Monitoring Fluid Responsiveness Research Articles

Hemodynamic management of septic shock: beyond the Surviving Sepsis Campaign guidelines.

Although the Surviving Sepsis Campaign guidelines provide standardized and generalized guidance, they are less individualized. This review focuses on recent updates in the hemodynamic management of septic shock. Monitoring and intervention for septic shock should be personalized according to the phase of shock. In the salvage phase, fluid resuscitation and vasopressors should be given to provide life-saving tissue perfusion. During the optimization phase, tissue perfusion should be optimized. In the stabilization and de-escalation phases, minimal fluid infusion and safe fluid removal should be performed, respectively, while preserving organ perfusion. There is controversy surrounding the use of restrictive versus liberal fluid strategies after initial resuscitation. Fluid administration after initial resuscitation should depend upon the patient's fluid responsiveness and requires individualized management. A number of dynamic tests have been proposed to monitor fluid responsiveness, which can help clinicians decide whether to give fluid or not. The optimal timing for the initiation of vasopressor agents is unknown. Recent data suggest that early vasopressor initiation should be considered. Inotropes can be considered in patients with decreased cardiac contractility associated with impaired tissue perfusion despite adequate volume status and arterial blood pressure. Venoarterial extracorporeal membrane oxygenation should be considered for refractory septic shock with severe cardiac systolic dysfunction.

POCUS measurements of the left brachiocephalic vein provide a novel site for monitoring fluid responsiveness in pediatric patients.

POCUS measurements of the left brachiocephalic vein provide a novel site for monitoring fluid responsiveness in pediatric patients.

Dynamic Indices for the Prediction of Fluid Responsiveness in Laparoscopic Urologic Surgery under General Anaesthesia: An Interventional Study

Objective: This study aims to evaluate the ability of stroke volume variation (SVV), pulse pressure variation (PPV), and change in PVV and SVV after tidal volume challenge testing (ΔPPV and ΔSVV) aiming to predict fluid responsiveness in patients undergoing laparoscopic urologic surgery. Material and Methods: A prospective interventional study was performed with 23 patients undergoing urologic surgery while they were placed in Trendelenburg positions. A Vigileo/FloTrac system was used for the analysis. Hemodynamic data such as: arterial pressure (MAP), heart rate (HR), peak airway pressure (PIP), stroke volume (SV), cardiac output (CO), SVV, and PPV were recorded at the tidal volume settings of 8 mL/kg and 12 mL/kg before, and after a fluid challenge (FC). Fluid responsiveness was defined as an increase in SV(ΔSV) ≥15.0%. Results: After tidal volume challenge tests, there were significant increases in PIP in both groups. PPV increased only in the responders, as opposed to SVV, which increased significantly only in non-responders after tidal volume challenge test. After fluid challenge, PVV and SVV decreased gradually and significantly in both groups. The area under the ROC curves of patients undergoing laparoscopic urologic surgery was 0.872 (95% CI: 0.57-0.96) for ΔPPV, this change was the highest compared to other parameters. The threshold of the ΔPPV of patients undergoing laparoscopic urologic surgery was 4% with a sensitivity at 0.75 and specificity at 0.93. Conclusion: Change in PPV after the tidal volume challenge test from 8 mL/kg to 12 mL/kg can be used as an effective indicator to monitor fluid responsiveness in regards to patients undergoing urologic surgery.

Passive leg raising test to predict fluid responsiveness using the right ventricle outflow tract velocity-time integral through a subcostal view.

