstracts screened, 289 studies underwent full-text review, with 108 studies (6739 patients) included. Most studies were retrospective (66%), performed in academic centers (84%), in the intensive care unit (73%), and were observational (55%). The most common indications for ccTEE were hemodynamic instability, trauma, cardiac arrest, respiratory failure, and procedural guidance. Across multiple indications, ccTEE was reported to change the diagnosis in 52% to 78% of patients and change management in 32% to79% patients. During cardiac arrest, ccTEE identified the cause of arrest in 25% to 35% of cases. Complications of ccTEE included two cases of significant gastrointestinal bleeding requiring intervention, but no other major complications (death or esophageal perforation) reported.

CONCLUSIONS

The use of ccTEE has been described for the diagnosis and management of a broad range of clinical problems. Overall, ccTEE was commonly reported to offer additional diagnostic yield beyond TTE with a low observed complication rate. Additional high quality ccTEE studies will permit stronger conclusions and a more precise understanding of the trends observed in this scoping review.

Carotid Doppler ultrasound for non-invasive haemodynamic monitoring: a narrative review

Objective.Accurate haemodynamic monitoring is the cornerstone in the management of critically ill patients. It guides the optimization of tissue and organ perfusion in order to prevent multiple organ failure. In the past decades, carotid Doppler ultrasound (CDU) has been explored as a non-invasive alternative for long-established invasive haemodynamic monitoring techniques. Considering the large heterogeneity in reported studies, we conducted a review of the literature to clarify the current status of CDU as a haemodynamic monitoring tool.Approach.In this article, firstly an overview is given of the equipment and workflow required to perform a CDU exam in clinical practice, the limitations and technical challenges potentially faced by the CDU sonographer, and the cerebrovascular mechanisms that may influence CDU measurement outcomes. The following chapter describes alternative techniques for non-invasive haemodynamic monitoring, detailing advantages and limitations compared to CDU. Next, a comprehensive review of the literature regarding the use of CDU for haemodynamic monitoring is presented. Furthermore, feasibility aspects, training requirements and technical developments of CDU are addressed.Main results.Based on the outcomes of these studies, we assess the applicability of CDU-derived parameters within three clinical domains (cardiac output, volume status, and fluid responsiveness), and amongst different patient groups. Finally, recommendations are provided to improve the quality and standardization of future research and clinical practice in this field.Significance.Although CDU is not yet interchangeable with invasive 'gold standard' cardiac output monitoring, the present work shows that certain CDU-derived parameters prove promising in the context of functional haemodynamic monitoring.

Point-of-care ultrasonography to predict fluid responsiveness in children: A systematic review and meta-analysis

BACKGROUND

Point-of-care ultrasonography (POCUS) is proposed as a valuable method for hemodynamic monitoring and several ultrasound-based predictors of fluid responsiveness have been studied. The main objective of this study was to assess the accuracy of these predictors in children.

METHODS

PubMed, Embase, Scopus, ClinicalTrials.gov, and Cochrane Library databases were searched for relevant publications through July 2022. Pediatric studies reporting accuracy estimates of ultrasonographic predictors of fluid responsiveness were included since they had used a standard definition of fluid responsiveness and had performed an adequate fluid challenge.

RESULTS

Twenty-three studies involving 1028 fluid boluses were included, and 12 predictors were identified. A positive response to fluid infusion was observed in 59.7% of cases. The vast majority of participants were mechanically ventilated (93.4%). The respiratory variation in aortic blood flow peak velocity (∆Vpeak) was the most studied predictor, followed by the respiratory variation in inferior vena cava diameter (∆IVC). The pooled sensitivity and specificity of ∆Vpeak were 0.84 (95% CI, 0.76-0.90) and 0.82 (95% CI, 0.75-0.87), respectively, and the area under the summary receiver operating characteristic curve (AUSROC) was 0.89 (95% CI, 0.86-0.92). The ∆IVC presented a pooled sensitivity and specificity of 0.79 (95% CI, 0.62-0.90) and 0.70 (95% CI, 0.51-0.84), respectively, and an AUSROC of 0.81 (95% CI, 0.78-0.85). Significant heterogeneity in accuracy estimates across studies was observed.

CONCLUSIONS

POCUS has the potential to accurately predict fluid responsiveness in children. However, only ∆Vpeak was found to be a reliable predictor. There is a lack of evidence supporting the use of POCUS to guide fluid therapy in spontaneously breathing children.

The association between carotid flow time and fluid responsiveness in children under general anesthesia

BACKGROUND

Fluid administration in children undergoing surgery requires precision, however, determining fluid responsiveness can be challenging. Ultrasound has been used widely in the emergency department and intensive care units as a noninvasive, bedside manner of determining volume status, but the intraoperative period presents unique challenges as often the chest and abdomen are inaccessible for ultrasound. We investigate whether carotid artery ultrasound, specifically carotid flow time, can be used to determine fluid responsiveness in children under general anesthesia.

