Matthieu Biais

Changes in stroke volume induced by passive leg raising in spontaneously breathing patients: comparison between echocardiography and Vigileo™/FloTrac™ device

IntroductionPassive leg raising (PLR) is a simple reversible maneuver that mimics rapid fluid loading and increases cardiac preload. The effects of this endogenous volume expansion on stroke volume enable the testing of fluid responsiveness with accuracy in spontaneously breathing patients. However, this maneuver requires the determination of stroke volume with a fast-response device, because the hemodynamic changes may be transient. The Vigileo™ monitor (Vigileo™; Flotrac™; Edwards Lifesciences, Irvine, CA, USA) analyzes systemic arterial pressure wave and allows continuous stroke volume monitoring. The aims of this study were (i) to compare changes in stroke volume induced by passive leg raising measured with the Vigileo™ device and with transthoracic echocardiography and (ii) to compare their ability to predict fluid responsiveness.MethodsThirty-four patients with spontaneous breathing activity and considered for volume expansion were included. Measurements of stroke volume were obtained with transthoracic echocardiography (SV-TTE) and with the Vigileo™ (SV-Flotrac) in a semi-recumbent position, during PLR and after volume expansion (500 ml saline). Patients were responders to volume expansion if SV-TTE increased ≥ 15%.ResultsFour patients were excluded. No patients received vasoactive drugs. Seven patients presented septic hypovolemia. PLR-induced changes in SV-TTE and in SV-Flotrac were correlated (r2 = 0.56, P < 0.0001). An increase in SV-TTE ≥ 13% during PLR was predictive of response to volume expansion with a sensitivity of 100% and a specificity of 80%. An increase in SV-Flotrac ≥16% during PLR was predictive of response to volume expansion with a sensitivity of 85% and a specificity of 90%. There was no difference between the area under the ROC curve for PLR-induced changes in SV-TTE (AUC = 0.96 ± 0.03) or SV-Flotrac (AUC = 0.92 ± 0.05). Volume expansion-induced changes in SV-TTE correlated with volume expansion-induced changes in SV-Flotrac (r2 = 0.77, P < 0.0001). In all patients, the highest plateau value of SV-TTE recorded during PLR was obtained within the first 90 s following leg elevation, whereas it was 120 s for SV-Flotrac.ConclusionsPLR-induced changes in SV-Flotrac are able to predict the response to volume expansion in spontaneously breathing patients without vasoactive support.

Evaluation of a new pocket echoscopic device for focused cardiac ultrasonography in an emergency setting

IntroductionIn the emergency setting, focused cardiac ultrasound has become a fundamental tool for diagnostic, initial emergency treatment and triage decisions. A new ultra-miniaturized pocket ultrasound device (PUD) may be suited to this specific setting. Therefore, we aimed to compare the diagnostic ability of an ultra-miniaturized ultrasound device (Vscan™, GE Healthcare, Wauwatosa, WI) and of a conventional high-quality echocardiography system (Vivid S5™, GE Healthcare) for a cardiac focused ultrasonography in patients admitted to the emergency department.MethodsDuring 4 months, patients admitted to our emergency department and requiring transthoracic echocardiography (TTE) were included in this single-center, prospective and observational study. Patients underwent TTE using a PUD and a conventional echocardiography system. Each examination was performed independently by a physician experienced in echocardiography, unaware of the results found by the alternative device. During the focused cardiac echocardiography, the following parameters were assessed: global cardiac systolic function, identification of ventricular enlargement or hypertrophy, assessment for pericardial effusion and estimation of the size and the respiratory changes of the inferior vena cava (IVC) diameter.ResultsOne hundred fifty-one (151) patients were analyzed. With the tested PUD, the image quality was sufficient to perform focused cardiac ultrasonography in all patients. Examination using PUD adequately qualified with a very good agreement global left ventricular systolic dysfunction (κ = 0.87; 95%CI: 0.76-0.97), severe right ventricular dilation (κ = 0.87; 95%CI: 0.71-1.00), inferior vena cava dilation (κ = 0.90; 95%CI: 0.80-1.00), respiratory-induced variations in inferior vena cava size in spontaneous breathing (κ = 0.84; 95%CI: 0.71-0.98), pericardial effusion (κ = 0.75; 95%CI: 0.55-0.95) and compressive pericardial effusion (κ = 1.00; 95%CI: 1.00-1.00).ConclusionsIn an emergency setting, this new ultraportable echoscope (PUD) was reliable for the real-time detection of focused cardiac abnormalities.