The passive leg raising test (PLR) produces a reversible increase in venous return and, if the patient's ventricles are preload dependent, in the cardiac output. As this effect occurs in seconds, the transthoracic echocardiography is optimal for its real time assessment. The utility of the PLR for monitoring fluid responsiveness through the measurement of the left ventricle outflow tract velocity-time integral (LVOT VTI) in an apical 5-chamber view is well stablished. To achieve this view in critically ill patients is often challenging. The aim of this study is to explore the accuracy for predicting fluid responsiveness of the change in the right ventricle outflow tract velocity-time integral (RVOT VTI) from a subcostal view during a PLR. This is a diagnostic accuracy study carried out in two centers in Argentina. We included patients admitted to the intensive care unit from January 2022 to April 2022, that required fluid expansion due to signs of tissular hypoperfusion. We measured the RVOT VTI from a subcostal view in a semi-recumbent position and during the PLR, and the LVOT VTI in an apical 5-chamber view before and after a fluid bolus. If the LVOT VTI increased by 15% after the fluid bolus, the patients were considered fluid responders. We included 43 patients. The area under the ROC curve for a change in the RVOT VTI during the PLR was 0.879 (95% CI 0.744-0.959). A change of 15.36% in the RVOT VTI with the PLR predicted fluid responsiveness with a sensitivity of 85.7% (95% CI 57.2%-98.2%) and specificity of 93.1% (95% CI 77.2-99.2). The positive predictive value was 85.7% (95% CI 60.8%-95.9%) and the negative predictive value was 93.1% (95% CI 78.8%-98%). The positive likelihood ratio was 12.43 and the negative predictive value was 0.15. The RVOT VTI change during a PLR is suitable for the prediction of fluid responsiveness in critically ill patients.

Assessment of shock in emergency: Narrative Review

Shock is an important clinical condition presenting to the emergency department. Pathophysiology of septic, cardiogenic, hemorrhagic, obstructive, and anaphylactic shock are different however clinical assessment tools are the same and limited. It is important to identify shock in its early phase or the patient at risk of shock in the emergency department. There is no accurate clinical tool to identify the early stage of shock. Moreover, it is also important to assess fluid responsiveness to shock, available clinical and biochemical parameters respond differently to fluid resuscitation and none of the tools had 100% sensitivity and specificity. Therefore, this article reviews the available clinical and biochemical parameters to assess and monitoring fluid responsiveness in shock.

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

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

Bedside Evaluation of Fluid Responsiveness in Shock State using Electrical Cardiometry

Background: The initial hemodynamic management for pediatric shocked patients is giving aggressive fluid resuscitation, however fluid overload increases mortality and morbidity, so assessment and monitoring of fluid status have greatest benefit for critical patients to keep hemodynamic stability. Electrical cardiometry is an accurate, easy, and safe method for hemodynamic measurement, and can be used to monitor fluid responsiveness in critically ill patients. Objectives: To examine stroke volume variation (SVV), evaluated through electrical cardiometry as a predictor of fluid responsiveness in management of shock. Patients & Method: This was a cohort study done by observation of 60 shocked pediatric patients who received fluid therapy in the Intensive care units at Cairo University Pediatric Hospitals from July till December 2018. Results: On comparing between patients who were volume non-responders versus volume responders, SVV was highly significant as it was higher in non-responders (P<0.000), also it was higher in patients who died than those who were discharged (p =0.002), it can be used as predictor of mortality with sensitivity of 80%, specificity of 75%, it also can be used as predictor of volume responsiveness with sensitivity of 85%, specificity of 92%. Conclusion: Monitoring SVV, using electrical cadiometery could guide fluid therapy in critically ill pediatric cases, with beneficial impacts on morbidities and mortalities.

Effect of obstructive jaundice on accuracy of left ventricular end-diastolic volume and stroke volume variability in monitoring fluid responsiveness

Objective To evaluate the effect of obstructive jaundice on the accuracy of left ventricular end-diastolic volume (LVEDV) and stroke volume variability (SVV) in monitoring fluid responsiveness. Methods Thirty patients of both sexes, aged 45-60 yr, weighing 55-70 kg, of American Society of Anesthesiologists physical status Ⅰ or Ⅱ, with New York Heart Association Ⅰ, scheduled for elective pancreatoduodenectomy, were divided into 2 groups according to the serum total bilirubin levels: A group (serum total bilirubin≥17 μmmol/L, n=16) and B group (serum total bilirubin<17 μmmol/L, n=14). Six percent hydroxyethyl starch 500 ml was infused over 40 min after anesthesia induction.The parameters of Vigileo™ such as cardiac output (CO), SVV, systemic vascular resistance (SVR) and pulmonary capillary wedge pressure and indices measured by transesophageal three-dimensional echocardiography such as LVEDV, left ventricular end-systolic volume, CO′, left ventricular ejection fraction (LVEF) and ratio of mitral peak velocity of early filling (E) to early diastolic mitral annular velocity (e′, E/e′ ratio) were recorded before and after fluid loading. Results Compared with that before fluid loading, SVV was significantly decreased in two groups, and CO, LVEDV, CO′ and LVEF were significantly increased in group B, and E/e′ ratio was significantly increased in group A (P<0.05). Compared with group B, CO, SVR, CO′ and LVEF were significantly decreased, and pulmonary capillary wedge pressure was increased in group A (P<0.05). Conclusion Obstructive jaundice causes decrease in the accuracy of LVEDV in monitoring fluid responsiveness and no effect on SVV. Key words: Load volume; Stroke volume variability; Left ventricular end-systolic volume; Three-dimensional transesophageal echocardiography; Obstructive jaundice.

