Evaluation of corrected flow time in oesophageal Doppler as a predictor of fluid responsiveness

The Reliability of Carotid Artery Doppler Ultrasonography Indices in Predicting Fluid Responsiveness during Surgery for Geriatric Patients: A Prospective, Observational Study

BACKGROUND

The reliability of determining fluid responsiveness during surgery in geriatric patients is challenging. Our primary outcome was to determine the reliability of Corrected Flow Time (FTc) in predicting fluid responsiveness.

METHODS

Elderly patients undergoing major surgery under general anesthesia were included. Measurements of common carotid artery diameter, velocity time integral, and systolic flow time (FT) were performed before and after a fluid challenge. FTc and carotid blood flow (CBF) were subsequently calculated.

RESULTS

The median change in carotid diameter was significantly higher in the fluid-responder (R) compared to the non-responder (NR) (6.51% vs. 0.65%, p = 0.049). The median change in CBF was notably higher in R compared to NR (30.04% vs. 9.72%, p = 0.024). Prior to the fluid challenge, systolic FT was significantly shorter in R than NR (285 ms vs. 315 ms, p = 0.027), but after the fluid challenge, these measurements became comparable among the groups. The change in systolic FT was higher in R (15.38% vs. 7.49%, p = 0.027). FTc and the change in FTc exhibited similarities among the groups at all study time points. Receiver operating characteristic analysis demonstrated an area under the curve of 0.682 (95% CI: 0.509-0.855, p = 0.039) for carotid diameter, 0.710 (95% CI: 0.547-0.872, p = 0.011) for CBF, 0.706 (95% CI: 0.540-0.872, p = 0.015) for systolic FT, and 0.580 (95% CI = 0.389-0.770, p = 0.413) for FTc.

CONCLUSIONS

In geriatric patients, potential endothelial changes in the carotid artery may influence the dynamic markers of fluid responsiveness. Despite the demonstrated effectiveness of FTc in predicting fluid responsiveness in the general population, this study underscores the limited reliability of carotid Doppler ultrasonography indices for prediction in a geriatric patient population.

Reliability of pulse pressure and stroke volume variation in assessing fluid responsiveness in the operating room: a metanalysis and a metaregression

BACKGROUND

Pulse pressure and stroke volume variation (PPV and SVV) have been widely used in surgical patients as predictors of fluid challenge (FC) response. Several factors may affect the reliability of these indices in predicting fluid responsiveness, such as the position of the patient, the use of laparoscopy and the opening of the abdomen or the chest, combined FC characteristics, the tidal volume (Vt) and the type of anesthesia.

METHODS

Systematic review and metanalysis of PPV and SVV use in surgical adult patients. The QUADAS-2 scale was used to assess the risk of bias of included studies. We adopted a metanalysis pooling of aggregate data from 5 subgroups of studies with random effects models using the common-effect inverse variance model. The area under the curve (AUC) of pooled receiving operating characteristics (ROC) curves was reported. A metaregression was performed using FC type, volume, and rate as independent variables.

RESULTS

We selected 59 studies enrolling 2,947 patients, with a median of fluid responders of 55% (46-63). The pooled AUC for the PPV was 0.77 (0.73-0.80), with a mean threshold of 10.8 (10.6-11.0). The pooled AUC for the SVV was 0.76 (0.72-0.80), with a mean threshold of 12.1 (11.6-12.7); 19 studies (32.2%) reported the grey zone of PPV or SVV, with a median of 56% (40-62) and 57% (46-83) of patients included, respectively. In the different subgroups, the AUC and the best thresholds ranged from 0.69 and 0.81 and from 6.9 to 11.5% for the PPV, and from 0.73 to 0.79 and 9.9 to 10.8% for the SVV. A high Vt and the choice of colloids positively impacted on PPV performance, especially among patients with closed chest and abdomen, or in prone position.

CONCLUSION

The overall performance of PPV and SVV in operating room in predicting fluid responsiveness is moderate, ranging close to an AUC of 0.80 only some subgroups of surgical patients. The grey zone of these dynamic indices is wide and should be carefully considered during the assessment of fluid responsiveness. A high Vt and the choice of colloids for the FC are factors potentially influencing PPV reliability.

TRIAL REGISTRATION

PROSPERO (CRD42022379120), December 2022. https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=379120.

Evaluating corrected carotid flow time as a non-invasive parameter for trending cardiac output and stroke volume in cardiac surgery patients

PURPOSE

The corrected carotid flow time (ccFT) is derived from a pulsed-wave Doppler signal at the common carotid artery. Several equations are currently used to calculate ccFT. Its ability to assess the intravascular volume status non-invasively has recently been investigated. The purpose of this study was to evaluate the correlation and trending ability of ccFT with invasive cardiac output (CO) and stroke volume (SV) measurements.

METHODS

Eighteen cardiac surgery patients were included in this prospective observational study. ccFT measurements were obtained at three time points: after induction of anesthesia (T1), after a passive leg raise (T2), and post-bypass (T3). Simultaneously, CO and SV were measured by calibrated pulse contour analysis. Three different equations (Bazett, Chambers, and Wodey) were used to calculate ccFT. The correlation and percentage change in time (concordance) between ccFT and CO and between ccFT and SV were evaluated.

RESULTS

Mean ccFT values differed significantly for the three equations (p < 0.001). The correlation between ccFT and CO and between ccFT and SV was highest for Bazett's (ρ = 0.43, p < 0.0001) and Wodey's (ρ = 0.33, p < 0.0001) equations, respectively. Concordance between ΔccFT and ΔCO and between ΔccFT and ΔSV was highest for Bazett's (100%) and Wodey's (82%) equations, respectively. Subgroup analysis demonstrated that correlation and concordance between SV and ccFT improved when assessed within limited heart rate (HR) ranges.

CONCLUSION

The use of different ccFT equations leads to variable correlation and concordance rates between ccFT and CO/SV measurements. Bazett's equation acceptably tracked CO changes in time, while the trending capability of SV was poor.

Non-invasive assessment of Pulse Wave Transit Time (PWTT) is a poor predictor for intraoperative fluid responsiveness: a prospective observational trial (best-PWTT study)

BACKGROUND

Aim of this study is to test the predictive value of Pulse Wave Transit Time (PWTT) for fluid responsiveness in comparison to the established fluid responsiveness parameters pulse pressure (ΔPP) and corrected flow time (FTc) during major abdominal surgery.

