A mini-fluid challenge of 150 mL predicts fluid responsiveness using Modelflow R pulse contour cardiac output directly after cardiac surgery

Predictors of fluid responsiveness in the operating room: a narrative review

Prediction of fluid responsiveness has been considered an essential tool for modern fluid management. However, most studies in this field have focused on patients in intensive care unit despite numerous research throughout several decades. Therefore, the present narrative review aims to show the representative method's feasibility, advantages, and limitations in predicting fluid responsiveness, focusing on the operating room environments. Firstly, we described the predictors of fluid responsiveness based on heart-lung interaction, including pulse pressure and stroke volume variations, the measurement of respiratory variations of inferior vena cava diameter, and the end-expiratory occlusion test and addressed their limitations. Subsequently, the passive leg raising test and mini-fluid challenge tests were also mentioned, which assess fluid responsiveness by mimicking a classic fluid challenge. In the last part of this review, we pointed out the pitfalls of fluid management based on fluid responsiveness prediction, which emphasized the importance of individualized decision-making. Understanding the available representative methods to predict fluid responsiveness and their associated benefits and drawbacks through this review will aid anesthesiologists in choosing the most reliable methods for optimal fluid administration in each patient during anesthesia in the operating room.

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

Introduction

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

Methods

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

Results

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

Conclusions

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

Feasibility to estimate mean systemic filling pressure with inspiratory holds at the bedside

Background: A decade ago, it became possible to derive mean systemic filling pressure (MSFP) at the bedside using the inspiratory hold maneuver. MSFP has the potential to help guide hemodynamic care, but the estimation is not yet implemented in common clinical practice. In this study, we assessed the ability of MSFP, vascular compliance (Csys), and stressed volume (Vs) to track fluid boluses. Second, we assessed the feasibility of implementation of MSFP in the intensive care unit (ICU). Exploratory, a potential difference in MSFP response between colloids and crystalloids was assessed. Methods: This was a prospective cohort study in adult patients admitted to the ICU after cardiac surgery. The MSFP was determined using 3-4 inspiratory holds with incremental pressures (maximum 35 cm H₂O) to construct a venous return curve. Two fluid boluses were administered: 100 and 500 ml, enabling to calculate Vs and Csys. Patients were randomized to crystalloid or colloid fluid administration. Trained ICU consultants acted as study supervisors, and protocol deviations were recorded. Results: A total of 20 patients completed the trial. MSFP was able to track the 500 ml bolus (p < 0.001). In 16 patients (80%), Vs and Csys could be determined. Vs had a median of 2029 ml (IQR 1605-3164), and Csys had a median of 73 ml mmHg^-1 (IQR 56-133). A difference in response between crystalloids and colloids was present for the 100 ml fluid bolus (p = 0.019) and in a post hoc analysis, also for the 500 ml bolus (p = 0.010). Conclusion: MSFP can be measured at the bedside and provides insights into the hemodynamic status of a patient that are currently missing. The clinical feasibility of Vs and Csys was judged ambiguously based on the lack of required hemodynamic stability. Future studies should address the clinical obstacles found in this study, and less-invasive alternatives to determine MSFP should be further explored. Clinical Trial Registration: ClinicalTrials.gov Identifier NCT03139929.

Existing fluid responsiveness studies using the mini-fluid challenge may be misleading: Methodological considerations and simulations

BACKGROUND

The mini-fluid challenge (MFC) is a clinical concept of predicting fluid responsiveness by rapidly infusing a small amount of intravenous fluids, typically 100 ml, and systematically assessing its haemodynamic effect. The MFC method is meant to predict if a patient will respond to a subsequent, larger fluid challenge, typically another 400 ml, with a significant increase in stroke volume.

METHODS

We critically evaluated the general methodology of MFC studies, with statistical considerations, secondary analysis of an existing study and simulations.

RESULTS

Secondary analysis of an existing study showed that the MFC could predict the total fluid response (MFC + 400 ml) with an area under the receiver operator characteristic curve (AUROC) of 0.92, but that the prediction was worse than random for the response to the remaining 400 ml (AUROC = 0.33). In a null simulation with no response to both the MFC and the subsequent fluid challenge, the commonly used analysis could predict fluid responsiveness with an AUROC of 0.73.