Meta-analyses on measurement precision of non-invasive hemodynamic monitoring technologies in adults

An ideal non-invasive monitoring system should provide accurate and reproducible measurements of clinically relevant variables that enables clinicians to guide therapy accordingly. The monitor should be rapid, easy to use, readily available at the bedside, operator-independent, cost-effective and should have a minimal risk and side effect profile for patients. An example is the introduction of pulse oximetry, which has become established for non-invasive monitoring of oxygenation worldwide. A corresponding non-invasive monitoring of hemodynamics and perfusion could optimize the anesthesiological treatment to the needs in individual cases. In recent years several non-invasive technologies to monitor hemodynamics in the perioperative setting have been introduced: suprasternal Doppler ultrasound, modified windkessel function, pulse wave transit time, radial artery tonometry, thoracic bioimpedance, endotracheal bioimpedance, bioreactance, and partial CO2 rebreathing have been tested for monitoring cardiac output or stroke volume. The photoelectric finger blood volume clamp technique and respiratory variation of the plethysmography curve have been assessed for monitoring fluid responsiveness. In this manuscript meta-analyses of non-invasive monitoring technologies were performed when non-invasive monitoring technology and reference technology were comparable. The primary evaluation criterion for all studies screened was aBland-Altman analysis. Experimental and pediatric studies were excluded, as were all studies without anon-invasive monitoring technique or studies without evaluation of cardiac output/stroke volume or fluid responsiveness. Most studies found an acceptable bias with wide limits of agreement. Thus, most non-invasive hemodynamic monitoring technologies cannot be considered to be equivalent to the respective reference method. Studies testing the impact of non-invasive hemodynamic monitoring technologies as atrend evaluation on outcome, as well as studies evaluating alternatives to the finger for capturing the raw signals for hemodynamic assessment, and, finally, studies evaluating technologies based on aflow time measurement are current topics of clinical research.

The ability of left ventricular end-diastolic volume variations measured by TEE to monitor fluid responsiveness in high-risk surgical patients during craniotomy: a prospective cohort study

BackgroundThis study was aimed to evaluate the ability of left ventricular end-diastolic volume variations (LVEDVV) measured by transesophageal echocardiography (TEE) compared with stroke volume variation (SVV) obtained by the FloTrac/Vigileo monitor to predict fluid responsiveness, in patients undergoing craniotomy with goal direct therapy.MethodsWe used SVV obtained by the FloTrac/Vigileo monitor to manage intraoperative hypotension in adult patients undergoing craniotomy (ASA III – IV) after obtaining IRB approval and informed consent. The LVEDVV were measured by TEE through the changes of left ventricular short diameter of axle simultaneously. When cardiac index (CI) ≤ 2.5 and SVV ≥ 15%, comparisons were made between the two devices before and after volume expansion.ResultsWe enrolled twenty-six patients referred for craniotomy in this study and 145 pairs of data were obtained. Mean Vigileo-SVV and TEE-LVEDVV were 17.8 ± 2.78% and 22.1 ± 7.25% before volume expansion respectively, and were 10.95 ± 2.8% and 13.58 ± 3.78% after volume expansion respectively (P < 0.001). The relationship between Vigileo-SVV and TEE-LVEDVV was significant (r2 = 0.55; p < 0.001). Agreement between Vigileo-SVV and TEE-LVEDVV was 3.3% ± 3.9% (mean bias ± SD, Bland-Altman).ConclusionsFor fluid responsiveness of patients during craniotomy in ASA III-IV, LVEDVV measured by left ventricular short diameter of axle using M type echocaidiographic measurement seems an acceptable monitoring indicator. This accessible method has promising clinical applications in situations where volume and cardiac function monitoring is of great importance during surgery.Trial registrationChinese Clinical Trial Registry, ChiCTR-TRC-13003583, August 20, 2013.