METHODS

Forty patients undergoing major abdominal surgery were enrolled with continuous monitoring of PWTT (LifeScope® Modell J BSM-9101 Nihon Kohden Europe GmbH, Rosbach, Germany) and stroke volume (Esophageal Doppler Monitoring CardioQ-ODM®, Deltex Medical Ltd, Chichester, UK). In case of hypovolemia (difference in pulse pressure [∆PP] ≥ 9%, corrected flow time [FTc] ≤ 350 ms) a fluid bolus of 7 ml/kg ideal body weight was administered. Receiver operating characteristics (ROC) curves and corresponding areas under the curve (AUCs) were used to compare different methods of determining PWTT. A Wilcoxon test was used to discriminate fluid responders (increase in stroke volume of ≥ 10%) from non-responders. The predictive value of PWTT for fluid responsiveness was compared by testing for differences between ROC curves of PWTT, ΔPP and FTc using the methods by DeLong.

RESULTS

AUCs (area under the ROC-curve) to predict fluid responsiveness for PWTT-parameters were 0.61 (raw c finger Q), 0.61 (raw c finger R), 0.57 (raw c ear Q), 0.53 (raw c ear R), 0.54 (raw non-c finger Q), 0.52 (raw non-c finger R), 0.50 (raw non-c ear Q), 0.55 (raw non-c ear R), 0.63 (∆ c finger Q), 0.61 (∆ c finger R), 0.64 (∆ c ear Q), 0.66 (∆ c ear R), 0.59 (∆ non-c finger Q), 0.57 (∆ non-c finger R), 0.57 (∆ non-c ear Q), 0.61 (∆ non-c ear R) [raw measurements vs. ∆ = respiratory variation; c = corrected measurements according to Bazett's formula vs. non-c = uncorrected measurements; Q vs. R = start of PWTT-measurements with Q- or R-wave in ECG; finger vs. ear = pulse oximetry probe location]. Hence, the highest AUC to predict fluid responsiveness by PWTT was achieved by calculating its respiratory variation (∆PWTT), with a pulse oximeter attached to the earlobe, using the R-wave in ECG, and correction by Bazett's formula (AUC best-PWTT 0.66, 95% CI 0.54-0.79). ∆PWTT was sufficient to discriminate fluid responders from non-responders (p = 0.029). No difference in predicting fluid responsiveness was found between best-PWTT and ∆PP (AUC 0.65, 95% CI 0.51-0.79; p = 0.88), or best-PWTT and FTc (AUC 0.62, 95% CI 0.49-0.75; p = 0.68).

CONCLUSION

ΔPWTT shows poor ability to predict fluid responsiveness intraoperatively. Moreover, established alternatives ΔPP and FTc did not perform better.

TRIAL REGISTRATION

Prior to enrolement on clinicaltrials.gov (NC T03280953; date of registration 13/09/2017).

Corrected flow time and respirophasic variation in blood flow peak velocity of radial artery predict fluid responsiveness in gynecological surgical patients with mechanical ventilation

BACKGROUND

Recent evidence suggests that ultrasound measurements of carotid and brachial artery corrected flow time (FTc) and respirophasic variation in blood flow peak velocity (ΔVpeak) are valuable for predicting fluid responsiveness in mechanical ventilated patients. We performed the study to reveal the performance of ultrasonic measurements of radial artery FTc and ΔVpeak for predicting fluid responsiveness in mechanical ventilated patients undergoing gynecological surgery.

METHODS

A total of eighty mechanical ventilated patients were enrolled. Radial artery FTc and ΔVpeak, and non-invasive pulse pressure variation (PPV) were measured before and after fluid challenge. Fluid responsiveness was defined as an increase in stroke volume index (SVI) of 15% or more after the fluid challenge. Multivariate logistic regression analyses and receiver operating characteristic (ROC) curve were used to screen multivariate predictors of fluid responsiveness and identify the predictive abilitie of non-invasive PPV, ΔVpeak and FTc on fluid responsiveness.

RESULTS

Forty-four (55%) patients were fluid responders. Multivariate logistic regression analysis showed that radial artery FTc, ΔVpeak, and non-invasive PPV were the independent predictors of fluid responsiveness, with odds ratios of 1.152 [95% confidence interval (CI) 1.045 to 1.270], 0.581 (95% CI 0.403 to 0.839), and 0.361 (95% CI, 0.193 to 0.676), respectively. The area under the ROC curve of fluid responsiveness predicted by FTC was 0.802 (95% CI, 0.706-0.898), and ΔVpeak was 0.812 (95% CI, 0.091-0.286), which were comparable with non-invasive PPV (0.846, 95%CI, 0.070-0.238). The optimal cut-off values of FTc for fluid responsiveness was 336.6 ms (sensitivity of 75.3%; specificity of 75.9%), ΔVpeak was 14.2% (sensitivity of 88.2%; specificity of 67.9%). The grey zone for FTc was 313.5-336.6 ms and included 40 (50%) of the patients, ΔVpeak was 12.2-16.5% and included 37(46%) of the patients.

CONCLUSIONS

Ultrasound measurement of radial artery FTc and ΔVpeak are the feasible and reliable methods for predicting fluid responsiveness in mechanically ventilated patients.

TRIAL REGISTRATION

The trial was registered at the Chinese Clinical Trial Registry (ChiCTR)(www.chictr.org), registration number ChiCTR2000040941.