METHODS

Prospective observational study of 87 children ages 1-12 years who were scheduled for elective noncardiac surgery. Ultrasound of the carotid artery and heart was performed at three time points: (1) after inhalational induction of anesthesia with the subject spontaneously breathing, (2) during positive pressure ventilation through endotracheal tube or supraglottic airway with tidal volume set at 8 ml/kg with PEEP of 10 cmH₂ O, and (3) after a 10 ml/kg fluid bolus. Carotid flow time and cardiac output were measured from saved images.

RESULTS

Corrected carotid flow time (FTc) increased with initiation of positive pressure ventilation in both fluid responders and nonresponders (352.7 vs. 365.3 msec, p = .005 in fluid responders; 348.3 vs. 365.2 msec, p = .001 in nonresponders). FTc increased after fluid bolus in both responders and nonresponders (365.3 vs. 397.6 msec, p < .001 in fluid responders; 365.2 vs. 397.2 msec, p < .001 in nonresponders). However, baseline FTc during spontaneous ventilation or positive pressure ventilation prior to fluid bolus was not associated with fluid responsiveness.

DISCUSSION

Flow time increases with initiation of positive pressure ventilation and after administration of a fluid bolus. FTc may serve as an indicator of fluid status but does not predict fluid responsiveness in children under general anesthesia.

The Validity of Carotid Doppler Peak Velocity and Inferior Vena Cava Collapsibility Index in Identifying the Fluid Responders in Mechanically Ventilated Septic Shock Patients

Introduction: Measures of carotid artery flow or inferior vena cava diameter were recently shown to predict fluid responsiveness. Both are relatively superficial large vessels which can provide straightforward ultrasound evaluation & high-qualityimages.Methods: Our study is a prospective observational study on 30 mechanically ventilated septic shock patients in ICUto assess the fluid responsivenessby measuring carotid Doppler peak velocity&respiratory variation in inferior vena cava diameter against the increase in the cardiac index by echocardiographic calculations as a reference. All patients were given a fluid bolus 7 ml/ Kg crystalloid solution within 30 minutes, static and dynamic indices which include CVP, MAP, pulse pressure, difference between diameter of IVC during inspiration and expiration (ΔIVC- d) & carotid Doppler peak velocity in a single respiratory cycle (ΔCDPV) were measured before (T0) & after (T1). Vasoactive drugs infusion rate and ventilation settings did not changed during follow up. Patients were categorized either fluid responders “R” or non-responders “NR” according to an increase in cardiac output “CO” (increase in CO > 15 %.Results: Comparing responders & Non responders group we found a significant difference in Cardiac output measures,MAP & Δ CDPV pre & post fluid boluses as (5.26±4.42 L/min Vs. 10.62±5.73 L/min, 69.48±9.70 mmHg Vs. 84.90±10.36 mmHg&24.43±11.87%Vs33.22±11.00%) respectively with P-value (0.007, 0.05&0.01) respectively, on the other side , ΔD-IVC & Δ CVP pre & post fluid boluses didn’t show any statistical difference as (11.91±9.41 % Vs. 13.51±9.56 %, 5.86±5.22 cmH2O Vs 7.22±4.82 cmH2O) with P-value (0.87&0.68)respectively.Δ CDPV increase in response to increased intravascular volume in R group showed sensitivity 81%, specificity 66.7%. APACHE II, SOFA day 0,5 didn’t showed any difference between the R & NR group (16.05±3.23 Vs 18.44±3.81, 11.48±2.82Vs12.11±2.80& 12.95±3.68Vs12.56±3.97) respectively with P-value (0.164,  0.625 & 0.79) respectively. Conclusion: ΔCDPV was a more precise & even easier assessment tool with better sensitivity and specificity for evaluation of fluid responsiveness than the ΔD-IVC in patients with septic shock upon mechanicalventilation. Also, ΔCDPV has a high correlation with SVI increasing parameters assessed by echocardiography after fluid boluses. On the other hand and in comparison, CVP showed low accuracy in predicting fluid responsiveness.    

Carotid vs aortic velocity time integral and peak velocity to predict fluid responsiveness in mechanically ventilated patients. A comparative study

BACKGROUND

The carotid artery velocity-time integral (CVTI) and the carotid Doppler peak velocity (cDPV), as well as measures of their variation induced by the respiratory cycle, have been proposed as fast and easy to obtain ultrasound measures for assessing fluid responsiveness in intensive care unit patients. To investigate this possibility, we conducted a prospective observational study in hemodynamically unstable patients under mechanical ventilation.

METHODS

From May 1 to December 31, 2019, we conducted a prospective observational study involving 50 hemodynamically unstable patients under mechanical ventilation. We obtained a total of 800 Doppler ultrasound measurements from the left common carotid artery and at the level of the aortic annulus in the apical five-chamber view. The two measurements were performed before and after a 7 mL/kg fluid challenge and within the first hour of the onset of hemodynamic instability. The maximum Doppler peak velocity, the minimum Doppler peak velocity, and the maximum and minimum VTI at both the aortic and carotid level were acquired.