Clinical relevance of pulse pressure variations for predicting fluid responsiveness in mechanically ventilated intensive care unit patients: the grey zone approach

IntroductionPulse pressure variation (PPV) has been shown to predict fluid responsiveness in ventilated intensive care unit (ICU) patients. The present study was aimed at assessing the diagnostic accuracy of PPV for prediction of fluid responsiveness by using the grey zone approach in a large population.MethodsThe study pooled data of 556 patients from nine French ICUs. Hemodynamic (PPV, central venous pressure (CVP) and cardiac output) and ventilator variables were recorded. Responders were defined as patients increasing their stroke volume more than or equal to 15% after fluid challenge. The receiver operating characteristic (ROC) curve and grey zone were defined for PPV. The grey zone was evaluated according to the risk of fluid infusion in hypoxemic patients.ResultsFluid challenge led to increased stroke volume more than or equal to 15% in 267 patients (48%). The areas under the ROC curve of PPV and CVP were 0.73 (95% confidence interval (CI): 0.68 to 0.77) and 0.64 (95% CI 0.59 to 0.70), respectively (P <0.001). A grey zone of 4 to 17% (62% of patients) was found for PPV. A tidal volume more than or equal to 8 ml.kg-1 and a driving pressure (plateau pressure - PEEP) more than 20 cmH2O significantly improved the area under the ROC curve for PPV. When taking into account the risk of fluid infusion, the grey zone for PPV was 2 to 13%.ConclusionsIn ventilated ICU patients, PPV values between 4 and 17%, encountered in 62% patients exhibiting validity prerequisites, did not predict fluid responsiveness.

Impact of norepinephrine on the relationship between pleth variability index and pulse pressure variations in ICU adult patients

IntroductionPleth Variability Index (PVI) is an automated and continuous calculation of respiratory variations in the perfusion index. PVI correlates well with respiratory variations in pulse pressure (ΔPP) and is able to predict fluid responsiveness in the operating room. ICU patients may receive vasopressive drugs, which modify vascular tone and could affect PVI assessment. We hypothesized that the correlation between PVI and ΔPP and the ability of PVI to identify patients with ΔPP > 13% is dependent on norepinephrine (NE) use.Methods67 consecutive mechanically ventilated patients in the ICU were prospectively included. Three were excluded. The administration and dosage of NE, heart rate, mean arterial pressure, PVI and ΔPP were measured simultaneously.ResultsIn all patients, the correlation between PVI and ΔPP was weak (r2 = 0.21; p = 0.001). 23 patients exhibited a ΔPP > 13%. A PVI > 11% was able to identify patients with a ΔPP > 13% with a sensitivity of 70% (95% confidence interval: 47%-87%) and a specificity of 71% (95% confidence interval: 54%-84%). The area under the curve was 0.80 ± 0.06. 35 patients (53%) received norepinephrine (NE(+)). In NE(+) patients, PVI and ΔPP were not correlated (r2 = 0.04, p > 0.05) and a PVI > 10% was able to identify patients with a ΔPP > 13% with a sensitivity of 58% (95% confidence interval: 28%-85%) and a specificity of 61% (95% confidence interval:39%-80%). The area under the ROC (receiver operating characteristics) curve was 0.69 ± 0.01. In contrast, NE(-) patients exhibited a correlation between PVI and ΔPP (r2 = 0.52; p < 0.001) and a PVI > 10% was able to identify patients with a ΔPP > 13% with a sensitivity of 100% (95% confidence interval: 71%-100%) and a specificity of 72% (95% confidence interval: 49%-90%). The area under the ROC curve was 0.93 ± 0.06 for NE(-) patients and was significantly higher than the area under the ROC curve for NE(+) patients (p = 0.02).ConclusionsOur results suggest that in mechanically ventilated adult patients, NE alters the correlation between PVI and ΔPP and the ability of PVI to predict ΔPP > 13% in ICU patients.