Changes in corrected carotid flow time induced by recruitment maneuver predict fluid responsiveness in patients undergoing general anesthesia

Non-invasive methods to assess patients' fluid responsiveness during lung-protective ventilation are needed. We hypothesized changes in the corrected carotid flow time induced by the recruitment maneuver predict fluid responsiveness under general anesthesia. Thirty patients undergoing general anesthesia in the supine position were prospectively enrolled. The study protocol was conducted when the patient was hemodynamically stable during surgery. Flow time was measured on Doppler images of the common carotid artery. Carotid flow time, heart rate, stroke volume, stroke volume variation, and pulse pressure variation were recorded before and after a recruitment maneuver at a continuous airway pressure of 30 cmH₂O for 30 s, and before and after volume expansion with 250 mL for 10 min. Patients were defined as fluid responders if the increase in stroke volume was > 10% after volume expansion. Twenty patients (67%) were fluid responders. All Doppler images for carotid flow time were obtained within 30 s. Changes in the corrected flow time accurately predicted fluid responsiveness (area under the curve: 0.82, 95% confidence interval [CI] 0.64-0.94, p = 0.002). The optimal threshold for changes in the corrected flow time was - 11.7% with a sensitivity of 95.0% (95% CI 75.1-99.9%) and a specificity of 80.0% (95% CI 44.4-97.5%). The gray-zone of changes in the corrected flow time was from - 25.1 to - 12.2% and included 12 patients (40%). Changes in the corrected carotid flow time were a useful, technically easy-to-perform, and non-invasive method to predict fluid responsiveness without a need for hemodynamic monitoring or arterial cannulation.

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.

Ultrasound Assessment of the Change in Carotid Corrected Flow Time in Fluid Responsiveness in Undifferentiated Shock

OBJECTIVES

Adequate assessment of fluid responsiveness in shock necessitates correct interpretation of hemodynamic changes induced by preload challenge. This study evaluates the accuracy of point-of-care Doppler ultrasound assessment of the change in carotid corrected flow time induced by a passive leg raise maneuver as a predictor of fluid responsiveness. Noninvasive cardiac output monitoring (NICOM, Cheetah Medical, Newton Center, MA) system based on a bioreactance method was used.

DESIGN

Prospective, noninterventional study.

SETTING

ICU at a large academic center.

PATIENTS

Patients with new, undifferentiated shock, and vasopressor requirements despite fluid resuscitation were included. Patients with significant cardiac disease and conditions that precluded adequate passive leg raising were excluded.

INTERVENTIONS

Carotid corrected flow time was measured via ultrasound before and after a passive leg raise maneuver. Predicted fluid responsiveness was defined as greater than 10% increase in stroke volume on noninvasive cardiac output monitoring following passive leg raise. Images and measurements were reanalyzed by a second, blinded physician. The accuracy of change in carotid corrected flow time to predict fluid responsiveness was evaluated using receiver operating characteristic analysis.

MEASUREMENTS AND MAIN RESULTS

Seventy-seven subjects were enrolled with 54 (70.1%) classified as fluid responders by noninvasive cardiac output monitoring. The average change in carotid corrected flow time after passive leg raise for fluid responders was 14.1 ± 18.7 ms versus -4.0 ± 8 ms for nonresponders (p < 0.001). Receiver operating characteristic analysis demonstrated that change in carotid corrected flow time is an accurate predictor of fluid responsiveness status (area under the curve, 0.88; 95% CI, 0.80-0.96) and a 7 ms increase in carotid corrected flow time post passive leg raise was shown to have a 97% positive predictive value and 82% accuracy in detecting fluid responsiveness using noninvasive cardiac output monitoring as a reference standard. Mechanical ventilation, respiratory rate, and high positive end-expiratory pressure had no significant impact on test performance. Post hoc blinded evaluation of bedside acquired measurements demonstrated agreement between evaluators.

CONCLUSIONS

Change in carotid corrected flow time can predict fluid responsiveness status after a passive leg raise maneuver. Using point-of-care ultrasound to assess change in carotid corrected flow time is an acceptable and reproducible method for noninvasive identification of fluid responsiveness in critically ill patients with undifferentiated shock.

A Robust Automatic Ultrasound Spectral Envelope Estimation

Accurate estimation of ultrasound Doppler spectrogram envelope is essential for clinical pathological diagnosis of various cardiovascular diseases. However, due to intrinsic spectral broadening in the power spectrum and speckle noise existing in ultrasound images, it is difficult to obtain the accurate maximum velocity. Each of the standard existing methods has their own limitations and does not work well in complicated recordings. This paper proposes a robust automatic spectral envelope estimation method that is more accurate in phantom recordings and various in-vivo recordings than the currently used methods. Comparisons were performed on phantom recordings of the carotid artery with varying noise and additional in-vivo recordings. The accuracy of the proposed method was on average 8% greater than the existing methods. The experimental results demonstrate the wide applicability under different blood conditions and the robustness of the proposed algorithm.

Utility of central venous pressure measurement in renal transplantation: Is it evidence based?

Adequate intravenous fluid therapy is essential in renal transplant recipients to ensure a good allograft perfusion. Central venous pressure (CVP) has been considered the cornerstone to guide the fluid therapy for decades; it was the only available simple tool worldwide. However, the revolutionary advances in assessing the dynamic preload variables together with the availability of new equipment to precisely measure the effect of intravenous fluids on the cardiac output had created a question mark on the future role of CVP. Despite the critical role of fluid therapy in the field of transplantation. There are only a few clinical studies that compared the CVP guided fluid therapy with the other modern techniques and their relation to the outcome in renal transplantation. Our work sheds some light on the available published data in renal transplantation, together with data from other disciplines evaluating the utility of central venous pressure measurement. Although lager well-designed studies are still required to consolidate the role of new techniques in the field of renal transplantation, we can confidently declare that the new techniques have the advantages of providing more accurate haemodynamic assessment, which results in a better patient outcome.

The plethysmographic variability index does not predict fluid responsiveness estimated by esophageal Doppler during kidney transplantation: A controlled study

Research is ongoing to find a noninvasive method of monitoring, which can predict fluid responsiveness in patients undergoing kidney transplantation.To compare the responses to fluid challenges with the Pleth Variability Index, a noninvasive dynamic index derived from plethysmographic variability (Radical 7 pulse oximeter; Masimo Corporation, Irvine, CA), and the esophageal Doppler, the criterion standard.Observational study.University hospital; study from May 2011 and May 2012.Forty-eight patients with end-renal function were included and 44 analyzed. Patients with cardiac failure were not eligible.Fluid challenges were administered during maintenance of general anesthesia but before skin incision and repeated if the patient was deemed to be a "responder" (increase in stroke volume ≥10%).The primary endpoint was to assess if the Pleth Variability Index is an accurate predictor of fluid responsiveness.Among 76 fluid challenges, 38 were considered as positive (increase in stroke volume measured by Doppler ≥10%). Pleth Variability Index was similar at baseline between responders and nonresponder patients. Fluid challenges were associated with a significant decrease in Pleth Variability Index in overall cases (12 [8-14] vs 10 [6-17], P = .050), but it was not able to discriminate between responders (12 [8-15] vs 10 [5-15], P = .650) and nonresponders (11 [6-16] vs 8 [5-14], P = .047). The area under the Receiver Operating Characteristic curve for Pleth Variability Index was 0.49 (0.36-0.62).Pleth Variability Index is not an accurate predictor of fluid responsiveness during kidney transplantation.