RESULTS

Twenty-eight (56%) patients showed a ≥15% increase in AoVTI after the fluid challenge, and were therefore identified as "fluid responders". All Doppler measurements were always significantly greater (p <0.0001) in fluid responders in relation to both carotid and aortic parameters. Good agreement between the above-mentioned measurements was found: Cohen's kappa coefficient between the carotid and aortic ΔDPV was 0.76 (95% CI 0.58 - 0.94); and between the Carotid and Aortic ΔVTI it was 0.84 (95% CI 0.68 - 0.99).

CONCLUSIONS

CDPV was found to predict fluid responsiveness in unstable mechanically ventilated patients.

Respiratory Variation in Carotid Artery Peak Systolic Velocity Is Unable to Predict Fluid Responsiveness in Spontaneously Breathing Critically Ill Patients When Assessed by Novice Physician Sonologists

BACKGROUND

Respiratory variation in carotid artery peak systolic velocity (ΔVpeak) assessed by point-of-care ultrasound (POCUS) has been proposed as a noninvasive means to predict fluid responsiveness. We aimed to evaluate the ability of carotid ΔVpeak as assessed by novice physician sonologists to predict fluid responsiveness.

METHODS

This study was conducted in 2 intensive care units. Spontaneously breathing, nonintubated patients with signs of volume depletion were included. Patients with atrial fibrillation/flutter, cardiogenic, obstructive or neurogenic shock, or those for whom further intravenous (IV) fluid administration would be harmful were excluded. Three novice physician sonologists were trained in POCUS assessment of carotid ΔVpeak. They assessed the carotid ΔVpeak in study participants prior to the administration of a 500 mL IV fluid bolus. Fluid responsiveness was defined as a ≥10% increase in cardiac index as measured using bioreactance.

RESULTS

Eighty-six participants were enrolled, 50 (58.1%) were fluid responders. Carotid ΔVpeak performed poorly at predicting fluid responsiveness. Test characteristics for the optimum carotid ΔVpeak of 8.0% were: area under the receiver operating curve = 0.61 (95% CI: 0.48-0.73), sensitivity = 72.0% (95% CI: 58.3-82.56), specificity = 50.0% (95% CI: 34.5-65.5).

CONCLUSIONS

Novice physician sonologists using POCUS are unable to predict fluid responsiveness using carotid ΔVpeak. Until further research identifies key limiting factors, clinicians should use caution directing IV fluid resuscitation using carotid ΔVpeak.

Carotid Doppler Measurement Variability in Functional Hemodynamic Monitoring: An Analysis of 17,822 Cardiac Cycles

Carotid Doppler ultrasound is used as a measure of fluid responsiveness, however, assessing change with statistical confidence requires an adequate beat sample size. The coefficient of variation helps quantify the number of cardiac cycles needed to adequately detect change during functional hemodynamic monitoring.

DESIGN

Prospective, observational, human model of hemorrhage and resuscitation.

SETTING

Human physiology laboratory at Mayo Clinic.

SUBJECTS

Healthy volunteers.

INTERVENTIONS

Lower body negative pressure.

MEASUREMENTS AND MAIN RESULTS

We measured the coefficient of variation of the carotid artery velocity time integral and corrected flow time during significant cardiac preload changes. Seventeen-thousand eight-hundred twenty-two cardiac cycles were analyzed. The median coefficient of variation of the carotid velocity time integral was 8.7% at baseline and 11.9% during lowest-tolerated lower body negative pressure stage. These values were 3.6% and 4.6%, respectively, for the corrected flow time.

CONCLUSIONS

The median coefficient of variation values measured in this large dataset indicates that at least 6 cardiac cycles should be averaged before and after an intervention when using the carotid artery as a functional hemodynamic measure.

Predictors of fluid responsiveness in critically ill patients mechanically ventilated at low tidal volumes: systematic review and meta-analysis

Introduction

Dynamic predictors of fluid responsiveness have shown good performance in mechanically ventilated patients at tidal volumes (Vt) > 8 mL kg⁻¹. Nevertheless, most critically ill conditions demand lower Vt. We sought to evaluate the operative performance of several predictors of fluid responsiveness at Vt ≤ 8 mL kg⁻¹ by using meta-regression and subgroup analyses.

Methods

A sensitive search was conducted in the Embase and MEDLINE databases. We searched for studies prospectively assessing the operative performance of pulse pressure variation (PPV), stroke volume variation (SVV), end-expiratory occlusion test (EEOT), passive leg raising (PLR), inferior vena cava respiratory variability (Δ-IVC), mini-fluid challenge (m-FC), and tidal volume challenge (VtC), to predict fluid responsiveness in adult patients mechanically ventilated at Vt ≤ 8 ml kg⁻¹, without respiratory effort and arrhythmias, published between 1999 and 2020. Operative performance was assessed using hierarchical and bivariate analyses, while subgroup analysis was used to evaluate variations in their operative performance and sources of heterogeneity. A sensitivity analysis based on the methodological quality of the studies included (QUADAS-2) was also performed.

