Physiological controversies and methods used to determine fluid responsiveness: a qualitative systematic review

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.

MAN VERSUS MACHINE: PROVIDER DIRECTED VERSUS PRECISION AUTOMATED CRITICAL CARE MANAGEMENT IN A PORCINE MODEL OF DISTRIBUTIVE SHOCK

ABSTRACT

Background: Critical care management of shock is a labor-intensive process. Precision Automated Critical Care Management (PACC-MAN) is an automated closed-loop system incorporating physiologic and hemodynamic inputs to deliver interventions while avoiding excessive fluid or vasopressor administration. To understand PACC-MAN efficacy, we compared PACC-MAN to provider-directed management (PDM). We hypothesized that PACC-MAN would achieve equivalent resuscitation outcomes to PDM while maintaining normotension with lower fluid and vasopressor requirements. Methods : Twelve swine underwent 30% controlled hemorrhage over 30 min, followed by 45 min of aortic occlusion to generate a vasoplegic shock state, transfusion to euvolemia, and randomization to PACC-MAN or PDM for 4.25 h. Primary outcomes were total crystalloid volume, vasopressor administration, total time spent at hypotension (mean arterial blood pressure <60 mm Hg), and total number of interventions. Results : Weight-based fluid volumes were similar between PACC-MAN and PDM; median and IQR are reported (73.1 mL/kg [59.0-78.7] vs. 87.1 mL/kg [79.4-91.8], P = 0.07). There was no statistical difference in cumulative norepinephrine (PACC-MAN: 33.4 μg/kg [27.1-44.6] vs. PDM: 7.5 [3.3-24.2] μg/kg, P = 0.09). The median percentage of time spent at hypotension was equivalent (PACC-MAN: 6.2% [3.6-7.4] and PDM: 3.1% [1.3-6.6], P = 0.23). Urine outputs were similar between PACC-MAN and PDM (14.0 mL/kg vs. 21.5 mL/kg, P = 0.13). Conclusion : Automated resuscitation achieves equivalent resuscitation outcomes to direct human intervention in this shock model. This study provides the first translational experience with the PACC-MAN system versus PDM.

Internal jugular vein collapsibility does not predict fluid responsiveness in spontaneously breathing patients after cardiac surgery

PURPOSE

The objective of our study was to evaluate the diagnostic accuracy of internal jugular vein (IJV) collapsibility as a predictor of fluid responsiveness in spontaneously breathing patients after cardiac surgery.

METHODS

In this prospective observational study, spontaneously breathing patients were enrolled on the first postoperative day after coronary artery bypass grafting. Hemodynamic data coupled with simultaneous ultrasound assessment of the IJV were collected at baseline and after passive leg raising test (PLR). Continuous cardiac index (CI), stroke volume (SV), and stroke volume variation (SVV) were assessed with FloTracTM/EV1000™. Fluid responsiveness was defined as an increase in CI ≥ 10% after PLR. We compared the differences in measured variables between fluid responders and non-responders and tested the ability of ultrasonographic IJV indices to predict fluid responsiveness.

RESULTS

Fifty-four patients were included in the study. Seventeen (31.5%) were fluid responders. The responders demonstrated significantly lower inspiratory and expiratory diameters of the IJV at baseline, but IJV collapsibility was comparable (P = 0.7). Using the cut-off point of 20%, IJV collapsibility predicted fluid responsiveness with a sensitivity of 76.5% and specificity of 38.9%, ROC AUC 0.55.

CONCLUSION

In spontaneously breathing patients after surgical coronary revascularisation, collapsibility of the internal jugular vein did not predict fluid responsiveness.

Precision Automated Critical Care Management: Closed-loop critical care for the treatment of distributive shock in a swine model of ischemia-reperfusion

BACKGROUND

Goal-directed blood pressure management in the intensive care unit can improve trauma outcomes but is labor-intensive. Automated critical care systems can deliver scaled interventions to avoid excessive fluid or vasopressor administration. We compared a first-generation automated drug and fluid delivery platform, Precision Automated Critical Care Management (PACC-MAN), to a more refined algorithm, incorporating additional physiologic inputs and therapeutics. We hypothesized that the enhanced algorithm would achieve equivalent resuscitation endpoints with less crystalloid utilization in the setting of distributive shock.

METHODS

Twelve swine underwent 30% hemorrhage and 30 minutes of aortic occlusion to induce an ischemia-reperfusion injury and distributive shock state. Next, animals were transfused to euvolemia and randomized into a standardized critical care (SCC) of PACC-MAN or an enhanced version (SCC+) for 4.25 hours. SCC+ incorporated lactate and urine output to assess global response to resuscitation and added vasopressin as an adjunct to norepinephrine at certain thresholds. Primary and secondary outcomes were decreased crystalloid administration and time at goal blood pressure, respectively.

RESULTS

Weight-based fluid bolus volume was lower in SCC+ compared with SCC (26.9 mL/kg vs. 67.5 mL/kg, p = 0.02). Cumulative norepinephrine dose required was not significantly different (SCC+: 26.9 μg/kg vs. SCC: 13.76 μg/kg, p = 0.24). Three of 6 animals (50%) in SCC+ triggered vasopressin as an adjunct. Percent time spent between 60 mm Hg and 70 mm Hg, terminal creatinine and lactate, and weight-adjusted cumulative urine output were equivalent.