Tissue perfusion and oxygenation to monitor fluid responsiveness in critically ill, septic patients after initial resuscitation: a prospective observational study.

Fluid therapy after initial resuscitation in critically ill, septic patients may lead to harmful overloading and should therefore be guided by indicators of an increase in stroke volume (SV), i.e. fluid responsiveness. Our objective was to investigate whether tissue perfusion and oxygenation are able to monitor fluid responsiveness, even after initial resuscitation. Thirty-five critically ill, septic patients underwent infusion of 250 mL of colloids, after initial fluid resuscitation. Prior to and after fluid infusion, SV, cardiac output sublingual microcirculatory perfusion (SDF: sidestream dark field imaging) and skin perfusion and oxygenation (laser Doppler flowmetry and reflectance spectroscopy) were measured. Fluid responsiveness was defined by a ≥5 or 10 % increase in SV upon fluids. In responders to fluids, SDF-derived microcirculatory and skin perfusion and oxygenation increased, but only the increase in cardiac output, mean arterial and pulse pressure, microvascular flow index and relative Hb concentration and oxygen saturation were able to monitor a SV increase. Our proof of principle study demonstrates that non-invasively assessed tissue perfusion and oxygenation is not inferior to invasive hemodynamic measurements in monitoring fluid responsiveness. However skin reflectance spectroscopy may be more helpful than sublingual SDF.

Systolic time intervals vs invasive predictors of fluid responsiveness after coronary artery bypass surgery†

Haemodynamic parameters for predicting fluid responsiveness in intensive care patients are invasive, technically challenging or not universally applicable. We compared the initial systolic time interval (ISTI), a non-invasive measure of the time interval between the electrical and mechanical activities of the heart measured by impedance cardiography, with invasively measured haemodynamic parameters in predicting fluid responsiveness after cardiac surgery. Thirty-two clinically hypovolemic patients admitted to the intensive care unit after coronary artery bypass surgery received 500 ml of gelatine solution in two volume loading steps of 250 ml at an infusion rate of 1000 ml/h. Haemodynamic and biochemical measurements were done at baseline and 15 min after each volume loading step with continuous recording of the impedance cardiogram and electrocardiogram. Forty-four percentage (n = 14) of patients showed a stroke volume (SV) index increase >10%. ISTI predicted fluid responsiveness with an optimum threshold of >153 ms (P = 0.023) and a sensitivity of 71% and specificity of 78%. The predictive values of ISTI did not differ from those of arterial pressure or SV at baseline. A decrease of ISTI of ≥8.3 ms predicted fluid responsiveness with the highest positive predictive value (88%, P = 0.004) among the variables, and absence thereof virtually excluded fluid responsiveness (specificity 94%). Non-invasively measured ISTI is able to predict and monitor fluid responsiveness after cardiac surgery non-inferiorly to invasively measured haemodynamic indices.

New analyses of standard physiological signals: the old pipes give the sweetest smoke