Results

A total of 33 studies involving 1,352 patients were included for analysis. Areas under the curve (AUC) values for predictors of fluid responsiveness were: for PPV = 0.82, Δ-IVC = 0.86, SVV = 0.90, m-FC = 0.84, PLR = 0.84, EEOT = 0.92, and VtC = 0.92. According to subgroup analyses, variations in methods to measure cardiac output and in turn, to classify patients as responders or non-responders significantly influence the performance of PPV and SVV (p < 0.05). Operative performance of PPV was also significantly affected by the compliance of the respiratory system (p = 0.05), while type of patient (p < 0.01) and thresholds used to determine responsiveness significantly affected the predictability of SVV (p = 0.05). Similarly, volume of fluids infused to determine variation in cardiac output, significantly affected the performance of SVV (p = 0.01) and PLR (p < 0.01). Sensitivity analysis showed no variations in operative performance of PPV (p = 0.39), SVV (p = 0.23) and EEOT (p = 0.15).

Conclusion

Most predictors of fluid responsiveness reliably predict the response of cardiac output to volume expansion in adult patients mechanically ventilated at tidal volumes ≤ 8 ml kg⁻¹. Nevertheless, technical and clinical variables might clearly influence on their operative performance

Predictors of fluid responsiveness in critically ill patients mechanically ventilated at low tidal volumes: systematic review and meta-analysis

Introduction

Dynamic predictors of fluid responsiveness have shown good performance in mechanically ventilated patients at tidal volumes (Vt) > 8 mL kg−1. Nevertheless, most critically ill conditions demand lower Vt. We sought to evaluate the operative performance of several predictors of fluid responsiveness at Vt ≤ 8 mL kg−1 by using meta-regression and subgroup analyses.

Methods

A sensitive search was conducted in the Embase and MEDLINE databases. We searched for studies prospectively assessing the operative performance of pulse pressure variation (PPV), stroke volume variation (SVV), end-expiratory occlusion test (EEOT), passive leg raising (PLR), inferior vena cava respiratory variability (Δ-IVC), mini-fluid challenge (m-FC), and tidal volume challenge (VtC), to predict fluid responsiveness in adult patients mechanically ventilated at Vt ≤ 8 ml kg−1, without respiratory effort and arrhythmias, published between 1999 and 2020. Operative performance was assessed using hierarchical and bivariate analyses, while subgroup analysis was used to evaluate variations in their operative performance and sources of heterogeneity. A sensitivity analysis based on the methodological quality of the studies included (QUADAS-2) was also performed.

Results

A total of 33 studies involving 1,352 patients were included for analysis. Areas under the curve (AUC) values for predictors of fluid responsiveness were: for PPV = 0.82, Δ-IVC = 0.86, SVV = 0.90, m-FC = 0.84, PLR = 0.84, EEOT = 0.92, and VtC = 0.92. According to subgroup analyses, variations in methods to measure cardiac output and in turn, to classify patients as responders or non-responders significantly influence the performance of PPV and SVV (p < 0.05). Operative performance of PPV was also significantly affected by the compliance of the respiratory system (p = 0.05), while type of patient (p < 0.01) and thresholds used to determine responsiveness significantly affected the predictability of SVV (p = 0.05). Similarly, volume of fluids infused to determine variation in cardiac output, significantly affected the performance of SVV (p = 0.01) and PLR (p < 0.01). Sensitivity analysis showed no variations in operative performance of PPV (p = 0.39), SVV (p = 0.23) and EEOT (p = 0.15).

Conclusion

Most predictors of fluid responsiveness reliably predict the response of cardiac output to volume expansion in adult patients mechanically ventilated at tidal volumes ≤ 8 ml kg−1. Nevertheless, technical and clinical variables might clearly influence on their operative performance

Functional Hemodynamic Monitoring With a Wireless Ultrasound Patch

In this Emerging Technology Review, a novel, wireless, wearable Doppler ultrasound patch is described as a tool for resuscitation. The device is designed, foremost, as a functional hemodynamic monitor-a simple, fast, and consistent method for measuring hemodynamic change with preload variation. More generally, functional hemodynamic monitoring is a paradigm that helps predict stroke volume response to additional intravenous volume. Because Doppler ultrasound of the left ventricular outflow tract noninvasively measures stroke volume in realtime, it increasingly is deployed for this purpose. Nevertheless, Doppler ultrasound in this manner is cumbersome, especially when repeat assessments are needed. Accordingly, peripheral arteries have been studied and various measures from the common carotid artery Doppler signal act as windows to the left ventricle. Yet, handheld Doppler ultrasound of a peripheral artery is susceptible to human measurement error and statistical limitations from inadequate beat sample size. Therefore, a wearable Doppler ultrasound capable of continuous assessment minimizes measurement inconsistencies and smooths inherent physiologic variation by sampling many more cardiac cycles. Reaffirming clinical studies, the ultrasound patch tracks immediate SV change with excellent accuracy in healthy volunteers when cardiac preload is altered by various maneuvers. The wearable ultrasound also follows jugular venous Doppler, which qualitatively trends right atrial pressure. With further clinical research and the application of artificial intelligence, the monitoring modalities with this new technology are manifold.