CONCLUSION

Refinement of the PACC-MAN algorithm decreased crystalloid administration without sacrificing time in normotension, reducing urine output, increasing vasopressor support, or elevating biomarkers of organ damage. Iterative improvements in automated critical care systems to achieve target hemodynamics in a distributive-shock model are feasible.

Perioperative Fluid Management

The medical complexity of the geriatric patients has been steadily rising. Still, as outcomes of surgical procedures in the elderly are improving, centers are pushing boundaries. There is also a growing appreciation of the importance of perioperative fluid management on postoperative outcomes, especially in the elderly. Optimal fluid management in this cohort is challenging due to the combination of age-related physiological changes in organ function, increased comorbid burden, and larger fluid shifts during more complex surgical procedures. The current state-of-the-art approach to fluid management in the perioperative period is outlined.

2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage: A Guideline From the American Heart Association/American Stroke Association

AIM

The "2023 Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage" replaces the 2012 "Guidelines for the Management of Aneurysmal Subarachnoid Hemorrhage." The 2023 guideline is intended to provide patient-centric recommendations for clinicians to prevent, diagnose, and manage patients with aneurysmal subarachnoid hemorrhage.

METHODS

A comprehensive search for literature published since the 2012 guideline, derived from research principally involving human subjects, published in English, and indexed in MEDLINE, PubMed, Cochrane Library, and other selected databases relevant to this guideline, was conducted between March 2022 and June 2022. In addition, the guideline writing group reviewed documents on related subject matter previously published by the American Heart Association. Newer studies published between July 2022 and November 2022 that affected recommendation content, Class of Recommendation, or Level of Evidence were included if appropriate. Structure: Aneurysmal subarachnoid hemorrhage is a significant global public health threat and a severely morbid and often deadly condition. The 2023 aneurysmal subarachnoid hemorrhage guideline provides recommendations based on current evidence for the treatment of these patients. The recommendations present an evidence-based approach to preventing, diagnosing, and managing patients with aneurysmal subarachnoid hemorrhage, with the intent to improve quality of care and align with patients' and their families' and caregivers' interests. Many recommendations from the previous aneurysmal subarachnoid hemorrhage guidelines have been updated with new evidence, and new recommendations have been created when supported by published data.

Update on the use of ultrasound in the diagnosis and monitoring of the critical patient

Hemodynamic and respiratory complications are the main causes of morbidity and mortality in in critical care units (CCU). Imaging techniques are a key tool in differential diagnosis and treatment. In the last decade, ultrasound has shown great potential for bedside diagnosis of respiratory disease, as well as for the hemodynamic assessment of critically ill patients. Ultrasound has proven to be a useful guide for identifying the type of shock, estimating cardiac output, guiding fluid therapy and vasoactive drugs, providing security in the performance of percutaneous techniques (thoracentesis, pericardiocentesis, evacuation of abscesses/hematomas), detecting dynamically in real time pulmonary atelectasis and its response to alveolar recruitment maneuvers, and predicting weaning failure from mechanical ventilation. Due to its dynamic nature, simple learning curve and absence of ionizing radiation, it has been incorporated as an essential tool in daily clinical practice in CCUs. The objective of this review is to offer a global vision of the role of ultrasound and its applications in the critically ill patient.

Respiratory-Cardiovascular Interactions During Mechanical Ventilation: Physiology and Clinical Implications

Positive-pressure inspiration and positive end-expiratory pressure (PEEP) increase pleural, alveolar, lung transmural, and intra-abdominal pressure, which decrease right and left ventricular (RV; LV) preload and LV afterload and increase RV afterload. The magnitude and clinical significance of the resulting changes in ventricular function are determined by the delivered tidal volume, the total level of PEEP, the compliance of the lungs and chest wall, intravascular volume, baseline RV and LV function, and intra-abdominal pressure. In mechanically ventilated patients, the most important, adverse consequences of respiratory-cardiovascular interactions are a PEEP-induced reduction in cardiac output, systemic oxygen delivery, and blood pressure; RV dysfunction in patients with ARDS; and acute hemodynamic collapse in patients with pulmonary hypertension. On the other hand, the hemodynamic changes produced by respiratory-cardiovascular interactions can be beneficial when used to assess volume responsiveness in hypotensive patients and by reducing dyspnea and improving hypoxemia in patients with cardiogenic pulmonary edema. Thus, a thorough understanding of the physiological principles underlying respiratory-cardiovascular interactions is essential if critical care practitioners are to anticipate, recognize, manage, and utilize their hemodynamic effects. © 2022 American Physiological Society. Compr Physiol 12:1-24, 2022.