CONCLUSION

Many existing MFC studies are likely overestimating the classification accuracy of the MFC. This should be considered before adopting the MFC into clinical practice. A better study design includes a second, independent measurement of stroke volume after the MFC. This measurement serves as reference for the response to the subsequent fluid challenge.

Hemodynamic effects of different fluid volumes for a fluid challenge in septic shock patients

Background:

It is still unclear what the minimal infusion volume is to effectively predict fluid responsiveness. This study was designed to explore the minimal infusion volume to effectively predict fluid responsiveness in septic shock patients. Hemodynamic effects of fluid administration on arterial load were observed and added values of effective arterial elastance (Ea) in fluid resuscitation were assessed.

Methods:

Intensive care unit septic shock patients with indwelling pulmonary artery catheter (PAC) received five sequential intravenous boluses of 100 mL 4% gelatin. Cardiac output (CO) was measured with PAC before and after each bolus. Fluid responsiveness was defined as an increase in CO >10% after 500 mL fluid infusion.

Results:

Forty-seven patients were included and 35 (74.5%) patients were fluid responders. CO increasing >5.2% after a 200 mL fluid challenge (FC) provided an improved detection of fluid responsiveness, with a specificity of 80.0% and a sensitivity of 91.7%. The area under the ROC curve (AUC) was 0.93 (95% CI: 0.84–1.00, P < 0.001). Fluid administration induced a decrease in Ea from 2.23 (1.46–2.78) mmHg/mL to 1.83 (1.34–2.44) mmHg/mL (P = 0.002), especially for fluid responders in whom arterial pressure did not increase. Notably, the baseline Ea was able to detect the fluid responsiveness with an AUC of 0.74 (95% CI: 0.59–0.86, P < 0.001), whereas Ea failed to predict the pressure response to FC with an AUC of 0.50 (95% CI: 0.33–0.67, P = 0.086).

Conclusion:

In septic shock patients, a minimal volume of 200 mL 4% gelatin could reliably detect fluid responders. Fluid administration reduced Ea even when CO increased. The loss of arterial load might be the reason for patients who increased their CO without pressure responsiveness. Moreover, a high level of Ea before FC was able to predict fluid responsiveness rather than to detect the pressure responsiveness.

Trial registration:

ClinicalTrials.gov, NCT04515511

Accuracy of cumulative volumes of fluid challenge to assess fluid responsiveness in critically ill patients with acute circulatory failure: a pharmacodynamic approach

BACKGROUND

The relationship between the dose (volume of fluid) and the effect (increase of stroke volume [SV]) has been poorly described. We hypothesised that the analysis of the dynamic response of SV during fluid challenge (FC) helps to determine the optimal volume of FC, along with its diagnostic accuracy parameters for fluid responsiveness.

METHODS

A prospective observational study was conducted in critically ill patients with circulatory failure. Patients monitored with oesophageal Doppler and assigned to an FC of 500 ml of crystalloid were included. The areas under the curve (AUC) and 95% confidence intervals (CI₉₅) of the receiver operating characteristic curves for cumulative volumes from 50 to 450 ml were determined for fluid responsiveness (SV increase ≥15% from baseline) along with other parameters of diagnostic accuracy. In the pharmacodynamic analysis, dose-effect and dose-response models were constructed, with determination of median and 90% effective dose (ED₅₀ and ED₉₀).

RESULTS

Forty-five patients were included. The AUC increased with cumulative volumes of FC up to 250 ml (AUC₂₅₀ 0.93 [CI₉₅: 0.85-1.00]), followed by a plateau above 0.95 of AUC. The optimal volume was 250 ml, associated with a specificity of 0.89 [CI₉₅: 0.78-1.00], a sensitivity of 0.92 [CI₉₅: 0.69-1.00], and a threshold of 9.6% increase in SV. The ED₅₀ was 156 [CI₉₅: 136-177] ml and the ED₉₀ was 312 [CI₉₅: 269-352] ml.