Efficacy of Left Ventricular Outflow Tract and Carotid Artery Velocity Time Integral as Predictors of Fluid Responsiveness in Patients with Sepsis and Septic Shock

Background: Transthoracic echocardiography is a reliable method to measure a dynamic change in left ventricular outflow tract velocity time integral (LVOTVTI) and stroke volume (SV) in response to passive leg raising (PLR) and can predict fluid responsiveness in critically ill patients. Measuring carotid artery velocity time integral (CAVTI) is easier, does not depend on adequate cardiac window, and requires less skill and expertise than LVOTVTI. The aim of this study is to identify the efficacy of ΔCAVTI and ΔLVOTVTI pre- and post-PLR in predicting fluid responsiveness in critically ill patients with sepsis and septic shock. Methods: After the institutional ethics committee's clearance and informed written consent, 60 critically ill mechanically ventilated patients aged 18-65 years were recruited in this prospective parallel-group study with 20 patients in each group: sepsis (group S), septic shock (group SS), and control (group C). Demographic parameters and baseline acute physiology, age and chronic health evaluation-II and sequential organ failure assessment scores were noted. LVOTVTI, SV, and CAVTI were measured before and after PLR along with other hemodynamic variables. Patients having a change in SV more than 15% following PLR were defined as "responders." Results: Twenty-three patients (38.33%) were responders. Area under receiver-operating characteristic curve for ΔCAVTI could predict responders in control and sepsis patients only. The correlation coefficients between pre- and post-PLR ΔCAVTI and ΔLVOTVTI were 0.530 (p = 0.016), 0.440 (p = 0.052), and 0.044 (p = 0.853) in control, sepsis, and septic shock patients, respectively. Conclusion: Following PLR, ΔCAVTI does not predict fluid responsiveness in septic shock patients and the correlation between ΔCAVTI and ΔLVOTVTI is weak in septic shock patients and only modest in sepsis patients. How to cite this article: Chowhan G, Kundu R, Maitra S, Arora MK, Batra RK, Subramaniam R, et al. Efficacy of Left Ventricular Outflow Tract and Carotid Artery Velocity Time Integral as Predictors of Fluid Responsiveness in Patients with Sepsis and Septic Shock. Indian J Crit Care Med 2021;25(3):310-316. CTRI/Trial Reg No: www.ctri.nic.in, CTRI/2017/11/010434.

Carotid Ultrasound to Predict Fluid Responsiveness: A Systematic Review

OBJECTIVES

To perform a systematic review of the accuracy of carotid ultrasound measures in determining volume responsiveness in adults.

METHODS

We conducted a systematic review of Ovid MEDLINE and Scopus from conception until January 1, 2019. Two independent reviewers used an iterative process to identify relevant articles and abstract information from them. The quality and risk of bias were assessed with the Quality Assessment of Diagnostic Accuracy Studies version 2 tool.

RESULTS

We identified 17 relevant articles with 956 patients. The 2 most frequently cited carotid measures of fluid responsiveness were corrected flow time and peak velocity or change in peak velocity with respiration (ΔCDPV). Accordingly, the diagnostic characteristics of corrected flow time in these studies varied widely, with sensitivities from 60% to 73%, specificities from 82% to 92%, and areas under the receiver operating characteristic curves from 0.75 to 0.88. Optimal cutoff values for ΔCDPV ranged from 9.1% to 14%, with areas under the receiver operating characteristic curves from 0.81 to 0.91, sensitivities from 73% to 86%, and specificities from 78% to 86%. Other measures, such as carotid blood flow and carotid diameter, had limited data to support their use. Heterogeneity of the studies prohibited a meta-analysis. Most studies had a moderate risk of bias and high applicability.

CONCLUSIONS

Preliminary research suggests that carotid ultrasound measures may be useful adjunct measures of fluid status; however, they should not be interpreted as absolute and should be placed in a clinical context. The most well-defined and supported measure currently is ΔCDPV, with cutoffs from 9% to 14%. Corrected flow time shows promise, because of heterogeneity of how this value is measured, an optimal cutoff has not been established.

A Carotid Doppler Patch Accurately Tracks Stroke Volume Changes During a Preload-Modifying Maneuver in Healthy Volunteers

Objectives:

Detecting instantaneous stroke volume change in response to altered cardiac preload is the physiologic foundation for determining preload responsiveness.

Design:

Proof-of-concept physiology study.

Setting:

Research simulation laboratory.

Subjects:

Twelve healthy volunteers.

Interventions:

A wireless continuous wave Doppler ultrasound patch was used to measure carotid velocity time integral and carotid corrected flow time during a squat maneuver. The Doppler patch measurements were compared with simultaneous stroke volume measurements obtained from a noninvasive cardiac output monitor.

