Assessing the diagnostic accuracy of pulse pressure variations for the prediction of fluid responsiveness: a "gray zone" approach
TL;DR: Despite a strong predictive value, PPV may be inconclusive (between 9% and 13%) in approximately 25% of patients during general anesthesia, and a range of PPV values for which fluid responsiveness could not be predicted reliably were identified.
Abstract: BACKGROUND: Respiratory arterial pulse pressure variations (PPV) are the best predictors of fluid responsiveness in mechanically ventilated patients during general anesthesia. However, previous studies were performed in a small number of patients and determined a single cutoff point to make clinical discrimination. The authors sought to test the predictive value of PPV in a large, multicenter study and to express it using a gray zone approach. METHODS: The authors studied 413 patients during general anesthesia and mechanical ventilation in four centers. PPV, central venous pressure, and cardiac output were recorded before and after volume expansion (VE). Response to VE was defined as more than 15% increase in cardiac output after VE. The following approaches were used to determine the gray zones: resampled and two-graph receiver operator characteristic curves. The impact of changes in the benefit-risk balance of VE on the gray zone was also evaluated. RESULTS: The authors observed 209 responders (51%) and 204 nonresponders (49%) to VE. The area under receiver operating characteristic curve was 0.89 (95% CI: 0.86-0.92) for PPV, compared with 0.57 (95% CI: 0.54-0.59) for central venous pressure (P < 10). The gray zone approach identified a range of PPV values (between 9% and 13%) for which fluid responsiveness could not be predicted reliably. These PPV values were seen in 98 (24%) patients. Changes in the cost ratio of VE moderately affected the gray zone limits. CONCLUSION: Despite a strong predictive value, PPV may be inconclusive (between 9% and 13%) in approximately 25% of patients during general anesthesia.
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University of Copenhagen1, Centre Hospitalier Universitaire de Grenoble2, University of Valladolid3, University of Naples Federico II4, Innsbruck Medical University5, Ludwig Maximilian University of Munich6, Maastricht University7, University of Valencia8, Royal Lancaster Infirmary9, University of Salzburg10
TL;DR: These guidelines are intended to provide an overview of current knowledge on the subject with an assessment of the quality of the evidence in order to allow anaesthetists throughout Europe to integrate this knowledge into daily patient care wherever possible.
Abstract: The aims of severe perioperative bleeding management are three-fold. First, preoperative identification by anamesis and laboratory testing of those patients for whom the perioperative bleeding risk may be increased. Second, implementation of strategies for correcting preoperative anaemia and stabilisation of the macro- and microcirculations in order to optimise the patient’s tolerance to bleeding. Third, targeted procoagulant interventions to reduce the amount of bleeding, morbidity, mortality and costs. The purpose of these guidelines is to provide an overview of current knowledge on the subject with an assessment of the quality of the evidence in order to allow anaesthetists throughout Europe to integrate this knowledge into daily patient care wherever possible. The Guidelines Committee of the European Society of Anaesthesiology (ESA) formed a task force with members of scientific subcommittees and individual expert members of the ESA. Electronic databases were searched without language restrictions from the year 2000 until 2012. These searches produced 20 664 abstracts. Relevant systematic reviews with meta-analyses, randomised controlled trials, cohort studies, case-control studies and cross-sectional surveys were selected. At the suggestion of the ESA Guideline Committee, the Scottish Intercollegiate Guidelines Network (SIGN) grading system was initially used to assess the level of evidence and to grade recommendations. During the process of guideline development, the official position of the ESA changed to favour the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. This report includes general recommendations as well as specific recommendations in various fields of surgical interventions. The final draft guideline was posted on the ESA website for four weeks and the link was sent to all ESA members. Comments were collated and the guidelines amended as appropriate. When the final draft was complete, the Guidelines Committee and ESA Board ratified the guidelines.
883 citations
TL;DR: There are no data to support the widespread practice of using central venous pressure to guide fluid therapy, and this approach to fluid resuscitation should be abandoned.