The ability of pulse pressure variations obtained with CNAP™ device to predict fluid responsiveness in the operating room.

BACKGROUND: Respiratory-induced pulse pressure variations obtained with an arterial line (&Dgr;PPART) indicate fluid responsiveness in mechanically ventilated patients. The Infinity® CNAP™ SmartPod® (Dräger Medical AG & Co. KG, Lübeck, Germany) provides noninvasive continuous beat-to-beat arterial blood pressure measurements and a near real-time pressure waveform. We hypothesized that respiratory-induced pulse pressure variations obtained with the CNAP system (&Dgr;PPCNAP) predict fluid responsiveness as well as &Dgr;PPART predicts fluid responsiveness in mechanically ventilated patients during general anesthesia. METHODS: Thirty-five patients undergoing vascular surgery were studied after induction of general anesthesia. Stroke volume (SV) measured with the Vigileo™/FloTrac™ (Edwards Lifesciences, Irvine, CA), &Dgr;PPART, and &Dgr;PPCNAP were recorded before and after intravascular volume expansion (VE) (500 mL of 6% hydroxyethyl starch 130/0.4). Subjects were defined as responders if SV increased by ≥15% after VE. RESULTS: Twenty patients responded to VE and 15 did not. The correlation coefficient between &Dgr;PPART and &Dgr;PPCNAP before VE was r = 0.90 (95% confidence interval [CI] = 0.84–0.96; P < 0.0001). Before VE, &Dgr;PPART and &Dgr;PPCNAP were significantly higher in responders than in nonresponders (P < 0.0001). The values of &Dgr;PPART and &Dgr;PPCNAP before VE were significantly correlated with the percent increase in SV induced by VE (respectively, r2 = 0.50; P < 0.0001 and r2 = 0.57; P < 0.0001). Before VE, a &Dgr;PPART >10% discriminated between responders and nonresponders with a sensitivity of 90% (95% CI = 69%–99%) and a specificity of 87% (95% CI = 60%–98%). The area under the receiver operating characteristic (ROC) curve was 0.957 ± 0.035 for &Dgr;PPART. Before VE, a &Dgr;PPCNAP >11% discriminated between responders and nonresponders with a sensitivity of 85% (95% CI = 62%–97%) and a specificity of 100% (95% CI = 78%–100%). The area under the ROC curve was 0.942 ± 0.040 for &Dgr;PPCNAP. There was no significant difference between the area under the ROC curve for &Dgr;PPART and &Dgr;PPCNAP. CONCLUSIONS: A value of &Dgr;PPCNAP >11% has a sensitivity of at least 62% in predicting preload-dependent responders to VE in mechanically ventilated patients during general anesthesia.

Evaluation of stroke volume variations obtained with the pressure recording analytic method.