Measurements and Main Results:

From stand to squat, stroke volume increased by 24% while carotid velocity time integral and carotid corrected flow time increased by 32% and 9%, respectively. From squat to stand, stroke volume decreased by 13%, while carotid velocity time integral and carotid corrected flow time decreased by 24% and 10%, respectively. Both changes in carotid velocity time integral and corrected flow time were closely correlated with changes in stroke volume (r² = 0.81 and 0.62, respectively). The four-quadrant plot found a 100% concordance rate between changes in stroke volume and both changes in carotid velocity time integral and changes in corrected flow time. A change in carotid velocity time integral greater than 15% predicted a change in stroke volume greater than 10% with a sensitivity of 95% and a specificity of 92%. A change in carotid corrected flow time greater than 4% predicted a change in stroke volume greater than 10% with a sensitivity of 90% and a specificity of 92%.

Conclusions:

In healthy volunteers, both carotid velocity time integral and carotid corrected flow time measured by a wireless Doppler patch were useful to track changes in stroke volume induced by a preload-modifying maneuver with high sensitivity and specificity.

Use of Pulse Pressure Variation as Predictor of Fluid Responsiveness in Patients Ventilated With Low Tidal Volume: A Systematic Review and Meta-Analysis

Introduction:

Pulse pressure variation (PPV) has been shown to be useful to predict fluid responsiveness in patients ventilated at tidal volume (Vt) >8 mL kg−1. Nevertheless, most conditions in critical care force to use lower Vt. Thus, we sought to evaluate the operative performance of PPV when a Vt ⩽8 mL kg−1 is used during mechanical ventilation support.

Methods:

We searched PubMed and Embase databases for articles evaluating the operative performance of PPV as a predictor of fluid responsiveness in critical care and perioperative adult patients ventilated with tidal volume ⩽8 mL kg−1 without respiratory effort and arrhythmias, between January 1990 and January 2019. We included cohort and cross-sectional studies. Two authors performed an Independently selection using predefined terms of search. The fitted data of sensitivity, specificity, and area under the curve (AUC) were assessed by bivariate and hierarchical analyses.

Results:

We retrieved 19 trials with a total of 777 patients and a total of 935 fluid challenges. The fitted sensitivity of PPV to predict fluid responsiveness during mechanical ventilation at Vt ⩽8 mL kg−1 was 0.65 (95% confidence interval [CI]: 0.57-0.73), the specificity was 0.79 (95% CI: 0.73-0.84), and the AUC was 0.75. The diagnostic odds ratio was 5.5 (95% CI: 3.08-10.01, P < .001) by the random-effects model.

Conclusions:

Pulse pressure variation shows a fair operative performance as a predictor of fluid responsiveness in critical care and perioperative patients ventilated with a tidal volume ⩽8 mL kg−1 without respiratory effort and arrhythmias.

Use of Pulse Pressure Variation as Predictor of Fluid Responsiveness in Patients Ventilated With Low Tidal Volume: A Systematic Review and Meta-Analysis

INTRODUCTION

Pulse pressure variation (PPV) has been shown to be useful to predict fluid responsiveness in patients ventilated at tidal volume (Vt) >8 mL kg-1. Nevertheless, most conditions in critical care force to use lower Vt. Thus, we sought to evaluate the operative performance of PPV when a Vt ⩽8 mL kg-1 is used during mechanical ventilation support.

METHODS

We searched PubMed and Embase databases for articles evaluating the operative performance of PPV as a predictor of fluid responsiveness in critical care and perioperative adult patients ventilated with tidal volume ⩽8 mL kg-1 without respiratory effort and arrhythmias, between January 1990 and January 2019. We included cohort and cross-sectional studies. Two authors performed an Independently selection using predefined terms of search. The fitted data of sensitivity, specificity, and area under the curve (AUC) were assessed by bivariate and hierarchical analyses.

RESULTS

We retrieved 19 trials with a total of 777 patients and a total of 935 fluid challenges. The fitted sensitivity of PPV to predict fluid responsiveness during mechanical ventilation at Vt ⩽8 mL kg-1 was 0.65 (95% confidence interval [CI]: 0.57-0.73), the specificity was 0.79 (95% CI: 0.73-0.84), and the AUC was 0.75. The diagnostic odds ratio was 5.5 (95% CI: 3.08-10.01, P < .001) by the random-effects model.

CONCLUSIONS

Pulse pressure variation shows a fair operative performance as a predictor of fluid responsiveness in critical care and perioperative patients ventilated with a tidal volume ⩽8 mL kg-1 without respiratory effort and arrhythmias.