CONCLUSIONS

A volume of FC of 250 ml with a threshold of 9.6% increase in SV showed the highest accuracy in detecting fluid responsiveness in critically ill patients with shock.

CLINICAL TRIAL REGISTRATION

.

Dynamic Tests to Predict Fluid Responsiveness After Off-Pump Coronary Artery Bypass Grafting

OBJECTIVE

To test the hypothesis that a positive end-expiratory pressure test and the mini-fluid challenge predict fluid responsiveness in patients after off-pump coronary artery bypass grafting.

DESIGN

Single-center pilot prospective observational study.

SETTING

City Hospital #1 of Arkhangelsk, Russian Federation.

PARTICIPANTS

Thirty-two adult patients after off-pump coronary artery surgery.

INTERVENTIONS

To assess fluid responsiveness, after arrival to the intensive care unit, all patients received a test with increase in positive end-expiratory pressure from 5 to 20 cmH₂O for 2 minutes, a mini-fluid challenge test with administration of crystalloids at 1.5 mL/kg during 2 minutes, and standard fluid challenge test using 7 mL/kg during 10 minutes.

MEASUREMENTS AND MAIN RESULTS

The patients with an increase in cardiac index by ≥15% after a standard fluid challenge test were defined as fluid responders. According to receiver operating characteristic analysis, a decrease in mean arterial pressure exceeding 5 mmHg in 120 seconds of the positive end-expiratory pressure test identified fluid responsiveness with an area under the curve of 0.73 (p = 0.03). The reduction in pulse pressure and stroke volume variations by more than 2% during mini-fluid challenge test predicted positive response to fluid load with an area under the curve of 0.77 and 0.75, respectively (p < 0.05).

CONCLUSION

Both the positive end-expiratory pressure test and the mini-fluid challenge test are feasible after off-pump coronary artery bypass grafting and can be used to predict fluid responsiveness in these patients.

Functional hemodynamic tests: a systematic review and a metanalysis on the reliability of the end-expiratory occlusion test and of the mini-fluid challenge in predicting fluid responsiveness

Background

Bedside functional hemodynamic assessment has gained in popularity in the last years to overcome the limitations of static or dynamic indexes in predicting fluid responsiveness. The aim of this systematic review and metanalysis of studies is to investigate the reliability of the functional hemodynamic tests (FHTs) used to assess fluid responsiveness in adult patients in the intensive care unit (ICU) and operating room (OR).

Methods

MEDLINE, EMBASE, and Cochrane databases were screened for relevant articles using a FHT, with the exception of the passive leg raising. The QUADAS-2 scale was used to assess the risk of bias of the included studies. In-between study heterogeneity was assessed through the I² indicator. Bias assessment graphs were plotted, and Egger’s regression analysis was used to evaluate the publication bias. The metanalysis determined the pooled area under the receiving operating characteristic (ROC) curve, sensitivity, specificity, and threshold for two FHTs: the end-expiratory occlusion test (EEOT) and the mini-fluid challenge (FC).

Results

After text selection, 21 studies met the inclusion criteria, 7 performed in the OR, and 14 in the ICU between 2005 and 2018. The search included 805 patients and 870 FCs with a median (IQR) of 39 (25–50) patients and 41 (30–52) FCs per study. The median fluid responsiveness was 54% (45–59). Ten studies (47.6%) adopted a gray zone analysis of the ROC curve, and a median (IQR) of 20% (15–51) of the enrolled patients was included in the gray zone. The pooled area under the ROC curve for the end-expiratory occlusion test (EEOT) was 0.96 (95%CI 0.92–1.00). The pooled sensitivity and specificity were 0.86 (95%CI 0.74–0.94) and 0.91 (95%CI 0.85–0.95), respectively, with a best threshold of 5% (4.0–8.0%). The pooled area under the ROC curve for the mini-FC was 0.91 (95%CI 0.85–0.97). The pooled sensitivity and specificity were 0.82 (95%CI 0.76–0.88) and 0.83 (95%CI 0.77–0.89), respectively, with a best threshold of 5% (3.0–7.0%).