Objective:To investigate whether stroke volume variations obtained with the pressure recording analytic method can predict fluid responsiveness in mechanically ventilated patients with circulatory failure. Design:Prospective study. Setting:Surgical intensive care unit of a university hospital. Patients:Thirty-five mechanically ventilated patients with circulatory failure for whom the decision to give fluid was taken by the physician were included. Exclusion criteria were: Arrhythmia, tidal volume <8 mL/kg, left ventricular ejection fraction<50%, right ventricular dysfunction, and heart rate/respiratory rate ratio <3.6. Interventions:Fluid challenge with 500 mL of saline over 15 mins. Measurements and Main Results:Stroke volume variations and cardiac output obtained with a pressure recording analytic method, pulse pressure variations, and cardiac output estimated by echocardiography were recorded before and after volume expansion. Patients were defined as responders if stroke volume obtained using echocardiography increased by ≥15% after volume expansion. Nineteen patients responded to the fluid challenge. Median [interquartile range, 25% to 75%] stroke volume variation values at baseline were not different in responders and nonresponders (10% [8–16] vs. 14% [12–16]), whereas pulse pressure variations were significantly higher in responders (17% [13–19] vs. 7% [5–10]; p < .0001). A 12.6% stroke volume variations threshold discriminated between responders and nonresponders with a sensitivity of 63% (95% confidence interval 38% to 84%) and a specificity of 69% (95% confidence interval 41% to 89%). A 10% pulse pressure variation threshold discriminated between responders and nonresponders with a sensitivity of 89% (95% confidence interval 67% to 99%) and a specificity of 88% (95% confidence interval 62% to 98%). The area under the receiver operating characteristic curves was different between pulse pressure variations (0.95; 95% confidence interval 0.82–0.99) and stroke volume variations (0.60; 95% confidence interval 0.43–0.76); p < .0001). Volume expansion-induced changes in cardiac output measured using echocardiography or pressure recording analytic method were not correlated (r2 = 0.14; p > .05) and the concordance rate of the direction of change in cardiac output was 60%. Conclusion:Stroke volume variations obtained with a pressure recording analytic method cannot predict fluid responsiveness in intensive care unit patients under mechanical ventilation. Cardiac output measured by this device is not able to track changes in cardiac output induced by volume expansion. (Crit Care Med 2012; 40:–1191)

Case Scenario: Respiratory Variations in Arterial Pressure for Guiding Fluid Management in Mechanically Ventilated Patients

M AINTAINING perioperative optimal cardiac preload in surgical patients is paramount for precise hemodynamic management. Hypovolemia may result in tissue hypoperfusion and worsened organ dysfunction, whereas fluid overload appears to impede oxygen delivery and compromise patient outcome. Several clinical and experimental studies have demonstrated the usefulness of dynamic indices based on heart–lung interactions for guiding volume resuscitation. Mechanical ventilation induces cyclic changes in intrathoracic and transpulmonary pressures that transiently affect left ventricular preload, resulting in cyclic changes in stroke volume that are more pronounced in preload-dependent, but not in preload-independent, patients. These cyclic changes in left ventricular stroke volume induce cyclic changes in arterial pressure waveform. Schematically, systolic pressure variations, pulse pressure variations, stroke volume variations, and deltadown ( Down) are dynamic indicators of preload dependence that can be obtained from arterial pressure waveform. They have been extensively studied in different clinical settings and are robust indicators of fluid responsiveness. The authors present a patient with hypovolemia and hemodynamic instability during emergency abdominal surgery. Hemodynamic optimization is detailed before, during and after surgery using or not using arterial pressure waveform. In addition, the physiologic basis for these dynamic indices, their use in clinical practice, recent progress, and future perspectives are discussed.

Uncalibrated Stroke Volume Variations Are Able to Predict the Hemodynamic Effects of Positive End-Expiratory Pressure in Patients with Acute Lung Injury or Acute Respiratory Distress Syndrome after Liver Transplantation