Diagnostic Accuracy of Ultrasonographic Respiratory Variation in the Inferior Vena Cava, Subclavian Vein, Internal Jugular Vein, and Femoral Vein Diameter to Predict Fluid Responsiveness: A Systematic Review and Meta-Analysis

This systematic review and meta-analysis aimed to investigate the ultrasonographic variation of the diameter of the inferior vena cava (IVC), internal jugular vein (IJV), subclavian vein (SCV), and femoral vein (FV) to predict fluid responsiveness in critically ill patients. Relevant articles were obtained by searching PubMed, EMBASE, and Cochrane databases (articles up to 21 October 2021). The number of true positives, false positives, false negatives, and true negatives for the index test to predict fluid responsiveness was collected. We used a hierarchical summary receiver operating characteristics model and bivariate model for meta-analysis. Finally, 30 studies comprising 1719 patients were included in this review. The ultrasonographic variation of the IVC showed a pooled sensitivity and specificity of 0.75 and 0.83, respectively. The area under the receiver operating characteristics curve was 0.86. In the subgroup analysis, there was no difference between patients on mechanical ventilation and those breathing spontaneously. In terms of the IJV, SCV, and FV, meta-analysis was not conducted due to the limited number of studies. The ultrasonographic measurement of the variation in diameter of the IVC has a favorable diagnostic accuracy for predicting fluid responsiveness in critically ill patients. However, there was insufficient evidence in terms of the IJV, SCV, and FV.

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

Noninvasive Beat-To-Beat Stroke Volume Measurements to Determine Preload Responsiveness During Mini-Fluid Challenge in a Swine Model: A Preliminary Study

ABSTRACT

Cardiac output (CO) is an important parameter in fluid management decisions for treating hemodynamically unstable patients in intensive care unit. The gold standard for CO measurements is the thermodilution method, which is an invasive procedure with intermittent results. Recently, electrical impedance tomography (EIT) has emerged as a new method for noninvasive measurements of stroke volume (SV). The objectives of this paper are to compare EIT with an invasive pulse contour analysis (PCA) method in measuring SV during mini-fluid challenge in animals and determine preload responsiveness with EIT. Five pigs were anesthetized and mechanically ventilated. After removing 25% to 30% of the total blood from each animal, multiple fluid injections were conducted. The EIT device successfully tracked changes in SV beat-to-beat during varying volume states, i.e., from hypovolemia and preload responsiveness to target volume and volume overload. From a total of 50 100-mL fluid injections on five pigs (10 injections per pig), the preload responsiveness value was as large as 32.3% in the preload responsiveness state while in the volume overload state it was as low as -4.9%. The bias of the measured SV data using EIT and PCA was 0 mL, and the limits of agreement were ±3.6 mL in the range of 17.6 mL to 51.0 mL. The results of the animal experiments suggested that EIT is capable of measuring beat-to-beat SV changes during mini-fluid challenge and determine preload responsiveness. Further animal and clinical studies will be needed to demonstrate the feasibility of the EIT method as a new tool for fluid management.

Central venous pressure estimation from ultrasound assessment of the jugular venous pulse

Objectives

Acquiring central venous pressure (CVP), an important clinical parameter, requires an invasive procedure, which poses risk to patients. The aim of the study was to develop a non-invasive methodology for determining mean-CVP from ultrasound assessment of the jugular venous pulse.

Methods

In thirty-four adult patients (age = 60 ± 12 years; 10 males), CVP was measured using a central venous catheter, with internal jugular vein (IJV) cross-sectional area (CSA) variation along the cardiac beat acquired using ultrasound. The resultant CVP and IJV-CSA signals were synchronized with electrocardiogram (ECG) signals acquired from the patients. Autocorrelation signals were derived from the IJV-CSA signals using algorithms in R (open-source statistical software). The correlation r-values for successive lag intervals were extracted and used to build a linear regression model in which mean-CVP was the response variable and the lagging autocorrelation r-values and mean IJV-CSA, were the predictor variables. The optimum model was identified using the minimum AIC value and validated using 10-fold cross-validation.

Results

While the CVP and IJV-CSA signals were poorly correlated (mean r = -0.018, SD = 0.357) due to the IJV-CSA signal lagging behind the CVP signal, their autocorrelation counterparts were highly positively correlated (mean r = 0.725, SD = 0.215). Using the lagging autocorrelation r-values as predictors, mean-CVP was predicted with reasonable accuracy (r² = 0.612), with a mean-absolute-error of 1.455 cmH₂O, which rose to 2.436 cmH₂O when cross-validation was performed.

Conclusions

Mean-CVP can be estimated non-invasively by using the lagged autocorrelation r-values of the IJV-CSA signal. This new methodology may have considerable potential as a clinical monitoring and diagnostic tool.

Effect of pneumoperitoneum on dynamic variables of fluid responsiveness (Delta PP and PVI) during Trendelenburg position

Background and Aims:

Pulse pressure variation (ΔPP) is considered as one of the best predictors of fluid responsiveness in patients under mechanical ventilation. Pleth Variability Index (PVI) has been proposed as a noninvasive alternative. However, pneumoperitoneum has been recently suggested as a limitation to their interpretation. The aim of this study was to compare changes in ΔPP and PVI related to autotransfusion associated with a Trendelenburg maneuver before and during pneumoperitoneum.