In this issue of the Journal of Clinical Monitoring and Computing, Giraud et al. investigated the impact of hypovolemia on the respiratory variations in the QRS amplitude on a classical DII EKG lead (DRDII) [1]. In this animal study, they were able to demonstrate that bleeding and volume expansion induced significant changes in DRDII and that these changes mirrored those observed in the respiratory variations in pulse pressure (PPV). These observations suggest that this non-invasive and potentially widely available parameter could predict fluid responsiveness and detect hypovolemia in operating rooms and intensive care units. Studies previously published in the Journal of Clinical Monitoring and Computing have already demonstrated a significant relationship between DRDII and PPV (and between DRDII and stroke volume variation) in mechanically ventilated patients under general anesthesia [2, 3]. The manuscript by Giraud et al. builds on these previous studies by showing that DRDII is also sensitive to manually induced changes in ventricular preload. The remaining steps before acceptance of this new index in clinical practice will be to: (1) show that it can independently predict fluid responsiveness; and (2) that its calculation can be automated and monitored continuously. Thus, while the study by Giraud et al. does not yet confirm this new index as an accurate predictor of fluid responsiveness, it is nevertheless a significant step towards validation. This study exemplifies a new trend in the analysis of physiological signals in which an old and readily available stream of data is processed in a novel way to yield new information. In the present case, the electrocardiogram (EKG) was first described over 100 years ago and has been in clinical use for patient monitoring for decades [4]. Despite this long history, the possible use of the EKG waveform in predicting fluid responsiveness is only now becoming clear. Interestingly, the approach described in the paper by Giraud et al. is very similar to what happened in the analysis of the plethysmographic waveform: both signals have been clinically available for decades but the analysis of their respiratory variations (DRDII for the EKG and DPOP for the plethysmographic waveform [5]) is a new concept which may have significant clinical utility [6]. The beauty of these new indices (if proven accurate) is that the equipment needed to obtain them is already available at the bedside and that they require very little computing in order to be obtained continuously and automatically. Additionally, they are cheap, and could be used almost anywhere. These old signals may thus provide universal, non-invasive, and inexpensive ways of monitoring fluid responsiveness in a variety of environments (hence the Irish proverb that ‘‘the old pipe gives the sweetest smoke’’). A similar trend has been observed in cardiac output (CO) monitoring [7]. The traditional clinical approach to monitoring CO is, of course, transpulmonary thermodilution, and this is still the preferred approach in many settings. The highly invasive nature of pulmonary artery catheters and the associated risk, however, makes them undesirable for routine CO monitoring across the full spectrum of surgical and intensive care patients. Newer J. Rinehart M. Cannesson (&) Department of Anesthesiology & Perioperative Care, University of California Irvine, 101 S City Drive, Orange, CA 92868, USA e-mail: mcanness@uci.edu

Cardiac filling volumes versus pressures for predicting fluid responsiveness after cardiovascular surgery: the role of systolic cardiac function

IntroductionStatic cardiac filling volumes have been suggested to better predict fluid responsiveness than filling pressures, but this may not apply to hearts with systolic dysfunction and dilatation. We evaluated the relative value of cardiac filling volume and pressures for predicting and monitoring fluid responsiveness, according to systolic cardiac function, estimated by global ejection fraction (GEF, normal 25 to 35%) from transpulmonary thermodilution.MethodsWe studied hypovolemic, mechanically ventilated patients after coronary (n = 18) or major vascular (n = 14) surgery in the intensive care unit. We evaluated 96 colloid fluid loading events (200 to 600 mL given in three consecutive 30-minute intervals, guided by increases in filling pressures), divided into groups of responding events (fluid responsiveness) and non-responding events, in patients with low GEF (<20%) or near-normal GEF (≥20%). Patients were monitored by transpulmonary dilution and central venous (n = 9)/pulmonary artery (n = 23) catheters to obtain cardiac index (CI), global end-diastolic volume index (GEDVI), central venous (CVP) and pulmonary artery occlusion pressure (PAOP).ResultsFluid responsiveness occurred in 8 (≥15% increase in CI) and 17 (≥10% increase in CI) of 36 fluid loading events when GEF was <20%, and 7 (≥15% increase in CI) and 17 (≥10% increase in CI) of 60 fluid loading events when GEF was ≥20%. Whereas a low baseline GEDVI predicted fluid responsiveness particularly when GEF was ≥20% (P = 0.002 or lower), a low PAOP was of predictive value particularly when GEF was <20% (P = 0.004 or lower). The baseline CVP was lower in responding events regardless of GEF. Changes in CVP and PAOP paralleled changes in CI particularly when GEF was <20%, whereas changes in GEDVI paralleled CI regardless of GEF.ConclusionsRegardless of GEF, CVP may be useful for predicting fluid responsiveness in patients after coronary and major vascular surgery provided that positive end-expiratory pressure is low. When GEF is low (<20%), PAOP is more useful than GEDVI for predicting fluid responsiveness, but when GEF is near-normal (≥20%) GEDVI is more useful than PAOP. This favors predicting and monitoring fluid responsiveness by pulmonary artery catheter-derived filling pressures in surgical patients with systolic left ventricular dysfunction and by transpulmonary thermodilution-derived GEDVI when systolic left ventricular function is relatively normal.

Dynamic and Static Parameters of Fluid Responsiveness, Volume 48, Number 1.