Background:Positive end-expiratory pressure (PEEP) may reduce cardiac output and total hepatic blood flow after liver transplantation. Pulse pressure variation is useful in predicting the PEEP-induced decrease in cardiac output. The aim of the study was to examine the relationships between stroke volume variations (SVV) obtained with the Vigileo monitor (Edwards Lifesciences, Irvine, CA), and the hemodynamic effects of PEEP. Methods:Over 2 yr, patients presenting an acute lung injury or an acute respiratory distress syndrome in the 72 h after liver transplantation were prospectively enrolled. Patients were monitored with a pulmonary artery catheter (stroke volume) and with the Vigileo system (stroke volume and SVV). Measurements were performed in duplicate, first during zero end-expiratory pressure and then 10 min after the addition of 10 cm H2O PEEP. Results:Twenty-six patients were included. Six patients were excluded from analysis. On PEEP, SVV and pulse pressure variation increased significantly and stroke volume decreased significantly. PEEP-induced changes in stroke volume measured by pulmonary artery catheter were significantly correlated with SVV (r2 = 0.69; P < 0.001) and pulse pressure variation on zero end-expiratory pressure (r2 = 0.66, P < 0.001). PEEP-induced decrease in stroke volume measured by pulmonary artery catheter ≥ 15% was predicted by an SVV > 7% (sensitivity = 100%, specificity = 80%) and by a pulse pressure variation > 8% (sensitivity = 80%, specificity = 100%). PEEP-induced changes in stroke volume measured by pulmonary artery catheter and Vigileo device were correlated (r2 = 0.51, P < 0.005). Conclusions:SVV obtained with Vigileo monitor is useful to predict decrease in stroke volume induced by PEEP. Moreover, this device is able to track changes in stroke volume induced by PEEP.

Fractional excretion of urea as a diagnostic index in acute kidney injury in intensive care patients

PURPOSE Acute kidney injury (AKI) is a dynamic process that evolves from an early reversible condition to an established disease. Value of urine indices in the event of AKI is uncertain in critically ill patients. The aim of this study was to evaluate the performance of fractional excretion of urea (FeU) for differentiating persistent from transient AKI in patients admitted to the intensive care unit. METHODS This was an observational study. Forty-seven patients with AKI according to the RIFLE classification were included. Transient AKI was defined as AKI resolved within 3 days after inclusion. Persistent AKI was defined as persistent serum creatinine elevation or oliguria. RESULTS Fractional excretion of urea was lower in case of transient, 33% (25-39), than persistent AKI, 47% (36-61) (P = .001). Areas under the receiver operating characteristic curve for FeU in case of transient AKI were better than those for other urinary indexes, 0.78 (95% confidence interval, 0.63-0.92). Optimal cutoff point according to the receiver operating characteristic curve was 40%. In patients treated with diuretics, FeU was the only predictive index of transient AKI. Fractional excretion of urea gradually increased from days 1 to 7 in transient AKI, whereas plasma creatinine decreased. CONCLUSIONS Fractional excretion of urea less than 40% was found to be a sensitive and specific index in differentiating transient from persistent AKI in intensive care unit patients especially if diuretics had been administered.

Using pulse pressure variation or stroke volume variation to diagnose right ventricular failure

We read with interest two recent studies suggesting that pulse pressure variation (PPV) is not an accurate predictor of fluid responsiveness in subjects with pulmonary hypertension [1,2]. We agree that PPV and stroke volume variation (SVV) may not work in patients with right ventricular (RV) failure. Indeed, when PPV and SVV are related to an inspiratory increase in RV afterload (and not to a decrease in RV preload), they cannot serve as indicators of fluid responsiveness [3]. This is indeed a limitation but can also be seen as useful information for clinicians who do not have an echo probe on the ends of their fingers. PPV and SVV are now available on virtually all bedside and hemodynamic monitors. These parameters have been shown to be very useful for predicting fluid responsiveness in many patients with an arterial line who are mechanically ventilated [3]. When part of goal-directed strategies, these parameters have also been shown able to improve patient outcome [4,5]. As a result, PPV and SVV are now widely used by clinicians in the decision-making process regarding fluid therapy. In this context, the lack of response to a volume load while PPV or SVV is high should be seen as an indicator of RV dysfunction, and should trigger an echocardiographic evaluation to confirm the diagnosis and to understand the underlying mechanisms. In other words, we believe PPV and SVV may actually help clinicians to diagnose quickly and treat properly shock states related to RV failure!