Methods:

50 patients undergoing elective abdominal laparoscopic surgery were enrolled in this prospective observational study. All patients were equipped with an invasive radial artery catheter and a PVI probe. After obtaining a stable signal with both ΔPP and PVI, baseline values were recorded, before and after head-down tilts of 10°, with or without abdominal insufflation (10-12 mmHg). All measurements were made before any fluid challenge under standardized anaesthesia, while patients were paralyzed and mechanically ventilated with 8 mL/kg tidal volume.

Results:

Changes in ΔPP and PVI associated with the Trendelenburg maneuver before and after insufflation of the pneumoperitoneum were significantly different (P < 0.001). In baseline conditions, the Trendelenburg maneuver was associated with a significant decrease in heart rate while mean arterial pressure remained unchanged. Both ΔPP and PVI decreased. After insufflation of the pneumoperitoneum, the Trendelenburg maneuver was associated with a significant decrease in heart rate and ΔPP and an increase in mean arterial pressure while PVI remained unchanged.

Conclusion:

Pneumoperitoneum did not alter the response of ΔPP to autotransfusion associated with the Trendelenburg maneuver, which was not the case for the PVI. This latter decreased during Trendelenburg maneuver performed alone and remained unchanged during Trendelenburg maneuver performed after insufflation of the pneumoperitoneum.

The Value of the Inferior Vena Cava Area Distensibility Index and its Diameter Ratio for Predicting Fluid Responsiveness in Mechanically Ventilated Patients

INTRODUCTION

It is necessary to evaluate fluid responsiveness before fluid resuscitation. We evaluated the value of inferior vena cava (IVC) area respiratory variation and the IVC diameter ratio (IVC DR) for predicting fluid responsiveness in mechanically ventilated patients.

METHODS

A prospective observational study was performed in the intensive care unit between December 2017 and March 2018. Mechanically ventilated patients were enrolled and received ultrasound monitoring. IVC diameter distensibility index from the subxiphoid area (IVC-sx DDI), IVC diameter distensibility index from the right midaxillary line (IVC-rm DDI), IVC area distensibility index (IVC ADI), and IVC DR in cross-section were calculated by ultrasound monitoring IVC parameters. The enrolled patients were classified as nonresponders group and responders group according to whether the cardiac output increased by >10% after passive leg raising.

RESULTS

Data from 67 mechanically ventilated patients were analyzed. 55.2% of patients had positive fluid responsiveness. The area of receiver operating characteristic curves evaluating the ability of the IVC-sx DDI, IVC-rm DDI, IVC ADI, and IVC DR to predict the fluid responsiveness were 0.702, 0.686, 0.749, and 0.829, respectively. IVC DR level of 1.43 was predictive of positive fluid responsiveness with 90.0% specificity and 67.6% sensitivity. IVC ADI level of 10.2% was predictive of positive fluid responsiveness with 40.0% specificity and 97.3% sensitivity.

CONCLUSIONS

IVC ADI and its diameter ratio in cross-section had more value than IVC diameter distensibility index for predicting fluid responsiveness in mechanically ventilated patients.

Continuous cardiac output assessment or serial echocardiography during septic shock resuscitation?

Septic shock is the leading cause of cardiovascular failure in the intensive care unit (ICU). Cardiac output is a primary component of global oxygen delivery to organs and a sensitive parameter of cardiovascular failure. Any mismatch between oxygen delivery and rapidly varying metabolic demand may result in tissue dysoxia, hence organ dysfunction. Since the intricate alterations of both vascular and cardiac function may rapidly and widely change over time, cardiac output should be measured repeatedly to characterize the type of shock, select the appropriate therapeutic intervention, and evaluate patient's response to therapy. Among the numerous techniques commercially available for measuring cardiac output, transpulmonary thermodilution (TPT) provides a continuous monitoring with external calibration capability, whereas critical care echocardiography (CCE) offers serial hemodynamic assessments. CCE allows early identification of potential sources of inaccuracy of TPT, including right ventricular failure, severe tricuspid or left-sided regurgitations, intracardiac shunt, very low flow states, or dynamic left ventricular outflow tract obstruction. In addition, CCE has the unique advantage of depicting the distinct components generating left ventricular stroke volume (large cavity size vs. preserved contractility), providing information on left ventricular diastolic properties and filling pressures, and assessing pulmonary artery pressure. Since inotropes may have deleterious effects if misused, their initiation should be based on the documentation of a cardiac dysfunction at the origin of the low flow state by CCE. Experts widely advocate using CCE as a first-line modality to initially evaluate the hemodynamic profile associated with shock, as opposed to more invasive techniques. Repeated assessments of both the efficacy (amplitude of the positive response) and tolerance (absence of side-effect) of therapeutic interventions are required to best guide patient management. Overall, TPT allowing continuous tracking of cardiac output variations and CCE appear complementary rather than mutually exclusive in patients with septic shock who require advanced hemodynamic monitoring.