Preload dependency determines the effects of phenylephrine on cardiac output in anaesthetised patients: A prospective observational study

BACKGROUND

Although phenylephrine is widely used in the operating room to control arterial pressure, its haemodynamic effects remain controversial.

OBJECTIVE

We hypothesised that the effect of phenylephrine on cardiac output is affected by preload dependency.

DESIGN

A prospective observational study.

SETTING

Single-centre, University Hospital of Caen, France.

PATIENTS

Fifty ventilated patients undergoing surgery were studied during hypotension before and after administration of phenylephrine.

MAIN OUTCOME MEASURES

Cardiac index (CI), stroke volume (SV), corrected flow time, mean arterial pressure, pulse pressure variations (PPV) and systemic vascular resistance index were used to assess effects of changes in preload dependency.

RESULTS

Twenty seven (54%) patients were included in the preload-dependent group (PPV ≥ 13%) and 23 (46%) in the preload-independent group (PPV < 13%) before administration of phenylephrine. For the whole cohort, phenylephrine increased mean arterial pressure [58 (±8) mmHg vs. 79 (±13) mmHg; P < 0.0001] and calculated systemic vascular resistance index [2010 (1338; 2481) dyn s cm m vs. 2989 (2155; 3870) dyn s cm m; P < 0.0001]. However, CI and SV decreased in the preload-independent group [2.3 (1.9; 3.7) l min m vs. 1.8 (1.5; 2.7) l min m; P < 0.0001 and 65 (44; 81) ml vs. 56 (39; 66) ml; P < 0.0001 for both] but not in the preload-dependent group [respectively 2.1 (1.8; 3.5) l min m vs. 2.1 (1.8; 3.3) l min m; P = 0.168 and 49 (41; 67) ml vs. 53 (41; 69) ml; P = 0.191]. Corrected flow time increased [294 (47) ms vs. 306 (56) ms; P = 0.031], and PPV decreased [17 (15; 19) % vs.12 (14; 16) %; P < 0.0003] only in the PPV at least 13% group.

CONCLUSION

The effects of phenylephrine on CI and SV depend on preload. CI and SV decreased in preload-independent patients through increase in afterload, but were unchanged in those preload-dependent through increased venous return.

Comparison of Hemodynamic Monitoring between Transesophageal Doppler and Ultrasonography-Guided Inferior Vena Cava Distensibility in Supine versus Prone Position: A Pilot Study

Introduction

Lung-protective ventilation strategy and prone positioning are the strategies practiced to manage patients suffering from acute respiratory distress syndrome (ARDS). Inferior Vena Cava Distensibility (dIVC) Index has been used for predicting fluid responsiveness (FR) in supine position. We conducted this study to observe the utility of dIVC in prone position in ARDS patients and compare it with esophageal Doppler (ED) parameters.

Materials and Methods

After ethical clearance, a prospective observational pilot study was conducted in a 12-bedded tertiary care hospital. Adult ARDS patients who were treated with prone ventilation were included. Informed consent was taken from the relatives. IVC was visualized through right lateral approach both in supine and prone positions. We compared IVC distensibility and ED parameters, first in 45° head up and then in prone. FR was defined as an increase in the stroke volume of ≥15% as measured by ED. The patients with dIVC >18% were assumed to be fluid responsive. Statistical analysis was done using SPSS software version 20.

Results

Twenty-five patients met the inclusion criteria. ARDS was (mean P/F ratio 116.64 ± 44.76) mostly due to pulmonary etiology. Out of 25 patients, 10 patients were fluid responsive based on dIVC (cutoff >18%) in supine position. When compared to ED values after passive leg raising, dIVC had a sensitivity and specificity of 77.78% and 81.25%, respectively, in predicting FR with a moderate-to-absolute agreement between the two methods. IVC distensibility showed statistically significant negative correlation with corrected flow time (FTc) values both in supine and in prone positions.

Conclusion

IVC variability can be observed in acute respiratory distress syndrome patients in prone position. Inferior Vena Cava Distensibility correlates with flow time in both the positions.

Time to correct the flow of corrected flow time

Recently published study of Ma et al. evaluates two relatively novel measures of fluid responsiveness, carotid blood flow and corrected carotid flow time (ccFT). Both measures have been recently quoted as possibly useful, technically simple, and noninvasive dynamic tools in predicting fluid responsiveness. Recently, more research interest has been focused on ccFT and, intrigued by the data presented in this study, we discuss here the impact of the data presented in the paper of Ma et al. to the significance of this metric as a potential tool in the assessment of fluid responsiveness.

What is the impact of the fluid challenge technique on diagnosis of fluid responsiveness? A systematic review and meta-analysis

Background

The fluid challenge is considered the gold standard for diagnosis of fluid responsiveness. The objective of this study was to describe the fluid challenge techniques reported in fluid responsiveness studies and to assess the difference in the proportion of ‘responders,’ (PR) depending on the type of fluid, volume, duration of infusion and timing of assessment.

Methods

Searches of MEDLINE and Embase were performed for studies using the fluid challenge as a test of cardiac preload with a description of the technique, a reported definition of fluid responsiveness and PR. The primary outcome was the mean PR, depending on volume of fluid, type of fluids, rate of infusion and time of assessment.

Results

A total of 85 studies (3601 patients) were included in the analysis. The PR were 54.4% (95% CI 46.9–62.7) where <500 ml was administered, 57.2% (95% CI 52.9–61.0) where 500 ml was administered and 60.5% (95% CI 35.9–79.2) where >500 ml was administered (p = 0.71). The PR was not affected by type of fluid. The PR was similar among patients administered a fluid challenge for <15 minutes (59.2%, 95% CI 54.2–64.1) and for 15–30 minutes (57.7%, 95% CI 52.4–62.4, p = 1). Where the infusion time was ≥30 minutes, there was a lower PR of 49.9% (95% CI 45.6–54, p = 0.04). Response was assessed at the end of fluid challenge, between 1 and 10 minutes, and >10 minutes after the fluid challenge. The proportions of responders were 53.9%, 57.7% and 52.3%, respectively (p = 0.47).