Surrogate indices of aortic peak systolic velocity variation to monitor fluid responsiveness in pediatric non-cardiac surgery: a prospective observational study

Aortic peak systolic velocity variation (ΔV_peakAo) is a reliable dynamic indicator of preload in mechanically ventilated children. However, easily measurable alternative parameters like carotid peak systolic velocity variation (ΔV_peakCa) and suprasternal peak systolic velocity variation (ΔV_peakSs) are not well evaluated in children. The aim of the study was to find correlation between ΔV_peakCa and ΔV_peakSs to ΔV_peakAo, as potential surrogate markers of fluid responsiveness. 52 children, 1-12 years old, undergoing major non-cardiac surgeries under general endotracheal anaesthesia were recruited for this single-centre prospective observational study. ΔV_peakAo, ΔV_peakCa and ΔV_peakSs were measured by pulsed wave Doppler in appropriate windows, measuring maximum and minimum peak flow velocity over a single respiratory cycle. Calculated parameters were compared by a repeated measures study design. Correlation coefficients were 0.82 between ΔV_peakAo and ΔV_peakSs and 0.73 between ΔV_peakAo and ΔV_peakCa. Bland-Altman analysis showed minimal bias of 1.86 percentage points with limits of agreement of 11.21 to - 7.49 (ΔV_peakAo and ΔV_peakSs) and 3.93 percentage points with limits of agreement of 14.04 to - 6.18 (ΔV_peakAo and ΔV_peakCa). ΔV_peakSs and ΔV_peakCa also showed good discrimination to predict ΔV_peakAo (lying in previously validated fluid responsive zones) with sensitivities and specificities of 82.25% and 85% with cut-off of 11% for ΔV_peakSs, and 88.52% and 70% with cut-off of 8.6% for ΔV_peakCa. Carotid peak systolic velocity variation (ΔV_peakCa) and suprasternal peak systolic velocity variation (ΔV_peakCa) can be potential surrogate markers for Aortic peak systolic velocity variation (ΔV_peakAo) in assessing fluid responsiveness in mechanically ventilated children.Study registration: Clinicaltrials.gov ID NCT03155555.

Effect of insonation angle on peak systolic velocity variation

OBJECTIVES

As point of care ultrasound (POCUS) has become more integrated into emergency and critical care medicine, there has been increased interest in utilizing ultrasound to assess volume status. However, recent studies of carotid POCUS on volume status and fluid responsiveness fail to recognize the effect insonation angle has on their results. To address this, we studied the effect of insonation angle on peak systolic velocity (PSV) change associated with respiratory variation (RV) and passive leg raise (PLR).

METHODS

Doppler measurements were obtained from 51 subjects presenting to the ED. Minimal and maximal PSV were obtained using insonation angles of 46°, 60°, and 90°. ∆PSV was calculated using PLR and RV as trial methods. Results were categorized into two groups, those with a ∆PSV > 10% and those with a ∆PSV ≤ 10%. ∆PSV mean and standard error, as well as measures of agreement were calculated.

RESULTS

Mean ∆PSV associated with PLR test was 9% in the 46° and 60° groups, and 18% in the 90° group, with standard errors of 6, 7, and 14%, respectively. Using 46° as our relative gold standard, Kappa was 0.23 at 60° and 0.11 at 90° with RV as the trial method, and 0.23 at 60° and 0.01 at 90° with a PLR as the trial method.

CONCLUSIONS

Variation in PSV is heavily dependent on insonation angle. There was only slight to fair agreement in ∆PSV among the various insonation angles. Further investigation of the optimal insonation angle to assess ∆PSV should be undertaken.

Respiratory variation in peripheral arterial blood flow peak velocity to predict fluid responsiveness in mechanically ventilated patients: a systematic review and meta-analysis

BACKGROUND

Fluid overloading is detrimental to organ function and results in a poor prognosis. It is necessary to evaluate fluid responsiveness before fluid loading. We performed a systematic meta-analysis to evaluate the diagnostic value of the respiratory variation in peripheral arterial blood flow peak velocity (△Vpeak PA) in predicting fluid responsiveness in mechanically ventilated patients.

METHODS

PubMed, Embase and The Cochrane Library databases were searched for studies that used △Vpeak PA to predict fluid responsiveness in mechanically ventilated patients. We calculated the pooled values of sensitivity, specificity and the area of the summary receiver operating characteristic curve by Meta-Disc 14.0 software.

RESULTS

Nine studies with a total of 402 patients were included. Two low quality studies were deleted in further analysis. Moreover, because of different locations of peripheral artery, the rest included studies were divided into brachial site group and carotid site group for meta-analysis individually. The pooled sensitivity, specificity and area under curve were 0.85 (95% confidence interval (CI) 0.77-0.92), 0.86 (95% CI 0.77-0.92) and 0.9268 in carotid site group. The pooled sensitivity, specificity and area under curve were 0.72 (95% CI 0.60-0.81), 0.85 (95% CI 0.74-0.93) and 0.8587 in brachial site group.

CONCLUSIONS

△Vpeak of carotid and brachial artery had a diagnostic value in predicting fluid responsiveness respectively. Moreover, △Vpeak of carotid artery had more value than brachial artery in predicting fluid responsiveness. However, there was some clinical heterogeneity; therefore, further studies are needed to confirm diagnostic accuracy.

Timing, method and discontinuation of hydrocortisone administration for septic shock patients

AIM

To characterize the prescribing patterns for hydrocortisone for patients with septic shock and perform an exploratory analysis in order to identify the variables associated with better outcomes.