Abstract: Background: Despite a previous meta-analysis that concluded that central venous pressure should not be used to make clinical decisions regarding fluid management, central venous pressure continues to be recommended for this purpose. Aim: To perform an updated meta-analysis incorporating recent studies that investigated indices predictive of fluid responsiveness. A priori subgroup analysis was planned according to the location where the study was performed (ICU or operating room). Data Sources: MEDLINE, EMBASE, Cochrane Register of Controlled Trials, and citation review of relevant primary and review articles. Study Selection: Clinical trials that reported the correlation coefficient or area under the receiver operating characteristic curve (AUC) between the central venous pressure and change in cardiac performance following an intervention that altered cardiac preload. From 191 articles screened, 43 studies met our inclusion criteria and were included for data extraction. The studies included human adult subjects, and included healthy controls (n = 1) and ICU (n = 22) and operating room (n = 20) patients. Data Extraction: Data were abstracted on study characteristics, patient population, baseline central venous pressure, the correlation coefficient, and/or the AUC between central venous pressure and change in stroke volume index/cardiac index and the percentage of fluid responders. Meta-analytic techniques were used to summarize the data. Data Synthesis: Overall 57% ± 13% of patients were fluid responders. The summary AUC was 0.56 (95% CI, 0.54–0.58) with no heterogenicity between studies. The summary AUC was 0.56 (95% CI, 0.52–0.60) for those studies done in the ICU and 0.56 (95% CI, 0.54–0.58) for those done in the operating room. The summary correlation coefficient between the baseline central venous pressure and change in stroke volume index/cardiac index was 0.18 (95% CI, 0.1–0.25), being 0.28 (95% CI, 0.16–0.40) in the ICU patients, and 0.11 (95% CI, 0.02–0.21) in the operating room patients. Conclusions: There are no data to support the widespread practice of using central venous pressure to guide fluid therapy. This approach to fluid resuscitation should be abandoned. (Crit Care Med 2013; 41:1774–1781)
655 citations
TL;DR: This update includes revisions to existing recommendations with respect to the wording, or changes in the grade of recommendation, and also the addition of new recommendations.
Abstract: The management of perioperative bleeding involves multiple assessments and strategies to ensure appropriate patient care. Initially, it is important to identify those patients with an increased risk of perioperative bleeding. Next, strategies should be employed to correct preoperative anaemia and to
613 citations
TL;DR: Several methods and tests are currently available to identify preload responsiveness, which have some limitations, but they are frequently complementary and should help clinicians to take the decision to administer fluids or not in a reasoned way.
Abstract: In patients with acute circulatory failure, the decision to give fluids or not should not be taken lightly. The risk of overzealous fluid administration has been clearly established. Moreover, volume expansion does not always increase cardiac output as one expects. Thus, after the very initial phase and/or if fluid losses are not obvious, predicting fluid responsiveness should be the first step of fluid strategy. For this purpose, the central venous pressure as well as other “static” markers of preload has been used for decades, but they are not reliable. Robust evidence suggests that this traditional use should be abandoned. Over the last 15 years, a number of dynamic tests have been developed. These tests are based on the principle of inducing short-term changes in cardiac preload, using heart–lung interactions, the passive leg raise or by the infusion of small volumes of fluid, and to observe the resulting effect on cardiac output. Pulse pressure and stroke volume variations were first developed, but they are reliable only under strict conditions. The variations in vena caval diameters share many limitations of pulse pressure variations. The passive leg-raising test is now supported by solid evidence and is more frequently used. More recently, the end-expiratory occlusion test has been described, which is easily performed in ventilated patients. Unlike the traditional fluid challenge, these dynamic tests do not lead to fluid overload. The dynamic tests are complementary, and clinicians should choose between them based on the status of the patient and the cardiac output monitoring technique. Several methods and tests are currently available to identify preload responsiveness. All have some limitations, but they are frequently complementary. Along with elements indicating the risk of fluid administration, they should help clinicians to take the decision to administer fluids or not in a reasoned way.
365 citations
TL;DR: The resuscitation of hemodynamically unstable patients requires an accurate assessment of the patients' intravascular volume status (cardiac preload) and the ability to predict the hemodynamic response after a fluid challenge (volume responsiveness) to minimize the risks of over- or under-resuscitation.
258 citations
References
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TL;DR: A nonparametric approach to the analysis of areas under correlated ROC curves is presented, by using the theory on generalized U-statistics to generate an estimated covariance matrix.
Abstract: Methods of evaluating and comparing the performance of diagnostic tests are of increasing importance as new tests are developed and marketed. When a test is based on an observed variable that lies on a continuous or graded scale, an assessment of the overall value of the test can be made through the use of a receiver operating characteristic (ROC) curve. The curve is constructed by varying the cutpoint used to determine which values of the observed variable will be considered abnormal and then plotting the resulting sensitivities against the corresponding false positive rates. When two or more empirical curves are constructed based on tests performed on the same individuals, statistical analysis on differences between curves must take into account the correlated nature of the data. This paper presents a nonparametric approach to the analysis of areas under correlated ROC curves, by using the theory on generalized U-statistics to generate an estimated covariance matrix.
16,496 citations
TL;DR: UNLABELLED ROCR is a package for evaluating and visualizing the performance of scoring classifiers in the statistical language R that features over 25 performance measures that can be freely combined to create two-dimensional performance curves.