Conclusions

The PR decreases with a long infusion time. A standard technique for fluid challenge is desirable.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1796-9) contains supplementary material, which is available to authorized users.

A new modality for the estimation of corrected flow time via electrocardiography as an alternative to Doppler ultrasonography

BACKGROUND

Evaluation of corrected flow time (FTc) via ultrasonography is one of the suggested modalities for the assessment of intravascular volume status. This study aimed to compare the results of FTc of carotid artery measured via ultrasonography, as a measure of mechanical outcome of the cardiac cycle, with the results of FTc estimation from a new modified formula via electrocardiography (ECG), as a measure of electrical function of the cardiac cycle.

METHODS

Healthy volunteers were evaluated before and after a passive leg raising (PLR) maneuver. FTc was measured concurrently before and after PLR via a modified method from ECG and via ultrasonography of the carotid artery.

RESULTS

A total number of 98 healthy volunteers (51 women and 47 men) with a mean age of 30.69 ± 6.28 years were included. There was a significant correlation between FTc measured by ultrasonography and estimated by ECG both before PLR and after PLR (r = .878, p < .0001 and r = .797, p < .0001, respectively). Changes in FTc were slightly higher in measurements by ultrasonography compared to estimations by ECG (22.33 ± 17.15 ms^0.5 vs. 15.86 ± 14.25 ms^0.5 , p = .001).

CONCLUSION

Estimation of FTc via ECG is potentially an effective and feasible method for the assessment of volume status at the clinical settings. Further investigations should determine the significance of differences that may be observed between ultrasonography and ECG in patients with either dehydration or volume overload and in the need of real-time volume status assessment.

Effects of postural change on transesophageal echocardiography views and parameters in healthy dogs

The purpose of the present study is to investigate the effect of postural change on transesophageal echocardiography (TEE) views and parameters of interest anesthesia monitoring in healthy dogs. Twelve Beagle dogs were anesthetized and randomly positioned in one of four postures: right lateral-recumbency, left lateral-recumbency, supine position and prone position. After examinations in one posture, the same examination was demonstrated in another posture and repeated in all postures. In each posture, several standard TEE views were demonstrated: longitudinal cranial-esophageal aorta long-axis-view, transverse middle-esophageal mitral valve long-axis-view and transgastric middle short-axis-view. Additionally, echocardiographic parameters were attempted to measure, and direct blood pressure monitoring was performed in each view. As a result, oriented views, except for transgastric middle short-axis-view, could be obtained in all postures. Stroke volume and peak early diastolic velocity of mitral inflow were lower in supine position compared with those in right and left lateral-recumbency. Heart rate (HR) and systemic vascular resistance were higher in supine position compared with those in right and left lateral-recumbency. Left ventricular pre-ejection period/left ventricular ejection time corrected and uncorrected by HR were higher in supine position compared with those in right and left lateral-recumbency. In conclusion, longitudinal cranial-esophageal aorta long-axis-view and transverse middle-esophageal mitral valve long-axis-view provide useful information of interest anesthesia monitoring, because of their views enable to certainly obtain TEE parameters in various postures. Furthermore, TEE parameters allow to detect the changes of preload, afterload and HR that occur in supine position dogs.

Preemptive hemodynamic intervention restricting the administration of fluids attenuates lung edema progression in oleic acid-induced lung injury

OBJECTIVE

A study is made of the influence of preemptive hemodynamic intervention restricting fluid administration upon the development of oleic acid-induced lung injury.

DESIGN

A randomized in vivo study in rabbits was carried out.

SETTING

University research laboratory.

SUBJECTS

Sixteen anesthetized, mechanically ventilated rabbits.

VARIABLES

Hemodynamic measurements obtained by transesophageal Doppler signal. Respiratory mechanics computed by a least square fitting method. Lung edema assessed by the ratio of wet weight to dry weight of the right lung. Histological examination of the left lung.

INTERVENTIONS

Animals were randomly assigned to either the early protective lung strategy (EPLS) (n=8) or the early protective hemodynamic strategy (EPHS) (n=8). In both groups, lung injury was induced by the intravenous infusion of oleic acid (OA) (0.133mlkg^-1h^-1 for 2h). At the same time, the EPLS group received 15mlkg^-1h^-1 of Ringer lactate solution, while the EPHS group received 30mlkg^-1h^-1. Measurements were obtained at baseline and 1 and 2h after starting OA infusion.

RESULTS

After 2h, the cardiac index decreased in the EPLS group (p<0.05), whereas in the EPHS group it remained unchanged. Lung compliance decreased significantly only in the EPHS group (p<0.05). Lung edema was greater in the EPHS group (p<0.05). Histological damage proved similar in both groups (p=0.4).

CONCLUSIONS

In this experimental model of early lung injury, lung edema progression was attenuated by preemptively restricting the administration of fluids.

Adaptive Spectral Envelope Estimation for Doppler Ultrasound

Estimation of accurate maximum velocities and spectral envelope in ultrasound Doppler blood flow spectrograms are both essential for clinical diagnostic purposes. However, obtaining accurate maximum velocity is not straightforward due to intrinsic spectral broadening and variance in the power spectrum estimate. The method proposed in this paper for maximum velocity point detection has been developed by modifying an existing method-signal noise slope intersection, incorporating in it steps from an altered version of another method called geometric method. Adaptive noise estimation from the spectrogram ensures that a smooth spectral envelope is obtained postdetection of these maximum velocity points. The method has been tested on simulated Doppler signal with scatterers possessing a parabolic flow velocity profile constant in time, steady and pulsatile string phantom recordings, as well as in vivo recordings from uterine, umbilical, carotid, and subclavian arteries. The results from simulation experiments indicate a bias of less than 2.5% in maximum velocities when estimated for a range of peak velocities, Doppler angles, and SNR levels. Standard deviation in the envelope is low-less than 2% in the case of experiments done by varying the peak velocity and Doppler angle for steady phantom and simulated flow, and also less than 2% in the case of experiments done by varying SNR but keeping constant flow conditions for in vivo and simulated flow. Low variability in the envelope makes the prospect of using the envelope for automated blood flow measurements possible and is illustrated for the case of pulsatility index estimation in uterine and umbilical arteries.