Conclusions

The EEOT and the mini-FC reliably predict fluid responsiveness in the ICU and OR. Other FHTs have been tested insofar in heterogeneous clinical settings and, despite promising results, warrant further investigations.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2545-z) contains supplementary material, which is available to authorized users.

Ability of mini-fluid challenge to predict fluid responsiveness in obese patients undergoing surgery in the prone position

BACKGROUND

Pulse pressure variation (PPV) and stroke volume variation (SVV) can predict fluid responsiveness effectively. However, high Body Mass Index (BMI) can restrict their use due to changes in respiratory system compliance (CS), intra-abdominal pressure, and stroke volume (SV) in the prone position. Therefore, we aimed to investigate the effectiveness of mini-fluid challenge (MFC) in predicting fluid responsiveness in obese (BMI ≥30 kg/m2) patients in the prone position.

METHODS

A total of 33 patients undergoing neurosurgery were included. After standardized anesthesia induction, patients' PPV, SVV, stroke volume index (SVI) and CS values were recorded in the prone position (T1), after the infusion of 100 mL of crystalloid named as MFC (T2) and after fluid loading was completed with additional 400 mL of crystalloid. Patients whose SVI increased more than 15% after the fluid loading were defined as volume responders.

RESULTS

Fifteen (45%) patients were responders to 500 mL fluid loading. After the 100 mL fluid load, a higher percentage increase in SVI was observed among responders (P<0.001), with values of 6.6% (6.2-8.6%) and 3.5% (1.7-4.8%) in responders and non-responders, respectively. Areas under the receiver operating characteristic curves of MFC, PPV, and SVV were 0.967 (95% CI: 0.838-0.999), 0.683 (95% CI: 0.499-0.834), and 0.709 (95% CI: 0.526-0.853), respectively. The area under the curve of MFC was significantly higher than that of PPV (P=0.003) and SVV (P=0.005).

CONCLUSIONS

The increase in SVI after a rapid infusion of 100 mL crystalloid could predict fluid responsiveness in patients with BMI ≥30 kg/m2 in the prone position.

Validity of mini-fluid challenge for predicting fluid responsiveness following liver transplantation

BACKGROUND

Mini-fluid challenge is a well tested and effective tool to predict fluid responsiveness under various clinical conditions. However, mini-fluid challenge has never been tested in patients with end-stage liver disease. This study investigated whether infusion of 150 ml albumin 5% can predict fluid responsiveness in cirrhotic patients following liver transplant.

METHODS

Fifty patients receiving living donor liver transplant were included in the analysis. Mini-fluid challenge composed of 150 ml of albumin 5% administered over 1 min in three consecutive 50-ml fluid boluses. An additional 350 ml was then infused at a constant rate over 15 min (for a total of 500 ml). Stroke volume (SV) was measured as the product of the subaortic velocity time integral (VTI) and left ventricular outflow tract (LVOT) area. Fluid responsiveness was defined as an increase in SV by ≥15% after the infusion.

RESULTS

Fifty patients were enrolled in the study. Fourteen patients were classified with Child A, 15 patients with Child B, and 21 patients with Child C cirrhosis. Thirty four patients were fluid responders and 16 patients were fluid non-responders. After 150 ml of albumin 5%, the SV increased significantly in our cohort. The area under receiver operating curve (AUROC) was 0.7 (95% confidence interval [CI] 0.5-0.8, P = 0.005). In subgroup analysis, the SV increased significantly after mini fluid challenge in the Child A group (P = 0.017) but not Child B or C groups (P = 0.3 and 0.29, respectively). The AUROC for mini-fluid challenge in the Child A group was 0.86 (95% confidence interval [CI] 0.6-0.9, P = 0.0004), while mini-fluid challenge failed to discriminate between responders and non-responders in Child B and C groups.

CONCLUSION

A mini-fluid challenge of 150 ml albumin 5% can predict fluid responsiveness in liver transplant patients with fair sensitivity and specifiicty. Subgroup analyis revealed that minifluid challenge can predict fluid responsiveness in patients with Child A cirrhosis but not patients with Child B or C cirrhosis.

TRIAL REGISTRATION

NCT03396159 . (Prospective registered). Initial registration date was 10/01/2018.