The effects of static and dynamic measurements using transpulmonary thermodilution devices on fluid therapy in septic shock: A systematic review

Transpulmonary thermodilution devices have been widely shown to be accurate in septic shock patients in assessing fluid responsiveness. We conducted a systematic review to assess the relationship between fluid therapy protocols guided by transpulmonary thermodilution devices on fluid balance and the amount of intravenous fluid used in septic shock. We searched MEDLINE, Embase and The Cochrane Library. Studies were eligible for inclusion if they were prospective, parallel trials that were conducted in an intensive care setting in patients with septic shock. The comparator group was either central venous pressure, early goal-directed therapy or pulmonary artery occlusion pressure. Studies assessing only the accuracy of fluid responsiveness prediction by transpulmonary thermodilution devices were excluded. Two reviewers independently performed the search, extracted data and assessed the bias of each study. In total 27 full-text articles were identified for eligibility; of these, nine studies were identified for inclusion in the systematic review. Three of these trials used dynamic parameters derived from transpulmonary thermodilution devices and six used primarily static parameters to guide fluid therapy. There was evidence for a significant reduction in positive fluid balance in four out of the nine studies. From the available studies, the results suggest the benefit of transpulmonary thermodilution monitoring in the septic shock population with regard to reducing positive fluid balance is seen when the devices are utilised for at least 72 hours. Both dynamic and static parameters derived from transpulmonary thermodilution devices appear to lead to a reduction in positive fluid balance in septic shock patients compared to measurements of central venous pressure and early goal-directed therapy.

The utility of point-of-care ultrasound in the assessment of volume status in acute and critically ill patients

BACKGROUND

Volume resuscitation has only been demonstrated to be effective in approximately fifty percent of patients. The remaining patients do not respond to volume resuscitation and may even develop adverse outcomes (such as acute pulmonary edema necessitating endotracheal intubation). We believe that point-of-care ultrasound is an excellent modality by which to adequately predict which patients may benefit from volume resuscitation.

DATA RESOURCES

We performed a search using PubMed, Scopus, and MEDLINE. The following search terms were used: fluid responsiveness, ultrasound, non-invasive, hemodynamic, fluid challenge, and passive leg raise. Preference was given to clinical trials and review articles that were most relevant to the topic of assessing a patient's cardiovascular ability to respond to intravenous fluid administration using ultrasound.

RESULTS

Point-of-care ultrasound can be easily employed to measure the diameter and collapsibility of various large vessels including the inferior vena cava, common carotid artery, subclavian vein, internal jugular vein, and femoral vein. Such parameters are closely related to dynamic measures of fluid responsiveness and can be used by providers to help guide fluid resuscitation in critically ill patients.

CONCLUSION

Ultrasound in combination with passive leg raise is a non-invasive, cost- and time-effective modality that can be employed to assess volume status and response to fluid resuscitation. Traditionally sonographic studies have focused on the evaluation of large veins such as the inferior vena cava, and internal jugular vein. A number of recently published studies also demonstrate the usefulness of evaluating large arteries to predict volume status.

The Right Ventricle During Selective Lung Ventilation for Thoracic Surgery

The right ventricle (RV) has been an area of evolving interest after decades of being ignored and considered less important than the left ventricle. Right ventricular dysfunction/failure is an independent predictor of mortality and morbidity in cardiac surgery; however, very little is known about the incidence or impact of RV dysfunction/failure in thoracic surgery. The pathophysiology of RV dysfunction/failure has been studied in the context of acute respiratory distress syndrome (ARDS), cardiac surgery, pulmonary hypertension, and left ventricular failure, but limited data exist in literature addressing the issue of RV dysfunction/failure in the context of thoracic surgery and one-lung ventilation (OLV). Thoracic surgery and OLV present as a unique situation where the RV is faced with sudden changes in afterload, preload, and contractility throughout the perioperative period. The authors discuss the possible pathophysiologic mechanisms that can affect adversely the RV during OLV and introduce the term RV injury to the myocardium that is affected adversely by the various intraoperative factors, which then makes it predisposed to acute dysfunction. The most important of these mechanisms seems to be the role of intraoperative mechanical ventilation, which potentially could cause both ventilator-induced lung injury leading to ARDS and RV injury. Identification of at-risk patients in the perioperative period using focused imaging, particularly echocardiography, is paramount. The authors also discuss the various RV-protective strategies required to prevent RV dysfunction and management of established RV failure.

The predictability of dynamic preload indices depends on the volume of fluid challenge: A prospective observational study in the operating theater

This study was designed to assess the association between volume of fluid challenge (FC) and predictability of respiratory variation of stroke volume (ΔrespSV) in the operating theater.Patients undergoing intermediate/high-risk surgery and monitored by esophageal Doppler monitoring (EDM) were prospectively included. All patients were under general anesthesia and mechanically ventilated. Exclusion criteria were frequent ectopic beats or preoperative arrhythmia, right ventricular failure, and spontaneous breathing. Hemodynamic parameters and esophageal Doppler indices (SV, cardiac output, ΔrespSV) were collected before, after infusion of 250 mL, and after infusion of 500 mL of crystalloid solution. Responders were defined by a >15% increase of stroke volume after FC at each step.After infusion of a 250 mL FC, 41 patients (32%) were classified as fluid responders (R250). After infusion of a 500 mL FC, 80 patients (63%) were classified as fluid responders (R500). The predictability of ΔrespSV was fair with an area under the curve (AUC) of 0.79 (95% CI 0.71-0.86, P < .001) to predict fluid responsiveness with a 250 mL FC. With an AUC of 0.94 (95% CI 0.88-0.97, P < .0001), ΔrespSV presented an excellent ability to predict fluid responsiveness with a 500-mL FC.Predictability of ΔrespSV changed with the volume of fluid infused to assess fluid responsiveness. The accuracy of ΔrespSV was higher with 500 mL than with 250 mL. Bedside studies evaluating the predictability of dynamic preload indices should define fluid responsiveness as a >15% increase of SV in response to a 500-mL FC.