A Review of Central Venous Pressure and Its Reliability as a Hemodynamic Monitoring Tool in Veterinary Medicine

OBJECTIVE

To review the current literature regarding central venous pressure (CVP) in veterinary patients pertaining to placement (of central line), measurement, interpretation, use in veterinary medicine, limitations, and controversies in human medicine.

ETIOLOGY

CVP use in human medicine is a widely debated topic, as numerous sources have shown poor correlation of CVP measurements to the volume status of a patient. Owing to the ease of placement and monitoring in veterinary medicine, CVP remains a widely used modality for evaluating the hemodynamic status of a patient. A thorough evaluation of the veterinary and human literature should be performed to evaluate the role of CVP measurements in assessing volume status in veterinary patients.

DIAGNOSIS

Veterinary patients that benefit from accurate CVP readings include those suffering from hypovolemic or septic shock, heart disease, or renal disease or all of these. Other patients that may benefit from CVP monitoring include high-risk anesthetic patients undergoing major surgery, trending of fluid volume status in critically ill patients, patients with continued shock, and patients that require rapid or large amounts of fluids.

THERAPY

The goal of CVP use is to better understand a patient's intravascular volume status, which would allow early goal-directed therapy.

PROGNOSIS

CVP would most likely continue to play an important role in the hemodynamic monitoring of the critically ill veterinary patient; however, when available, cardiac output methods should be considered the first choice for hemodynamic monitoring.

Minimally Invasive Cardiac Output Monitoring: Agreement of Oesophageal Doppler, LiDCOrapid™ and Vigileo FloTrac™ Monitors in Non-Cardiac Surgery

There is lack of data about the agreement of minimally invasive cardiac output monitors, which make it impossible to determine if they are interchangeable or differ objectively in tracking physiological trends. We studied three commonly used devices: the oesophageal Doppler and two arterial pressure–based devices, the Vigileo FloTrac™ and LiDCOrapid™. The aim of this study was to compare the agreement of these three monitors in adult patients undergoing elective non-cardiac surgery. Measurements were taken at baseline and after predefined clinical interventions of fluid, metaraminol or ephedrine bolus. From 24 patients, 131 events, averaging 5.2 events per patient, were analysed. The cardiac index of LiDCOrapid versus FloTrac had a mean bias of −6.0% (limits of agreement from −51% to 39%) and concordance of over 80% to the three clinical interventions. The cardiac index of Doppler versus LiDCOrapid and Doppler versus FloTrac, had an increasing negative bias at higher mean cardiac outputs and there was significantly poorer concordance to all interventions. Of the preload-responsive parameters, Doppler stroke volume index, Doppler systolic flow time and FloTrac stroke volume variation were fair at predicting fluid responsiveness while other parameters were poor. While there is reasonable agreement between the two arterial pressure–derived cardiac output devices (LiDCOrapid and Vigileo FloTrac), these two devices differ significantly to the oesophageal Doppler technology in response to common clinical intraoperative interventions, representing a limitation to how interchangeable these technologies are in measuring cardiac output.

Corrected flow time is a good indicator for preload responsiveness during living donor liver donation

BACKGROUND

Corrected flow time (FTc) has been utilized as preload indicator in recent literature. Accurate estimation of preload status during living donor liver donation (LDLD) is important due to fluid restriction. We evaluate the effectiveness of FTc as a surrogate of preload indicator during LDLD.

MATERIALS AND METHODS

Twenty-five patients undergoing LDLD were enrolled in the study. Administration of intravenous fluid was restricted before lobectomy was performed. After the organ was harvest, fluid challenge with 500 mL of Voluven (130/0.42, Fresenius, Friedberg, Germany) was performed. Stroke volume (SV) was measured with ultrasonic cardiac output monitor (USCOM; USCOM Pty, Ltd, Sydney, Australia) before and after the fluid challenge. The FTc value obtained with USCOM before fluid challenge was recorded. Fluid responsiveness was defined as an increase in SV of more than 15%. Receiver operating characteristic (ROC) curve was performed.

RESULTS

The area under ROC curve was 0.9. The optimal cutoff FTc value was 340 milliseconds during LDLD.

CONCLUSIONS

FTc is a noninvasive, easily obtainable, and essentially good preload indicator during LDLD.

Assessing volume status and fluid responsiveness in the emergency department

Resuscitation with intravenous fluid can restore intravascular volume and improve stroke volume. However, in unstable patients, approximately 50% of fluid boluses fail to improve cardiac output as intended. Increasing evidence suggests that excess fluid may worsen patient outcomes. Clinical examination and vital signs are unreliable predictors of the response to a fluid challenge. We review the importance of fluid management in the critically ill, methods of evaluating volume status, and tools to predict fluid responsiveness.

The correlation between the Trendelenburg position and the stroke volume variation

Background

The stroke volume variation (SVV), based on lung-heart interaction during mechanical ventilation, is a useful dynamic parameter for fluid responsiveness. However, it is affected by many factors. The aim of this study was to evaluate the effects of SVV on Trendelenburg (T) and reverse Trendelenburg (RT) position and to further elaborate on the patterns of the SVV with position.

Methods

Forty-two patients undergoing elective surgery were enrolled in this study. Fifteen minutes after standardized induction of anesthesia with propofol, fentanyl, and rocuronium with volume controlled ventilation (tidal volume of 8 ml/kg of ideal body weight, inspiration : expiration ratio of 1 : 2, and respiratory rate of 10-13 breaths/min), the patients underwent posture changes as follows: supine, T position at slopes of operating table of -5°, -10°, and -15°, and RT position at slopes of operating table of 5°, 10°, and 15°. At each point, SVV, cardiac output (CO), peak airway pressure (PAP), mean blood pressure, and heart rate (HR) were recorded.

Results

The SVV was significant decreased with decreased slopes of operating table in T position, and increased with increased slopes of operating table in RT position (P = 0.000). Schematically, it was increased by 1% when the slope of operating table was increased by 5°. But, the CO and PAP were significant increased with decreased slopes of operating table in T position, and decreased with increased slopes of operating table in RT position (P = 0.045, 0.027).