Abstract: Summary: ROCR is a package for evaluating and visualizing the performance of scoring classifiers in the statistical language R. It features over 25 performance measures that can be freely combined to create two-dimensional performance curves. Standard methods for investigating trade-offs between specific performance measures are available within a uniform framework, including receiver operating characteristic (ROC) graphs, precision/recall plots, lift charts and cost curves. ROCR integrates tightly with R's powerful graphics capabilities, thus allowing for highly adjustable plots. Being equipped with only three commands and reasonable default values for optional parameters, ROCR combines flexibility with ease of usage.
Availability:http://rocr.bioinf.mpi-sb.mpg.de. ROCR can be used under the terms of the GNU General Public License. Running within R, it is platform-independent.
Contact: tobias.sing@mpi-sb.mpg.de
2,838 citations
"Assessing the diagnostic accuracy o..." refers methods in this paper
...Statistical analysis was performed with R software** and specific packages.(24)...
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TL;DR: These data provide empirical evidence that diagnostic studies with methodological shortcomings may overestimate the accuracy of a diagnostic test, particularly those including nonrepresentative patients or applying different reference standards.
Abstract: ContextThe literature contains a large number of potential biases in the evaluation
of diagnostic tests. Strict application of appropriate methodological criteria
would invalidate the clinical application of most study results.ObjectiveTo empirically determine the quantitative effect of study design shortcomings
on estimates of diagnostic accuracy.Design and SettingObservational study of the methodological features of 184 original studies
evaluating 218 diagnostic tests. Meta-analyses on diagnostic tests were identified
through a systematic search of the literature using MEDLINE, EMBASE, and DARE
databases and the Cochrane Library (1996-1997). Associations between study
characteristics and estimates of diagnostic accuracy were evaluated with a
regression model.Main Outcome MeasuresRelative diagnostic odds ratio (RDOR), which compared the diagnostic
odds ratios of studies of a given test that lacked a particular methodological
feature with those without the corresponding shortcomings in design.ResultsFifteen (6.8%) of 218 evaluations met all 8 criteria; 64 (30%) met 6
or more. Studies evaluating tests in a diseased population and a separate
control group overestimated the diagnostic performance compared with studies
that used a clinical population (RDOR, 3.0; 95% confidence interval [CI],
2.0-4.5). Studies in which different reference tests were used for positive
and negative results of the test under study overestimated the diagnostic
performance compared with studies using a single reference test for all patients
(RDOR, 2.2; 95% CI, 1.5-3.3). Diagnostic performance was also overestimated
when the reference test was interpreted with knowledge of the test result
(RDOR, 1.3; 95% CI, 1.0-1.9), when no criteria for the test were described
(RDOR, 1.7; 95% CI, 1.1-2.5), and when no description of the population under
study was provided (RDOR, 1.4; 95% CI, 1.1-1.7).ConclusionThese data provide empirical evidence that diagnostic studies with methodological
shortcomings may overestimate the accuracy of a diagnostic test, particularly
those including nonrepresentative patients or applying different reference
standards.
1,651 citations
TL;DR: A systematic review of the literature demonstrated a very poor relationship between CVP and blood volume as well as the inability of CVP/DeltaCVP to predict the hemodynamic response to a fluid challenge.
1,295 citations
TL;DR: This article concentrates on the dimensions of study quality and the advantages and disadvantages of different summary statistics for combining studies in meta-analysis.
Abstract: This is the third in a series of four articles
Tests are routinely used in medicine to screen for, diagnose, grade, and monitor the progression of disease. Diagnostic information is obtained from a multitude of sources, including imaging and biochemical technologies, pathological and psychological investigations, and signs and symptoms elicited during history taking and clinical examinations.1 Each of these items of information can be regarded as a result of a separate diagnostic or screening “test.” Systematic reviews of evaluations of tests are undertaken for the same reasons as systematic reviews of treatment interventions: to produce estimates of test performance and impact based on all available evidence, to evaluate the quality of published studies, and to account for variation in findings between studies.2–5 Reviews of studies of diagnostic accuracy involve the same key stages of defining questions, searching the literature, evaluating studies for eligibility and quality, and extracting and synthesising data. However, studies that evaluate the accuracy of tests have a unique design requiring different criteria to appropriately assess the quality of studies and the potential for bias. Additionally, each study reports a pair of related summary statistics (for example, sensitivity and specificity) rather than a single statistic (such as a risk ratio) and hence requires different statistical methods to pool the results of the studies. This article concentrates on the dimensions of study quality and the advantages and disadvantages of different summary statistics for combining studies in meta-analysis. Other aspects, including searching the literature and further technical details, are discussed elsewhere.6
#### Summary points
Systematic reviews of studies of diagnostic accuracy differ from other systematic reviews in the assessment of study quality and the statistical methods used to combine results
Important aspects of study quality include the selection of a clinically relevant cohort, the consistent use of a …
1,272 citations