Dynamic and Static Parameters of Fluid Responsiveness, Volume 48, Number 1. Edited by Balachundhar Subramanian, M.B.B.S., M.D., M.P.H., and Kyung W. Park, M.D. Philadelphia, International Anesthesiology Clinics-Lippincott Williams and Wilkins, Winter 2010. Pages: 128. Price: $162.00.Fluid management in perioperative and critically ill patients remains a highly debated topic. There is a wide variety of practice, even within institutions, and, if you think of fluid as a drug, it is unique in that even the most junior member of the team can double or triple the dose without fear of comment by other members of the team. In recent years, there has been a renewed interest in the assessment of fluid responsiveness in critically ill patients to identify those patients for whom fluid therapy will be of benefit and, equally importantly, those for whom it will not. This interest has been driven by the emergence of a number of exciting new technologies. Dynamic and Static Parameters of Fluid Responsiveness reviews these technologies and increases the reader's understanding of the important concept of dynamic fluid responsiveness.The book is well organized into eight original articles. The first article illustrates the limitations of traditional static parameters of fluid responsiveness, such as central venous pressure, and outlines the physiologic concepts related to fluid loading. This leads to the next article that discusses the physiology behind dynamic fluid responsiveness and outlines the different technologies available to illustrate and use this approach in routine clinical practice. In many ways, these first two articles are the key to the book, providing the background information necessary to understand the subject. They are very well written and easy to understand, yet provide sufficient information to be recommended reading for both novice and expert.The next five articles look, in turn, at the different technologies available to monitor fluid responsiveness. The discussion of each device includes technical considerations behind how the device works as well as a detailed review of the evidence base for the technology. The text is necessarily detailed at times because the authors seek to provide the reader with a thorough understanding of the different systems available. The article on echocardiography was a useful inclusion and suitably brief because this technology is not widely used to predict fluid responsiveness, although it may have more of a role in the future as its use expands into noncardiac surgery. We particularly recommend the article on the FloTrac System (Edwards Life Science, Irvine, CA), which expertly reviews the device, particularly in relation to the different versions available, because the company has sought to improve its performance. The PiCCO (Pulsion Medical System AG, Munich, Germany) Monitor is also very well reviewed, although this technology is not yet widely available in the United States.We would have liked to see more information about the LiDCO system (Covidien, Mansfield, MA), particularly with respect to the newer LiDCO rapid device that was only briefly mentioned, despite its widespread use. There was also insufficient discussion of the use of stroke volume variation, as opposed to accurate cardiac output measurement with this system. The use of a noncalibrated device to trend cardiac output and optimize fluid status perioperatively during major surgery is, in our opinion, quite different compared with needing more precise cardiac output values in a critically ill patient. We also believe the editors could have included a separate article to review the esophageal Doppler monitor. As mentioned in the final article, the esophageal Doppler monitor has more outcome data for perioperative goal-directed fluid management than any other monitor. It can also be used to assess the corrected flow time, or duration of flow during systole, as a measure of preload.Using plethysmography to assess dynamic preload responsiveness is an emerging area and is expertly covered, with respect to both the possibilities and the limitations of these new devices. Finally, the last article summarizes the outcome data from randomized controlled trials involving restrictive or goal-directed fluid strategies. It is noteworthy that the limitations of nomenclature and fixed-volume amounts in the restrictive literature, as well as the confusion surrounding the third space, are well reviewed.Overall, the book offers a good and thorough review of the subject, with the caveats mentioned above. We are delighted to see an increasing interest and more publications devoted to this important subject, with the hope that the increasing body of evidence behind dynamic fluid responsiveness can be translated into a widespread change in practice. We would recommend this book to anyone with an interest in this important subject, and it would be a useful addition to any anesthesia or critical care departmental library.*Duke University Medical Center, Durham, North Carolina. tjgan@duke.edu

The Ability of Stroke Volume Variations Obtained with Vigileo/FloTrac System to Monitor Fluid Responsiveness in Mechanically Ventilated Patients