Comparison of conventional fluid management with PVI-based goal-directed fluid management in elective colorectal surgery

Intraoperative fluid management is quite important in terms of postoperative organ perfusion and complications. Different fluid management protocols are in use for this purpose. Our primary goal was to compare the effects of conventional fluid management (CFM) with the Pleth Variability Index (PVI) guided goal-directed fluid management (GDFM) protocols on the amount of crystalloids administered, blood lactate, and serum creatinine levels during the intraoperative period. The length of hospital stay was our secondary goal. Seventy ASA I–II elective colorectal surgery patients were randomly assigned to CFM or GDFM for fluid management. The hemodynamic data and the data obtained from ABG were recorded at the end of induction and during the follow-up period at 1 h intervals. In the preoperative period and at 24 h postoperatively, blood samples were taken for the measurement of hemoglobin, Na, K, Cl, serum creatinine, albumin and blood lactate. In the first 24 h after surgery, oliguria and the time of first bowel movement were recorded. Length of hospital stay was also recorded. Intraoperative crystalloid administration and urine output were statistically significantly higher in CFM group (p < 0.001, p: 0.018). The end-surgery fluid balance was significantly lower in Group GDFM. Preoperative and postoperative Na, K, Cl, serum albumin, serum creatinine, lactate and hemoglobin values were similar between the groups. The time to passage of stool was significantly short in Group-GDFM compared to Group-CFM (p = 0.016). The length of hospital stay was found to be similar in both group. PVI-guided GDFM might be an alternative to CFM in ASA I–II patients undergoing elective colorectal surgery. However, further studies need to be carried out to search the efficiency and safety of PVI.

Prediction of fluid responsiveness in mechanically ventilated cardiac surgical patients: the performance of seven different functional hemodynamic parameters

Background

Functional hemodynamic parameters such as stroke volume and pulse pressure variation (SVV and PPV) have been shown to be reliable predictors of fluid responsiveness in mechanically ventilated patients. Today, different minimally- and non-invasive hemodynamic monitoring systems measure functional hemodynamic parameters. Although some of these parameters are described by the same name, they differ in their measurement technique and thus may provide different results. We aimed to test the performance of seven functional hemodynamic parameters simultaneously in the same clinical setting.

Methods

Hemodynamic measurements were done in 30 cardiac surgery patients that were mechanically ventilated. Before and after a standardized intravenous fluid bolus, hemodynamics were measured by the following monitoring systems: PiCCOplus (SVV_PiCCO, PPV_PiCCO), LiDCO_rapid (SVV_LiDCO, PPV_LiDCO), FloTrac (SVV_FloTrac), Philips Intellivue (PPV_Philips) and Masimo pulse oximeter (pleth variability index, PVI). Prediction of fluid responsiveness was tested by calculation of receiver operating characteristic (ROC) curves including a gray zone approach and compared using Fisher’s Z-Test.

Results

Fluid administration resulted in an increase in cardiac output, while all functional hemodynamic parameters decreased. A wide range of areas under the ROC-curve (AUC’s) was observed: AUC-SVV_PiCCO = 0.91, AUC-PPV_PiCCO = 0.88, AUC-SVV_LiDCO = 0.78, AUC-PPV_LiDCO = 0.89, AUC-SVV_FloTrac = 0.87, AUC-PPV_Philips = 0.92 and AUC-PVI = 0.68. Optimal threshold values for prediction of fluid responsiveness ranged between 9.5 and 17.5%. Lowest threshold values were observed for SVV_LiDCO, highest for PVI.

Conclusion

All functional hemodynamic parameters tested except for PVI showed that their use allows a reliable identification of potential fluid responders. PVI however, may not be suitable after cardiac surgery to predict fluid responsiveness.

Trial registration

NCT02571465, registered on October 7th, 2015 (retrospectively registered).

Peripheral Intravenous Volume Analysis (PIVA) for Quantitating Volume Overload in Patients Hospitalized With Acute Decompensated Heart Failure-A Pilot Study

BACKGROUND

To determine the feasibility of peripheral intravenous volume analysis (PIVA) of venous waveforms for assessing volume overload in patients admitted to the hospital with acute decompensated heart failure (ADHF).

METHODS

Venous waveforms were captured from a peripheral intravenous catheter in subjects admitted for ADHF and healthy age-matched controls. Admission PIVA signal, brain natriuretic peptide, and chest radiographic measurements were related to the net volume removed during diuresis.