Conclusions

SVV is subjected to the posture, and we should take these findings into account on reading SVV for fluid therapy.

Oesophageal Doppler cardiac output monitoring: a longstanding tool with evolving indications and applications

Much work has been done over the years to assess cardiac output and better grasp haemodynamic profiles of patients in critical care and during major surgery. Pulmonary artery catheterization has long been considered as the standard of care, especially in critical care environments, however this dogma has been challenged over the last 10-15 years. This has led to a greater focus on alternate, lesser invasive technologies. This review focuses on the scientific and clinical outcomes basis of oesophageal Doppler monitoring. The science underpinning Doppler shift assessment of velocity stretches back over 100 years, whereas the clinical applicability, and specifically clinical outcomes improvement can be attributed to the last 20 years. Oesophageal Doppler monitoring (ODM), and its associated protocol-guided fluid administration, has been shown to reduce complications, length of stay, and overall healthcare cost when incorporated into perioperative fluid management algorithms. However, more recent advances in enhanced recovery after surgery programs have led to similar improvements, leading the clinician to consider the role of Oesophageal Doppler Monitor to be more focused in high-risk surgery and/or the high-risk patient.

An improved Doppler model for obtaining accurate maximum blood velocities

Maximum blood velocity estimates are frequently required in diagnostic applications, including carotid stenosis evaluation, arteriovenous fistula inspection, and maternal-fetal examinations. However, the currently used methods for ultrasound measurements are inaccurate and often rely on applying heuristic thresholds to a Doppler power spectrum. A new method that uses a mathematical model to predict the correct threshold that should be used for maximum velocity measurements has recently been introduced. Although it is a valuable and deterministic tool, this method is limited to parabolic flows insonated by uniform pressure fields. In this work, a more generalized technique that overcomes such limitations is presented. The new approach, which uses an extended Doppler spectrum model, has been implemented in an experimental set-up based on a linear array probe that transmits defocused steered waves. The improved model has been validated by Field II simulations and phantom experiments on tubes with diameters between 2mm and 8mm. Using the spectral threshold suggested by the new model significantly higher accuracy estimates of the peak velocity can be achieved than are now clinically attained, including for narrow beams and non-parabolic velocity profiles. In particular, an accuracy of +1.2±2.5 cm/s has been obtained in phantom measurements for velocities ranging from 20 to 80 cm/s. This result represents an improvement that can significantly affect the way maximum blood velocity is investigated today.

Evaluating the adequacy of fluid resuscitation in patients with septic shock: controversies and future directions

Fluid resuscitation is a cornerstone in the treatment of severe sepsis and septic shock. However, there is little evidence to guide clinicians in its administration. Current guidelines recommend targeting fluid therapy based on measurements of cardiac filling pressures, such as central venous pressure. Static pressures are poor predictors of a patient's response to fluid. Such response can be better predicted by measuring changes in hemodynamic parameters caused by positive pressure ventilation or maneuvers designed to simulate increased preload. These changes can be measured by analysis of arterial waveforms, echocardiography or Doppler, or with emerging noninvasive technologies. This article reviews the current role of fluid replacement strategies and the use of monitoring systems in the overall resuscitation of patients with severe sepsis and septic shock.

Transoesophageal Doppler compared to central venous pressure for perioperative hemodynamic monitoring and fluid guidance in liver resection

PURPOSE

Major hepatic resections may result in hemodynamic changes. Aim is to study transesophageal Doppler (TED) monitoring and fluid management in comparison to central venous pressure (CVP) monitoring. A follow-up comparative hospital based study.

METHODS

59 consecutive cirrhotic patients (CHILD A) undergoing major hepatotomy. CVP monitoring only (CVP group), (n=30) and TED (Doppler group), (n=29) with CVP transduced but not available on the monitor. Exclusion criteria include contra-indication for Doppler probe insertion or bleeding tendency. An attempt to reduce CVP during the resection in both groups with colloid restriction, but crystalloids infusion of 6 ml/kg/h was allowed to replace insensible loss. Post-resection colloids infusion were CVP guided in CVP group (5-10 mmHg) and corrected flow time (FTc) aortic guided in Doppler group (>0.4 s) blood products given according to the laboratory data.

RESULTS

Using the FTc to guide Hydroxyethyl starch 130/0.4 significantly decreased intake in TED versus CVP (1.03 [0.49] versus 1.74 [0.41] Liter; P<0.05). Nausea, vomiting, and chest infection were less in TED with a shorter hospital stay (P<0.05). No correlation between FTc and CVP (r=0.24, P > 0.05). Cardiac index and stroke volume of TED increased post-resection compared to baseline, 3.0 (0.9) versus 3.6 (0.9) L/min/m(2), P<0.05; 67.1 (14.5) versus 76 (13.2) ml, P<0.05, respectively, associated with a decrease in systemic vascular resistance (SVR) 1142.7 (511) versus 835.4 (190.9) dynes.s/cm(5), P<0.05. No significant difference in arterial pressure and CVP between groups at any stage. CVP during resection in TED 6.4 (3.06) mmHg versus 6.1 (1.4) in CVP group, P=0.6. TED placement consumed less time than CVP (7.3 [1.5] min versus 13.2 [2.9], P<0.05).

CONCLUSION

TED in comparison to the CVP monitoring was able to reduced colloids administration post-resection, lower morbidity and shorten hospital stay. TED consumed less time to insert and was also able to present significant hemodynamic changes. Advanced surgical techniques of resection play a key role in reducing blood loss despite CVP more than 5 cm H2O. TED fluid management protocols during resection need to be developed.

Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense

BACKGROUND

Despite a previous meta-analysis that concluded that central venous pressure should not be used to make clinical decisions regarding fluid management, central venous pressure continues to be recommended for this purpose.

AIM

To perform an updated meta-analysis incorporating recent studies that investigated indices predictive of fluid responsiveness. A priori subgroup analysis was planned according to the location where the study was performed (ICU or operating room).

DATA SOURCES

MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and citation review of relevant primary and review articles.