METHODS

This prospective cohort study included 59 patients with septic shock who received stress-dose hydrocortisone. It was performed at 2 critical care units in academic hospitals from June 1^st, 2015, to July 31^st, 2016. Demographic data, comorbidities, medical management details, adverse effects related to corticosteroids, and outcomes were collected after the critical care physician indicated initiation of hydrocortisone. Univariate comparison between continuous and bolus administration of hydrocortisone was performed, including multivariate analysis, as well as Kaplan-Meier analysis to compare the proportion of shock reversal at 7 d after presentation. Receiver operating characteristic (ROC) curves determined the best cut-off criteria for initiation of hydrocortisone associated with the highest probability of shock reversal. We addressed the effects of the taper strategy for discontinuation of hydrocortisone, noting risk of shock relapse and adverse effects.

RESULTS

All-cause 30-d mortality was 42%. Hydrocortisone was administered as a continuous infusion in 54.2% of patients; time to reversal of shock was 49 h longer in patients who were given a bolus administration [59 h (range, 47.5-90.5) vs 108 h (range, 63.2-189); P = 0.001]. The maximal dose of norepinephrine after initiation of hydrocortisone was lower in patients on continuous infusion [0.19 μg/kg per minute (range, 0.11-0.28 μg)] compared with patients who were given bolus [0.34 μg/kg per minute (range, 0.16-0.49); P = 0.004]. Kaplan-Meier analysis revealed a higher proportion of shock reversal at 7 d in patients with continuous infusion compared to those given bolus (83% vs 63%; P = 0.004). There was a good correlation between time to initiation of hydrocortisone and time to reversal of shock (r = 0.80; P < 0.0001); ROC curve analysis revealed that the best criteria for prediction of shock reversal was a time to initiation of hydrocortisone of ≤ 13 h after administration of norepinephrine, with an area under the curve of 0.81 (P < 0.001). The maximal dose of norepinephrine at initiation of hydrocortisone with the highest association with shock reversal was ≤ 0.28 μg/kg per minute, with an area under the curve of 0.75 (P = 0.0002). On a logistic regression model, hydrocortisone taper was not associated with a lower risk of shock relapse (RR = 1.29; P = 0.17) but was related to a higher probability of hyperglycemia [odds ratio (OR), 5.3; P = 0.04] and hypokalemia (OR = 10.6; P = 0.01).

CONCLUSION

Continuous infusion of hydrocortisone could hasten the resolution of septic shock compared to bolus administration. Earlier initiation corresponds with a higher probability of shock reversal. Tapering strategy is unnecessary.

Fluid responsiveness in acute circulatory failure

Although fluid resuscitation of patients having acute circulatory failure is essential, avoiding unnecessary administration of fluids in these patients is also important. Fluid responsiveness (FR) is defined as the ability of the left ventricle to increase its stroke volume (SV) in response to fluid administration. The objective of this review is to provide the recent advances in the detection of FR and simplify the physiological basis, advantages, disadvantages, and cut-off values for each method. This review also highlights the present gaps in literature and provides future thoughts in the field of FR.

Static methods are generally not recommended for the assessment of FR. Dynamic methods for the assessment of FR depend on heart-lung interactions. Pulse pressure variation (PPV) and stroke volume variation (SVV) are the most famous dynamic measures. Less-invasive dynamic parameters include plethysmographic-derived parameters, variation in blood flow in large arteries, and variation in the diameters of central veins. Dynamic methods for the assessment of FR have many limitations; the most important limitation is spontaneous breathing activity.

Fluid challenge techniques were able to overcome most of the limitations of the dynamic methods. Passive leg raising is the most popular fluid challenge method. More simple techniques have been recently introduced such as the mini-fluid challenge and 10-s fluid challenge. The main limitation of fluid challenge techniques is the need to trace the effect of the fluid challenges on SV (or any of its derivatives) using a real-time monitor. More research is needed in the field of FR taking into consideration not only the accuracy of the method but also the ease of implementation, the applicability on a wider range of patients, the time needed to apply each method, and the feasibility of its application by acute care physicians with moderate and low experience.

A rational approach to fluid therapy in sepsis

Aggressive fluid resuscitation to achieve a central venous pressure (CVP) greater than 8 mm Hg has been promoted as the standard of care, in the management of patients with severe sepsis and septic shock. However recent clinical trials have demonstrated that this approach does not improve the outcome of patients with severe sepsis and septic shock. Pathophysiologically, sepsis is characterized by vasoplegia with loss of arterial tone, venodilation with sequestration of blood in the unstressed blood compartment and changes in ventricular function with reduced compliance and reduced preload responsiveness. These data suggest that sepsis is primarily not a volume-depleted state and recent evidence demonstrates that most septic patients are poorly responsive to fluids. Furthermore, almost all of the administered fluid is sequestered in the tissues, resulting in severe oedema in vital organs and, thereby, increasing the risk of organ dysfunction. These data suggest that a physiologic, haemodynamically guided conservative approach to fluid therapy in patients with sepsis would be prudent and would likely reduce the morbidity and improve the outcome of this disease.