RESULTS

ADHF patients had a significantly greater PIVA signal on admission compared with the control group (P = .0013, n = 18). At discharge, ADHF patients had a PIVA signal similar to the control group. PIVA signal, not brain natriuretic peptide or chest radiographic measures, accurately predicted the amount of volume removed during diuresis (R² = 0.781, n = 14). PIVA signal at time of discharge greater than 0.20, demonstrated 83.3% 120-day readmission rate.

CONCLUSIONS

This study demonstrates the feasibility of PIVA for assessment of volume overload in patients admitted to the hospital with ADHF.

Comprehensive Assessment of the Psychological Burden for Students in Physical Education Classes in Chinese Universities

Background

Physical education (PE) is part of the curriculum in Chinese universities. The psychological burden, or anxiety levels, for students in PE classes, can result from several factors, including teaching content, teaching environment, and the organization of the teaching methods. The aim of this study was to assess the psychological burden on students in PE classes in Chinese universities.

Material/Methods

The study included 400 students (200 men and 200 women) from a Chinese university, who participated in PE classes. The distribution of the levels of psychological burden associated with PE was assessed using subjective measurements and a fuzzy comprehensive evaluation method that to provide an integrated framework combining the results of judgments made at multiple stages of the evaluation process.

Results

Of the 400 study participants who attended PE classes, 61.5% of male students and 47.5% of female students coped well or very well when dealing with the perceived psychological burden; 33.5% of male students and 42.5% of female students reported a medium level of psychological burden. Few students reported a high level of psychological burden associated with PE classes. The average psychological burden in female students was greater than for male students who participated in PE classes.

Conclusions

The combination of subjective measurement of the psychological burden associated with PE classes by university students in China, combined with a fuzzy comprehensive evaluation method showed that female university students might require more support than male students to overcome any psychological burden associated with PE classes.

Accuracy of Ultrasonographic Measurements of Inferior Vena Cava to Determine Fluid Responsiveness: A Systematic Review and Meta-Analysis

OBJECTIVE

Fluid responsiveness is the ability to increase the cardiac output in response to a fluid challenge. Only about 50% of patients receiving fluid resuscitation for acute circulatory failure increase their stroke volume, but the other 50% may worsen their outcome. Therefore, predicting fluid responsiveness is needed. In this purpose, in recent years, the assessment of the inferior vena cava (IVC) through ultrasound (US) has become very popular. The aim of our work was to systematically review all the previously published studies assessing the accuracy of the diameter of IVC or its respiratory variations measured through US in predicting fluid responsiveness.

DATA SOURCES

We searched in the MEDLINE (PubMed), Embase, Web of Science databases for all relevant articles from inception to September 2017.

STUDY SELECTION

Included articles specifically addressed the accuracy of IVC diameter or its respiratory variations assessed by US in predicting the fluid responsiveness in critically ill ventilated or not, adult or pediatric patients.

DATA EXTRACTION

We included 26 studies that investigated the role of the caval index (IVC collapsibility or distensibility) and 5 studies on IVC diameter.

DATA SYNTHESIS

We conducted a meta-analysis for caval index with 20 studies: The pooled area under the curve, logarithmic diagnostic odds ratio, sensitivity, and specificity were 0.71 (95% confidence interval [CI]: 0.46-0.83), 2.02 (95% CI: 1.29-2.89), 0.71 (95% CI: 0.62-0.80), and 0.75 (95% CI: 0.64-0.85), respectively.

CONCLUSION

An extreme heterogeneity of included studies was highlighted. Ultrasound evaluation of the diameter of the IVC and its respiratory variations does not seem to be a reliable method to predict fluid responsiveness.

Does pneumoperitoneum affect perfusion index and pleth variability index in patients receiving combined epidural and general anesthesia?

Plethysmographic variability index (PVI) is a dynamic index used for the purpose of fluid responsiveness in patients, and the effect of pneumoperitoneum on PVI is still unclear. We therefore attempted to determine whether PVI and perfusion index (PI) change before/after pneumoperitoneum in patients receiving combined epidural and general anesthesia, which is a common anesthesia method with intravenous remifentanil. Twenty patients underwent laparoscopic cholecystectomy or colectomy. Immediately before pneumoperitoneum, variables were measured at baseline I and were then measured every min for 5 min after pneumoperitoneum start. Immediately before pneumoperitoneum release, variables were measured at baseline II and were measured every min for 5 min after pneumoperitoneum release. Compared with baseline I values, after pneumoperitoneum start, significant increases occurred in stroke volume variation (SVV) at 1-5 min, and significant decreases occurred in PI at 1-5 min. PVI did not change. Compared with baseline II values, after pneumoperitoneum release, significant increases occurred in PI at 1-5 min, and significant decreases occurred in PVI at 4-5 min and SVV at 1-5 min. In patients receiving combined epidural and general anesthesia, we newly found that PI decreased but PVI remained unchanged with a sufficient dose of remifentanil and epidural anesthesia that can block noxious stimuli and also most sympathetic activity. Furthermore, we reconfirmed that PI increased and PVI decreased upon release of pneumoperitoneum. PI and PVI values must be estimated cautiously during and after pneumoperitoneum.