Respiratory variations in arterial pulse pressure (DeltaPP) are accurate predictors of fluid responsiveness in mechanically ventilated patients. The aim of our study was to assess the ability of a novel algorithm for automatic estimation of stroke volume variation (SVV) to predict fluid responsiveness in mechanically ventilated patients. We studied 25 patients referred for coronary artery bypass grafting. SVV was continuously displayed by the Vigileo/FloTrac system. All patients were under general anesthesia, mechanical ventilation and were also monitored with a pulmonary artery catheter. SVV and DeltaPP were recorded simultaneously before and after an intravascular volume expansion (VE) (500 mL hetastarch). Responders to VE were defined as patients whose cardiac index obtained using thermodilution increased by more than 15% after VE. Agreement between DeltaPP and SVV over the 50 pairs of collected data was -1.3% +/- 2.8% (mean bias +/- sd). Seventeen patients were responders to VE. A threshold DeltaPP value of 10% allowed discrimination of responders to VE with a sensitivity of 88% and a specificity of 87%. A threshold SVV value of 10% allowed discrimination of responders to VE with a sensitivity of 82% and a specificity of 88%. SVV predicts fluid responsiveness with an acceptable sensitivity and specificity and is also a potential surrogate for continuous monitoring of DeltaPP.

Relative value of pressures and volumes in assessing fluid responsiveness after valvular and coronary artery surgery

Cardiac function may differ after valvular (VS) and coronary artery (CAS) surgery and this may affect assessment of fluid responsiveness. The aim of the study was to compare VS and CAS in the value of cardiac filling pressures and volumes herein. There were eight consecutive patients after VS and eight after CAS, with femoral and pulmonary artery catheters in place. In each patient, five sequential fluid loading steps of 250 ml of colloid each were done. We measured central venous pressure (CVP), pulmonary artery occlusion pressure (PAOP) and, by transpulmonary thermodilution, cardiac index (CI) and global end-diastolic (GEDVI) and intrathoracic blood volume (ITBVI) indices. Fluid responsiveness was defined by a CI increase >5% or >10% per step. Global ejection fraction was lower and PAOP was higher after VS than CAS. In responding steps after VS (n=9-14) PAOP and volumes increased, while CVP and volumes increased in responding steps (n=12-19) after CAS. Baseline PAOP was lower in responding steps after VS only. Hence, baseline PAOP as well as changes in PAOP and volumes were of predictive value after VS and changes in CVP and volumes after CAS, in receiver operating characteristic curves. After VS, PAOP and volume changes equally correlated to CI changes. After CAS, only changes in CVP and volumes correlated to those in CI. While volumes are equally useful in monitoring fluid responsiveness, the predictive and monitoring value of PAOP is greater after VS than after CAS. In contrast, the CVP is of similar value as volume measurements in monitoring fluid responsiveness after CAS. The different value of pressures rather than of volumes between surgery types is likely caused by systolic left ventricular dysfunction in VS. The study suggests an effect of systolic cardiac function on optimal parameters of fluid responsiveness and superiority of the pulmonary artery catheter over transpulmonary dilution, for haemodynamic monitoring of VS patients.

The Ability of a Novel Algorithm for Automatic Estimation of the Respiratory Variations in Arterial Pulse Pressure to Monitor Fluid Responsiveness in the Operating Room

Respiratory variations in arterial pulse pressure (deltaPP(man)) are accurate predictors of fluid responsiveness in mechanically ventilated patients. However, they cannot be continuously monitored. In our study, we assessed the clinical utility of a novel algorithm for automatic estimation of deltaPP (deltaPP(auto)). We studied 25 patients referred for coronary artery bypass grafting. DeltaPP(auto) was continuously displayed using a method based on automatic detection algorithms, kernel smoothing, and rank-order filters. All patients were under general anesthesia, mechanical ventilation, and were also monitored with a pulmonary artery catheter. DeltaPP(man) and deltaPP(auto) were recorded simultaneously at eight steps during surgery including before and after intravascular volume expansion (500 mL hetastarch). Responders to volume expansion were defined as patients whose cardiac index increased by more than 15% after volume expansion. Agreement between deltaPP(man) and deltaPP(auto) over the 200 pairs of collected data was 0.7% +/- 3.4% (mean bias +/- SD). Seventeen patients were responders to volume expansion. A threshold deltaPP(man) value of 12% allowed discrimination of responders to volume expansion with a sensitivity of 88% and a specificity of 100%. A threshold deltaPP(auto) value of 10% allowed discrimination of responders to volume expansion with a sensitivity of 82% and a specificity of 88%. DeltaPP(auto) is strongly correlated to deltaPP(man) is an accurate predictor of fluid responsiveness, and allows continuous monitoring of deltaPP. This novel algorithm has potential clinical applications.