STUDY SELECTION

Clinical trials that reported the correlation coefficient or area under the receiver operating characteristic curve (AUC) between the central venous pressure and change in cardiac performance following an intervention that altered cardiac preload. From 191 articles screened, 43 studies met our inclusion criteria and were included for data extraction. The studies included human adult subjects, and included healthy controls (n = 1) and ICU (n = 22) and operating room (n = 20) patients.

DATA EXTRACTION

Data were abstracted on study characteristics, patient population, baseline central venous pressure, the correlation coefficient, and/or the AUC between central venous pressure and change in stroke volume index/cardiac index and the percentage of fluid responders. Meta-analytic techniques were used to summarize the data.

DATA SYNTHESIS

Overall 57% ± 13% of patients were fluid responders. The summary AUC was 0.56 (95% CI, 0.54-0.58) with no heterogenicity between studies. The summary AUC was 0.56 (95% CI, 0.52-0.60) for those studies done in the ICU and 0.56 (95% CI, 0.54-0.58) for those done in the operating room. The summary correlation coefficient between the baseline central venous pressure and change in stroke volume index/cardiac index was 0.18 (95% CI, 0.1-0.25), being 0.28 (95% CI, 0.16-0.40) in the ICU patients, and 0.11 (95% CI, 0.02-0.21) in the operating room patients.

CONCLUSIONS

There are no data to support the widespread practice of using central venous pressure to guide fluid therapy. This approach to fluid resuscitation should be abandoned.

Renal perfusion assessment by renal Doppler during fluid challenge in sepsis

OBJECTIVES

To assess renal resistive index variations in response to fluid challenge.

DESIGN

Prospective cohort study.

SETTING

Three ICUs in French teaching hospitals.

PATIENTS

Consecutive patients receiving mechanical ventilation and requiring a fluid challenge.

INTERVENTION

Resistive index measurement before and after fluid challenge.

MEASUREMENTS AND MAIN RESULTS

Renal Doppler was used to measure resistive index and esophageal Doppler to monitor aortic blood flow. Of the 35 included patients, 17 (49%) met our definition for fluid challenge responsiveness, that is, had at least a 10% increase in aortic blood flow. After fluid challenge, mean arterial pressure increased from 73 mm Hg (interquartile range 68-79) to 80 mm Hg (75-86; p < 0.0001) and stroke volume from 50 mL (30-77) to 55 mL (39-84; p < 0.0001). Stroke volume changes after fluid challenge were +28.6% (+18.8% to +38.8%) in fluid challenge responders and +3.1% (-1.6% to 7.4%) in fluid challenge nonresponders. Renal resistive index was unchanged after fluid challenge in both nonresponders (0.72 [0.67-0.75] before and 0.71 [0.67-0.75] after fluid challenge; p = 0.62) and responders (0.70 [0.65-0.75] before and 0.72 [0.68-0.74] after fluid challenge; p = 0.11). Stroke volume showed no correlations with resistive index changes after fluid challenge in the overall population (r² = 0.04, p = 0.25), in fluid challenge responders (r² = -0.02, p = 0.61), or in fluid challenge nonresponders (r² = 0.08, p = 0.27). Stroke volume did not correlate with resistive index changes after fluid challenge in the subgroups without acute kidney injury (AKIN definition), with transient acute kidney injury, or with persistent acute kidney injury.

CONCLUSION

Systemic hemodynamic changes induced by fluid challenge do not translate into resistive index variations in patients without acute kidney injury, with transient acute kidney injury, or with persistent acute kidney injury.

Intraoperative esophageal Doppler hemodynamic monitoring in free perforator flap surgery

Goal-directed fluid therapy optimizes cardiac output and flap perfusion during anesthesia. Intraoperative esophageal Doppler (ED) monitoring has been reported as more accurate and reliable, demonstrating improved surgical outcomes compared with central venous pressure and arterial catheter monitoring. A prospective study of patients undergoing free perforator (deep inferior epigastric artery perforator/anterolateral thigh) flap surgery with intraoperative ED monitoring (51 patients) or central venous pressure monitoring (53 patients) was undertaken. Fluid input included crystalloids, colloids, or blood products. Fluid output included urine, blood, or suctioned fluid. Postoperative fluid balance was calculated as fluid input - output. Fluid input between groups was not different. Fluid output was greater in the ED group (P = 0.008). The ED group showed less fluid balance (P = 0.023), less anesthetic time (P = 0.001), less hospital stay (mean 1.9 days; P = 0.147), less monitoring and flap complications (P = 0.062). ED monitoring demonstrated no monitoring complications, provides a favorable postoperative fluid balance, and may reduce flap complications and hospital stay.

Ability of stroke volume variation measured by oesophageal Doppler monitoring to predict fluid responsiveness during surgery

BACKGROUND

The objective of this study was to test whether non-invasive assessment of respiratory stroke volume variation (ΔrespSV) by oesophageal Doppler monitoring (ODM) can predict fluid responsiveness during surgery in a mixed population. The predictive value of ΔrespSV was evaluated using a grey zone approach.

METHODS

Ninety patients monitored using ODM who required i.v. fluids to expand their circulating volume during surgery under general anaesthesia were studied. Patients with a preoperative arrhythmia, right ventricular failure, frequent ectopic beats, or breathing spontaneously were excluded. Haemodynamic variables and oesophageal Doppler indices [peak velocity (PV), stroke volume (SV), corrected flow time (FTc), cardiac output (CO), ΔrespSV, and respiratory variation of PV (ΔrespPV)] were measured before and after fluid expansion. Responders were defined by a >15% increase in SV after infusion of 500 ml crystalloid solution.

RESULTS

SV was increased by ≥15% after 500 ml crystalloid infusion in 53 (59%) of the 90 patients. ΔrespSV predicted fluid responsiveness with an area under the receiver-operating characteristic (AUC) curve of 0.91 [95% confidence interval (95% CI): 0.85-0.97, P<0.0001]. The optimal ΔrespSV cut-off was 14.4% (95% CI: 14.3-14.5%). The grey zone approach identified 12 patients (14%) with a range of ΔrespSV values between 14% and 15%. FTc was not predictive of fluid responsiveness (AUC 0.49, 95% CI: 0.37-0.62, P=0.84).

CONCLUSIONS

ΔrespSV predicted fluid responsiveness accurately during surgery over a ΔrespSV range between 14% and 15%. In contrast, FTc did not predict fluid responsiveness.