The New Kidney Donor Allocation System and Implications for Anesthesiologists

Given potential disparity and limited allocation of deceased donor kidneys for transplantation, a new federal kidney allocation system was implemented in 2014. Donor organ function and estimated recipient survival in this system has implications for perioperative management of kidney transplant recipients. Early analysis suggests that many of the anticipated goals are being attained. For anesthesiologists, implications of increased dialysis duration and burdens of end-stage renal disease include increased cardiopulmonary disease, challenging fluid, hemodynamic management, and central vein access. With no recent evidence to guide anesthesia care within this new system, we describe the kidney allocation system, summarize initial data, and briefly review organ systems of interest to anesthesiologists. As additional invasive and echocardiographic monitoring may be indicated, one consideration may be development of a dedicated anesthesiology team experienced in management and monitoring of complex patients, in a similar manner as has been done for liver transplant recipients.

Does stroke volume variation predict fluid responsiveness in children: A systematic review and meta-analysis

OBJECTIVE

Stroke volume variation (SVV) is a reliable predictor of fluid responsiveness in adult patients. However, the predictive value of SVV is uncertain in pediatric patients. We performed the first systematic meta-analysis to evaluate the diagnostic value of SVV in predicting fluid responsiveness in children.

METHODS

PUBMED, EMBASE, and Cochrane Central Register of Controlled Trials were searched up to December 2016. Original studies assessing the diagnostic accuracy of SVV in predicting fluid responsiveness in children were considered to be eligible. A random-effects model was used to calculate pooled values of sensitivity, specificity and diagnostic odds ratio with 95% CI. The summary receiver operating characteristic curve was estimated and area under the curve was calculated. Quality of the studies was assessed with the QUADAS-2 tool.

RESULTS

Six studies with a total of 279 fluid boluses in 224 children were included. The analysis demonstrated a pooled sensitivity of 0.68 (95% CI,0.59-0.76), pooled specificity of 0.65 (95% CI, 0.57-0.73), pooled diagnostic odds ratio of 8.24 (95% CI, 2.58-26.30), and the summary area under the summary receiver operating characteristic curve of 0.81. However, significant inter-study heterogeneity was found (p<0.05, I2 = 61.3%), likely due to small sample size and diverse study characteristics.

CONCLUSIONS

Current evidence suggests that SVV was of diagnostic value in predicting fluid responsiveness in children under mechanical ventilation. Given the high heterogeneity of published data, further studies are needed to confirm the diagnostic accuracy of SVV in predicting fluid responsiveness in pediatric patients.

The haemodynamic dilemma in emergency care: Is fluid responsiveness the answer? A systematic review

BACKGROUND

Fluid therapy is a common and crucial treatment in the emergency department (ED). While fluid responsiveness seems to be a promising method to titrate fluid therapy, the evidence for its value in ED is unclear. We aim to synthesise the existing literature investigating fluid responsiveness in ED.

METHODS

MEDLINE, Embase and the Cochrane library were searched for relevant peer-reviewed studies published from 1946 to present.

RESULTS

A total of 249 publications were retrieved of which 22 studies underwent full-text review and eight relevant studies were identified. Only 3 studies addressed clinical outcomes - including 2 randomised controlled trials and one feasibility study. Five articles evaluated the diagnostic accuracy of fluid responsiveness techniques in ED. Due to marked heterogeneity, it was not possible to combine results in a meta-analysis.

CONCLUSION

High quality, adequately powered outcome studies are still lacking, so the place of fluid responsiveness in ED remains undefined. Future studies should have standardisation of patient groups, the target response and the underpinning theoretic concept of fluid responsiveness. The value of a fluid responsiveness based fluid resuscitation protocol needs to be established in a clinical trial.

The Right Ventricle in ARDS

ARDS is associated with poor clinical outcomes, with a pooled mortality rate of approximately 40% despite best standards of care. Current therapeutic strategies are based on improving oxygenation and pulmonary compliance while minimizing ventilator-induced lung injury. It has been demonstrated that relative hypoxemia can be well tolerated, and improvements in oxygenation do not necessarily translate into survival benefit. Cardiac failure, in particular right ventricular dysfunction (RVD), is commonly encountered in moderate to severe ARDS and is reported to be one of the major determinants of mortality. The prevalence rate of echocardiographically evident RVD in ARDS varies across studies, ranging from 22% to 50%. Although there is no definitive causal relationship between RVD and mortality, severe RVD is associated with increased mortality. Factors that can adversely affect RV function include hypoxic pulmonary vasoconstriction, hypercapnia, and invasive ventilation with high driving pressure. It might be expected that early diagnosis of RVD would be of benefit; however, echocardiographic markers (qualitative and quantitative) used to prospectively evaluate the right ventricle in ARDS have not been tested in adequately powered studies. In this review, we examine the prognostic implications and pathophysiology of RVD in ARDS and discuss available diagnostic modalities and treatment options. We aim to identify gaps in knowledge and directions for future research that could potentially improve clinical outcomes in this patient population.